This document describes a study that evaluated a hybrid membrane bioreactor process for removing hydrogen sulfide (H2S) from biogas. The process used a polydimethylsiloxane membrane to first absorb H2S from biogas into an alkaline liquid, followed by biological oxidation of H2S in the liquid. The effects of absorption liquid pH, biogas flowrate, and dissolved oxygen concentration on H2S removal efficiency and selectivity were investigated. The results showed that pH 7 performed better than pH 8.5, and H2S removal exceeded 97% at flowrates below 148 g H2S/m3d and dissolved oxygen below 1 mg/L. This novel hybrid process provides an effective and low-cost
This document describes a study that evaluated the use of a gas-liquid membrane contactor process for selective removal of hydrogen sulfide (H2S) from biogas. The effects of biogas retention time (GRT), membrane thickness, and liquid absorbent pH were investigated. The results showed that H2S removal efficiency improved with increasing GRT and absorbent pH, and decreased with increasing membrane thickness. Lower GRT and thicker membranes resulted in higher desulfurization selectivity. The methane content of the treated biogas increased with GRT and the process achieved high H2S removal without significant methane loss. SEM-EDS analysis found inorganic deposits on the membrane surface but no membrane clogging or fouling issues. Overall,
This document summarizes a study that evaluated using an autotrophic denitrification process to remove hydrogen sulfide (H2S) from biogas produced by anaerobic digestion of chicken manure. A laboratory upflow fixed bed reactor was fed scrubbed H2S from the biogas and nitrate. Over 95% H2S and 90% nitrate removal were achieved. When fed directly scrubbed H2S, the reactor experienced clogging from elemental sulfur particles. Feeding scrubbed H2S from biogas at pH 8-9 achieved 98% H2S and 97% nitrate removal without clogging. This process biologically converted H2S to elemental sulfur while denitrifying wastewater.
This study investigated using a bio-electrochemical system (BES) for the simultaneous removal of nitrate and sulfide from different sources without mixing the sources. The anode chamber of the BES was fed with effluent from a sulfate reducing reactor as an electron donor source, while the cathode chamber was fed with nitrate-rich groundwater as an electron acceptor source. The BES was effective at simultaneously removing 10 gS/m3/d of sulfide and 7.26 gN/m3/d of nitrate without mixing the sources. Denitrification in the cathode chamber was supported by electrons from sulfide oxidation in the anode chamber passing through the membrane, and possibly from corrosion of
Distillery Wastewater Decontamination by the Fenton Advanced Oxidation MethodIJRES Journal
This study evaluated the effect of Fenton advanced oxidation process on the treatment of an industrial wastewater (distillery). The comparison of the effects of Fe2+ loadings, H2O2 dosages (2%(v/v)and 4%(v/v)), reaction temperature and reaction time, established optimum efficiency in terms of BOD and COD reductions. The best operating conditions for the treatment of the distillery wastewater containing 43.85 mg/L BOD concentration and 274.28 mg/L COD concentration in the raw effluent was 2% H2O2 dosage at constant loadings of Fe2+ (1.5 g), 80 oC pretreatment temperature, and 1 h reaction time. At this optimized condition, the BOD content reduced to about 35 mg/L (about 21% removal) and COD content reduced to about 53 mg/L (about 81% removal). There was a complete removal of the initial colour present in the wastewater after the treatment process. The process proved the ability to effectively reduce the COD content which when high in industrial wastewaters can lead to serious impacts to the environment.
This document summarizes a study that investigated the adsorption of lead (Pb) from aqueous solution using modified beech sawdust. Some key findings include:
- Maximum Pb removal efficiency of 91.3% occurred at pH 5, while minimum efficiency of 28.04% occurred at pH 7. Maximum adsorption capacity was 0.3841 mg/g.
- As the initial Pb concentration increased from 1 to 7 mg/L, removal efficiency decreased from 91.3% to 33.88%. Increasing adsorbent dose from 2 to 8 g/L improved removal efficiency from 50% to 97.3%.
- Removal efficiency had a decreasing trend after equilibrium was reached
The document summarizes a study that used a hollow fiber membrane bioreactor (MBR) system to treat municipal wastewater. The MBR consisted of influent and effluent tanks and submerged PVDF hollow fiber membrane modules. Over a 120-day period, the MBR achieved over 99.5% removal of chemical oxygen demand (COD) and 88.9% removal of biochemical oxygen demand (BOD5). Results showed the MBR system is effective at treating high-strength wastewaters and can maintain performance during fluctuations in influent levels.
The document summarizes a study on using a combined anaerobic-aerobic reactor system to treat textile wastewater. Key findings include:
- Over 84.62% of ammonia nitrogen and about 98.9% of volatile suspended solids were removed by the system.
- Dissolved oxygen, pH, and organic changes were investigated during the nitrification and denitrification processes. Dissolved oxygen and pH were found to have only slight influences on nitrification, and a 10% removal of nitrogen resulted in about a 3% change in pH.
- The system was able to effectively remove nitrogen and organic materials from textile wastewater through the coupled anaerobic and aer
Gravimetric, mechanical and chemical characterization of different materials used in sewers systems: Polyvinyl chloride (PVC), polypropylene (PP) and high density polyethylene (HDPE), aged in sulfuric acid at 60°C
This document describes a study that evaluated the use of a gas-liquid membrane contactor process for selective removal of hydrogen sulfide (H2S) from biogas. The effects of biogas retention time (GRT), membrane thickness, and liquid absorbent pH were investigated. The results showed that H2S removal efficiency improved with increasing GRT and absorbent pH, and decreased with increasing membrane thickness. Lower GRT and thicker membranes resulted in higher desulfurization selectivity. The methane content of the treated biogas increased with GRT and the process achieved high H2S removal without significant methane loss. SEM-EDS analysis found inorganic deposits on the membrane surface but no membrane clogging or fouling issues. Overall,
This document summarizes a study that evaluated using an autotrophic denitrification process to remove hydrogen sulfide (H2S) from biogas produced by anaerobic digestion of chicken manure. A laboratory upflow fixed bed reactor was fed scrubbed H2S from the biogas and nitrate. Over 95% H2S and 90% nitrate removal were achieved. When fed directly scrubbed H2S, the reactor experienced clogging from elemental sulfur particles. Feeding scrubbed H2S from biogas at pH 8-9 achieved 98% H2S and 97% nitrate removal without clogging. This process biologically converted H2S to elemental sulfur while denitrifying wastewater.
This study investigated using a bio-electrochemical system (BES) for the simultaneous removal of nitrate and sulfide from different sources without mixing the sources. The anode chamber of the BES was fed with effluent from a sulfate reducing reactor as an electron donor source, while the cathode chamber was fed with nitrate-rich groundwater as an electron acceptor source. The BES was effective at simultaneously removing 10 gS/m3/d of sulfide and 7.26 gN/m3/d of nitrate without mixing the sources. Denitrification in the cathode chamber was supported by electrons from sulfide oxidation in the anode chamber passing through the membrane, and possibly from corrosion of
Distillery Wastewater Decontamination by the Fenton Advanced Oxidation MethodIJRES Journal
This study evaluated the effect of Fenton advanced oxidation process on the treatment of an industrial wastewater (distillery). The comparison of the effects of Fe2+ loadings, H2O2 dosages (2%(v/v)and 4%(v/v)), reaction temperature and reaction time, established optimum efficiency in terms of BOD and COD reductions. The best operating conditions for the treatment of the distillery wastewater containing 43.85 mg/L BOD concentration and 274.28 mg/L COD concentration in the raw effluent was 2% H2O2 dosage at constant loadings of Fe2+ (1.5 g), 80 oC pretreatment temperature, and 1 h reaction time. At this optimized condition, the BOD content reduced to about 35 mg/L (about 21% removal) and COD content reduced to about 53 mg/L (about 81% removal). There was a complete removal of the initial colour present in the wastewater after the treatment process. The process proved the ability to effectively reduce the COD content which when high in industrial wastewaters can lead to serious impacts to the environment.
This document summarizes a study that investigated the adsorption of lead (Pb) from aqueous solution using modified beech sawdust. Some key findings include:
- Maximum Pb removal efficiency of 91.3% occurred at pH 5, while minimum efficiency of 28.04% occurred at pH 7. Maximum adsorption capacity was 0.3841 mg/g.
- As the initial Pb concentration increased from 1 to 7 mg/L, removal efficiency decreased from 91.3% to 33.88%. Increasing adsorbent dose from 2 to 8 g/L improved removal efficiency from 50% to 97.3%.
- Removal efficiency had a decreasing trend after equilibrium was reached
The document summarizes a study that used a hollow fiber membrane bioreactor (MBR) system to treat municipal wastewater. The MBR consisted of influent and effluent tanks and submerged PVDF hollow fiber membrane modules. Over a 120-day period, the MBR achieved over 99.5% removal of chemical oxygen demand (COD) and 88.9% removal of biochemical oxygen demand (BOD5). Results showed the MBR system is effective at treating high-strength wastewaters and can maintain performance during fluctuations in influent levels.
The document summarizes a study on using a combined anaerobic-aerobic reactor system to treat textile wastewater. Key findings include:
- Over 84.62% of ammonia nitrogen and about 98.9% of volatile suspended solids were removed by the system.
- Dissolved oxygen, pH, and organic changes were investigated during the nitrification and denitrification processes. Dissolved oxygen and pH were found to have only slight influences on nitrification, and a 10% removal of nitrogen resulted in about a 3% change in pH.
- The system was able to effectively remove nitrogen and organic materials from textile wastewater through the coupled anaerobic and aer
Gravimetric, mechanical and chemical characterization of different materials used in sewers systems: Polyvinyl chloride (PVC), polypropylene (PP) and high density polyethylene (HDPE), aged in sulfuric acid at 60°C
The document outlines various methods for determining types of solids in wastewater samples, including total solids, total suspended solids, volatile solids, fixed solids, total dissolved solids, and their significance for classifying wastewater and designing wastewater treatment processes. Gravimetric analysis methods are described for evaporating and igniting samples to separate organic and inorganic fractions. Standards for discharge of treated wastewater are also provided.
This document provides information about the chemical oxygen demand (COD) test for measuring organic matter in wastewater. It discusses that COD measures the oxygen required to chemically oxidize organic material using potassium dichromate and sulfuric acid. COD and BOD both measure how much oxygen water will consume, but COD can oxidize more material so values are higher than BOD. The document outlines the COD test procedure and calculations for determining COD levels in wastewater samples. It also discusses standards, sources of BOD and COD, and limitations of the COD test.
Activation of hydrogen peroxide by chemical reagent to reduce cod in petroche...MOHAMED SAAD BALA
This document discusses reducing COD levels in petrochemical wastewater using hydrogen peroxide activated by two reagents - iron-catalyzed H2O2 (Fenton's reagent) and Al2(SO4)3-catalyzed H2O2. The objective is to compare COD removal efficiency of the two reagents. The methodology involves treating wastewater samples with varying dosages of the reagents and hydrogen peroxide and measuring reductions in COD, pH, and TSS. Results found Fenton's reagent achieved 68-88% removal of COD and TSS, while aluminum reagent showed little to no COD removal.
The document summarizes a study that used forward osmosis (FO) to remove cadmium (Cd+2) ions from simulated wastewater using a cellulose acetate (CA) membrane. Magnesium sulfate (MgSO4.7H2O) was used as the draw solution. The effects of parameters like draw solution concentration, feed solution concentration, operating time, flow rates, and temperature on water flux and Cd+2 ion removal efficiency were investigated. Key findings include: 1) water flux increased with higher draw concentration and temperature but decreased with higher feed concentration and time; 2) Cd+2 ion concentration in the feed effluent increased with feed concentration but decreased with draw flow rate; 3) FO
This document summarizes a study that investigated the removal of nitrate from groundwater using activated carbon prepared from rice husk and sludge from a paper industry wastewater treatment plant. The key findings are:
- Activated carbon from rice husk achieved a maximum nitrate removal of 93.5 mg/g at pH 4 and 4 hours of contact time. Activated carbon from paper industry sludge achieved 79.5 mg/g removal under the same conditions.
- Adsorption was best fitted by the Langmuir isotherm model and followed pseudo-second order kinetics.
- Increasing the ratio of ZnCl2 used for activation improved adsorption capacity, with a 1:
Oily wastewater treatment using polyamide thin film composite membraneMedhat Elzahar
This document summarizes a study that used polyamide thin film composite reverse osmosis membrane filtration to treat edible oil wastewater emulsions. The membrane was characterized and its performance was tested for treating wastewater with oil concentrations between 3000-6000 mg/L. Experimental results showed that adding an activated carbon pre-treatment unit prior to the reverse osmosis membrane increased chemical oxygen demand removal from 94% to 99% and permeate flux from 34 L/m2hr to 75 L/m2hr. The reverse osmosis membrane filtration coupled with activated carbon was found to be an effective hybrid technique for removing over 99% of contaminants from high concentration edible oil wastewater.
The document discusses using forward osmosis (FO) to treat reverse osmosis concentrate (ROC) from water treatment plants. It examines using FO alone and with granular activated carbon (GAC) pretreatment to reduce the volume of ROC and remove organic micropollutants. Five steps of FO using 2-3M NaCl as the draw solution reduced the ROC volume to 8%. FO rejected some organic micropollutants but GAC pretreatment followed by FO removed almost all organic micropollutants from the ROC. Reducing the pH of the ROC feed solution arrested flux decline caused by fouling during FO.
Evaluation of the levels of haloacetic acids in gharbiya governorate, egypt[#...Ahmed Hasham
The occurrence of haloacetic acids (HAAs) was studied in the drinking water samples from Gharbiya
governorate water treatment plants and its water supply network that served more than 5 million people. Drinking
water disinfection by-products are formed when a disinfectant reacts with natural organic matter and/or
bromide/iodide present in a raw water source. Trihalomethanes and haloacetic acids are the two most prevalent
classes of DBPs and are regulated by the US Environmental Protection Agency as well as being subject to World
Health Organization guidelines due to their potential health risk. Drinking water samples were collected from 4
sites monthly over one year (2017-2018). The aims of the present study are to investigate the levels of HAAs in
Gharbiya governorate (middle of Delta Egypt) drinking water. monochloroacetic acid ranged from 6.8 to 32.5
µg/L, dichloroacetic acid ranged from 9.8 to 43.7 µg/L, and the trichloroacetic acid ranged from 6.5 to 31.8 µg/L,
the minimum values observed during winter 2018 and the maximum value observed during summer 2017., The
HAAs species values were complying with the Egyptian standard (Ministerial Decree No.458/2007) and as well
as WHO 2012) standards for drinking water
This document provides information about biochemical oxygen demand (BOD) including:
1. BOD is a measure of the oxygen used by microorganisms to decompose organic waste in water. A high BOD level indicates a large amount of decomposable organic waste.
2. The key difference between biochemical oxygen demand and biological oxygen demand is that BOD measures oxygen used to oxidize inorganic materials like sulfides in addition to decomposing organic matter, while biological oxygen demand only measures oxygen used for decomposing organic substances.
3. BOD tests are used to determine pollution levels, design treatment methods, and evaluate treatment plant performance by measuring how much oxygen is depleted during the decomposition of organic matter.
Enhancing the adsorption of disinfection by products onto activated carbon us...Ahmed Hasham
The removal of contaminants from consumable waters by the traditional water treatment techniques is highly difficult. Disinfection of water alludes to the inactivation or pulverization of unsafe living pathogenic beings, which living in the water. Occurrence of disinfection by products (DBPs) during disinfection normally demonstrates lethal impacts on human health. Granular activated carbon (GAC) has the oldest history of decreasing of organic matters, but its role is reducing by time. TiO2 is used to accelerate the removal of the DBPs. TiO2 nanoparticles have good adsorption phenomena on the removal of those organic compounds at various pHs and temperatures and give good results. This study proved that TiO2 nanoparticles enhanced the efficiency of GAC to remove DBPs from water. While the elimination of trihalomethanes (THMs), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) using 0.5 g of GAC was determined as 61.7, 69.8 and 83.2% respectively, the elimination of them by 0.1 g of TiO2 nanoparticles :GAC (1:1) was estimated as 100, 96 and 100%, respectively.
Water pollution is one of the environmental challenges facing the world society. Consequently, the pollutants both domestic and industrial wastewater are identified as an environmental threat. Hydrochar (HC) appears as a cost-effective and eco-friendly solution to this environmental threat. HC is the solid produced from the wet pyrolysis process for biomass that is rich in carbon in a sub-critical liquid phase, called the Hydro-Thermal Carbonization Process (HTC). This review aims to address the possibility of using HC as the most effective solution to the industrial wastewater. HTC has proven a greater yield than dry pyrolysis (30%-60% wt). To date, HC is listed as a promising lower-cost alternate adsorbent for removing wastewater pollutants. In Egypt for example, only few studies have been published investigating the properties of HC and its environmental applications. In this review, we will shed light on the preparation, characterization, and previous studies on the development and recent applications of HC. In addition, we will discuss the challenges to produce HC at a commercial scale. To the best of our knowledge, there is only few research studies addressing the HC production in the Middle East countries. Therefore, the door is still opened for more research on developing production techniques on HC from different biomass, and implementation in various environmental applications
Fertilizer plant waste carbon slurry has been investigated after some processing as an adsorbent for the removal of dyes and phenols using columns. The results show that the carbonaceous adsorbent prepared from carbon slurry being porous and having appreciable surface area (380 m2/g) can remove dyes both cationic (meldola blue, methylene blue, chrysoidine G, crystal violet) as well as anionic (ethyl orange, metanil yellow, acid blue 113), and phenols (phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol) fruitfully from water. The column type continuous flow operations were used to obtain the breakthrough curves. The breakthrough capacity, exhaustion capacity and degree of column utilization were evaluated from the plots. The results shows that the degree of column utilization for dyes lies in the range 60 to 76% while for phenols was in the range 53-58%. The exhaustion capacities were quite high as compared to the breakthrough capacities and were found to be 217, 211, 104, 126, 233, 248, 267 mg/g for meldola blue, crystal violet, chrysoidine G, methylene blue, ethyl orange, metanil yellow, acid blue 113, respectively and 25.6, 72.2, 82.2 and 197.3 mg/g for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol, respectively
This document summarizes a study that investigated the effectiveness of using activated carbon produced from snail shells for treating wastewater from beverage industries. Snail shells were pyrolyzed and activated with phosphoric acid. Characterization of the activated samples showed they had higher surface area, porosity, and pH than the non-activated sample. Treatment of beverage wastewater with the activated carbon significantly reduced parameters like BOD, COD, turbidity and phosphate over treatment times of 10-40 minutes. The study concluded that activated carbon from snail shells is effective for wastewater treatment from beverage industries.
Development of an experimental rig for bioremediation studiesAlexander Decker
The document describes the development of an experimental rig for bioremediation studies using indigenous technology. Key details include:
- The rig consists of various units like air pretreatment, fixed bed bioreactors, volatile organic compound traps, air flow meter, and carbon dioxide traps.
- Components were sized, designed, and fabricated locally at low cost. Testing showed the rig effectively degraded 75% of oil and grease from contaminated soil over 10 weeks.
- The rig was used to study bioremediation of soil contaminated with spent motor oil in 6 treatments with various additives over room temperature.
This document outlines a procedure to determine the total phosphate content of a water sample. Phosphorus plays an important role in biochemical processes and eutrophication of surface water. The main sources of phosphorus in wastewater are human excreta, household detergents, and some industrial effluents. The procedure involves preparing a calibration curve using standard phosphate solutions, then measuring the absorbance of the water sample reacted with ammonium molybdate and stannous chloride reagents to determine its phosphate concentration based on the calibration curve. The total phosphate content is calculated based on the volume of the water sample. The results will help assess eutrophication levels in surface waters affected by wastewater discharges.
A short description of thermal technologies for the recovery of ammonia from N-rich wastewaters and expirementing with membrane distillation for getting better results.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Study of abiotic factors across the brahmaputra belt in relation to its suita...eSAT Journals
Abstract
A healthy ecosystem is a result of balanced interaction between biotic and abiotic factors. Water temperature, pH, DO, FCO2, TA, TH etc are the most important abiotic factors influencing the physico-chemical and biological events of water body (Rahman et al., 2008). All species have their own optimal range for these abiotic parameters. In relation to aquatic life, there maturation time is also dependent on these parameters. These factors have great influence on aquatic life (DuttaMunshi and DuttaMunshi, 1995). This paper deals with the observation of fluctuation of these abiotic factors across the Brahmaputra Belt and its relation with aquatic life, mostly fishes.
Keywords: Water temperature, pH, DO, FCO2, TA, TH etc…
DNAPL Remediation with ClO2_UV-published paperDarcy Bye
This study investigated the sorption of PAHs, PCBs, phenols, and BTEX hydrocarbons from groundwater onto a subsoil core sample. It also examined the destruction of these contaminants in ClO2/UV solution systems using methanol as the carrier solvent. Sorption experiments showed the contaminants formed S-type isotherms and could be modeled using the Freundlich equation. Off-site travel times for the contaminants in groundwater ranged from 145 to 80,817 years based on sorption. Treatment with ClO2/UV destroyed 76-98% of the contaminants and produced no dioxins or furans as byproducts, demonstrating this method's potential for remediating recal
This study investigated the impact of removing carbon dioxide (CO2) from the headspace of a continuous flow biohydrogen production system on hydrogen (H2) yield, microbial communities, and metabolic pathways. The system was operated with and without potassium hydroxide (KOH) in the reactor headspace to sequester CO2. Headspace CO2 sequestration increased the H2 yield by 22% and influenced the metabolic pathways. Analysis of microbial communities before and after CO2 sequestration revealed significant impacts on diversity and species distribution, rationalizing changes in metabolic pathways.
This research article summarizes a study that tested a new wastewater treatment technology called a fluidized immobilized carbon catalytic oxidation (FICCO) reactor. The FICCO reactor uses activated carbon produced from rice husks as a catalyst to remove organic contaminants like COD and BOD from domestic wastewater. Six FICCO reactor models were constructed with triangular sheets at the top to improve catalyst retention. Testing found the optimum catalyst dosage was 12g of rice husk-activated carbon per 620ml of wastewater, achieving 75.6-92.4% COD removal and 74.9-89.5% BOD removal. The FICCO reactor effectively treated organic pollutants and
The document outlines various methods for determining types of solids in wastewater samples, including total solids, total suspended solids, volatile solids, fixed solids, total dissolved solids, and their significance for classifying wastewater and designing wastewater treatment processes. Gravimetric analysis methods are described for evaporating and igniting samples to separate organic and inorganic fractions. Standards for discharge of treated wastewater are also provided.
This document provides information about the chemical oxygen demand (COD) test for measuring organic matter in wastewater. It discusses that COD measures the oxygen required to chemically oxidize organic material using potassium dichromate and sulfuric acid. COD and BOD both measure how much oxygen water will consume, but COD can oxidize more material so values are higher than BOD. The document outlines the COD test procedure and calculations for determining COD levels in wastewater samples. It also discusses standards, sources of BOD and COD, and limitations of the COD test.
Activation of hydrogen peroxide by chemical reagent to reduce cod in petroche...MOHAMED SAAD BALA
This document discusses reducing COD levels in petrochemical wastewater using hydrogen peroxide activated by two reagents - iron-catalyzed H2O2 (Fenton's reagent) and Al2(SO4)3-catalyzed H2O2. The objective is to compare COD removal efficiency of the two reagents. The methodology involves treating wastewater samples with varying dosages of the reagents and hydrogen peroxide and measuring reductions in COD, pH, and TSS. Results found Fenton's reagent achieved 68-88% removal of COD and TSS, while aluminum reagent showed little to no COD removal.
The document summarizes a study that used forward osmosis (FO) to remove cadmium (Cd+2) ions from simulated wastewater using a cellulose acetate (CA) membrane. Magnesium sulfate (MgSO4.7H2O) was used as the draw solution. The effects of parameters like draw solution concentration, feed solution concentration, operating time, flow rates, and temperature on water flux and Cd+2 ion removal efficiency were investigated. Key findings include: 1) water flux increased with higher draw concentration and temperature but decreased with higher feed concentration and time; 2) Cd+2 ion concentration in the feed effluent increased with feed concentration but decreased with draw flow rate; 3) FO
This document summarizes a study that investigated the removal of nitrate from groundwater using activated carbon prepared from rice husk and sludge from a paper industry wastewater treatment plant. The key findings are:
- Activated carbon from rice husk achieved a maximum nitrate removal of 93.5 mg/g at pH 4 and 4 hours of contact time. Activated carbon from paper industry sludge achieved 79.5 mg/g removal under the same conditions.
- Adsorption was best fitted by the Langmuir isotherm model and followed pseudo-second order kinetics.
- Increasing the ratio of ZnCl2 used for activation improved adsorption capacity, with a 1:
Oily wastewater treatment using polyamide thin film composite membraneMedhat Elzahar
This document summarizes a study that used polyamide thin film composite reverse osmosis membrane filtration to treat edible oil wastewater emulsions. The membrane was characterized and its performance was tested for treating wastewater with oil concentrations between 3000-6000 mg/L. Experimental results showed that adding an activated carbon pre-treatment unit prior to the reverse osmosis membrane increased chemical oxygen demand removal from 94% to 99% and permeate flux from 34 L/m2hr to 75 L/m2hr. The reverse osmosis membrane filtration coupled with activated carbon was found to be an effective hybrid technique for removing over 99% of contaminants from high concentration edible oil wastewater.
The document discusses using forward osmosis (FO) to treat reverse osmosis concentrate (ROC) from water treatment plants. It examines using FO alone and with granular activated carbon (GAC) pretreatment to reduce the volume of ROC and remove organic micropollutants. Five steps of FO using 2-3M NaCl as the draw solution reduced the ROC volume to 8%. FO rejected some organic micropollutants but GAC pretreatment followed by FO removed almost all organic micropollutants from the ROC. Reducing the pH of the ROC feed solution arrested flux decline caused by fouling during FO.
Evaluation of the levels of haloacetic acids in gharbiya governorate, egypt[#...Ahmed Hasham
The occurrence of haloacetic acids (HAAs) was studied in the drinking water samples from Gharbiya
governorate water treatment plants and its water supply network that served more than 5 million people. Drinking
water disinfection by-products are formed when a disinfectant reacts with natural organic matter and/or
bromide/iodide present in a raw water source. Trihalomethanes and haloacetic acids are the two most prevalent
classes of DBPs and are regulated by the US Environmental Protection Agency as well as being subject to World
Health Organization guidelines due to their potential health risk. Drinking water samples were collected from 4
sites monthly over one year (2017-2018). The aims of the present study are to investigate the levels of HAAs in
Gharbiya governorate (middle of Delta Egypt) drinking water. monochloroacetic acid ranged from 6.8 to 32.5
µg/L, dichloroacetic acid ranged from 9.8 to 43.7 µg/L, and the trichloroacetic acid ranged from 6.5 to 31.8 µg/L,
the minimum values observed during winter 2018 and the maximum value observed during summer 2017., The
HAAs species values were complying with the Egyptian standard (Ministerial Decree No.458/2007) and as well
as WHO 2012) standards for drinking water
This document provides information about biochemical oxygen demand (BOD) including:
1. BOD is a measure of the oxygen used by microorganisms to decompose organic waste in water. A high BOD level indicates a large amount of decomposable organic waste.
2. The key difference between biochemical oxygen demand and biological oxygen demand is that BOD measures oxygen used to oxidize inorganic materials like sulfides in addition to decomposing organic matter, while biological oxygen demand only measures oxygen used for decomposing organic substances.
3. BOD tests are used to determine pollution levels, design treatment methods, and evaluate treatment plant performance by measuring how much oxygen is depleted during the decomposition of organic matter.
Enhancing the adsorption of disinfection by products onto activated carbon us...Ahmed Hasham
The removal of contaminants from consumable waters by the traditional water treatment techniques is highly difficult. Disinfection of water alludes to the inactivation or pulverization of unsafe living pathogenic beings, which living in the water. Occurrence of disinfection by products (DBPs) during disinfection normally demonstrates lethal impacts on human health. Granular activated carbon (GAC) has the oldest history of decreasing of organic matters, but its role is reducing by time. TiO2 is used to accelerate the removal of the DBPs. TiO2 nanoparticles have good adsorption phenomena on the removal of those organic compounds at various pHs and temperatures and give good results. This study proved that TiO2 nanoparticles enhanced the efficiency of GAC to remove DBPs from water. While the elimination of trihalomethanes (THMs), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) using 0.5 g of GAC was determined as 61.7, 69.8 and 83.2% respectively, the elimination of them by 0.1 g of TiO2 nanoparticles :GAC (1:1) was estimated as 100, 96 and 100%, respectively.
Water pollution is one of the environmental challenges facing the world society. Consequently, the pollutants both domestic and industrial wastewater are identified as an environmental threat. Hydrochar (HC) appears as a cost-effective and eco-friendly solution to this environmental threat. HC is the solid produced from the wet pyrolysis process for biomass that is rich in carbon in a sub-critical liquid phase, called the Hydro-Thermal Carbonization Process (HTC). This review aims to address the possibility of using HC as the most effective solution to the industrial wastewater. HTC has proven a greater yield than dry pyrolysis (30%-60% wt). To date, HC is listed as a promising lower-cost alternate adsorbent for removing wastewater pollutants. In Egypt for example, only few studies have been published investigating the properties of HC and its environmental applications. In this review, we will shed light on the preparation, characterization, and previous studies on the development and recent applications of HC. In addition, we will discuss the challenges to produce HC at a commercial scale. To the best of our knowledge, there is only few research studies addressing the HC production in the Middle East countries. Therefore, the door is still opened for more research on developing production techniques on HC from different biomass, and implementation in various environmental applications
Fertilizer plant waste carbon slurry has been investigated after some processing as an adsorbent for the removal of dyes and phenols using columns. The results show that the carbonaceous adsorbent prepared from carbon slurry being porous and having appreciable surface area (380 m2/g) can remove dyes both cationic (meldola blue, methylene blue, chrysoidine G, crystal violet) as well as anionic (ethyl orange, metanil yellow, acid blue 113), and phenols (phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol) fruitfully from water. The column type continuous flow operations were used to obtain the breakthrough curves. The breakthrough capacity, exhaustion capacity and degree of column utilization were evaluated from the plots. The results shows that the degree of column utilization for dyes lies in the range 60 to 76% while for phenols was in the range 53-58%. The exhaustion capacities were quite high as compared to the breakthrough capacities and were found to be 217, 211, 104, 126, 233, 248, 267 mg/g for meldola blue, crystal violet, chrysoidine G, methylene blue, ethyl orange, metanil yellow, acid blue 113, respectively and 25.6, 72.2, 82.2 and 197.3 mg/g for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol, respectively
This document summarizes a study that investigated the effectiveness of using activated carbon produced from snail shells for treating wastewater from beverage industries. Snail shells were pyrolyzed and activated with phosphoric acid. Characterization of the activated samples showed they had higher surface area, porosity, and pH than the non-activated sample. Treatment of beverage wastewater with the activated carbon significantly reduced parameters like BOD, COD, turbidity and phosphate over treatment times of 10-40 minutes. The study concluded that activated carbon from snail shells is effective for wastewater treatment from beverage industries.
Development of an experimental rig for bioremediation studiesAlexander Decker
The document describes the development of an experimental rig for bioremediation studies using indigenous technology. Key details include:
- The rig consists of various units like air pretreatment, fixed bed bioreactors, volatile organic compound traps, air flow meter, and carbon dioxide traps.
- Components were sized, designed, and fabricated locally at low cost. Testing showed the rig effectively degraded 75% of oil and grease from contaminated soil over 10 weeks.
- The rig was used to study bioremediation of soil contaminated with spent motor oil in 6 treatments with various additives over room temperature.
This document outlines a procedure to determine the total phosphate content of a water sample. Phosphorus plays an important role in biochemical processes and eutrophication of surface water. The main sources of phosphorus in wastewater are human excreta, household detergents, and some industrial effluents. The procedure involves preparing a calibration curve using standard phosphate solutions, then measuring the absorbance of the water sample reacted with ammonium molybdate and stannous chloride reagents to determine its phosphate concentration based on the calibration curve. The total phosphate content is calculated based on the volume of the water sample. The results will help assess eutrophication levels in surface waters affected by wastewater discharges.
A short description of thermal technologies for the recovery of ammonia from N-rich wastewaters and expirementing with membrane distillation for getting better results.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Study of abiotic factors across the brahmaputra belt in relation to its suita...eSAT Journals
Abstract
A healthy ecosystem is a result of balanced interaction between biotic and abiotic factors. Water temperature, pH, DO, FCO2, TA, TH etc are the most important abiotic factors influencing the physico-chemical and biological events of water body (Rahman et al., 2008). All species have their own optimal range for these abiotic parameters. In relation to aquatic life, there maturation time is also dependent on these parameters. These factors have great influence on aquatic life (DuttaMunshi and DuttaMunshi, 1995). This paper deals with the observation of fluctuation of these abiotic factors across the Brahmaputra Belt and its relation with aquatic life, mostly fishes.
Keywords: Water temperature, pH, DO, FCO2, TA, TH etc…
DNAPL Remediation with ClO2_UV-published paperDarcy Bye
This study investigated the sorption of PAHs, PCBs, phenols, and BTEX hydrocarbons from groundwater onto a subsoil core sample. It also examined the destruction of these contaminants in ClO2/UV solution systems using methanol as the carrier solvent. Sorption experiments showed the contaminants formed S-type isotherms and could be modeled using the Freundlich equation. Off-site travel times for the contaminants in groundwater ranged from 145 to 80,817 years based on sorption. Treatment with ClO2/UV destroyed 76-98% of the contaminants and produced no dioxins or furans as byproducts, demonstrating this method's potential for remediating recal
This study investigated the impact of removing carbon dioxide (CO2) from the headspace of a continuous flow biohydrogen production system on hydrogen (H2) yield, microbial communities, and metabolic pathways. The system was operated with and without potassium hydroxide (KOH) in the reactor headspace to sequester CO2. Headspace CO2 sequestration increased the H2 yield by 22% and influenced the metabolic pathways. Analysis of microbial communities before and after CO2 sequestration revealed significant impacts on diversity and species distribution, rationalizing changes in metabolic pathways.
This research article summarizes a study that tested a new wastewater treatment technology called a fluidized immobilized carbon catalytic oxidation (FICCO) reactor. The FICCO reactor uses activated carbon produced from rice husks as a catalyst to remove organic contaminants like COD and BOD from domestic wastewater. Six FICCO reactor models were constructed with triangular sheets at the top to improve catalyst retention. Testing found the optimum catalyst dosage was 12g of rice husk-activated carbon per 620ml of wastewater, achieving 75.6-92.4% COD removal and 74.9-89.5% BOD removal. The FICCO reactor effectively treated organic pollutants and
This document summarizes a study that investigated the use of Parthenium stem powder for biosorption of lead from aqueous solutions. The study optimized various process parameters like pH, contact time, temperature, adsorbent dosage and initial lead concentration using response surface methodology. Batch experiments using Box-Behnken design showed that the optimum conditions for maximum lead biosorption were a pH of 5, initial lead concentration of 20 mg/L, and adsorbent dosage of 30 g/L. Kinetic, thermodynamic and isotherm studies demonstrated that the adsorption process was spontaneous and fit the pseudo-second order kinetic model and Langmuir isotherm model. The Parthenium stem powder was found to
This document summarizes a study that investigated the use of Parthenium stem powder for biosorption of lead from aqueous solutions. The study optimized various process parameters like pH, contact time, temperature, adsorbent dosage and initial lead concentration using response surface methodology. Batch experiments using Box-Behnken design showed that the optimum conditions for maximum lead biosorption were a pH of 5, initial lead concentration of 20 mg/L, and adsorbent dosage of 30 g/L. Kinetic, thermodynamic, and isotherm studies demonstrated that the adsorption process was spontaneous and fit the pseudo-second order kinetic model and Langmuir isotherm model. The Parthenium stem powder was found
This document describes a study investigating the use of Parthenium stem powder for removing lead from aqueous solutions. Response surface methodology was used to optimize the conditions for lead biosorption based on variables like pH, initial lead concentration, and adsorbent dosage. Experiments were conducted using a Box-Behnken design. The results showed that Parthenium stem powder can reduce lead concentration by up to 72.74% at pH 5, 20 mg/L initial concentration, and 30 g/L adsorbent dosage. Kinetic, thermodynamic, and isotherm studies provided insights into the adsorption process.
Synthesis of novel and tunable Micro Mesoporous carbon nitrides for Ultra Hig...farnaztabarkhoon
Carbon nitride (CN) materials with intrinsic high nitrogen content are potential candidates for acidic gas
adsorption. However, these nanomaterials should be further treated to achieve tunable textural properties for
ultra-high gas adsorption. Herein, we synthesized dual-pore carbon nitride materials (DP-CN) with a series of
ethylenediamine to carbon tetrachloride ratios with different amounts of potassium hydroxide (KOH) as a
chemical activator using nanosilica (SiO2) as a hard template to tune the physicochemical properties of the
materials. The prepared DP-CN adsorbents had a large surface area (up to 2036.9 m2/g), great pore volume (up
to 1.15 cm3/g), and high nitrogen content (10.6 to 15.1 wt%). The best DP-CN displayed ultra-high CO2 and H2S
adsorption capacity at 1 bar (8.3 and 13.8 mmol/g, respectively), 10 bar (16.9 and 23.1 mmol/g, respectively),
and 30 bar (22.9 mmol/g for CO2) at 25 ◦C, which was significantly higher than those of other pure mesoporous
carbon nitrides (M-CN) and carbon-based adsorbents. Moreover, the best adsorbent exhibited good CO2/N2,
CO2/CH4, H2S/N2, and H2S/CH4 selectivity, suitable heat of adsorption, and excellent cyclic stability. According
to density functional theory calculations, H2S adsorbs more strongly than CO2 on carbon nitride surfaces, and the
adsorption energies of CO2 and H2S are related to charge-transfer values from the surface to the adsorbed species.
The results revealed that the exceptional textural properties and high nitrogen content of the materials could play
the main role in the superior adsorption of CO2 and H2S. This generation of CN materials is expected to be
practical for a various range of separation processes, catalysis, capacitors, and energy storage.
This document describes a study that aimed to select Spirulina strains with high CO2 fixation capabilities for large-scale cultivation. Nine Spirulina species were screened in column bioreactors with 10% CO2 addition. Strains 208 and 220 were selected and optimized in 4 m2 raceway ponds for pH, dissolved inorganic carbon, and phosphate levels. The optimized conditions were then used to cultivate the two strains on a large scale of 605 m2 raceway ponds aerated with purified CO2 from a coal plant, achieving daily biomass production of up to 18.7 and 13.2 g/m2.
This document summarizes a study on using biomass gasification to capture CO2 from engine exhaust. Experiments were conducted introducing 0-15% CO2 into a gasifier along with oxygen and nitrogen. Higher CO2 fractions decreased bed temperature but increased CO production from 13.1% to 16.3% due to the endothermic reaction of char and CO2. Over 55% of input CO2 was converted. Cold gas efficiency increased 30% with higher char conversion. Using engine exhaust eliminates the cost of separating and storing CO2, as condensing water and mixing with oxygen is sufficient. The paper addresses using biomass gasification to capture CO2 from engine exhaust via recycling into the gasification process.
This study examined the bioregeneration of granular activated carbon (GAC) contaminated with hydrocarbon using Pseudomonas putida bacteria. The rate of bioregeneration was analyzed by varying the volume of bacteria from 10-40ml and the temperature from 25-45°C over 21 days. Increasing the bacteria volume and temperature both increased the rate of bioregeneration. The highest regeneration efficiency occurred with 40ml of bacteria at 40°C, as increasing temperature further to 45°C did not provide additional benefit. Characterization of the GAC before and after regeneration showed that its properties were largely preserved through the bioregeneration process.
Experimental Studies on Bioregeneration of Activated Carbon Contaminated With...IOSR Journals
The document summarizes an experimental study on bioregenerating activated carbon contaminated with hydrocarbons. The researchers characterized virgin and regenerated activated carbon and found the regeneration process maintained the carbon's key properties. They conducted experiments regenerating contaminated carbon using different volumes of Pseudomonas Putida bacteria and temperatures. Increasing bacteria volume and temperature both increased regeneration rates by reducing total hydrocarbon content more quickly. The optimal conditions were 30-40ml of bacteria at 35-40°C, providing effective regeneration while remaining economical.
This document discusses bio-CNG (compressed biogas) as a transportation fuel alternative to fossil fuels. It begins by introducing the problems of increasing fossil fuel usage and outlines biogas production methods from waste sources. The main processes for cleaning biogas - including water scrubbing, pressure swing adsorption, amine adsorption and membrane permeation - are then summarized. The paper also covers converting cleaned biogas into bio-CNG and its storage. Key advantages of bio-CNG are highlighted such as reduced greenhouse gas emissions compared to diesel and potential cost savings versus petrol and diesel. The conclusion promotes bio-CNG as a viable replacement for fossil fuels that could support more sustainable living.
This document reviews various techniques for optimizing biogas production and upgrading biogas quality through CO2 removal. It discusses pretreatment of substrates, co-digestion, use of serial digesters, and different methods for biogas upgrading including pressure swing adsorption, membrane separation, and CO2 absorption to purify biogas. The optimization of biogas production and upgrading is important as biogas can be a substitute for conventional fossil fuels but the presence of CO2 and other components can reduce its quality and economic feasibility for certain applications.
IRJET- Improvement of Sludge Reduction Efficiency of Ozonation by Microbubble...IRJET Journal
This document discusses improving the efficiency of sludge reduction through ozonation using microbubble aeration technology and catalysis. It finds that adding hydrogen peroxide (H2O2) as a catalyst and using microbubbles generated by a linear mixer pipe can significantly increase the biodegradability and reduce the mass of sludge. Key results include an oil content reduction from 77.48% to 51.7% after ozonation. Mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) were also reduced, while COD and NH4+ levels increased. The linear mixer pipe was found to be more effective for microbubble generation and sludge treatment than a jet
The document describes a study that used a compact jet loop reactor to treat industrial wastewater from a paper industry. The reactor was able to achieve over 91% reduction in chemical oxygen demand and over 98% reduction in biochemical oxygen demand when operated at a mixed liquor volatile suspended solids concentration of 3000 mg/L and aeration time of 1 hour. Synthetic wastewater was also tested in the reactor to analyze reduction in chemical oxygen demand, biochemical oxygen demand, suspended solids, and sludge volume index over time. Results demonstrated the reactor's effectiveness at treating both synthetic wastewater and actual industrial wastewater from a paper industry.
Sipma, 2004, Effect Of Carbon Monoxide, Hydrogen And Sulfate On Thermophilic ...roelmeulepas
This document summarizes a study on the conversion of carbon monoxide (CO) by two anaerobic sludge samples at 55°C. The study aimed to elucidate the conversion routes and determine the effect of substrate (CO) concentration and the presence of hydrogen gas. Inhibition experiments showed CO conversion occurred via a hydrogenogenic population producing hydrogen and carbon dioxide, with the products then used by methanogens, acetogens, or sulfate reducers depending on sludge source and inhibitors. Both sludges could produce hydrogen from CO, indicating potential for biological hydrogen production from synthesis gas containing CO. The paper mill sludge was also capable of sulfate reduction using hydrogen produced from high CO concentrations, showing CO-rich synthesis gas can efficiently
This document presents a comparative study of the performance of activated sludge processes in a bubble column reactor and compact jet loop reactor. Experiments were conducted using synthetic wastewater in laboratory scale models of each reactor type. The chemical oxygen demand (COD) removal efficiency was measured at different mixed liquor volatile suspended solids (MLVSS) concentrations and hydraulic retention times. The results showed that a COD removal efficiency of over 85% could be achieved in the bubble column reactor, and over 95% in the compact jet loop reactor, when operated at an MLVSS of 3000 mg/L and aeration time of 1 hour. The compact jet loop reactor demonstrated better COD reduction performance than the bubble column reactor under the conditions tested.
COD reduction of aromatic polluted waste water by Advanced Oxidation Process ...Wade Bitaraf
In most petrochemical complexes and oil refineries the wastewater contains the aromatic compounds among which Benzene, Toluene, Ethyl Benzene and Xylene (BTEX) have harmful effects on environment and human health. The present work mainly deals with the UV-based advanced oxidation processes (AOPs), UV/H2O2 were tested in batch reactor systems to evaluate the removal efficiencies and optimal conditions for the photodegradation of BTEX in order to wastewater treatment. The efficiency of this method was analyzed by evaluating the Chemical Oxygen Demand (COD) as a pollution criterion through the COD reactor. The influence of the basic operational parameters such as initial concentration of H2O2, pH, Temperature, irradiation time and UV amount on the photo degradation of BTEX were also studied. The oxidation rate of BTEX and respectively the reduction rate of COD were low when the oxidation was carried out in the absence of H2O2 or UV light. The addition of proper amount of hydrogen peroxide improved the degradation, while the excess hydrogen peroxide could quench the formation of hydroxyl radicals (•OH). The optimal conditions of suspended slurry with 1.11(g/l) initial concentration of H2O2 and pH value of 3.1 were obtained under three UV lights illumination (6 W). Under the optimal conditions, COD reduction during the initial period of 180 min in UV/H2O2 systems reached about 90%.
Activation of hydrogen peroxide by chemical reagent to reduce COD in petroche...Universiti Malaysia Pahang
This document discusses reducing chemical oxygen demand (COD) in petrochemical wastewater. The objective is to reduce COD using hydrogen peroxide activated by two reagents: iron-catalyzed H2O2 (Fenton's reagent) and Al2(SO4)3-catalyzed H2O2. The methodology involves treating wastewater samples with different dosages of the reagents and hydrogen peroxide. Results show Fenton's reagent achieved 68-70% COD removal, while Al2(SO4)3 removal was not effective for COD but achieved up to 55% removal of total suspended solids.
Absorption of CO2 gas from CO
2/Air mixture into aqueous sodium hydroxide solution has been
achieved using packed column in pilot scale at constant temperature (T) of 25±1℃.The aim of the present work
was to improve the Absorption rate of this process, to find the optimal operation conditions, and to contribute to
the using of this process in the chemical industry. Absorption rate (RA) was measured by using different
operating parameters: gas mixture flow rate (G) of 360 -540 m3/h, carbon dioxide inlet concentration (CCO
2) of
0.1-0.5 vol. %, NaOH solution concentration (CNaOH) of 1-2 M, and liquid holdup in the column (VL) of 0.022-0.028 m3 according to experimental design. The measured RA was in the range of RA = 3.235 – 22.340 k-mol/h.
Computer program (Statgraphics/Experimental Design) was used to estimate the fitted linear model of RA in
terms of (G, CCO2, CNaOH, and VL), and the economic aspects of the process. R -squared of RA model was
91.7659 percent, while the standard error of the estimate shows the standard deviation of the residuals to be
1.7619. The linear model of RA was adequate, the operating parameters were significant except the liquid holdup
was not significant, and the interactions were negligible.
Equilibrium and Kinetics Adsorption of Cadmium and Lead Ions from Aqueous Sol...theijes
This document summarizes a study on the adsorption of cadmium and lead ions from aqueous solution using bamboo-based activated carbon. Key findings include:
1) Unwashed chemical activated bamboo carbon achieved 87.81% removal of cadmium at pH 5 and 96.45% removal of lead at pH 11.
2) Adsorption equilibrium was reached within 1 hour for cadmium and 2.5 hours for lead.
3) Adsorption isotherm data fitted the Freundlich, Temkin, and Hills isotherm models well, suggesting chemisorption as the adsorption mechanism.
4) Kinetic data correlated best with the pseudo-
Optimizing Post Remediation Groundwater Performance with Enhanced Microbiolog...Joshua Orris
Results of geophysics and pneumatic injection pilot tests during 2003 – 2007 yielded significant positive results for injection delivery design and contaminant mass treatment, resulting in permanent shut-down of an existing groundwater Pump & Treat system.
Accessible source areas were subsequently removed (2011) by soil excavation and treated with the placement of Emulsified Vegetable Oil EVO and zero-valent iron ZVI to accelerate treatment of impacted groundwater in overburden and weathered fractured bedrock. Post pilot test and post remediation groundwater monitoring has included analyses of CVOCs, organic fatty acids, dissolved gases and QuantArray® -Chlor to quantify key microorganisms (e.g., Dehalococcoides, Dehalobacter, etc.) and functional genes (e.g., vinyl chloride reductase, methane monooxygenase, etc.) to assess potential for reductive dechlorination and aerobic cometabolism of CVOCs.
In 2022, the first commercial application of MetaArray™ was performed at the site. MetaArray™ utilizes statistical analysis, such as principal component analysis and multivariate analysis to provide evidence that reductive dechlorination is active or even that it is slowing. This creates actionable data allowing users to save money by making important site management decisions earlier.
The results of the MetaArray™ analysis’ support vector machine (SVM) identified groundwater monitoring wells with a 80% confidence that were characterized as either Limited for Reductive Decholorination or had a High Reductive Reduction Dechlorination potential. The results of MetaArray™ will be used to further optimize the site’s post remediation monitoring program for monitored natural attenuation.
Kinetic studies on malachite green dye adsorption from aqueous solutions by A...Open Access Research Paper
Water polluted by dyestuffs compounds is a global threat to health and the environment; accordingly, we prepared a green novel sorbent chemical and Physical system from an algae, chitosan and chitosan nanoparticle and impregnated with algae with chitosan nanocomposite for the sorption of Malachite green dye from water. The algae with chitosan nanocomposite by a simple method and used as a recyclable and effective adsorbent for the removal of malachite green dye from aqueous solutions. Algae, chitosan, chitosan nanoparticle and algae with chitosan nanocomposite were characterized using different physicochemical methods. The functional groups and chemical compounds found in algae, chitosan, chitosan algae, chitosan nanoparticle, and chitosan nanoparticle with algae were identified using FTIR, SEM, and TGADTA/DTG techniques. The optimal adsorption conditions, different dosages, pH and Temperature the amount of algae with chitosan nanocomposite were determined. At optimized conditions and the batch equilibrium studies more than 99% of the dye was removed. The adsorption process data matched well kinetics showed that the reaction order for dye varied with pseudo-first order and pseudo-second order. Furthermore, the maximum adsorption capacity of the algae with chitosan nanocomposite toward malachite green dye reached as high as 15.5mg/g, respectively. Finally, multiple times reusing of algae with chitosan nanocomposite and removing dye from a real wastewater has made it a promising and attractive option for further practical applications.
Evolving Lifecycles with High Resolution Site Characterization (HRSC) and 3-D...Joshua Orris
The incorporation of a 3DCSM and completion of HRSC provided a tool for enhanced, data-driven, decisions to support a change in remediation closure strategies. Currently, an approved pilot study has been obtained to shut-down the remediation systems (ISCO, P&T) and conduct a hydraulic study under non-pumping conditions. A separate micro-biological bench scale treatability study was competed that yielded positive results for an emerging innovative technology. As a result, a field pilot study has commenced with results expected in nine-twelve months. With the results of the hydraulic study, field pilot studies and an updated risk assessment leading site monitoring optimization cost lifecycle savings upwards of $15MM towards an alternatively evolved best available technology remediation closure strategy.
Improving the viability of probiotics by encapsulation methods for developmen...Open Access Research Paper
The popularity of functional foods among scientists and common people has been increasing day by day. Awareness and modernization make the consumer think better regarding food and nutrition. Now a day’s individual knows very well about the relation between food consumption and disease prevalence. Humans have a diversity of microbes in the gut that together form the gut microflora. Probiotics are the health-promoting live microbial cells improve host health through gut and brain connection and fighting against harmful bacteria. Bifidobacterium and Lactobacillus are the two bacterial genera which are considered to be probiotic. These good bacteria are facing challenges of viability. There are so many factors such as sensitivity to heat, pH, acidity, osmotic effect, mechanical shear, chemical components, freezing and storage time as well which affects the viability of probiotics in the dairy food matrix as well as in the gut. Multiple efforts have been done in the past and ongoing in present for these beneficial microbial population stability until their destination in the gut. One of a useful technique known as microencapsulation makes the probiotic effective in the diversified conditions and maintain these microbe’s community to the optimum level for achieving targeted benefits. Dairy products are found to be an ideal vehicle for probiotic incorporation. It has been seen that the encapsulated microbial cells show higher viability than the free cells in different processing and storage conditions as well as against bile salts in the gut. They make the food functional when incorporated, without affecting the product sensory characteristics.
2. However, the performance of HFMC declines when it is used for long
operational periods, owing to penetration of solvent through the pores
of wetted membranes (Table S1, Supplementary materials). By selecting
non-porous dense polymeric membranes, these problems can be
eliminated.
Accordingly, in this study a PDMS membrane gas purification and
bio-oxidation processes were combined. During the process, H2S is first
dissolved in an aqueous absorption liquid according to reaction 1, fol-
lowed by two dissociation reactions 2 and 3. In order to maintain a high
H2S diffusion rate, mildly alkaline solution is generally used. Then, bio-
oxidation of H2S occurs in the bioreactor according to reactions 4 and 5.
The route of H2S oxidation is dependent on the concentration of
oxygen, i.e., it is oxidized to elemental sulfur (So
) or sulfate under
oxygen limiting and non-limiting conditions, respectively.
↔
H S H S
2 gas 2 aq (1)
+ − ↔ + =
− − +
H S OH HS H (pKa 7.0)
2 aq (2)
+ ↔ + =
− − −
HS OH S H O (pKa 12.9)
2
2 (3)
+ ↔ + = −
− − −
Δ
HS 0.5O S OH ( G 169.35 kJ.mol )
2
o o 1
(4)
+ ↔ + = −
− − + −
Δ
HS 2O SO H ( G 732.58 kJ.mol )
2 4
2 o 1
(5)
It is clear that the concentration of CO2 in biogas is much higher
than H2S, and both have similar acidic behavior. CO2 and H2S can both
be absorbed in an alkaline solution (Miltner et al., 2017; Ryckebosch
et al., 2011). Absorption, hydrolysis and dissociation of CO2 in alkaline
solutions are indicated in reactions 6–9. Hence the removal of CO2
generates additional H+
, which can decrease the pH of the absorption
liquid according to reactions 8 and 9. In order to maintain a high H2S
removal efficiency, pH of the absorption liquid needs to be high;
therefore, extra alkali should be supplemented, which increases the
operational costs.
↔
CO CO
2gas 2aq (6)
+ ↔
CO H O H CO
2aq 2 2 3aq (7)
↔ + =
− +
H CO HCO H (pKa 6.4)
2 3aq 3 (8)
+ ↔ + =
− − −
HCO OH CO H O (pKa 10.3)
3 3
2
2 (9)
The CO2 removal should be minimized to reduce the alkali chemical
consumption, which can be achieved by using non-porous dense PDMS
membranes due to its higher selectivity towards H2S compared to CO2
(Montoya, 2010; Tilahun et al., 2017). The objective of this study was
to evaluate the performance of a novel hybrid membrane bio-scrubber
(MBS) process for selective H2S removal from a simulated biogas. In
addition, the effects of the absorption liquid pH, gas flowrate (loading)
and DO concentration on biogas desulfurization performance were
discussed.
2. Materials and methods
2.1. Experimental set-up and operation
The laboratory scale hybrid membrane bio-scrubber contactor setup
used in this study was shown in Fig. 1. It was consisted of a cylindrical
glass reactor with 120 mm of diameter and 200 mm of depth and a
working volume of 1.5 l. The glass reactor was filled completely with
tap water to minimize the volatilization of the sulfur compounds. Be-
sides, it was operated by feeding with a simulated biogas (Hat Industrial
Gases PLC, Kocaeli, Turkey) containing 60% (v/v) CH4, 39% (v/v) CO2,
and 1% (v/v) (10,000 ppmv) H2S through the PDMS tubular mem-
brane. The membrane was folded and fully submerged into the ab-
sorption liquid. The flowrate of the biogas was adjusted and controlled
by using mass flow controller at outlet of the gas cylinder and measured
by gas counters (MGC, Ritter) both in the influent and effluent of the
membrane contactor. The commercial tubular PDMS membrane
(EUROFLEX GmbH, Germany) had an internal diameter of 7.0 mm, wall
thickness of 1.0 mm and length of 3.25 m, corresponding to a total
surface area of 9.2 dm2
. The reactor was inoculated with the sludge
taken from a laboratory scale aerobic membrane bioreactor treating
sulfide containing textile wastewater. The inoculum consisted of two
dominating sulfide oxidizing bacteria, Thiobacillus spp. and Thioalk-
alivibrio sulfidiphilus (Yurtsever et al., 2017). The liquid medium was
composed of (g/l): K2HPO4 2.0, NH4Cl 0.4, MgCl2·6H2O 0.2 and tap
water. Due to low cost and its effectiveness, NaOH was used as alkaline
chemical (Jegatheesan et al., 2015). Conductivity of the absorption li-
quid in the bioreactor increased during the operation due to NaOH
addition and sulfate generation. Hence, around 2/3 of the absorption
liquid was periodically removed from the bioreactor not to disturb the
bacterial activity when conductivity raised over 7 mS/cm. During the
operation, the absorption liquid was aerated to supply oxygen to sulfide
oxidizing bacteria as electron acceptor. The reactor content was con-
tinuously stirred with a magnetic stirrer at 550 rpm to achieve complete
mixing and to control the attachment of biomass on the membrane
surface. The pH of the absorption liquid was controlled automatically
by addition of NaOH (1N) with a pH transmitter and a dosing pump
(Seko, PR 40/Q). The temperature was kept at 30 ± 1 °C using an
electric heating pad wrapped around the bioreactor. During the ex-
periments, conductivity, oxidation reduction potential (ORP) and dis-
solved oxygen (DO) were monitored online using a digital multimeter
(Multi 9430, WTW GmbH, Germany). The hybrid membrane bio-
scrubber (MBS) operating parameters were shown in Table 1.
2.2. Analytical methods
The CO2, H2S and CH4 compositions in the inlet and outlet of the
membrane contactor were measured using a gas chromatograph
(Shimadzu GC-2014, Japan) equipped with thermal conductivity de-
tector (TCD) (Reddy et al., 2016). Sulfide concentrations in the ab-
sorption liquid were determined spectrometrically (DR/2800, HACH,
USA) following the methylene blue method described by Standard
Methods (APHA/AWWA/WEF, 2012). In the MBS liquor samples, fol-
lowing 0.45 μm filtration, sulfate, thiosulfate and sulfite concentrations
were analyzed daily using an ion chromatography. Biomass con-
centration in the bioreactor was estimated by measuring Total Kjeldahl
(TKN) according to standard methods (APHA/AWWA/WEF, 2012).
Before analyzing TKN, the liquid sample was centrifuged and the bio-
mass was washed 3 times with deionized water to remove dissolved
nitrogen compounds. The presence and crystal structure of elemental
sulfur (So
) and other byproducts from the suspended biofilms of the
MBS reactor was examined using X-Ray diffraction (XRD). The mor-
phology of clean and used membrane surface at the end of the experi-
ment period was examined using an optical microscope and scanning
electron microscopy (SEM) images. In addition, SEM coupled with
Energy Dispersive X-ray Spectroscopy (EDS) analyses were conducted
to determine the inorganic content of the biofilm attached on the ex-
ternal surface area of the membrane.
2.3. Calculations
In this study, the CO2 or H2S gas phase removal efficiencies (R) and
CH4 loss were calculated according to Eq. (10).
=
−
R (%)
(Q in*C in) (Q out*C out)
(Q in*C in)
*100
g g g g
g g (10)
where, R-gas phase removal efficiencies, Qg
in
– inlet biogas flowrate
(m3
/d), Qg
out
– outlet biogas flowrate (m3
/d), Cg
in
- inlet gas con-
centrations (mg/l), Cg
out
- outlet gas concentrations (mg/l). In gas
purification processes the performance of the system can be indicated
also by computing the selectivity factor. Selectivity of the gas-liquid-
E. Tilahun et al. International Biodeterioration & Biodegradation 127 (2018) 69–76
70
3. membrane contacting system for H2S may be defined as the ratio of H2S
over CO2 concentrations in the liquid phase to that in the gas phase (Eq.
(11)). Likewise, the selectivity of H2S over CH4 was calculated ac-
cording to Eq. (12).
=
α(H S/CO )
(xH S/xCO )
(yH S/yCO )
2 2
2 2
2 2 (11)
=
α(H S/CH )
(xH S/xCH )
(yH S/yCH )
2 4
2 4
2 4 (12)
where, α is dimensionless which represents the selectivity factor, x -
denotes the mole fraction of the biogas components absorbed in the
liquid phase and y - denotes the mole fraction of the biogas components
in the feed gas. Surface removal rate or absorption flux (J) of the
membrane contactor is another performance indicator, which can be
estimated as Eq. (13).
=
−
J
(Q in*C in) (Q out*C out)
A
g g g g
(13)
where, J is the flux of the gas components (g/m2
.d) and A is the
membrane surface area (m2
). The total H2S removal efficiency (TSR) of
the system was calculated according to Eq. (14).
=
− −
TSR (%)
(Q in*C in(H S)) (Q out*C out(H S)) (Q out*C out(H S))
(Q in*C in(H S))
*
100
g g 2 g g 2 L L 2
g g 2
(14)
where: QL
out
– outlet liquid flowrate (m3
/d), CL
out
- outlet liquid con-
centrations (mg/l). The process capacity for H2S removal was also
calculated as volumetric removal rate (VSRR) according to Eq. (15).
=
− −
VSRR (g/m . d)
(Q in*C in(H S)) (Q out*C out(H S)) (Q out*C out(H S))
V
3
g g 2 g g 2 L L 2
(15)
where: V is the active volume of the reactor (m3
). The quantity of
elemental sulfur (So
) produced can be estimated theoretically by sub-
tracting the aqueous sulfur species that exist in the absorption liquid.
Since the concentrations of thiosulfate and sulfite were below the de-
tection limit throughout the study, the mass balance calculation was
performed according to Eq. (16).
− = −
+ − + − + −
− −
Q in*C in(S H S) Q out*C out(S H S)
Q out*C out [(S HS ) (S SO ) (S S )]
g g 2 g g 2
L L 4
2 o
(16)
where: (S-So
) is the concentration of So
produced (g So
/1), (S-H2S) is the
concentration of H2S in the gas phase (g S-H2S/l), (S–SO4
−2
) is the
concentration of SO4
−2
generation (g S–SO4
−2
/1) and (S–HS−
) is the
concentration of non-oxidized sulfide ion in the liquid (g S–HS−
/1).
3. Results and discussion
3.1. Desulfurization performance of MBS process
The influence of different operational parameters on the perfor-
mance of the system was investigated with long-term experiments. The
desulfurization of biogas in the hybrid MBS occurred in two steps.
Firstly, the H2S diffused across the membrane and dissolved in the
mildly alkaline absorption liquid. Secondly the dissolved sulfide was
oxidized by the sulfide oxidizing bacteria (SOB) on the membrane
Fig. 1. Schematic diagram of experimental setup: (1) synthetic biogas cylinder, (2) milligas counter, (3) air pump, (4) magnetic stirrer, (5) pH transmitter and temperature sensor, (6)
NaOH dosage pump, (7) NaOH solution, (8) tubular PDMS membrane, (9) effluent biogas bag, (10) heating blanket, (11) Multi probes meter.
Table 1
The MBS operational parameters.
Parameters Unit Period I Period II
Operation duration d 105 75
Biogas flowrate l/d 8–32 14
DO concentration mg/l 4 1–4
ORP mV 80–100 100 to −300
Conductivity mS/cm 2–7 2–7
pH of absorption liquid 7–8.5 7
Inlet surface H2S loading g/m2
.d 1.29–5.1 2.3
Inlet volumetric H2S loading g/m3
.d 79–316 140
Temperature of absorption liquid o
C 30 30
Operating absolute pressure pa ≈105
≈105
E. Tilahun et al. International Biodeterioration & Biodegradation 127 (2018) 69–76
71
4. surface or in the suspension. The DO concentration kept constant (about
4 mg/l) in the first operational period (Table 1). As a general trend the
gas phase H2S removal efficiency (R) was enhanced when the gas
flowrate decreased due to longer contact time between the gas and
membrane (Table 2). Besides, altering the pH of the absorption liquid
affect H2S removal efficiency. Particularly at pH 7 with a gas flowrate of
8 l/d, a gas phase H2S removal efficiency (R) reached above
99.5 ± 0.3%. This efficiency was higher compared to the results we
achieved formerly at pH 7 (94%) using an abiotic membrane scrubber
(AMS) (Tilahun et al., 2017). Moreover, when the gas flowrate was
raised four fold (32 l/d), the biotic MBS removed H2S more effectively
than AMS by about 44%. In the former study, the maximum gas phase
H2S removal, at pH 7 with gas flowrate of 32 l/d, was only 36%. It is
understood that in the abiotic process the diffused H2S accumulated in
the liquid phase, but not oxidized, therefore the liquid becomes satu-
rated. However, in the biotic MBS the diffused H2S immediately oxi-
dized by SOB and kept greater H2S driving force between the gas and
liquid (biofilm) phase. Marzouk et al. (2010) studied on removal of H2S
using hollow fiber membrane contactor and they reported a drop in
removal efficiency from 100 to 74%, when the gas flowrate increased
from 0.576 to 1.44 m3
/d. As shown in Table 2, at about 15 l/d of gas
flowrate, the effluent biogas contained less than 300 ppmv of H2S gas.
The achievement of such relatively low concentration of H2S in the
outlet stream proves the adequacy and applicability of the hybrid MBS
process. In this way, a biogas desulfurized with the hybrid MBS can be
directly used in a co-generation unit without any hesitation (Díaz et al.,
2011; Ramos and Fdz-Polanco, 2014). On the other hand, increasing the
gas flowrate by four times resulted in an increase in H2S and CO2 flux
from 1.29 ± 0.01 to 3.99 ± 0.012 g/m2
.d and from 43 ± 1 to
58 ± 1 g/m2
.d, respectively (Table 2). This result revealed that high
H2S removal capacity was achieved while CO2 removal was kept low,
because H2S could easily diffused through the membrane and became
available for SOB. With AMS we formerly (Tilahun et al., 2017) ob-
served a maximum H2S and CO2 flux capacity of 1.9 g/m2
.d and 58 g/
m2
.d. Hence, in the present study H2S flux was significantly higher than
that obtained in our earlier report. In summary, the preliminary results
indicated that the biotic MBS was more effective than abiotic mem-
brane scrubber (AMS) for desulfurization of biogas and has a great
potential for real scale applications.
In conventional biodesulfurization processes, especially the ni-
trogen in air which introduced into the reactor dilutes the biogas
(Jenicek et al., 2010, 2008; Krayzelova et al., 2015). However, in this
study, the biogas stream was separated from aerated liquid by a
membrane. As a result, dilution problem was not observed here, instead
the CH4 content in the outlet stream increased from 60% to 81 ± 1%
and from 60 to 67 ± 0.5%, when the gas flowrate was 8 and 32 l/d,
respectively. The CH4 content of the biogas increased mainly due to the
reduction in CO2 concentration, because CO2 has significantly higher
permeability across the membrane and higher solubility in water
compared to CH4. The loss of CH4 in this particular study was minimal
(less than 3.4%) due to its lower transfer ability across the PDMS
membrane (Table 2). In general, the results obtained here was able to
conserve the energy content of the biogas. Charnnok et al. (2013) stu-
died on biogas desulfurization using a biofilter process, and they stated
an increase in the CH4 content of the biogas from 80 to 83%. In con-
trast, Chaiprapat et al. (2011) reported a decrease of about 20% in total
CH4 content, due to the dilution of biogas with air that was fed to the
biofilter to maintain the aerobic conditions. Thereby, the process used
here could achieve a high biogas desulfurization performance with a
considerable CH4 enrichment at the outlet stream of the membrane
contactor without any dilution problem.
According to the result shown in Table 2, the higher the gas flow-
rate, the higher the selectivity of H2S/CO2 and H2S/CH4. This phe-
nomenon could be explained by the differences of H2S permeability and
solubility in the membrane and mildly alkali absorption liquid, re-
spectively (Baker, 2004; Kennedy et al., 2015; Tilahun et al., 2017).
Former studies revealed that the dominant mass transfer resistance for
H2S absorption is on the gas side, while CO2 is on the liquid-side, which
means that the dissociation of H2S in the alkali absorption liquid (re-
action 2) is much faster than that of CO2 (reaction 8). In addition, the
biological oxidation of sulfide increases the driving force and allows
gaseous H2S to dissolve more in the aqueous phase. Thus desulfuriza-
tion selectivity could be retained at high level compared to CO2 and
CH4. In this study the highest H2S/CO2 and H2S/CH4 selectivity values
were 3.5 and 63 at the highest gas flowrate (32 l/d) and pH 7, which
was 2 times higher than those reported in our previous study where the
H2S was chemically absorbed by an alkaline solution after being dif-
fused through the PDMS membrane (Tilahun et al., 2017). Similar
conclusions were also drawn by the others indicating that rising the gas
flowrate improved the selective removal of H2S gas (Bontozoglou and
Karabelas, 1993; Lu et al., 2006). On the other hand, the selectivity was
inversely proportional to gas phase H2S removal efficiency. Therefore,
the gas flowrate and pH should be optimized to achieve a selective
biogas desulfurization and to maintain a high gas phase H2S removal
efficiency with minimal caustic consumption.
3.2. The effects of pH and volumetric H2S loading on sulfide oxidation
In this study, the first 23 days of operation were considered as
adaptation period of the SOB. The rest of the period 1 was divided into
three stages, i.e. stages I (pH 7), II (pH 7.75), III (pH 8.5), to evaluate
the impact of operational pH on the total system performance (Fig. 2).
During each of these stages the reactor was subjected to a range of
loading conditions, A (79 g H2S/m3
.d), B (148 g H2S/m3
.d), C (227 g
H2S/m3
.d), D (316 g H2S/m3
.d). The vertical dotted lines in Fig. 2 in-
dicate the days at which the H2S loading rate increased. At this period
Table 2
The effects of different operational parameters on the performance efficiency of the membrane (DO concentration in the absorption liquid was 4 mg/l).
pH Gas flowrate
(l/d)
Gas phase removal (R) (%) Selectivity Gas flux (g/m2
.d)
H2S CO2 CH4 H2S/CH4 H2S/CO2 H2S CO2 CH4
7.0 8 99.5 67.2 2.80 36.0 1.48 1.29 43.6 1.00
15 96.8 44.4 2.00 47.6 2.18 2.28 52.4 1.34
23 84.6 33.2 1.53 55.3 2.55 3.02 59.4 1.53
32 80.4 23.4 1.30 62.9 3.44 4.00 58.1 1.77
7.75 8 99.2 62.8 3.10 32.1 1.58 1.27 40.3 1.11
15 96.2 42.6 2.40 40.5 2.26 2.24 49.8 1.55
23 83.3 33.7 1.80 47.2 2.47 3.03 61.3 1.79
32 79.0 25.4 1.60 50.4 3.11 3.85 61.9 2.13
8.5 8 99.8 65.9 3.38 29.5 1.51 1.30 42.9 1.23
15 96.1 40.9 2.67 36.0 2.35 2.25 47.9 1.74
23 82.5 35.9 2.13 38.8 2.29 2.97 64.9 2.14
32 79.9 27.6 1.69 47.4 2.89 3.92 67.8 2.31
E. Tilahun et al. International Biodeterioration & Biodegradation 127 (2018) 69–76
72
5. the DO concentration inside the reactor was maintained at about 4 mg/l
by controlling the airflow rate.
At all tested pH values, total H2S removal (TSR) efficiency of
97.9 ± 0.7% was observed at volumetric loading rate (VLR) of 79 g
H2S/m3
.d (8 l/d), while the TSR decreased to 78.2 ± 1.2% when the
volumetric loading rate increased to 316 g H2S/m3
.d (32 l/d). The TSR
reduction at higher volumetric loading presumably due to the limita-
tion of the membrane mass transfer capacity. Moreover, the maximum
volumetric H2S removal rate (VSRR) of the system reached up to 251 g
H2S/m3
.d, at the highest VLR (316 g H2S/m3
.d) (Table 3). Other lit-
erature (Kumar et al., 2010) used PDMS/polyacrylonitrile (PAN) com-
posite membrane biofilm reactor for the reduction of dimethyl sulfide
from waste air, and they observed removal rate of 258 g/m3
.h. De Bo
et al. (2003) also studied on removal of dimethyl sulfide using PDMS/
Polyvinylidene Fluoride (PVDF) composite membrane bioreactor, and
they achieved a maximum of 120 g/m3
.h dimethyl sulfide removal rate.
It is clear that, a composite membrane bioreactor combines the best
characteristics of both porous (high mass transfer rate) and dense
nonporous materials (prevent wetting and biofouling problem). The
removal rate reported here was similar to those found in biofilters or
biotrickling filters (Bak et al., 2017; Ma et al., 2006; Ramírez et al.,
2009; Sublette et al., 1994).
Fig. 2 illustrated, under low volumetric H2S loading rate (79 g/
m3
.d) sulfate generation capacity was 233 ± 8 g SO4/m3
.d and it
accounts 75% of the theoretical sulfate generation. The theoretical
sulfate concentrations were calculated based on the assumption of
complete sulfide oxidation to sulfate. It was also displayed in the route
of H2S oxidation that at limited sulfide loading the biological sulfide
oxidation is in favor of reaction 5. When the VLR elevated to 316 g H2S/
m3
.d, the sulfate generation gradually increased up to 524 ± 49 g
SO4/m3
.d, (only 54% of the theoretical sulfate generation) (Fig. 2). The
reduction in the theoretical sulfate generation efficiency was related to
the incomplete oxidation of sulfide due to the decreased oxygen con-
centration in the biofilm or flocs at high loadings and the precipitation
of sulfate ions particularly at higher pH, which was also verified by XRD
analyses. As seen in Fig. 2, at higher pH value, the alkaline consumption
was greater. In addition to this, when the pH raised to 8.5, the corre-
sponding non-oxidized sulfide concentration in the liquid increased up
to 11 mg/l. This happened due to decreased biomass activity at higher
pH values. Ramírez et al. (2009) studied on the elimination of hydrogen
sulfide using a biotrickling filter containing Thiobacillus thioparus spe-
cies, and they described that the biological removal efficiency de-
creased from 88 to 72% when the pH of the liquid increased from 7.5 to
8.5. Specific to the desulfurization system of this work, optimal treat-
ment performance was obtained at a loading rate of approximately
148 g H2S/m3
.d and absorption liquid pH of 7 with TSR of above 97%.
3.3. Fate of sulfide oxidation at different DO concentrations
In period 2, the DO concentration decreased stepwise to investigate
its effects on elemental sulfide (So
) formation, sulfide removal effi-
ciency and caustic consumption. Three stages were established, stage I2
(DO 4 ± 0.5 mg/l), II2 (DO 2 ± 0.3 mg/l) and III2 (DO
0.9 ± 0.15 mg/l) (Fig. 3). Throughout the 75 days of operation, VLR,
gas flowrate and reactor pH were maintained at 140 g H2S/m3
.d, 14 l/
d, 7, respectively. From day 112 to day 126, due to failure of the
temperature control unit the system run at room temperature. Ac-
cordingly, the lower temperature (12–18 °C) adversely affected the
activity of SOB. Starting from day 127, the liquid temperature again
increased to 30 ± 1 °C and the ionic sulfur species in the liquid were
monitored to evaluate the fate of sulfur in the MBS system.
In summary, the results revealed that So
formation was significantly
affected by DO concentrations. Even though the biologically produced
So
was not directly measured, the analyses of the solid deposits by SEM-
EDS confirmed that the deposit was mainly composed of So
and other
inorganic components, such as C, N, O, P, Na, K, Si, Ca and Mg attached
on the external surface of the membrane (Fig. 4). Moreover, the results
of XRD analysis showed the presence of So
and other compounds which
were suspended in the liquid side of the membrane. Although So
and
other inorganics were detected on the membrane surface and sus-
pended in the liquid but not any fouling, clogging and wetting problems
were observed in the long run experiments. This happened possibly
because of two reasons; (i) the hydrophobic nature of the membrane
resists the excess attachment of inorganics, (ii) in nonporous membrane
there is no liquid flow through the membrane. However, in previous
studies due to the blockage and conventional liquid flow through the
membrane pores wetting and fouling were the main drawbacks
(Atchariyawut et al., 2007; Attaway et al., 2002; Wang et al., 2014).
The major sulfur species detected in the absorption liquid were
sulfate and So
, and it accounts more than 97% of the diffused H2S, while
less than 3% of the diffused H2S was found to be in dissolved form. Our
result was in agreement with the earlier study (Buisman et al., 1989).
They observed comparable outcomes as a result of the oxidation of
dissolved sulfide in a continuously stirred tank bioreactor. On other
hand, the production of sulfate and So
were varied significantly de-
pending on the DO concentration in the membrane bio reactor (Fig. 3a
and b). The absorption liquid was replaced (2/3 of the active volume) at
days 134, 143, 151, 158 and 171 in order to remove the accumulated
salts of sulfate and alkalinity, which could negatively affect the activity
of SOB. As seen in Fig. 3b, the So
production increased significantly
(100 mg/d) when the DO concentration decreased to approximately
1 mg/l. Reaction 4 also confirms, the greater the oxygen limitation the
Time (day)
0 20 40 60 80 100
)
d
/
l
/
g
m
(
n
o
i
t
c
u
d
o
r
p
e
t
a
f
l
u
S
0
200
400
600
800
1000
1200
NaOH
consumption
(g/d)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Stage I Stage II Stage III
A B D
C A B C D B D
A C
Measured sulfate
NaOH
Theoretical sulfate
Fig. 2. Sulfate production and NaOH consumption at different absorption liquid pH and
volumetric sulfide loading.
Table 3
The effects of absorption liquid pH and volumetric loading rate on sulfide oxidation.
pH Gas flowrate
(l/d)
Total H2S
removal
efficiency
Volumetric H2S
removal rate
Non-oxidized HS−
in liquid effluent
(mg/l)
TSR (%) VSRR (g/m3
.d)
7.0 8 98.62 77.91 0.7
15 95.78 141.8 1.6
23 83.37 189.3 2.9
32 79.54 251.4 4.8
7.75 8 97.95 77.38 1.0
15 94.92 140.5 2.0
23 81.44 184.9 3.7
32 77.67 245.4 6.2
8.5 8 97.20 76.79 2.1
15 92.84 137.4 4.9
23 78.97 179.3 8.1
32 77.28 244.2 11
E. Tilahun et al. International Biodeterioration & Biodegradation 127 (2018) 69–76
73
6. more the So
and less sulfate formation, because So
formation requires
only one-fourth of oxygen needed for the conversion to sulfate. In ad-
dition, a white to yellowish color was observed in the reactor indicating
the accumulation of biologically produced So
particles. This finding was
in consistent with the observation of other studies (Bayrakdar et al.,
2016; Cardoso et al., 2006). The So
formation was also confirmed with
the measured ORP values which fluctuated in range of −50 to
−300 mV. Low ORP values are usually reported when So
was the main
end product of sulfide oxidation (Khanal and Huang, 2003; Kobayashi
et al., 2012).
As illustrated in Fig. 3b, at DO concentration of about 4 mg/l, the
average caustic consumption was around 0.248 ± 0.012 g/d. De-
creasing the DO concentration to 1 mg/l induced a saving of 0.1 g/d of
NaOH, due to alkalinity generation during the oxidation of HS−
to So
according to reaction 4. Former studies also investigated the advantage
of operating the process with limited oxygen and decreased the ORP
value to minimize the caustic consumption (Janssen et al., 1995;
Kleinjan et al., 2006). A better control of DO concentration should be
applied in order to have steady and cost effective operation. Operating
the MBS at very low DO concentrations may lead to additional mem-
brane resistance due to the attachment of excess biomass on the
membrane surface as a result of limited oxygen. Whereas, supplying
excess DO may lead to sulfate accumulation in the liquid which can
negatively affect the activity of SOB and requires high alkaline con-
sumption for neutralizing the absorption liquid (reaction 5).
4. Conclusions
In this study, almost all of the H2S and half of the CO2 were suc-
cessfully removed and accordingly the calorific value of the biogas in-
creased by about 25%. Partial oxidation of the membrane separated
H2S to So
rather than sulfate decreased the operational cost by reducing
the caustic consumption and aeration requirement. During the long-
term operation fouling, wetting and dilution problems were not
)
d
/
l
/
g
m
(
n
o
i
t
c
u
d
o
r
p
e
t
a
f
l
u
S
0
200
400
600
800
Measured sulfate
Theoretical sulfate
I2 III2
II2
)
d
/
g
(
H
O
a
N
0.0
0.1
0.2
0.3
S
o
Production
(g/d)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
NaOH So Production
Time (day)
120 140 160 180
CH
4
O
C
d
n
a
2
)
%
(
t
n
e
u
l
f
f
e
0
20
40
60
80
H
2
S
effluent
(%)
0.0
0.2
0.4
0.6
0.8
CO2
CH4 H2S
a
b
c
Fig. 3. The effect of DO concentration on (a)
sulfate production, (b) So
production and NaOH
consumption, (c) effluent biogas components. The
dotted lines in this figure indicates the days when
2/3 of the reactor medium was replaced by tap
water due to salinity accumulation.
E. Tilahun et al. International Biodeterioration & Biodegradation 127 (2018) 69–76
74
7. observed. The hybrid membrane bio-scrubbing process developed in
this study is an easy-to-operate and cost-effective alternative than
conventional desulfurization technologies and has a great potential for
real scale applications.
Acknowledgments
This study was financially supported by YTB (Hükümet Bursu-
Doktora-11ET057350) (Presidency for Turks Abroad and Related
Communities) and Marmara University Scientific Research Committee
BAPKO (Project No. FEN-C-DRP-070317-0109).
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://dx.
doi.org/10.1016/j.ibiod.2017.11.015.
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