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Anaerobic treatment of industrail wastewater

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Anaerobic treatment of industrail wastewater

  1. 1. A report on Anaerobic Process in Industrial Wastewater Treatment Master of Technology in Environmental Engineering Under the guidance of Dr. Athar Hussain HOD CIVIL School of engineering Gautam Buddha University Submitted by- 14EEN 001 ABHISHEK SINGH KHEVARIYA 14EEN 002 AVANEESH KUMAR 14EEN 004 NITIN YADAV 14EEN 005 SANJAY KUMAR
  2. 2. CERTIFICATE This is certify that the report entitled “Anaerobic Process in Industrial Wastewater Treatment” is submitted by Abhishek Singh Khevariya, Avaneesh Kumar, Nitin Yadav and Sanjay Kumar for the project in Master of Technology (Environmental Engineering) submitted to Gautam Buddha University, Greater Noida. This matter embodied in this report is original & has not been submitted earlier. Date: 13 / 12/ 2014 Mr Athar Hussain HOD (CIVIL DEPARTMENT)
  3. 3. CONTENTS  Certificate (ii)  Abstract (v)  Introduction Inorganic Industrial Wastewater Treatment 01 Organic Industrial Wastewater Treatment 02  Literature review Sources of Industrial Wastewater Treatment 03 Anaerobic Treatment 07 Aerobic Treatment 07 Difference between Aerobic & Anaerobic Process 08 Anaerobic Fermentation 09 Aerobic Respiration 10  Process Microbiology Fermentative Bacteria 11 Acetogenic 11 Homoactegenes 12 Methenogenes 13  Factors Affecting Anaerobic Process Temperature 14 pH Control 15 Nutrients 15 Toxicity 15 Retention Time 16 Feeding Strategy 16 Agitation Strategy 16  Types of Anaerobic Reactors Anaerobic Filter Bed Reactors 17 Anaerobic Contact Process Reactors 18 Anaerobic Fluidized Bed Reactors 18 UASB 18  Design of Anaerobic Reactors Conditions 20 Design Parameters 20 Design Procedure 22
  4. 4.  Advantages of Anaerobic Process 24  Limitations of Anaerobic Process 25  Applications in the Industries 26  Bibliography 27
  5. 5. ABSTRACT The motivations for treatment of wastewater are manifold. Treatment and reuse of wastewater conserves the supply of freshwater and this presents clear advantages with respect to environmental protection. The main objective of this project report was to study Anaerobic Process in Wastewater Treatment Process. Anaerobic Process is a biological process that can degrade waste organic material by the concerted action of a wide range of microorganisms in the absence of oxygen. The process consists of a complex series of reactions that convert a wide array of polymeric substances such as carbohydrates, proteins, and lipids, having carbon atoms at various oxidation and/or reduction states, to one-carbon molecules in its most oxidized state (CO ) and its most reduced state 2 (CH ). 4
  6. 6. INTRODUCTION During the last century a huge amount of industrial wastewater was discharged into rivers, lakes and coastal areas. This resulted in serious pollution problems in the water environment and caused negative effects to the eco-system and human’s life. Until the mid-18th century, water pollution was essentially limited to small, localized areas. Then came the Industrial Revolution, the development of the internal combustion engine, and the petroleum-fuelled explosion of the chemical industry. With the rapid development of various industries, a huge amount of fresh water is used as a raw material, as a means of production (process water), and for cooling purposes. Many kinds of raw material, intermediate products and wastes are brought into the water when water passes through the industrial process. So in fact the wastewater is an "essential by-product” of modern industry, and it plays a major role as a pollution sources in the pollution of water environment. There are many types of industrial wastewater based on different industries and contaminants; each sector produces its own particular combination of pollutants. Generally, industrial wastewater can be divided into two types: inorganic industrial wastewater and organic industrial wastewater. Inorganic industrial wastewater Inorganic industrial wastewater is produced mainly in the coal and steel industry, in the nonmetallic minerals industry, and in commercial enterprises and industries for the surface processing of metals (iron picking works and electroplating plants). These wastewaters contain a large proportion of suspended matter, which can be eliminated by sedimentation, often together with chemical flocculation through the addition of iron or aluminum salts, flocculation agents and some kinds of organic polymers. The purification of warm and dust-laden waste gases from blast furnaces, converters, cupola furnaces, refuse and sludge incineration plants, and aluminum works results in wastewater containing mineral and inorganic substances in dissolved and un- 1 Anaerobic Process in Industrial Wastewater Treatment
  7. 7. dissolved form. Other wastewater from rolling mills contain mineral oil and require additional installations, such as scum boards and skim-off apparatus, for the retention and removal of mineral oils. Residues of emulsified oil remaining in the water also need chemical flocculation. In many cases, wastewater is produced in addition to solid substances and oils, and also contains extremely harmful solutes. These include blast-furnace gas-washing wastewater containing cyanide, wastes from the metal processing industry containing acids or alkaline solutions (mostly containing non-ferrous metals and often cyanide or chromate), wastewater from eloxal works and from the waste gas purification of aluminum works, which in both cases contain fluoride. Organic industrial wastewater Organic industrial wastewater contains organic industrial waste flow from those chemical industries and large-scale chemical works, which mainly use organic substances for chemical reactions. The effluents contain organic substances having various origins and properties. These can only be removed by special pretreatment of the wastewater, followed by biological treatment. Most organic industrial wastewaters are produced by the following industries and plants: pharmaceuticals, cosmetics, organic dye-stuffs, glue and adhesives, soaps, synthetic detergents, pesticides and herbicides, Tanneries and leather factories. Industrial wastewater treatment covers the mechanisms and processes used to treat waters that have been contaminated in some way by anthropogenic industrial or commercial activities prior to its release into the environment or its re-use. 2 Anaerobic Process in Industrial Wastewater Treatment
  8. 8. LITERATURE REVIEW SOURCES OF INDUSTRIAL WASTEWATER Various sources of Industrial wastewater are listed in the table below – Sector Pollutants Iron & Steel BOD, COD, Oil, Metal, Cyanide, Phenols & Acids Textile & Leather BOD, Solids, Sulfates & Chromium Pulp & Paper BOD, COD, Solids, Chlorinated Organic Compound Petrochemical & Refineries BOD, COD, Phenols & Chromium Chemicals COD, Heavy Metals, Cyanide, SS Non- Ferrous Metal Fluoride & SS Microelectronics COD & Organic Chemicals Mining Metal, SS, Acids & Salts 1. Iron and steel Industry: The production of iron from its ores involves powerful reduction reactions in blast furnaces. Cooling waters are inevitably contaminated with products especially ammonia and cyanide. Production of coke from coal in coking plants also requires water cooling and the use of water in by-products separation. Contamination of waste streams includes 3 Anaerobic Process in Industrial Wastewater Treatment
  9. 9. gasification products such as benzene, naphthalene, cyanide, ammonia, phenols, cresols together with a range of more complex organic compounds known collectively as polycyclic aromatic hydrocarbons (PAH). Wastewaters include acidic rinse waters together with waste acid. Although many plants operate acid recovery plants (particularly those using hydrochloric acid), where the mineral acid is boiled away from the iron salts, there remains a large volume of highly acid ferrous sulfate or ferrous chloride to be disposed of. Many steel industry wastewaters are contaminated by hydraulic oil, also known as soluble oil. 2. Mines and quarries: The principal waste-waters associated with mines and quarries are slurries of rock particles in water. These arise from rainfall washing exposed surfaces and haul roads and also from rock washing and grading processes. Volumes of water can be very high, especially rainfall related arising on large sites. Some specialized separation operations, such as coal washing to separate coal from native rock using density gradients, can produce wastewater contaminated by fine particulate hematite and surfactants. 3. Pulp and paper Industry: Effluent from the pulp and paper industry is generally high in suspended solids and BOD. Standalone paper mills using imported pulp may only require simple primary treatment, such as sedimentation or dissolved air flotation. Increased BOD or chemical oxygen demand (COD) loadings, as well as organic pollutants, may require biological treatment such as activated sludge or up flow anaerobic sludge blanket reactors. For mills with high inorganic loadings like salt, tertiary treatments may be required, either general membrane treatments like ultrafiltration or reverse osmosis or treatments to remove specific contaminants, such as nutrients. 4 Anaerobic Process in Industrial Wastewater Treatment
  10. 10. 4. Textile Industry: Dye bath wastewater generated by textile mills is often rated as the most polluting among all industrial sectors. The pollution load is characterized by high color content, suspended solids, salts, nutrients and toxic substances such as heavy metals and chlorinated organic compounds. Many textile mills in the state currently discharge their wastewater to local wastewater treatment plants with minimum treatment such as pH neutralization. This process removes much of the residual dye color. Larger mills can discharge more than 2 million gallons of wastewater of this kind per day. 5. Petrochemical Refineries: Refineries can generate a significant amount of wastewater that has been in contact with hydrocarbons. Wastewater can also include water rejected from boiler feed water pretreatment processes (or generated during regenerations). Wastewater can also refer to cooling tower blow downstream, or even once-through cooling water that leaves the refinery. Once-through cooling water typically does not receive any treatment before discharge. Cooling tower blow down water and wastewater from raw water treating may or may not receive treatment at the wastewater treatment plant (WWTP) before discharge. Contaminated wastewater is typically sent to either a wastewater treatment plant that is located at the facility, or it can be pretreated and sent to the local publicly owned treatment works or third-party treatment facility for further treatment. Water that has not been in direct contact with hydrocarbons or which has only minimal. 5 Anaerobic Process in Industrial Wastewater Treatment
  11. 11. 6 Anaerobic Process in Industrial Wastewater Treatment
  12. 12. INDUSTRIAL WASTEWATER TREATMENT PROCESS AEROBIC TREATMENT: Organic material decomposing with oxygen is an "aerobic" process. When organisms that use oxygen feed upon organic matter, they develop cell protoplasm from the nitrogen, phosphorus, some of the carbon, and other required nutrients. Carbon serves as a source of energy for organisms and is burned up and respired as carbon dioxide (CO2). Since carbon serves both as a source of energy and as an element in the cell protoplasm, much more carbon than nitrogen is needed. Generally, organisms respire about two-thirds of the carbon they consume as CO2, while the other third is combined with nitrogen in the living cells. In nature, the aerobic process is most common in areas such as the forest floor, where droppings from trees and animals are converted into relatively stable organic matter. This decomposition doesn’t smell when adequate oxygen is present. We can try to imitate these natural systems when we plan and maintain our landscapes. As we learn more about the biology and chemistry of composting, we can actually hasten the decomposition process. ANAEROBIC TREATMENT: Anaerobic process is a collection of processes by which microorganisms break down biodegradable material in the absence of oxygen. The process is used for industrial or domestic purposes to manage waste and/or to produce fuels. Much of the fermentation used industrially to produce food and drink products, as well as home fermentation, uses anaerobic digestion. Anaerobic digestion occurs naturally in some soils and in lake and oceanic basin sediments, where it is usually referred to as "anaerobic activity". The digestion process begins with bacterial hydrolysis of the input materials. Insoluble organic polymers, such as carbohydrates, are broken down to soluble derivatives that become available for other bacteria. Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. These bacteria convert these resulting 7 Anaerobic Process in Industrial Wastewater Treatment
  13. 13. organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. Finally, methanogens convert these products to methane and carbon dioxide. The methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments. Difference between Anaerobic & Aerobic Process: Anaerobic Aerobic Organic loading rate 3 -day Low loading rates:0.5-1.5 kg COD/m High loading rates:10-40 kg COD/m Biomass yield Low biomass yield:0.05-0.15 kg VSS/kg COD High biomass yield:0.35-0.45 kg VSS/kg COD (Biomass yield is not constant but depends on types of substrates metabolized) (Biomass yield is fairly constant irrespective of types of substrates metabolized) Specific substrate utilization rate High rate: 0.75-1.5 kg COD/kg VSS-day Low rate: 0.15-0.75 kg COD/kg VSS-day Long start-up: 1-2 months for mesophilic Short start-up: 1-2 weeks 8 Anaerobic Process in Industrial Wastewater Treatment 3 -day SRT Longer SRT is essential to retain the slow growing methanogens within the reactor SRT of 4-10 days is enough for the activated sludge process Start-up time
  14. 14. ANAEROBIC PROCESS Anaerobic treatment is a biological process carried out in the absence of O2 for the stabilization of organic materials by conversion to CH4 and inorganic end-products such as CO2 and NH3. Anaerobic processes Anaerobic fermentation Anaerobic respiration Anaerobic Fermentation In anaerobic fermentation, there is no external electron acceptor. The product generated during the process accepts the electrons released during the breakdown of organic matter. Thus, organic matter acts as both electron donor and acceptor. The process releases less energy and the major portion of the energy is still contained in the fermentative product such as ethanol. Through this method, a cell is able to regenerate nicotinamide adenine dinucleotide (NAD+) from the reduced form of nicotinamide adenine dinucleotide (NADH), a molecule necessary to continue glycolysis. Anaerobic fermentation relies on enzymes to add a phosphate group to an individual adenosine diphosphate (ADP) molecule to produce ATP, which means it is a form of substrate-level phosphorylation. This contrasts with oxidative phosphorylation, which uses energy from an established proton gradient to produce ATP. There are two major types of anaerobic fermentation: ethanol 9 Anaerobic Process in Industrial Wastewater Treatment
  15. 15. fermentation and lactic acid fermentation. Both restore NAD+ to allow a cell to continue generating ATP through glycolysis. Anaerobic Respiration Anaerobic respiration on the other hand requires external electron acceptor. The electron acceptors in this case could be SO4 2-, NO3 - or CO2. These terminal acceptors have smaller reduction potentials than O2, meaning that less energy is released per oxidized molecule. The energy released under such a condition is higher than anaerobic fermentation. In order for the electron transport chain to function, an exogenous final electron acceptor must be present to allow electrons to pass through the system. In aerobic organisms, this final electron acceptor is oxygen. Molecular oxygen is a highly oxidizing agent and, therefore, is an excellent acceptor. Anaerobic respiration is, therefore, in general energetically less efficient than aerobic respiration. Anaerobic respiration is used mainly by prokaryotes that live in environments devoid of oxygen. Many anaerobic organisms are obligate anaerobes, meaning that they can respire only using anaerobic compounds and will die in the presence of oxygen. 10 Anaerobic Process in Industrial Wastewater Treatment
  16. 16. PROCESS MICROBIOLOGY The anaerobic degradation of complex matter is carried out by a series of bacteria. There exists a coordinated interaction among these microbes. The process may fail if certain of these organisms are inhibited. TYPES OF BACTERIA ON THE BASIS OF PROCESS MICROBIOLOGY Fermentative bacteria: This group of bacteria is responsible for the first stage of anaerobic digestion - hydrolysis and acidogenesis. Fermentation bacteria are anaerobic, but use organic molecules as their final electron acceptor to produce fermentation end-products. Streptococcus, Lactobacillus, and Bacillus, for example, produce lactic acid, while Escherichia and Salmonella produce ethanol, lactic acid, succinic acid, acetic acid, CO2, and H2. Fermenting bacteria have characteristic sugar fermentation patterns, i.e., they can metabolize some sugars but not others. For example, Neisseria meningitidis ferments glucose and maltose, but not sucrose and lactose, while Neisseria gonorrhoea ferments glucose, but not maltose, sucrose or lactose. Such fermentation patterns can be used to identify and classify bacteria. The anaerobic species belonging to the family of Streptococcaceae and Enterobacteriaceae and to the genera of Bacteroides, Clostridium, Butyrivibrio, Eubacterium, Bifidobacterium and Lactobacillus are most common. Hydrogen producing acetogenic bacteria: Acetogenic bacteria are a specialized group of strictly anaerobic bacteria that are ubiquitous in nature. Together with the methane‐forming archaea they constitute the last limbs in the anaerobic food web that leads to the production of methane from polymers in the 11 Anaerobic Process in Industrial Wastewater Treatment
  17. 17. absence of oxygen. Acetogens are characterized by a unique pathway, the Wood– Ljungdahl pathway of carbon dioxide reduction with the acetyl‐CoA synthase as the key enzyme. This pathway also allows chemolitho-autotrophic growth on hydrogen and carbon dioxide and it is the only pathway known that combines carbon dioxide fixation with adenosine triphosphate (ATP) synthesis. Thus, it is considered the first biochemical pathway on earth. ATP is synthesized by a chemi-osmotic mechanism with Na+ or H+ as coupling ion, depending on the organism. In cytochrome‐free acetogens, energy is conserved by reduction followed by dependent Na+ (or H+) translocation across the membrane (Rnf complex). Acetogens may represent ancestors of the first bio energetically active cells in evolution. CH3CH2COO -  CH3COO - + CO2 + H2 Homoacetogenes: The homoacetogens are much more adaptable than methanogens because in addition to being autotrophic they can also live as chemoheterotrophs. Clostridium aceticum and Acetobacterium woodii are the two homoacetogenic bacteria isolated from the sludge. In the heterotrophic growth mode they can ferment glucose and derive some ATP by substrate level phosphorylation. In so doing they generate carbon dioxide and hydrogen which can then be used to power the chemiosmotic mechanism which allows them to derive some ATP also by anaerobic respiration. The overall stoichiometry of this growth mode of homoacetogens is shown below. 12 Anaerobic Process in Industrial Wastewater Treatment
  18. 18. Methanogens: Methanogens are autotrophic archebacteria that use anaerobic respiration for ATP synthesis. Methanogens use CO2 taken up from their growth environment as the carbon substrate for growth. They use some CO2 as the ultimate oxidizing agent of an electron transport chain which, by a chemiosmotic mechanism, maintains a transmembrane electrochemical ion gradient which powers ATP production. Methanogens use this hydrogen and this process maintains a lowered hydrogen partial pressure in the reticulo-rumen. Some of the hydrogen producing heterotrophic microorganisms show altered patterns of metabolism because of methanogen usage of the hydrogen they produce. Methanogens affect the growth of some but not all hydrogen producing species of microorganism in the reticulo-rumen. The equation shows the reduction of CO2 by H2 to produce methane. This redox reaction sustains anaerobic respiration which allows the production of ATP. The methane produced by reduction of the carbon dioxide is lost from the reticulo-rumen by eructation. It is a waste of feed carbon because the rumen does not have methanotrophic bacteria and the host ruminant cannot utilize this gas. 13 Anaerobic Process in Industrial Wastewater Treatment
  19. 19. FACTORS AFFECTING ANAEROBIC PROCESS The successful operation of anaerobic reactor depends on maintaining the environmental factors close to the comfort of the microorganisms involved in the process. They are as follows- 1. Temperature: Anaerobic processes like other biological processes operate in certain temperature ranges. Mesophilic (25-450C) and thermophilic (45-650C) anaerobic digestion are commonly applied in the field. Most full-scale anaerobic digesters are operated at mesophilic temperature. Since wastewater and bio solids is discharged at relatively low temperature (e.g., 18 0C), recent research toward anaerobic treatment under psychrophilical condition becomes attractive. For instance, microbial communities involved in digestion are sensitive to temperature changes. The rate of anaerobic degradation of organic substrates generally increases in the order of psychrophilic, mesophilic and thermophilic digestion. 14 Anaerobic Process in Industrial Wastewater Treatment
  20. 20. 2. pH Control: pH is an important factor for keeping functional anaerobic digestion. A typical pH is in the range of 6.5-7.6. The accumulation of intermediate acids leads to pH drop during fermentation. In order to maintain stable operation, it is necessary to add bicarbonate or carbonate as an alkalinity buffer to neutralize volatile fatty acids and carbon dioxide. 3. Nutrients: Macronutrients are the elements that the cellular material of the anaerobic microorganisms comprises, including hydrogen, nitrogen, oxygen, carbon, sulfur, phosphorus, potassium, calcium, magnesium and iron. Normally, anaerobic microorganisms require these elements presented with a concentration around 10 -4 M. In addition to the micronutrients, a number of other elements, such as Ni and Co must be present in small amount, i.e. below10 15 Anaerobic Process in Industrial Wastewater Treatment -4 M. This is because that these elements are important for the growth of anaerobic organisms. For example, Ni is necessary for activating factor F , which is a co 430 factor involved in methanogenesis. But it can be inhibitory for fermentative as well as methanogens if it is present in high concentration. 4. Toxicity: Besides ammonia and nitrate/nitrite, heavy metals, such as Zn, Cu and Cd can be toxic to acidogenic bacteria. However, many of these elements and compounds can be tolerated in relatively high concentration due to absorption in inert material contained in the reactor.
  21. 21. 5. Retention Time: For the CSTR reactors, which are the most prevailingly used types of reactors, hydraulic and solid retention time is the same. Retention time is an important operational parameter that is easy to operate and control. Tremendous efforts have been put into the research of the effect of retention time on anaerobic digestion. Biologically, only those who are doubling time are shorter than the retention time can be kept in the reactor, so retention time is one of the best parameter to be manipulated for separating and enriching different groups of the microbes involved in the anaerobic process. Also, retention time determines the time that substrates can be attacked by the enzymes in the reactor. 6. Feeding Strategy: Practically, anaerobic reactors treating sewage sludge in wastewater treatment plants are fed semi-continuously instead of continuously. Feeding frequency determines the ratio of food to microbe (F/M) when the retention time and the working volume have been fixed. Normally, the ratio can be satisfied so that there is no negative effect on the stability and on the performance of the anaerobic reactors. 7. Agitation Strategy: It is normally believed that agitation is necessary to help the diffusion of substrate and increase their contacts with the microbes, especially when raw sludge is intermittently fed into the reactor. Agitation strategy can affect anaerobic digestion of sewage sludge and optimum agitation strategy should be found. In addition, it was also found that mixing levels might be used as an operational tool to stabilize unstable anaerobic reactor. 16 Anaerobic Process in Industrial Wastewater Treatment
  22. 22. TYPES OF ANAEROBIC REACTORS There are five principal process variants which are proper in anaerobic wastewater treatment. These are as follows: Anaerobic Filter Reactor: The anaerobic filter is similar to a trickling filter in that a biofilm is generated on media. The bed is fully submerged and can be operated either upflow or down flow. As wastewater flows through the filter, particles are trapped and organic matter is degraded by the active biomass that is attached to the surface of the filter material. With this technology, suspended solids and BOD removal can be as high as 90%, but is typically between 50% and 80%. Nitrogen removal is limited and normally does not exceed 15% in terms of total nitrogen (TN). Anaerobic filters are usually operated in upflow mode because there is less risk that the fixed biomass will be washed out. The water level should cover the filter media by at least 0.3 m to guarantee an even flow regime. The hydraulic retention time (HRT) is the most important design parameter influencing filter performance. An HRT of 12 to 36 hours is recommended. The ideal filter should have a large surface area for bacteria to grow, with pores large enough to prevent clogging. The surface area ensures increased contact between the organic matter and the attached biomass that effectively degrades it. Ideally, the material should provide between 90 to 300 m2 of surface area per m3 of occupied reactor volume. Typical filter material sizes range from 12 to 55 mm in diameter. Materials commonly used include gravel, crushed rocks or bricks, cinder, pumice, or specially formed plastic pieces, depending on local availability. 17 Anaerobic Process in Industrial Wastewater Treatment
  23. 23. Anaerobic Contact Process Reactor: This process can be considered as an anaerobic activated sludge because sludge is recycled from a clarifier or separator to the reactor. Since the material leaving the reactor is a gas-liquid-solid mixture, a vacuum Degasifier is required to separate the gas and avoid floating sludge in the clarifier. Here a set of reactors are created in series, often with recycling. This recycled material is pumped up into the bottom of the first reactor, an upflow reactor. The upflow anaerobic process is a large reactor which allows the waste to flow up from the bottom and separates the waste into 3 zones. At the very top is the biogas zone where the gas is collected. Bacteria digest waste in the lowest portion of the upflow reactor; the bioreactor zone. In between these two stages is the clarifier zone where the which exports the stabilized waste. Fluidized Bed Reactor: This reactor consists of a sand bed on which the biomass is grown. Since the sand particles are small, a very large biomass can be developed in a small volume of reactor. In order to fluidize the bed, a high recycle is required. In this type of reactor, a fluid (gas or liquid) is passed through a granular solid material (usually a catalyst possibly shaped as tiny spheres) at high enough velocities to suspend the solid and cause it to behave as though it were a fluid. This process, known as fluidization, imparts many important advantages to the FBR. As a result, the fluidized bed reactor is now used in many industrial applications. Upflow Anaerobic Sludge Blanket Reactor: Under proper conditions anaerobic sludge will develop as high density granules. These will form a sludge blanket in the reactor. The wastewater is passed upward through the blanket. Because of its density, a high concentration of biomass can be developed in the blanket. The UASB reactor is a methanogenic (methane-producing) digester that evolved from the clarifier. A similar but variant technology to UASB is the expanded granular sludge bed (EGSB) digester. 18 Anaerobic Process in Industrial Wastewater Treatment
  24. 24. UASB uses an anaerobic process whilst forming a blanket of granular sludge which suspends in the tank. Wastewater flows upwards through the blanket and is processed (degraded) by the anaerobic microorganisms. The upward flow combined with the settling action of gravity suspends the blanket with the aid of flocculants. The blanket begins to reach maturity at around 3 months. Small sludge granules begin to form whose surface area is covered in aggregations of bacteria. In the absence of any support matrix, the flow conditions create a selective environment in which only those microorganisms, capable of attaching to each other, survive and proliferate. Eventually the aggregates form into dense compact biofilms referred to as "granules". Schematic diagrams of anaerobic wastewater treatment processes: (a) anaerobic filter reactor; (b) anaerobic contact reactor; (c) fluidized-bed reactor; (d) upflow anaerobic sludge blanket (UASB). 19 Anaerobic Process in Industrial Wastewater Treatment
  25. 25. DESIGN OF ANAEROBIC REACTORS Conditions for efficient anaerobic treatment – • Avoid excessive air/O 2 exposure • No toxic/inhibitory compounds present in the influent • Maintain pH between 6.8 –7.2 • Sufficient alkalinity present (mainly bicarbonates) • Low volatile fatty acids (VFAs) • Temperature around mesophilic range (30-38 o C) • Enough nutrients (N & P) and trace metals especially, Fe, Co, Ni, etc. COD - N: P = 350:7:1 (for highly loaded system) 1000:7:1 (lightly loaded system) • SRT/HRT >>1 (use high rate anaerobic reactors) DESIGN PARAMETERS Anaerobic Filter:  Width to diameter ratio of reactor =2-6(usually)  Height of reactor =2-12 m(usually)  Hydraulic retention time =20-30 d(for domestic wastewater)  Volumetric loading =0.2-0.8 kg COD/m3 –d  Specific area for the media =100 m2/m3 of volume 20 Anaerobic Process in Industrial Wastewater Treatment
  26. 26. Fluidized Bed Reactor:  Up –flow velocity =2.0 m/h  Specific area of media =10000 m2/m3 of media volume  Void space =50%  Organic loading =4-5 kg COD/m3-d Anaerobic Contact Process:  Up-flow velocity =15-20 m/h  Rector depth =3-6 m  Volumetric loading =10-30 kg COD/m3.d  Reactor biomass =15000-20000 mg MLVSS/L  HRT =3-6 h UASB:  Up-flow velocity =0.5-0.9 m/h  Volumetric loading =6-20 kg COD/m3.d  HRT =6-48 hr  MLSS concentration (i) at the bottom of reactor =100000-150000 mg/l (ii) at the top of reactor =5000-4000 mg/l  Reactor depth = 3-5 m (for domestic water)  Biomass production =0.2-0.5 m3/kg of COD removed 21 Anaerobic Process in Industrial Wastewater Treatment
  27. 27. DESIGN PROCEDURE a) Design based on volumetric organic loading rate (VOLR) VOLR: Volumetric organic loading rate (kg COD/m3-day) So : Wastewater biodegradable COD (mg/L) Q : Wastewater flow rate (m3/day) V : Bioreactor volume (m3) b) Design based on hydraulic loading rate H : Reactor height (m) a : Allowable hydraulic retention time (hr) Q : Wastewater flow rate (m3/h) A : Surface area of the reactor (m2) 22 Anaerobic Process in Industrial Wastewater Treatment
  28. 28. , 23 Anaerobic Process in Industrial Wastewater Treatment
  29. 29. ADVANTAGES OF ANAEROBIC PROCESS • Less energy requirement as no aeration is needed. • Energy generation in the form of methane gas. • Less biomass (sludge) generation. • Less nutrients (N & P) required. • Application of higher organic loading rate. • Space saving. • Ability to transform several hazardous solvents. 24 Anaerobic Process in Industrial Wastewater Treatment
  30. 30. LIMITATIONS OF ANAEROBIC PROCESS • Long start-up time. • Long recovery time. • Specific nutrients/trace metal requirements. • More susceptible to changes in environmental conditions. • Effluent quality of treated wastewater. • Treatment of high protein & nitrogen containing wastewater. 25 Anaerobic Process in Industrial Wastewater Treatment
  31. 31. APPLICATIONS OF ANAEROBIC PROCESS (INDUSTRIES) • Alcohol production • Brewery and Winery • Sugar processing • Starch (barley, corn, potato, wheat, tapioca) • Waste from textile industry. • Food processing • Bakery plant • Pulp and paper • Dairy • Slaughterhouse • Petrochemical waste 26 Anaerobic Process in Industrial Wastewater Treatment
  32. 32. BIBLIOGRAPHY  en.wikipedia.org/wiki/AnaerobicProcess  books.google.com  Metcalf and Eddy, 1981. Wastewater Engineering: Collection and pumping of Wastewater. McGraw Hill Inc., New York.  Research Paper- Anaerobic Treatment of Industrial Effluents, by Mustafa Evren Ersahin, Istanbul Technical University, Turkey.  Research Paper- ANAEROBIC DIGESTION TECHNOLOGY FOR INDUSTRIAL WASTEWATER TREATMENT by Medhat M. A. Saleh and Usama F. Mahmood, El Azhar Univ., Egypt. 27 Anaerobic Process in Industrial Wastewater Treatment

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