This document discusses a study that assessed the leaching of heavy metals like zinc, lead, nickel, and cadmium from ash and soil samples taken from an unsanitary waste dump at the University of Zimbabwe. The study found that samples from the waste dump had significantly higher concentrations of heavy metals compared to control samples, indicating they could contaminate groundwater. The mobility of the heavy metals decreased with increasing pH for zinc, lead, and nickel, but cadmium mobility increased with pH in old ash samples. Cadmium levels in fresh ash samples exceeded WHO limits for hazardous waste, posing concerns for surrounding soil and groundwater quality. The study aims to better understand the relationship between leaching of pollutants from waste dumps
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Remediation of contaminated soil using soil washing-a reviewIJERA Editor
Pb, Zn, Ni, Cu, Mn and Cd are heavy metals occur naturally as trace elements in many soils. The present paper
reviews the remediation of heavy metals of contaminated soil by soil washing using different agents. It was
noted that the contact time, pH, concentration of extract ant and agitation speed were affected the process while
remediation, so accordingly select the conditions to obtain efficiency which is mainly depend upon the type of
soil, contaminationtype, contamination period and metals present in it.EDTA is effective when compared with
other chelating agents for heavy metals especially for lead but it has low biodegradation. Because of the nature
of low biodegradability, EDTA can be reusedfurther by membrane separation and electrochemical treatment, or
degraded by advanced oxidation processes.
Physico-Chemical Evaluation of Wastewater from Abattoir, Brewery, Soap and Oi...IJERA Editor
The discharge of industrial wastewater in the city of Moundou deteriorates the quality of surface and
underground water and soils. In this study the physicochemical quality of industrial effluents was investigated in
different seasons (summer, winter and rainy). Three sampling sites were used (Central Abattoir discharge,
Cotontchad (soap and oil factory) discharge, and Brewery discharge), for sampling from July 2013 to December
2014. The following physico-chemical parameters were determined: pH, Temperature, EC, dissolved oxygen,
COD, BOD5, NO3,PO4,SO4. Also, the heavy metals: Cu, Cd, Mn, Ni, Pb, As, Zn, Cr, Fe, Al, was analyzed on
spectrophotometers and results were compared with World Health Organization (WHO) permissible limits.
This study revealed that most parameters were much higher than the permissible limit for wastewater
discharges:some parameters were to higher: pH (12,6), Temperature (37,8 °C), C.E (4270 μS/cm), organic
matters: COD (1200 mg/l), SO4 (1280 mg/l), PO4(4460 mg/l), NO3 (63,6 mg/l), (Fe (63,34 mg/l), Zn (13,27
mg/l), Pb (4,0 mg/l), Cu (25,34 mg/l), Cd (31,78 mg/l), Cr (5,9 mg/l), Ni (39,5 mg/l. The study concludes that
discharge of effluents by the companies; factory and materials from other anthropogenic sources severely
pollute the Logone River with heavy metals and other pollutants. We recommended that each industry recycle
its wastewater and put in place specific treatment plants, because pollutants to eliminate vary depending on the
industry.
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
Remediation of contaminated soil using soil washing-a reviewIJERA Editor
Pb, Zn, Ni, Cu, Mn and Cd are heavy metals occur naturally as trace elements in many soils. The present paper
reviews the remediation of heavy metals of contaminated soil by soil washing using different agents. It was
noted that the contact time, pH, concentration of extract ant and agitation speed were affected the process while
remediation, so accordingly select the conditions to obtain efficiency which is mainly depend upon the type of
soil, contaminationtype, contamination period and metals present in it.EDTA is effective when compared with
other chelating agents for heavy metals especially for lead but it has low biodegradation. Because of the nature
of low biodegradability, EDTA can be reusedfurther by membrane separation and electrochemical treatment, or
degraded by advanced oxidation processes.
Physico-Chemical Evaluation of Wastewater from Abattoir, Brewery, Soap and Oi...IJERA Editor
The discharge of industrial wastewater in the city of Moundou deteriorates the quality of surface and
underground water and soils. In this study the physicochemical quality of industrial effluents was investigated in
different seasons (summer, winter and rainy). Three sampling sites were used (Central Abattoir discharge,
Cotontchad (soap and oil factory) discharge, and Brewery discharge), for sampling from July 2013 to December
2014. The following physico-chemical parameters were determined: pH, Temperature, EC, dissolved oxygen,
COD, BOD5, NO3,PO4,SO4. Also, the heavy metals: Cu, Cd, Mn, Ni, Pb, As, Zn, Cr, Fe, Al, was analyzed on
spectrophotometers and results were compared with World Health Organization (WHO) permissible limits.
This study revealed that most parameters were much higher than the permissible limit for wastewater
discharges:some parameters were to higher: pH (12,6), Temperature (37,8 °C), C.E (4270 μS/cm), organic
matters: COD (1200 mg/l), SO4 (1280 mg/l), PO4(4460 mg/l), NO3 (63,6 mg/l), (Fe (63,34 mg/l), Zn (13,27
mg/l), Pb (4,0 mg/l), Cu (25,34 mg/l), Cd (31,78 mg/l), Cr (5,9 mg/l), Ni (39,5 mg/l. The study concludes that
discharge of effluents by the companies; factory and materials from other anthropogenic sources severely
pollute the Logone River with heavy metals and other pollutants. We recommended that each industry recycle
its wastewater and put in place specific treatment plants, because pollutants to eliminate vary depending on the
industry.
An Analysis and Study in Light of Phytoremediation of Heavy Metal Contaminate...ijtsrd
"The modern movement quickens contamination of the
biosphere, particularly the soil. These days soil
contamination is getting impressive open
consideration since the size of this issue is developing
quickly. Heavy metals are the most hazardous
substances in the earth because of their abnormal state
of toughness and harmfulness to the biota. Various
examinations have been led around there went for
building up an effective and prudent approach to
remediate the soil contaminated with heavy metals.
Regular remediation techniques, for example,
physical, warm and concoction medications are
exceptionally costly. Phytoremediation is a creating
innovation which utilizes plants and their related
organisms for the remediation of soil defilement. This
procedure is practical without making unsettling
influence to the scene. This paper resembles a point of
reference or resource in distinguishing the issues
related with heavy metal contaminated soil and other
term known as Phytoremediation."
Macroscopic and modeling evidence for nickel(II) adsorption onto selected man...Dr. Md. Aminul Islam
Ni(II) polluted water becomes a significant issue in recent years. Excessive levels of Ni(II) are detrimental to the plant, animal and human life, so it is important to reduce the amount of Ni(II) that enters the environment from polluted water. Manganese oxides, found in soils are important in determining the availability of Ni(II) in soil systems as they absorb Ni(II) onto their surface. Therefore, they may be able to be used to remove Ni(II) from wastewater so it is important to understand the interaction mechanisms of Ni(II) with manganese- containing minerals. As a consequence, Ni(II) adsorption onto birnessite, pyrolusite, hausmannite, manganite, boehmite, and Mn-Al binary oxide were investigated as a function of solution pH using an initial Ni(II) concentration in 1 mM NaNO 3 solution at 22 ± 2 °C. The adsorption data were modeled using Langmuir, Freundlich and extended constant capacitance model (ECCM) approach to predict the possible adsorption reactions. The accumulation process was strongly dependent on pH, initial Ni(II) concentration, and the nature of the mineral. The position of adsorption edges (pH 50 ) varied significantly between the minerals investigated. Birnessite exhibited maximum Ni(II) uptake, while pyrolusite exhibited minimum uptake. The Langmuir equation provided a reasonable correlation of data. ECCM results indicate that Ni(II) formed outer-sphere complexes at low pH, and inner- sphere complexes and surface precipitation at higher pH. Proton stoichiometry suggests that more than one reaction involved in the overall Ni(II) adsorption process. This study on Mn- oxides as sorbents for Ni(II) demonstrates that MnOs may be effective in removing Ni(II) pollutants from wastewater.
Heavy metals contamination of Pakistani soil (zohaib Hussain) sp13bty001Zohaib HUSSAIN
The long-term usage of industrial wastewater makes heavy metals to accumulate in soil and increases the absorption and accumulation by the plants. Heavy metal contamination of soil and water caused by industrialization has become a major environmental issue in Pakistan. Therefore, it is important to determine the level of contamination of soil and water close to industrial areas
A promising chitosan/fluorapatite composite for efficient removal of lead (II...Dr. Md. Aminul Islam
Lead (II) is one of the most important metal ion pollutants commonly found in industrial wastewater. It is harmful to animal kingdom and prolong exposure can cause severe health trouble including cancer. Therefore, its removal to a permissible level is warranted for an eco-friendly and sustainable environment. The use of low-cost chitisan based composite material as an adsorbent can be a promising approach for Pb(II) decontamination. In this study, a novel chitosan/fluorapatite (Cs-Fap) composite has been prepared from chitosan (Cs) and fluorapatite (Fap) for the efficient removal of Pb(II) from water. Exploration of the effect of contact time, solution pH, initial Pb(II) concentration, adsorbent dosage, and the temperature was performed to understand the adsorption process. Pb(II) adsorption performance was compared among Cs, Fap and Cs-Fap composite. Pb(II) adsorption was fast and approched equlibrium in 30 min. Maximum Pb(II) adsorption was achieved at pH 4.0 for an optimum dose of 2g/L. Pb(II) adsorption kinetics data followed a pseudo-second order (PSO) model, while equilibrium isotherm data best described by Langmuir equation nicely. The maximum adsorption capacity (mg/g) follows the order: Cs-Fap (60.24) > Fap (48.31) > Cs (43.29) at pH 4.0. Thermodynamic analysis revealed that adsorption process was a feasible, endothermic and spontaneous in nature. The proposed mechanism of Pb(II) uptake involved physisorption, ion-exchange, electrostatic attraction, and surface complexation. Cs-Fap composite showed excellent regeneration capacity. After 4 (four) subsequent regeneration cycles, there was no notable loss of its adsorption capacity. The results of this study showed that the Cs-Fap composite is promising for the removal of Pb(II) and it can be used as an adsorbent for the removal of other metal ions from real environmental samples.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
Manganese oxides and their application to metal ion and contaminant removal f...Dr. Md. Aminul Islam
Manganese oxides are ubiquitous in soil, sediment and aquatic environment. Over the years, manganese oxides and their composites have proved to be effective as adsorbents for the removal of metal ions and contaminants from water/wastewater. Because of their unique chemical and physical properties, they have attracted widespread attention as excellent adsorbents. This review reports on recent research on the synthesis, characterization, and application of manganese oxides and their composites for wastewater treatment. The adsorption characteristics, including experimental conditions and mechanisms involved in the pollutant removal processes, are discussed. The review provides an overview of the research related to manganese oxides and their application, including future areas of research and limitations in the current body of research.
REMOVAL OF TOXIC CHEMICALS AND BIOLOGICAL POLLUTANTS FROM GROUNDWATER WELLS U...ijac123
Water pollution is one of the most important environmental problems in the world. In developing countries,
contaminated water has frequently caused water diseases. Today, water borne toxic chemicals (anions and
heavy metal ions) and biological pollutants pose a great threat to the safety of water supplies. Currently,
the quality of groundwater with respect to pollutants is of great concern. Modified Downflow Hanging
Sponge (DHS) reactor will be a good groundwater treatment technology in the near future, it is used for
excellent removal of heavy metals, anions, organic pollutants and harmful microbes, and also the reactor
has advantages like low cost, easy to apply and satisfaction level. In order to achieve these objectives,
treatment scheme has been investigated. It consists of mixing organic chelator with impure groundwater in
different concentrations followed by a downflow hanging sponge (DHS) reactor. In the presence of 0.5 g/L
of the chelator, the average removal of total NO3 and NO2 and (total dissolved solids) TDS are respectively
72%, 62% and 75%. The results show that, when Cd treated with chelator, the amount decreases from
0.0063 to 0.0 mgL-1 (100%) after 1 h, Cu decreases from 0.0023 to 0.0 mgL-1 (100%) after 1 h, Fe
decreases from 0.4 to 0.0 mgL-1 (100%) after 1 h, Mn decreases from 0.3 to 0.0 mgL-1 (100%) after 1 h and
Zn decreases from 0.012 to 0.0 mgL-1 (100%) after 1 h. Also, the results show removal of fecal coliform .
Decreased from 50 to 0 and the overall removal efficiency of fecal coliform is (100%).
The metals, which are required in a very minute amount and are considered toxic, are
termed as heavy metals. Researchers have widely investigated and studied these metals
due to their dangerous and harmful influence on health and the environment. Due to their
ability to accumulate and toxic nature these are addressed to be a vital source of environmental
contamination. Heavy metals have critically polluted the environment and its components.
This has severely damaged its abilities to promote life and provide its intrinsic
values. These are naturally available compounds and because of their anthropogenic origin
they are commonly found in various environmental domain. This results in deterioration of
the environment competence to support life and health of human, animals and plants
becomes threatened. This takes place because of bioaccumulation of these heavy metals in
the food chain which is a direct consequence of nondegradable state of the heavy metals.
The surroundings within which the human life exists is referred as the environment. It basically
comprises of the water, land, microorganisms, animal and plant life and the atmosphere
of the earth.
An Analysis and Study in Light of Phytoremediation of Heavy Metal Contaminate...ijtsrd
"The modern movement quickens contamination of the
biosphere, particularly the soil. These days soil
contamination is getting impressive open
consideration since the size of this issue is developing
quickly. Heavy metals are the most hazardous
substances in the earth because of their abnormal state
of toughness and harmfulness to the biota. Various
examinations have been led around there went for
building up an effective and prudent approach to
remediate the soil contaminated with heavy metals.
Regular remediation techniques, for example,
physical, warm and concoction medications are
exceptionally costly. Phytoremediation is a creating
innovation which utilizes plants and their related
organisms for the remediation of soil defilement. This
procedure is practical without making unsettling
influence to the scene. This paper resembles a point of
reference or resource in distinguishing the issues
related with heavy metal contaminated soil and other
term known as Phytoremediation."
Macroscopic and modeling evidence for nickel(II) adsorption onto selected man...Dr. Md. Aminul Islam
Ni(II) polluted water becomes a significant issue in recent years. Excessive levels of Ni(II) are detrimental to the plant, animal and human life, so it is important to reduce the amount of Ni(II) that enters the environment from polluted water. Manganese oxides, found in soils are important in determining the availability of Ni(II) in soil systems as they absorb Ni(II) onto their surface. Therefore, they may be able to be used to remove Ni(II) from wastewater so it is important to understand the interaction mechanisms of Ni(II) with manganese- containing minerals. As a consequence, Ni(II) adsorption onto birnessite, pyrolusite, hausmannite, manganite, boehmite, and Mn-Al binary oxide were investigated as a function of solution pH using an initial Ni(II) concentration in 1 mM NaNO 3 solution at 22 ± 2 °C. The adsorption data were modeled using Langmuir, Freundlich and extended constant capacitance model (ECCM) approach to predict the possible adsorption reactions. The accumulation process was strongly dependent on pH, initial Ni(II) concentration, and the nature of the mineral. The position of adsorption edges (pH 50 ) varied significantly between the minerals investigated. Birnessite exhibited maximum Ni(II) uptake, while pyrolusite exhibited minimum uptake. The Langmuir equation provided a reasonable correlation of data. ECCM results indicate that Ni(II) formed outer-sphere complexes at low pH, and inner- sphere complexes and surface precipitation at higher pH. Proton stoichiometry suggests that more than one reaction involved in the overall Ni(II) adsorption process. This study on Mn- oxides as sorbents for Ni(II) demonstrates that MnOs may be effective in removing Ni(II) pollutants from wastewater.
Heavy metals contamination of Pakistani soil (zohaib Hussain) sp13bty001Zohaib HUSSAIN
The long-term usage of industrial wastewater makes heavy metals to accumulate in soil and increases the absorption and accumulation by the plants. Heavy metal contamination of soil and water caused by industrialization has become a major environmental issue in Pakistan. Therefore, it is important to determine the level of contamination of soil and water close to industrial areas
A promising chitosan/fluorapatite composite for efficient removal of lead (II...Dr. Md. Aminul Islam
Lead (II) is one of the most important metal ion pollutants commonly found in industrial wastewater. It is harmful to animal kingdom and prolong exposure can cause severe health trouble including cancer. Therefore, its removal to a permissible level is warranted for an eco-friendly and sustainable environment. The use of low-cost chitisan based composite material as an adsorbent can be a promising approach for Pb(II) decontamination. In this study, a novel chitosan/fluorapatite (Cs-Fap) composite has been prepared from chitosan (Cs) and fluorapatite (Fap) for the efficient removal of Pb(II) from water. Exploration of the effect of contact time, solution pH, initial Pb(II) concentration, adsorbent dosage, and the temperature was performed to understand the adsorption process. Pb(II) adsorption performance was compared among Cs, Fap and Cs-Fap composite. Pb(II) adsorption was fast and approched equlibrium in 30 min. Maximum Pb(II) adsorption was achieved at pH 4.0 for an optimum dose of 2g/L. Pb(II) adsorption kinetics data followed a pseudo-second order (PSO) model, while equilibrium isotherm data best described by Langmuir equation nicely. The maximum adsorption capacity (mg/g) follows the order: Cs-Fap (60.24) > Fap (48.31) > Cs (43.29) at pH 4.0. Thermodynamic analysis revealed that adsorption process was a feasible, endothermic and spontaneous in nature. The proposed mechanism of Pb(II) uptake involved physisorption, ion-exchange, electrostatic attraction, and surface complexation. Cs-Fap composite showed excellent regeneration capacity. After 4 (four) subsequent regeneration cycles, there was no notable loss of its adsorption capacity. The results of this study showed that the Cs-Fap composite is promising for the removal of Pb(II) and it can be used as an adsorbent for the removal of other metal ions from real environmental samples.
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
Manganese oxides and their application to metal ion and contaminant removal f...Dr. Md. Aminul Islam
Manganese oxides are ubiquitous in soil, sediment and aquatic environment. Over the years, manganese oxides and their composites have proved to be effective as adsorbents for the removal of metal ions and contaminants from water/wastewater. Because of their unique chemical and physical properties, they have attracted widespread attention as excellent adsorbents. This review reports on recent research on the synthesis, characterization, and application of manganese oxides and their composites for wastewater treatment. The adsorption characteristics, including experimental conditions and mechanisms involved in the pollutant removal processes, are discussed. The review provides an overview of the research related to manganese oxides and their application, including future areas of research and limitations in the current body of research.
REMOVAL OF TOXIC CHEMICALS AND BIOLOGICAL POLLUTANTS FROM GROUNDWATER WELLS U...ijac123
Water pollution is one of the most important environmental problems in the world. In developing countries,
contaminated water has frequently caused water diseases. Today, water borne toxic chemicals (anions and
heavy metal ions) and biological pollutants pose a great threat to the safety of water supplies. Currently,
the quality of groundwater with respect to pollutants is of great concern. Modified Downflow Hanging
Sponge (DHS) reactor will be a good groundwater treatment technology in the near future, it is used for
excellent removal of heavy metals, anions, organic pollutants and harmful microbes, and also the reactor
has advantages like low cost, easy to apply and satisfaction level. In order to achieve these objectives,
treatment scheme has been investigated. It consists of mixing organic chelator with impure groundwater in
different concentrations followed by a downflow hanging sponge (DHS) reactor. In the presence of 0.5 g/L
of the chelator, the average removal of total NO3 and NO2 and (total dissolved solids) TDS are respectively
72%, 62% and 75%. The results show that, when Cd treated with chelator, the amount decreases from
0.0063 to 0.0 mgL-1 (100%) after 1 h, Cu decreases from 0.0023 to 0.0 mgL-1 (100%) after 1 h, Fe
decreases from 0.4 to 0.0 mgL-1 (100%) after 1 h, Mn decreases from 0.3 to 0.0 mgL-1 (100%) after 1 h and
Zn decreases from 0.012 to 0.0 mgL-1 (100%) after 1 h. Also, the results show removal of fecal coliform .
Decreased from 50 to 0 and the overall removal efficiency of fecal coliform is (100%).
The metals, which are required in a very minute amount and are considered toxic, are
termed as heavy metals. Researchers have widely investigated and studied these metals
due to their dangerous and harmful influence on health and the environment. Due to their
ability to accumulate and toxic nature these are addressed to be a vital source of environmental
contamination. Heavy metals have critically polluted the environment and its components.
This has severely damaged its abilities to promote life and provide its intrinsic
values. These are naturally available compounds and because of their anthropogenic origin
they are commonly found in various environmental domain. This results in deterioration of
the environment competence to support life and health of human, animals and plants
becomes threatened. This takes place because of bioaccumulation of these heavy metals in
the food chain which is a direct consequence of nondegradable state of the heavy metals.
The surroundings within which the human life exists is referred as the environment. It basically
comprises of the water, land, microorganisms, animal and plant life and the atmosphere
of the earth.
Detection of the Presence of Heavy Metal Pollutants in Eleme Industrial Area ...theijes
The presenceof some heavy metal pollutants which are deposited on soil in the Eleme environment due to the operational activities of some companies in the area have been studied. Some soil samples in areas situated around industrial installations were collected and analyzed using Atomic Absorption Spectrophotometer (AAS). Results obtained show the presence and concentration distributions of nine heavy metals. The metals are Iron (Fe), Manganese (Mn), Zinc (Zn), Lead (Pb), Copper (Cu), Chromium (Cr), Cobalt (Co) and Cadmium (Cd). It was observed that over 90% of each of the metals was located in communities hosting the industrial corporations while the remaining 10% is distributed to areas away from the source or host communities. This reveals that, a link exists between the pollutants and the activities of these industries.
COMPARATIVE STUDY ON HEAVY METAL CHARACTERISTICS OF LEACHATE FROM MUNICIPAL ...IJSIT Editor
Rapid urbanization and population growth are largely responsible for very high increasing rate of
solid waste in the urban areas, its proper management and recycling is major problems of Municipal
Corporation. The analytical analysis revealed that the leachate show high concentration of heavy metals viz.,
Pb, Zn, Fe, Mn and Cu. However, their high concentration in municipal solid waste leachate may cause
contaminants for environmental pollution. Therefore, present investigation deals with analyze the heavy
metals concentration in municipal solid waste leachate.
This ppt covers sources, natural and anthropogenic processes, and impacts of heavy metals pollution on environment with Mechanisms of Remediating Heavy Metals.
Quantification of Heavy Metals using Contamination and Pollution Index in Sel...IJEAB
Many sites in urban cities are used for dumping of domestic, industrial and municipal wastes because of high human population density in the area. Most often, people use these dumpsites for growing of crops without knowing the level of heavy metal contamination in soils of these areas. This study evaluated the quantification and contamination level of heavy metals in some refuse dumpsites in communities of the State Nigeria. Three replicate soil samples were collected from the dumpsites and at 20 m away from the non - dumpsite which do not receive sewage water within the root zone of 0 – 40 cm depth using soil auger sampler. Samples were analysed for soil properties and heavy metal concentrations using standard methods. The concentrations of the studied heavy metals (Cu, Pb, Zn and Cd) were compared with the permissible limits of other countries. Results showed that in the three studied locations, soil pH at dumpsites were 40 .6%, 39.4% and 38.9% higher than the values in the control sites while soil organic carbon were higher in the dumpsites by 50.1%, 31.3% and 41.1% as compared to the control sites. Cu concentrations at the three locations were below the standard limits of United Kingdom, European Union (EU), USA and WHO. The concentrations of the studied heavy metals passed the contamination stage and therefore will pose negative effect on plant and soil environment. Use of the dumpsite for crop cultivation or as compost materials should be avoided and construction of shallow wells near these areas should be discouraged.
Mobility and Distribution of Some Selected Trace Metals in Soil from Dumpsite...ijtsrd
Mobility and distribution of some selected trace metal was carried out using Tessier et al 1979sequential extraction method and the results obtained shows from dumpsite A, samples taken from 0 - 5cm the result ranges from 0.56 - 21.56 , 0.34 - 40.66 , 1.34 - 29.18 , 0.06 to 45.91 and 0.37 - 12.95 for the exchangeable, Fe - Mn oxide, organic carbonate and residual fractions respectively. For the samples taken from 10 - 15cm at dumpsite A, the results of the fractions are 0.42 - 13.63 , 0.03 - 18.48 , 1.01 - 25.34 , 0.03 - 35.19 and 0.27 - 9.31 for exchangeable, Fe - Mn oxide, organic, carbonate and residual fractions. The results of dumpsite Bare 0.48-27.36 , 0.28-40.07 , 2.93-31.15 , 3.87-42.50 and 0.84-30.67 for exchangeable, Fe-Mn oxide, Organic, carbonate and residual fractions for sample taken from 0-5cm while for samples taken from 10 - 15cm the results show 0.32 - 36.38 , 0.23 - 16.49 , 0.53 - 15.83 , 1.53 - 34.88 and 0.04 - 5.27 for exchangeable Fe - Mn oxide, carbonate and residual fractions respectively. The dumpsite C has the concentration of the various fractions ranging from 0.25 - 18.34 , 2.73 to 15.58, 4.02 - 23.28 , 0.07 - 45.25 and 1.57 - 37.43 for exchangeable, Fe - Mn oxide, organic, carbonate and residual for samples taken from 0 - 5cm while for samples taken between 10 - 15cm the concentrations are 0.42 - 12 .62 0.80 - 11.59 , 2.16 - 17.33 , 9.86 - 34.48 and 0.99 - 32.99 respectively. Gube-Ibrahim Mercy Ayinya | Ibrahim Ezekiel Gube "Mobility and Distribution of Some Selected Trace Metals in Soil from Dumpsite in Lafia, Nasarawa State" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-1 , December 2018, URL: http://www.ijtsrd.com/papers/ijtsrd19106.pdf
http://www.ijtsrd.com/chemistry/analytical-chemistry/19106/mobility-and-distribution-of-some-selected-trace-metals-in-soil-from-dumpsite-in-lafia-nasarawa-state/gube-ibrahim-mercy-ayinya
IOSR Journal of Applied Chemistry (IOSR-JAC) is an open access international journal that provides rapid publication (within a month) of articles in all areas of applied chemistry and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in Chemical Science. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
Research Inventy : International Journal of Engineering and Science is published by the group of young academic and industrial researchers with 12 Issues per year. It is an online as well as print version open access journal that provides rapid publication (monthly) of articles in all areas of the subject such as: civil, mechanical, chemical, electronic and computer engineering as well as production and information technology. The Journal welcomes the submission of manuscripts that meet the general criteria of significance and scientific excellence. Papers will be published by rapid process within 20 days after acceptance and peer review process takes only 7 days. All articles published in Research Inventy will be peer-reviewed.
International journal of science technologyMiftahur Rizqi
Sand is an important mineral for our society in protecting the
environment, where this practice of sand and soil mining is becoming an
environmental issue as the demand for sand increases in industry and construction.
Mining and its associated activities can be responsible for considerable
environmental damage. In this article we are discussing about the direct and indirect
impacts due to soil and sand mining to the environment in Indian regions. Pollution
of the water is evident by the colouration of water which in most of the rivers and
streams in the mining area varies from brownish to reddish orange. Low pH (between 2-
3), high electrical conductivity, high concentration of ions of sulphate and iron and toxic
heavy metals, low dissolved oxygen (DO) and high BOD are some of the physicochemical
and biological parameters which characterize the degradation of water quality.
Contamination of Acid Mine Drainage (AMD) originating from mines and spoils,
leaching of heavy metals, organic enrichment and silting by sand particles are major
causes of degradation of water quality.
ENVIRONMENTAL IMPACT OF SOIL AND SAND MINING: A REVIEW
dorcas gora AES360 final draft
1. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
Page | 1
ABSTRACT
Heavy metal leaching from unsanitary solid waste dumps has potential to cause groundwater and
soil pollution. Despite the researches done, the relationship between leaching of pollutants from
solid waste dumpsites and groundwater pollution is still unclear. This study was aimed at
assessing the leaching potential of zinc, lead, nickel and cadmium from the University of
Zimbabwe waste dump and effect of pH of leaching solution. It was found that fresh ash, old ash
and soil beneath the waste dump had significantly higher concentrations of heavy metals
leaching than the control indicating that they could be sources of ground water contamination.
The mobility of the cations was dependent on the pH of leaching solution and decreased with
increasing pH for Zn, Pb and Ni. Cd however, increased its mobility in old ash with increasing
pH. Heavy metals leached were below the WHO limit values for hazardous waste: 10 mg/l for
Ni, 3 mg/l for Pb, and 50 mg/l for Zn with the exception of Cd, 0.3mg/l in fresh ash. This implies
Cd leaching may be a cause for concern as it may affect surrounding soil and groundwater
quality. It may thus be recommended that the waste dump is lined to minimize leaching of Cd.
Detailed characterization of materials and retention mechanisms in different materials may be
conducted in further research to assess leaching of these heavy metals from an unsanitary waste
dump.
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CHAPTER ONE: INTRODUCTION
1.1 Background
Unsanitary disposal of solid waste is predominant in developing countries such as Zimbabwe and
poses serious threats to the environment. Zimbabwe’s population is increasing rapidly and thus
ultimately waste generated annually is increasing. Zimbabwe generates an average of 2.5 million
tons of solid waste annually (TARSC, 2007). Currently solid waste is being disposed of in non-
engineered landfills which are not properly lined, unsanitary and overloaded. This poses a threat
to the soil and ground water as the risk of leaching of contaminants like heavy metals, is
heightened. Air pollution from landfill emissions, health problems due to breeding of disease
causing pests and social problems such as decreasing land values and aesthetic appeal of an area,
are some associated problems. Typically, the solid waste dumps consist of domestic, organic,
electronic, industrial, clinical, agricultural and other types of wastes.
In Harare, the capital city of Zimbabwe, many of these open pits are located near residential
areas. The major dumpsites such as the Pomona dumpsite are not even designed for their
purpose. There are just mere landfills in which waste is disposed of in. Landfills have been
identified as one of the major threats to quality of groundwater water (Fatta et al., 1999; US
EPA, 1984). The absence of containment systems at the sites allows the possible percolation of
leachate into groundwater (Aderemi and Falade, 2012). Leachate is liquid containing
innumerable organic and inorganic compounds which accumulates at the bottom of a landfill and
percolates through the soil. Leachability is an indication of potential migration or mobilization of
contaminants from solid waste by moving water or infiltrating water. The leachate generated will
have the tendency to move in a downward motion through the underlying soils (UNEP, 2005).
The environmental problem posed by heavy metals is that they are non-biodegradable like
organic waste and have toxic effects on living organisms when exceeding a threshold
concentration (Esakku et al., 2003). Areas close to landfills have a greater possibility of
groundwater contamination because of the potential pollution source of leachate originating from
the nearby dumpsite. Groundwater forms as a part of the natural water cycle present in aquifers.
This contamination of groundwater resource poses a considerable risk to local resource users and
the natural environment (Mor et al, 2005). This is particularly important in Zimbabwe where
both rural and urban populations are dependent on groundwater for drinking and domestic uses.
Several studies have been done on the leaching behavior of heavy metals. Examples include Buy
et al, (2003) investigated the leaching behavior of magnesium phosphate cements containing
high quantities of heavy metals and their environmental implication on groundwater quality.
Robinson (2009) and Wiles (1996) stated that e-waste is a major source of leachable Pb, Ni, Hg,
Cd. Hjelmar (1990) and Bosshard et al (1996), carried out studies on municipal incineration ash
and found out that metals present in the leachate decrease as the number of pores increase with
the average percentage of leachable toxic metals. Also the impact of fly ash on ground water
seems to be mainly dependent on site conditions. Wasay (2005) studied the leaching
characteristics of Cr (III), Cr (VI), Hg (II) and as of a fly ash sample at various pH values and
found 40% of these toxic elements in the leachate at pH 7.0. Johnson et al (1996) studied the
3. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
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leaching behavior and solubility controlling solid phases of heavy metals in municipal solid
waste incinerator ash.
Despite the researches done, the relationship between leachability of pollutants from solid waste
dumpsites and groundwater pollution is still unclear. Most of these studies were carried out in
developed countries where proper landfills and incinerators are available. By comparison, there
is limited reliable information specific to developing countries on heavy metal and nitrate
leachability from waste dumps (UNEP, 2005).Therefore, this study seeks to investigate the
leaching of heavy metals from solid waste dumps using column and batch experiments.
1.2 Problem Statement and Justification
Zimbabwe produces approximately over 2.7 million tons of solid waste annually (TARSC, 2010)
and has currently no properly engineered dumpsite for disposal of solid waste. This is mainly due
to several economic constraints such as lack of capital, personnel and reliable information
applicable to the nation (UNEP, 2005). Due to lack of properly designed sanitary landfills, the
bulk of which is disposed of in unsanitary dumpsites which could potentially cause
environmental problems like groundwater pollution. The bulk of solid waste generated in
Zimbabwe is disposed of in unlined waste dumps which could potentially cause environmental
problems like groundwater pollution.
However, the impacts of the leachable heavy metals on groundwater quality are still poorly
understood. Information on leachability of heavy metal and nitrate content from solid waste
dumpsites will facilitate the development of suitable remedial measures (Esakku et al., 2003). It
is thus important to assess leaching of heavy metals which are major components of urban solid
waste. Although a few studies have investigated the leachability of heavy metals in developing
countries, limited information is available. Although there is existing research on urban solid
waste management in Zimbabwe which stretches over a decade, limited information on
environmental problems such as soil and ground water contamination by leaching of heavy
metals associated with poor waste disposal (Tevera, 1991 and Mandimutsa, 2009).
The study site which is the University of Zimbabwe dumpsite is located at the main campus
which is surrounded by the Mt pleasant and Alexandra Park residential areas. Due to water
supply issues in the city of Harare, most residents have drilled boreholes as sources of water.
This is also the case with the university which accommodates over 5000 students and staff
members. Thus the threat of contamination of ground water by leachate from the dumpsite poses
serious public health risks. Therefore this study seeks to investigate the leaching of and heavy
metals from the University of Zimbabwe solid waste dump and the results will help pollution
remediation and reduction measures as well as designing of sanitary landfills.
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1.3 Hypotheses
1.3.1 Soil and ash from solid waste dumps has significantly higher concentrations of leachable
heavy metals than the control
1.3.2 Leaching of heavy metals in ash and soil is significantly related to the pH of the leaching
solution.
1.4 Objectives
1.4.1 Main Objective
The main objective of the study is to investigate the leaching of heavy metals from
unsanitary solid waste dumps and its dependence on pH of leaching solution
1.4.2 Specific Objectives
To investigate the leaching of heavy metals from soil and residual ash from a solid waste
dump.
To evaluate the effect of pH of leaching solution on the leaching of heavy metals from
soil and ash from a solid waste dump
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CHAPTER TWO: LITERATURE REVIEW
2.1 The Problem of Waste Generation
Solid waste is mainly generated from households and industrial activities. Thus whenever
people exist, waste must be generated and managed either fully or partially (Taylor et al, 2006).
The EPA (1972) defines solid waste as useless, unwanted or discarded material with insufficient
liquid content to be free flowing. Truthfully, there are no ways of dealing with waste that have
not been known for many years. Principally, incineration, source reduction, recycling,
composting and landfills are usually common. The site onto which solid wastes are often
dumped include valleys, old quarries sites, excavations, or a selected portion within the
residential and commercial areas in many urban settlement where the capacity to collect, process,
dispose of, or re-use solid waste in a cost-efficient, safer manner is limited (Eludoyin and Oyeku,
2010).
Landfills have historically been the primary method of waste disposal due to its convenience
and the threat of groundwater contamination was not initially recognized. However, modern
landfills are far different from a simple hole in the ground into which waste is disposed of in
developed nations. Examples of waste disposed of in dumpsites are shown in Figure 2.1;
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(a) (b)
(c) (d)
Figure 2.1. Typical examples of solid waste; (a)(http://harmonyfdn.ca/?p=349),(b)
http://www.rnw.nl/africa/article/zimbabwes-growing-electronic-waste-becomes-a-real-danger-
0):e-waste,(c)http://www.infrastructurene.ws/2013/10/31/offenders-pay-the-price-in-illegal-
dumping-clampdown/ and (d) http://dchigundu.blogspot.com /: unsorted general waste
The ever-increasing population, industrialization and changing consumption patterns in
Zimbabwe have resulted in the generation of increasing amounts of solid waste and
diversification of the type of the solid waste generated. Visvanathan and Ulrich (2006) stated that
the environmental degradation caused by inadequate disposal of waste can be expressed by the
contamination of surface and groundwater through leachate, soil contamination through direct
waste contact or leachate, air pollution by burning of wastes, spreading of diseases by different
vectors like birds, insects, rodents or uncontrolled release of methane by anaerobic
decomposition of waste.
Disposal of solid waste in landfills has been acknowledged as a major source of groundwater
contamination (Afzal et al., 2000). Waste that is disposed of in unsanitary landfills or in refuse
dumps immediately becomes part of the prevailing hydrological system. Fluid derived from
rainfall, snowmelt and groundwater, together with liquids generated by the waste itself through
processes of hydrolysis and solubilisation, brought about by a whole series of complex
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biochemical reactions during degradation of organic wastes, percolate through the deposit and
mobilize other components within the wastes. The resulting leachate subsequently migrates
either through direct infiltration on site or by infiltration of leachate-laden runoff offsite (Taylor
and Allen, 2006).
2.2 Solid Waste Management in Zimbabwe
Solid waste disposal in Zimbabwe is regulated by the Environmental Management Act of 2007
under Effluent and Solid Waste Disposal Regulations, Statutory Instrument 6 of 2007 (Statutory
Instrument 6 of 2007). The Environmental Management Agency under the Ministry of
Environment, Water and Climate enforces the regulations. Section 22 of the SI 6:2007 states that
disposal of waste in an unlicensed dumpsite is illegal and the characteristics for a legal dumpsite
are stipulated. The statutory instrument (section 22.3), states that use of unlined dumpsites five
years from date of the regulations’ publication is illegal. However, it’s been seven years since
publication of the regulations and no properly engineered landfill exists in Zimbabwe with
special reference to the capital, Harare. This is mainly due to economic hardships.
Solid wastes disposed of in Zimbabwean households are a mixture of domestic, industrial,
electronic and clinical wastes. The co-disposal of household hazardous waste such as batteries,
paint residues, ash, treated woods and electronic wastes increases the heavy metal content in
municipal solid waste dumpsite environments (Pare et al., 1999). In Zimbabwe, the sanitary
disposal of solid wastes is one of the most pressing challenges facing urban authorities. In recent
years, there has been considerable increase in illegal waste dumping, which indicates that
throughout the country, urban waste disposal systems are inefficient and environmentally unsafe.
While there are various studies, which have focused on solid waste management in Zimbabwe,
existing research has concentrated mostly on: (i) large cities especially Harare and sidelined
small towns; and (ii) some elements of the solid waste management system and accorded least
attention to disposal (Masocha, 2004). Very little is known about the impacts of all these
unsanitary landfills on soil and ground water contamination. Leaching or migration of
contaminations poses public health risks especially in areas where communities depend on
groundwater for domestic supply.
2.3 Chemical Composition of Leachate
Limited data is available on leachate quality in Zimbabwe. Studies done elsewhere show that
rainfall that runs over solid waste or infiltrates through solid waste extracts dissolved and
suspended constituents and thus becomes leachate (Robinson, 2009). As the waste decomposes
through aerobic and anaerobic microbial action, waste-derived constituents increasingly become
available to form leachate of greater concentration. Leachate from sanitary landfills can reach
high organic concentrations well in excess of 20,000 mg/l of COD (chemical oxygen demand)
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and 10,000mg/l of BOD5 (five-day biological oxygen demand) in the first several years after
land disposal. It can also have high concentrations of total dissolved solids, ammonia, nitrate,
phosphate, chloride, calcium, potassium, sulfate, and iron, as well as numerous heavy metals
(commonly including lead, zinc, cadmium, and nickel) and organic trace constituents (commonly
including byproducts of decomposing solvents, pesticides, and polychlorinated biphenyls) . In
addition, high numbers of fecal bacteria are typical, while viruses seldom survive in leachate
because of their sensitivity to the low pH values common to leachate.
2.4 Public Health Risks
Figure 2.4. Public health and environmental hazard risks of inappropriate solid waste disposal
2.5 Effects of Heavy Metals on Soil and Groundwater Quality
Heavy metals in soil are considered to be distributed among several phases; soil solution phase,
exchangeable phase, sorbed and organically bound phase, bound and occluded in oxides and
secondary clay minerals phase, and residual, within the primary mineral lattice phase.
Operationally distinct extractant solutions to tap into these phases have been developed and used
to devise indices of heavy metal (bio)-availability based on the relationship between extracted
metal and plant performance or metal uptake. In contrast to analysis of total metal, such
extractants give an idea of the geochemical forms of the heavy metals in the soil. This, in turn,
allows us to distinguish between metal derived from the mineral matrix and metal added to the
soil in, for example, waste leachates, assuming that the latter has a different solubility and/or
availability(Speir et al.,2002).
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2.6 Leaching Studies
Information of leaching of heavy metals from solid waste dumps is important to evaluate the risk
of landfills to human health and environment (Scott et al., 1990). Leaching tests are frequently
used in assessing worst case environmental scenario where components of the wastes turn out to
be soluble and mobile. The mobility and toxicity of heavy metals present in landfills depend on
the chemical form of the metals. It has been reported that a major portion of the total metal
content in MSW is inert form, unlikely to undergo chemical reactions in landfills but leach from
the waste bed (Tessier et al., 1979). The toxic effects of solid wastes are known to be greatly
influenced by their heavy metal contents (Lottermoser, 1985).
Knowledge of heavy metal content, their speciation and the leachability at various
environmental conditions from the dumpsite is a prerequisite for the assessment of reclamation
and hazardous potential of the reclaimed waste, when it is used as compost for agricultural
applications. Since the effect of heavy metals is influenced by their form of existence (Norvell,
1984). Assessment of the species of metal ions enables to evaluate the sustainability of mined
waste as compost or cover material.
Batchelor (1999) stated that when a solid waste is in contact with a fluid, some contaminants will
leach from the solid to the fluid. One can look at the process as a continuous one, measuring the
concentration of the contaminant in the fluid and the flow rate of the fluid. Alternatively, a batch
process may be considered and the volume of fluid measured instead of the flow. Two important
issues to be considered in leaching tests are equilibrium and kinetics. When the flow of fluid
through the waste is low, there is time for many of the contaminants in the waste to reach
equilibrium with the fluid, and the concentration of a contaminant in the leachant reflects its
solubility at equilibrium. Conversely, when the fluid flow is high, the concentration of the
contaminants in the leachant is controlled by the rate at which they can dissolve or otherwise be
transformed. In some cases the concentration of a contaminant is a function of both the
equilibrium process and kinetics. A leaching test may be designed to gather information on the
equilibrium aspects of the process, the kinetic aspects, or both.
2.7 Methods of Evaluating Leachability
Various leaching methods such as acid digestion, TCLP, ELT, SE and MEP,are used to remove
soluble components from solid matrix have been cited in literature (Hesbach et al., 2001). A lot
of these are regulatory methods, directed to characterize materials and others are approved by
organizations for establishing compliance to particular standards and are related to hazardous
waste. The methods vary depending upon the amount and particle size of leached samples, the
type and volume of leachant solutions and the leachant delivery time (Kim, 2002).
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Toxicity characteristics leaching procedure (TCLP) developed by the United States
Environmental Protection Agency (USEPA) is widely used to classify hazardous solid wastes
and evaluate the worst leaching conditions in a landfill environment (USEPA, 1986). The TCLP
is designed to determine the mobility of both organic and inorganic analytes present in liquid,
solid, and multiphasic wastes. When applied to solid waste, i.e., waste containing greater than or
equal to 0.5% solids, the liquid, if any, is separated from the solid phase and stored for later
analysis; the particle size of the solid phase is reduced, if necessary. The solid phase is extracted
with an amount of extraction fluid equal to 20 times the weight of the solid phase. The extraction
fluid employed is a function of the alkalinity of the solid phase of the waste. A special extractor
vessel is used when testing for volatile analytes. Following extraction, the liquid extract is
separated from the solid phase by filtration through a 0.6 to 0.8 μm glass fiber filter (USEPA,
1984).
Multiple extraction procedure (MEP) was designed to simulate the leaching from repetitive
precipitation of acid rain on an improperly designed sanitary landfill (Testing methods, Canada,
1986). The repetitive extractions reveal the highest concentration of each constituent that is likely
to leach in a natural environment. This method is applicable to liquid, solid, and multiphase
samples (USEPA, 1984). Equilibrium leach test (ELT) is meant for the evaluation of the
maximum leachate concentration under mild conditions (Prudent et al., 1996).
Leaching tests can be used to compare the effectiveness of various solid-solid processes.
Leaching of waste constituents from stabilized matrix will be influenced by the following
factors:
Chemical composition of stabilized matrix and leaching medium
Physical engineering properties of stabilized matrix
Hydraulic gradient across the waste
Polarity and leaching sum and waste type
Redox conditions and competing reaction kinetics
Bulk chemical diffusion of the waste or reactive species within the leachate pore solution
or solid matrix
Concentration of reactive species, and
Accumulation of waste in the pore solution at particle surface
(Suthersan, 1996)
Leachability testing is used to predict the degree to which this objective has been met (Wilson,
1993).
Numerous leaching tests have been established to test solid waste. Extraction tests refer to a
leaching test that generally involves agitation of ground or pulverized waste forms in a leaching
solution which may be acidic or neutral. Extraction tests are generally used to determine the
maximum leachate concentrations under a given set of environmental conditions. A typical
example is the ELT extraction test (Sutherson, 1996). Leach tests involve the monolithic waste
mass. They may be run under 2 conditions: (1) static conditions were leaching velocities are
low, because leaching takes place under static hydraulic conditions and, (2) dynamic conditions
in which leaching takes place under non-equilibrium conditions because leaching solution is
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replaced periodically with new solution (Sharma,1994). In column leach tests waste is initially
pulverized and then placed in a column at a predetermined density, and the leaching solution is
finally passed under pressure in an upward flow mode. This method is more representative of
field conditions. However, simple care is required during set up to avoid errors due to certain
factors like channeling effects, non-uniform packing of waste, biological growth, and changing
of the column (Sharma,1994). Batch and column experiments thus complement each other.
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CHAPTER THREE: MATERIALS AND METHODS
3.1 Description of study site and soil sampling
The study site was the University of Zimbabwe dumpsite which is located at the main campus
behind the Crop Science Department (31º02’56.13” E; 17º46’50.13”S). Waste disposed of at the
dumpsite includes electronic and electrical waste, office waste papers, domestic waste from halls
of residence and staff quarters, litter from university grounds, solid laboratory waste and
demolition waste. The dumpsite has been in operation for over 50 years and is a non-sanitary
dump as it is not lined. Waste management practices such as burning of waste occur every 5-6
weeks.
The study included four treatments, (1) fresh ash from recently burnt waste, (2) aged ash that had
accumulated over the years from burning of waste, (3) soil from beneath the dump and (4) soil
unaffected by the dump as the control. Fresh ash, aged ash and soil from beneath the waste
where randomly collected from five sampling sites. Fresh ash from waste burnt three weeks prior
to sampling was collected from the five selected sites. About 4 kg samples were collected from
each sampling site and mixed to make a 20 kg composite sample.
Aged ash was collected after scrapping off fresh ash and some waste from the five sampling
sites in the same manner as fresh ash. The aged ash was dark in colour, moist and had
accumulated over the years as burning of waste is a frequent activity at the dumpsite. Soil
beneath the dump was collected at a depth of 35-50 cm depending with the location of the
sampling areas. The soil samples were obtained below the aged ash layer of the dump from the
five sampling sites. Aged ash and soil samples were collected in the same manner as the fresh
ash. Soil samples from an uncontaminated area surrounding the dumpsite were collected as the
control. Soil beneath waste dump and control were UZ red ferisialitic clay soils (Series 5E)
(Nyamapfene, 1991).
3.2 Physical and chemical characterization
Soil samples were air-dried, ground and passed through a 2 µm sieve. Samples were subjected to
Aqua Regia digestion followed by assaying for Zn, Cd, Mn, Pb, Fe, Cu and Ni. Aqua Regia
solution was prepared using concentrated nitric acid and 6 M hydrochloric acid at a ratio of 1:3
respectively (Alloway, 1995). Aqua Regia was added to the solid media at a ratio of 1:5 and
digested for an hour. Solutions were allowed to cool and made up to 50 ml with deionized water
(Esakku et al., 2003). The solutions were filtered through a Whatman No. 45 filter paper. The
filtrate was assayed for the heavy metals using a Varian Version 1.13 Atomic absorption
spectrophotometer (Australia). Electrical conductivity of the filtrate was measured using an EC
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meter which uses a conductivity electrode (YSI 3200). pH of the different media was measured
using a Eutech Instruments ION700 pH meter with an electrode that was immersed into each
filtrate separately.
3.3Batch experiments
Three leaching solutions were prepared using distilled water and pH regulated using nitric acid
and sodium hydroxide to attain pHs of; 5, 7 and 9. The pH of leachate in solid waste dumps
varies in the range of 4.5-9 (Christensen et al, 2001). 10 g of samples of ash and soil were
weighed into plastic bottles and leaching solutions were added at a ratio of 1:20 (ASTM D3987,
1999). The samples were agitated for 18 hours at 25ºC at a shaking rate of 29 revolutions per
minute (ASTM D3987, 1999). The samples were allowed to settle and filtered through a
Whatman No. 45 filter paper. The control samples had to be subjected to centrifugation as
filtrate was very cloudy. pH and electrical conductivity of filtrate were measured as previously
described. The leachate solutions were assayed for the following heavy metals; Cd, Ni, Pb, and
Zn.
10g soil/ash 200ml leaching solution shaking at 29revolutionsmin-1 filtration
Figure 3.3. Batch experimental setup.
Assaying for heavy metals
with AAS and nitrate with
Cd reduction method
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3.4 Column Experiments
Columns made of inert glass material with a volume of 1.61 m3, cross-sectional area of 8.04 cm2
were used and set up as illustrated in figure 3.4.1 below.
Figure 3.4.1. Column experimental set-up
Duplicate leaching columns were packed with untreated, air-dried and sieved solid material (< 2
mm) up to a height of approximately 18,5cm ±0.05. Estimated porosity of media was 0.43 and
pore volume was approximately 63.98 cm3. To obtain uniform packing, the media was added to
the columns in small portions with a spoon and pressed with a plunger under simultaneous gentle
column vibration until the top of the soil column did not sink in further (OECD Method 312).
The columns were packed at a uniform density of 1.5±0.1 gcm-3 (USEPA). After packing, the
soil columns were pre-wetted with distilled water from bottom to top in order to displace the air
in the soil pores by water (figure 3.4.2) Thereafter the soil columns were allowed to equilibrate
and the excess water is drained off by gravity (Shackelford, 1991).
The surfaces of the soil columns were then covered by a glass wool to distribute the artificial rain
evenly over the entire surface and to avoid disturbance of the soil surface by the rain drops. Then
Soil/ashfrom
waste dump
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the artificial rainfall was added to the soil columns drop-wise with the aid of a dropping funnel
(OECD Method 312). The leaching solutions of pH 5 and 7 were applied to the soil columns
evenly at a rate of 0.3 ml/min (USEPA 2008: OPPTS 835.1240). Leachate collection for every
32±0.5 ml equivalent to 0.5 pore volumes and leachate assayed for heavy metals.
Figure 3.4.2. Columns of soil and ash packed to uniform density and pre-wetted from bottom to
top with distilled water in glass bottles.
3.5 Laboratory analytical methods
The pH values of the solution were measured by a Eutech Instruments ION700 pH meter .The
concentrations of heavy metals (Pb, Zn, Cr, Fe, Mn, Ni and Cu) in the solutions were analyzed
using AAS (Varian Version 1.13 Atomic absorption spectrophotometer (Australia). Because the
concentration of solutions and different metals varied substantially, the serial dilution method
was needed in some solutions before analysis.
3.6 Data Analysis
Statistical tests were performed using Minitab version 16 at 95% confidence interval. ANOVA
assumptions test first before data analysis. One- way Analysis of Variance (ANOVA) was used
to test the significant difference of the means for pH and electrical conductivity for the solid
media. Two- way ANOVA was used to test the significant effect of pH, material and their
interactions on leaching of heavy metals from soil and ash from waste dump.
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CHAPTER FOUR: RESULTS
4.1 pH and electrical conductivity of soil and ash from waste dump
The pH varied significant (p<0.05) among the materials. Specifically, the pH values of the fresh
ash (7.9±0.02) was significantly (p=0.02) higher than that of old ash (7.3±0.01), and soil from
beneath the waste dump (7.2±0.01) were comparable. Both fresh and old ash and soil from
beneath the dump had significantly higher pH than that of the control (6.9±0.02).
Electrical conductivity was significantly higher in soil and ash from solid waste dump than in the
control (25.40±0.55 mS). Old ash had significantly higher electrical conductivity (64.70±
0.24mS) than fresh ash and soil beneath waste dump (28.7±0.24 mS and 43.10±0.26 mS
respectively).
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4.2 Total Aqua Regia extractable heavy metals
The concentration of Cd and Ni was comparatively less than that of other heavy metals in the
soil and ash samples. Descending order of heavy metal contents in solid waste was iron,
manganese, zinc, copper, lead, nickel, cadmium. There were no significant differences between
the treatment means (p>0.05).
Treatment Zn Cu Pb Cd Fe Mn Ni
Control 52.00
± 0.50b
122.33
± 0.88c
11.73
±0.31b
0 3252.00
± 0.58a
597.67
± 0.88b
11.73
± 0.07b
Fresh Ash 401.00
± 0.55b
255.00
± 0.58a
88.33
± 0.87a
9.43
± 0.11a
3031.00
± 0.58b
355.33
± 0.88bc
15.12
± 0.1b
Old Ash 517.00
± 0.40a
186.00
± 0.58b
88.15
± 0.08a
3.70
± 0.12a
3176.70
± 0.88a
487.70
± 0.67b
20.16
±0.05a
Soil 97.00
± 0.50c
178.00
± 0.58b
22.19
± 0.07c
1.68
± 0.07b
3227.70
± 0.67b
797.00
± 0.58a
19.50
± 0.02a
Table 4.2. Total aqua regia extractable Zn, Cu, Pb, Cd, Ni, Mn and Fe in fresh ash, old ash, soil
beneath the dump from waste dump and control. Data shown are concentration means in mgkg-1
± standard error of the mean. Different letters show significant differences amongst the
treatments down a column.
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4.3 Batch leaching
4.3.1Influence of pH on leaching of heavy metals
Samples collected from dumpsite had a lower buffering capacity than the control samples.
Buffering capacities were in ascending order Fresh ash< Soil beneath the dump< Old ash
<Control. Final pH was predominantly above 7 as shown in figure 4.3.
Metal solubility generally decreased with increasing pH. This can be seen in figure 1 that
amounts of Zn, Pb, Ni leached from soil and ash from the solid waste dump decreased
significantly with increasing pH. Cd however showed a different trend in its leaching from old
ash as it increased with increasing pH. Soil beneath waste dump leached the greatest amount of
heavy metals, Zn and Pb in particular under acidic conditions (pH 5). (figure1).
19. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
Page | 19
Figure 4.3. Comparison of leaching behavior of the different media under varied pH conditions error
bars represent standard error of the heavy metal concentration means at sample size n=3
0
0.5
1
1.5
2
2.5
3
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
Control SBWD OA FA
[M+]/mg/l
Cd/mg/l
0
0.5
1
1.5
2
2.5
3
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
Control SBWD OA FA
[M+]/mg/l
Ni/mg/l
0
0.5
1
1.5
2
2.5
3
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
Control SBWD OA FA
[M+]/mg/l
Zn/mg/l
0
0.5
1
1.5
2
2.5
3
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
pH
5
pH
7
pH
9
Control SBWD OA FA
[M+]/mg/l
Pb/mg/l
20. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
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4.3.2Effect of heavy metal concentrations in soil and ash on leaching behavior
The leaching concentrations of heavy metals from the batch leaching test were rather low, and no
significant correlation was found between the total contents of heavy metals in the soil and ash
from waste dump and their leaching toxicity. Correlation analysis also showed the same result,
since the correlation coefficients ranged from −0.15 to 0.18, indicating the minor influence of the
existence of heavy metals in the bottom ash on their leachability.
The leaching behavior of the soil and ash proved to be relatively low, i.e., below the limit values
for hazardous waste: 10 mg/l for Ni, 3 mg/l for Pb, and 50 mg/l for Zn with the exception of Cd,
0.3mg/l. All metal concentrations were less than 3 mg/l, and for Cd, no more than 0.5 mg/l was
observed.
Percentage of total extractable heavy metals under batch experimental conditions and varied pH
is rather low although there are significant differences between the four media. The behavior of
the heavy metals under these leaching conditions suggests a low mobility under experimental
conditions.
There was no significant effect on the leaching of heavy metals from soil and ash from waste
dump by the interaction of the material and pH of leaching solution (p>0.05).
21. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
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Treatment
pH of
leaching
solution
% of heavy metal leached of total in soil and ash
from waste dump
Cd Ni Pb Zn
Fresh Ash 5.03 2.12 1.32 0 0.17
7.10 2.12 1.32 0 0.20
8.99 13.79 1.32 0 0
Old Ash 5.03 5.41
5.41
12.7
0
4.61 0.76
0.76
.
0.22
7.10 5.41 1.98 0.23 0.10
8.99 12.70 0.99 0.37 0.08
Soil beneath dump 5.03 4.22 4.46 11.13 3.51
7.10 19.64 5.79 2.12 0.62
8.99 5.49 4.46 0 1.64
Control 5.03 0 5.12 7.42 1.79
7.10 0 9.12 12.53 1.40
8.99 0 4.52 2.30 1.67
Table 4.3.2. Percentage means of total extractable heavy metals leached during batch
experiments at pH values 5.03, 7.10, and 8.99 (n=3)
22. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
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4.4 Column leaching
The cumulative concentrations of leached heavy metals from soil beneath waste dump, old ash and fresh
ash was significantly (p=0.00) higher than that of the control. There were significant differences in the
amounts of heavy metals leached from the ash and soil from the dump (p=0.03 and the control p=0.01).
Fresh ash leached the highest amount of heavy metals (Zn, Pb, Ni and Cd) at both pH values 5 and 7.
Area under the breakthrough curve is proportional to the mass of heavy metal leached. Since the pore
volumes are a function of time, as time increased the release of heavy metals declined as expected.
The pH of leaching solution had a significant effect on the leaching of Pb (p=0.002), Zn (p=0.001) and
Ni (p=0.001). There was no significant effect of pH of leaching solution on Cd leaching as p= 0.176.
Interaction of pH of leaching solution and nature of material had a significant effect on heavy metal
leaching from soil and ash from the waste dump (Cd; p=0.03, Zn and Pb; p=0.00, Ni; p=0.008).
Figure 4.4 shows a comparison of the heavy metals eluted from soil and ash samples from the
dumpsite at intervals of 0.5 pore volume using leaching solutions of pH 5, 7 and 9 (figure 4.4).
23. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
Page | 23
Figure 4.4. Comparison of heavy metals leached by the four media ( -old ash from waste
dump, -control, - soil beneath waste dump, - fresh ash) using cumulative heavy metal
concentrations from column experiments. Graphs (a), (b), (c) and (d) represent leaching from
the four media of; Zn, Cd, Pb and Ni respectively at pH 5.05 and (e), (f), (g), (h) show leaching
at pH 7.1
0
0.5
1
1.5
2
2.5
3
3.5
Cumulativeconcentration
mg/l
(e) Zn
-2
0
2
4
6
8
10
12
14
16
Cumulativeconcentration
mg/l
0
1
2
3
4
5
6
Cumulativeconcentration
mg/l
(b) Cd
0
2
4
6
8
10
12
14
0 2 4 6
Cumulativeconcentration
mg/l
Pore volume
(h) Ni
0
0.5
1
1.5
2
2.5
3
3.5Cumulativeconcentration
mg/l (a) Zn
0
1
2
3
4
5
6
Cumulativeconcentration
Mg/l
(f) Cd
-2
0
2
4
6
8
10
12
14
16
Cumulativeconcentration
mg/l
(g) Pb
0
2
4
6
8
10
12
14
0 2 4 6
Cumulativeconcentration
mg/l
Pore volume
(d) Ni
(c)
24. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
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CHAPTER FIVE: DISCUSSION
The current study investigated the leaching of heavy metals from an unsanitary solid waste dump
at the University of Zimbabwe and its dependence on the pH of leaching solution. The key
findings were; (1) heavy metal content in soil and ash from waste dump is significantly higher
than that in uncontaminated soils ;( 2) the leaching behavior of heavy metals in soil and ash from
waste dump is significantly dependent on pH of leaching solution and decreases as pH increased.
The highest leaching was observed from soil beneath waste dump at pH 5; (3) fresh ash, old ash
and soil beneath the waste dump have significantly higher concentrations of heavy metals
leaching than the control indicating that they could be sources of ground water contamination.
Here, we discuss the key findings of the effect of pH of leaching solution and type of solid
material on the leaching of heavy metals (Zn, Pb, Cd, Ni) from soil and ash from the waste dump
and their implications will be discussed.
Typical waste found at the waste dump were electronic and electrical waste, office waste papers,
domestic waste from halls of residence and staff quarters, litter from university grounds, solid
laboratory waste and demolition waste. Robinson (2009) found that electronic waste is a major
source of heavy metals such as lead, nickel, zinc and cadmium from solid waste dumps. This
agrees with the significantly higher heavy metal content in soil, fresh ash and old ash from waste
dump than the control. Several field-based experiments have been conducted were the apparent
migration of metals to depth has been found (Lund et al., 1976; Hinesly et al., 1979; Bell et al.,
1991; McBride et al., 1997). In column leaching experiments, it has also been shown by several
studies that heavy metals can leach through many tens of centimeters of soil (Giusquiani et al.,
1992; Antoniadis and Alloway, 2002).
The differences in the heavy metal contents of soil and ash from waste dump are due to
differences in the nature of the materials and age of material. Fresh ash was collected three
weeks after burning and old ash had accumulated over 50years since the waste dump had been
established. Soil beneath the dump has been in existence for a longer period of time and as a
result could have accumulated HM leached from underlying materials. Therefore heavy metal
contents are bound to differ as heavy metal solubility is affected by different mechanisms.
(Figure 5.1).
25. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
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Figure 5.1. Sketch of mechanisms that may control heavy metal solubility (Johnson et al., 1996).
Leachability depends on the geochemical nature of the matrix in which the metal is bound and
physical factors (Johnson et al., 1996). This study suggested that heavy metal leaching is
dependent on the pH of leaching solution with the highest leaching under acidic conditions, as
evidenced by results observed at pH 5. The residual metal content is strongly bound, probably
confined within the matrix of an insoluble solid. Heavy metal leaching decreased with increasing
pH probably due to formation of precipitates with leaching solution which cannot be leached
from the solid material.
The high pH observed for fresh ash compared to old ash indicates that aging influences pH. The
high pH for fresh ash relative to old ash could be attributed to formation of carbonates during
waste combustion. Moreover, leaching of basic cations from old ash could also lead to low pH.
However, the magnitude of pH differences between fresh and old ash was about two times lower
than values reported in previous studies, probably due to differences in the chemical composition
and age differences between the ash. The observed differences in pH could affect the leaching
behavior of heavy metals under field conditions
The observed decrease in leaching of Zn, Pb and Ni with increasing pH of leaching solution
could be attributed to decreased solubility of heavy metals with increasing pH. Solubility of Cd
could be controlled by formation of CdCO3 (Johnson et al., 1996).Alloway et al., (1985) showed
that pH, organic matter and hydrous oxide contents were the key factors controlling specific
adsorption of Cd which in turn influence leaching. This may explain Cd leaching at pH 9 in old
ash. The maximum concentrations of Ni, Pb, Cd and Zn represent 16, 12, 12 and 7%,
respectively, of the total extractable heavy metal content of soil beneath waste dump ,old ash and
fresh ash used in this experiment. It can be assumed that the remaining heavy metal cations are
bound within matrices insoluble under the given experimental conditions.
Fresh ash showed the greatest buffering capacity as pH of media returned to almost near its
initial state (pH 7.88) after pH had been altered by the three different leaching solutions in batch
26. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
Page | 26
experiments. Buffering capacities were in descending order fresh ash, control, soil beneath the
waste dump, old ash.
Zimbabwe’s Environmental Management Act (EMA) currently has no prescribed limits for
hazardous waste thus World Health Organization (WHO) limits were used for comparison in the
study. Heavy metals leached were below the WHO limit values for hazardous waste: 10 mg/l for
Ni, 3 mg/l for Pb, and 50 mg/l for Zn with the exception of Cd, 0.3mg/l in fresh ash. Thus in
environmental terms, leaching of Zn, Pb and Ni from soil, fresh and old ash from the waste dump
seems rather insignificant constituting less than 20% of total aqua regia extractable
concentrations. Cadmium leaching from fresh ash may exceed the limits may be a cause for
concern as the Cd relatively mobile in soil and very bioavailable (European Commission DG
ENV. E3, 2002).
It is noteworthy that this is a short-term study. Cumulative effects could be significant; hence
remedial or preventive measures are needed. Heavy metals were not easily leached probably due
to high adsorption capacity, CEC of the soil, or the presence of organic matter. Although the
concentration of organic matter were not measured, it is also possible that organic carbon from
waste could account for high heavy metal retention. It is thus important to put remedial measures
such as lining of the waste dump to reduce leaching of heavy metals from waste. Groundwater
processes are rather slow and eventually after long periods of time, heavy metals in leachate may
exceed limits and result in groundwater pollution.
27. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
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CHAPTER SIX: CONCLUSION AND FUTRURE RESEARCH
This study was conducted to assess heavy metal leaching from an unsanitary waste dump by
investigating the leaching of heavy metals from unsanitary solid waste dumps and its dependence
on pH of leaching solution using column and batch experiment. The key findings of the study
were:
1. Heavy metal content in soil and ash from waste dump is significantly higher than that in
uncontaminated soils posing the risk of soil and groundwater contamination
2. The leaching behavior of heavy metals in soil and ash from waste dump is significantly
dependent on pH of leaching solution and decreases as pH increased. The highest
leaching was observed from soil beneath waste dump at pH 5
3. Fresh ash, old ash and soil beneath the waste dump have significantly higher
concentrations of heavy metals leaching than the control indicating that they could be
sources of ground water contamination.
The high leaching at acidic pH suggest that acid rain may enhance heavy metal mobility in soil
and ash in the waste dump. Results showed that pH varied significantly among materials, which
could in turn affect heavy metal leaching. The high pH observed for fresh ash compared to other
materials could be attributed to the presence of carbonates from waste combustion. The results
on ash could provide some indications on what could happen if solid waste is subjected
incineration and the ash subsequently disposed of in unlined waste dumps. Also the fresh and old
ash could be sources of heavy metals observed in soil below.
Current study only investigated pH, therefore there is need for a more detailed study of factors
influencing retention and mobility of heavy metals in ash and soil beneath the waste dump.
Moreover, current study used laboratory batch and column experiments. Therefore, there is need
for field measurements of heavy metal leaching from an unsanitary waste dump using lysimeters.
Long-term assessments of waste material, the total heavy metal content should be considered
when conducted long term studies, since the metal speciation may change as a function of time
(Johnson et al, 1996).
28. Heavy metal leaching from ash and soil from an unsanitary waste dump 2014
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