E. O. Dada; K. L. Njoku; A. A. Osuntoki; M. O. Akinola
Abstract
Wetlands play important strategic ecological and life-supporting roles. As a result, they are continuously exposed to pollutants inflow including heavy metals. The aim of this research was to evaluate the heavy metal remediation potential of a tropical wetland earthworm, Libyodrilus violaceus. L. violaceus ...
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Wetlands play important strategic ecological and life-supporting roles. As a result, they are continuously exposed to pollutants inflow including heavy metals. The aim of this research was to evaluate the heavy metal remediation potential of a tropical wetland earthworm, Libyodrilus violaceus. L. violaceus were exposed to soils contaminated with different concentrations of heavy metals using natural optimal soil density of 18 worms per kg soil, for 12 weeks. Relative to their initial concentrations, there were significant reductions of Zn, Pb and Cd at the end of the experiment. From the soil contaminated with a combination of Zn, Pb and Cd, the highest significant (p < 0.05) Cd reduction of 8.08 mg/kg soil occurred in the 12th week, the highest significant (p < 0.05) Zn reduction of 37.47 mg/kg soil occurred in the 8th week, while Pb recorded the highest but not significant (p > 0.05) reduction of 19.07 mg/kg in the 12th week. The effect of addition of cow dung on the ability of L. violaceus to reduce heavy metals was generally low. L. violaceus is recommended as a good candidate for the remediation of low to moderate heavy metal contamination in wetland ecosystem..
I. M. Rafizul; M. Alamgir
Abstract
This study illustrates the leachate treatment efficiency based on leachate pollution index (LPI) of pre- treatment leachate as well as post-treatment leachate with chemical coagulants. Leachate samples were collected at regular intervals of time from the leachate collection chamber of the landfill lysimeter ...
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This study illustrates the leachate treatment efficiency based on leachate pollution index (LPI) of pre- treatment leachate as well as post-treatment leachate with chemical coagulants. Leachate samples were collected at regular intervals of time from the leachate collection chamber of the landfill lysimeter at KUET campus, Bangladesh to compute its pollution potential. The landfill lysimeter consists of one open dump lysimeter-A with leachate detection (A1) and collection system (A2) as well as two sanitary landfill lysimeters B and C having two different types of cap liner. The relevant parameters of leachate sample were measured in the laboratory to evaluate sub-pollution (sub-LPIs) in terms of LPI in organic pollutant (LPIor), inorganic pollutant (LPIin) and heavy metal (LPIhm) as well as the overall LPI. Moreover, the values of LPI in pre-treatment leachate were to be found 19.53, 25.33, 23.48 and 23.74 for the A1 and A2 systems of open lysimeter-A, as well as the collection systems of sanitary lysimeters- B and C, respectively. It reveals significantly the higher values than that of LPI of 5.77, 7.38 and 7.38 for the maximum leachate discharge standards of Bangladesh, India and Hong Kong, respectively. The leachate was then treated with ferric chloride (FeCl3), poly alluminum chloride (PAC), ferrus sulphate (FeSO4) and aluminum sulphate (Al2(SO4)3) in various dosages and pH values. The concentrations in post-treatment leachate by using FeCl3 at optimum dosage were to be found below the limit of maximum leachate discharge standards. Study also reveals the values of LPI of 5.32, 5.69, 5.32 and 5.24 in post-treatment leachate for the A1 and A2 systems of open lysimeter-A, as well as the collection systems of sanitary lysimeters-B and C, respectively belowthe values of LPI in leachate of maximum discharge standards. Finally, it can be concluded that differences in the level of contaminants of pre- treatment and post-treatment leachate indicated the role of leachate treatment system in minimizing the level of contaminants and lowering the risk of leachate contamination based on LPI.