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|Title: ||Leachability and leaching patterns from aluminium-based water treatment residual used as media in laboratory-scale engineered wetlands|
|Authors: ||Babatunde, A.O.|
|Keywords: ||Engineered wetlands|
Water treatment residual
|Issue Date: ||Aug-2010|
|Citation: ||Environmental Science and Pollution Research|
|Abstract: ||Concept and purpose
Virtually all water treatment facilities worldwide generate an enormous amount of water treatment residual (WTR) solids for which environmentally-friendly end-use options are continually being sought as opposed to their landfilling. Aluminium-based WTR (Al-WTR) can offer huge benefits particularly for phosphorus (P) removal and biofilm attachment when used as media in engineered wetlands. However, potential environmental risks that may arise from the leaching out of its constituents must be properly evaluated before such reuse can be assured. This paper presents results of an assessment carried out to monitor and examine the leachability and leaching patterns of the constituents of an Al-WTR used as media in laboratory scale engineered wetland systems.
Main features, materials and methods
Al-WTR was used as media in four different configurations of laboratory scale engineered wetland systems treating agricultural wastewater. Selected metal levels were determined in the Al-WTR prior to being used while levels of total and dissolved concentration for the metals were monitored in the influent and effluent samples. The increase or decrease of these metals in the used Al-WTR and their potential for leaching were determined. Leached metal levels in the effluents were compared with relevant environmental quality standards to ascertain if they pose considerable risks.
Aluminium, arsenic, iron, lead, and manganese were leached into the treated effluent, but aluminium exhibited the least leaching potential relative to the initial content in the fresh Al-WTR. Levels of P increased from 0.13 mg-P/g (fresh Al-WTR) to 33.9 mg-P/g – 40.6 mg-P/g (used Al-WTR). Dissolved levels of lead and arsenic (except on one instance) were below the prescribed limits for discharge. However, total and dissolved levels of aluminium were in most cases above the prescribed limits for discharge, especially at the beginning of the experiments.
Conclusions, recommendations and perspectives
Overall, the study indicate that when Al-WTR is beneficially reused for enhanced P removal in engineered wetlands as opposed to landfilling it, the leaching out of aluminium into the treated effluent beyond the prescribed limits of 0.2mg/l may be a potential problem. However, since the results obtained indicate that most of the aluminium leached out are associated with solids, a post-treatment unit which can further reduce the level of aluminium in the treated effluent by filtering out the solids could serve to mitigate this. Notwithstanding, the use of Al-WTR as a media in engineered wetlands can serve to greatly enhance the removal of P from wastewaters and also serve as support material for biofilm attachment.|
|Appears in Collections:||Centre for Water Resources Research Collection|
Urban Institute Ireland Research Collection
Critical Infrastructure Group Research Collection
Civil, Structural and Environmental Engineering Research Collection
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