Abstract

This research was undertaken to study the treatability of leachate from sanitary landfills using aerobic biological processes and physical-chemical treatment methods. Treatment for polishing effluents from aerobic biological systems was also evaluated.

To ensure uniform characteristics throughout these treatability studies, leachate was collected from a laboratory lysimeter in the Water Resources Laboratory at the University of Waterloo.

The effectiveness of aerobic biological treatment was investigated using both batch and continuous flow bench-scale reactors for COD concentrations in the range of 8000 to 12000 mg/l. Removal of COD efficiencies greater than 95% was achieved. The mean hydraulic residence time was of the order of 10 days and mixed liquor suspended solids ranged from 2500 to 5500 mg/1. Phosphorus was found to be deficient and supplements were required to promote sludge growth. Design parameters were developed to model process performance and unit costs were estimated for a range of flow rates and influent COD concentrations.

Physical-chemical treatment studies were performed using a conventional jar test apparatus. Lime and alum were found to be ineffective in treating raw leachate. Lime, used in conjunction with polyelectrolyte coagulant aids, was effective for removal of suspended solids from the effluents of the biological reactor.

Activated carbon adsorption was evaluated as a tertiary process for polishing biological effluents and was shown to be effective for removing residual concentrations of COD, colour, suspended solids and trace concentrations of metallic ions.

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