Assessing the impact of a landfill leachate on a Canadian waste water treatment plant

In the late 1980s, the Erb Street landfill, located in Waterloo, Ontario, Canada, had a very large leachate mound, thus a perimeter toe-drain system was installed. The leachate was sent to the Waterloo Waste Water Treatment Plant via the sewer system. This study investigated possible effects of the leachate on the treatability of the sewage with respect to oxygen demand, BOD 5 loading, nitrification capacity, and the metal concentrations in the sewage biosolids. The quantitity of leachate produced at the landfill and its contaminant concentrations were predicted and compared with measured values. Based on the predictions, it was shown that the leachate strength would not exceed its current strength in the future. The average BOD 5 and ammonia loads of the leachate were estimated to represent ∼2% of the total loads of the sewage. Also, the leachate metal contribution to the sewage was significant.