Leachate treatment: Assessment of the systemic changes in the composition and biodegradability of leachates originating in an open co-composting facility in Canada

Abstract

Leachate characterization is critical in order to design adequate treatment systems as well as establish effective management strategies that take into account systemic factors affecting the composition and biodegradability of the contamination. The purpose of this study is to provide an exhaustive analysis of composting leachate composition, with a particular focus on leachate from Northern climates. Leachate samples were analyzed on a monthly basis (from May to October) for 25 water quality parameters in three different locations (fresh leachate and two retention basins) at a co-composting facility located in Quebec, Canada. The highest concentrations of total nitrogen, ammoniacal nitrogen, total phosphorus, chemical oxygen demand and hazardous metals (Al, Cd, Cr, Ni, Pb, and Zn) were all measured in July and August, which correlates with the thermophilic phase of the composting process. A statistical analysis was performed to correlate both the climatic and operational influence factors to the leachate contamination. Temperature was found to be positively correlated, while precipitations were negatively correlated, with most quality parameters in fresh leachate. The biodegradability of organic contamination was also studied. The lowest biodegradability was observed in July and August as well. During these two months, the organic contamination was comprised of >85% of fulvic- and humic-like substance due to the humification of organic waste during the composting process. BOD5/COD ratios were <0,1 for at all locations. Finally, the suggested treatment option for this wastewater is the combination of membrane bioreactors with advanced oxidation processes.