Effects of the Fredericton Landfill Leachate on the Municipal Wastewater System

Abstract

Like many municipal landfills, the Fredericton Region Solid Waste Commission discharges landfill leachate directly into the public sewage system, allowing leachate to mix with incoming wastewater as it travels to the Fredericton Area Pollution Control Commission. Inorganic analysis was performed on the landfill leachate and three samples of leachate/wastewater mixture taken from various points along the leachate flow path. Sulfate and phosphate anions were analysed spectrophotometrically, and analysis of chloride was performed by ISE. Inductively coupled plasma-mass spectrophotometry was the analytical method used to determine major cation and heavy metal concentrations in the samples. A steady dilution trend of the landfill leachate by wastewater was studied in elements showing conservative behavior in the system, including Mg, B, alkalinity, K, and Zn. Saturation indices calculated by geochemical modeling also show similar trends in decreasing saturation of minerals composed of the conservative elements with increasing distance from the landfill. Other elements including Na, Cl, Al, Ba, Pb, and Sb have elevated concentrations at a number of sample points after the landfill site, implying enriched wastewater is entering the sewage network from external sources. Copper concentration fluctuates randomly throughout the network, therefore it is a component in numerous types of wastewater with no specific point source. Levels of contaminates in the influent entering the plant are well below recommended inhibitory levels for the activated sludge sewage treatment process. Therefore, the sewage treatment process is not expected to be affected by contaminates in the wastewater from the landfill leachate and other wastewater sources. Effluent discharged into the St. John River meets water quality guidelines for every element analyzed, with the exception of Ca. With dilution factors in the river long term problems from Ca entering the water are not expected, but point source problems associated with fish toxicity should be addressed