Evaluation of the Efficacy of a Treatment Pond System for Removal of Concentrated Iron and Arsenic Produced from Water Treatment Plant (WTP) Wastewater

Abstract

AbstractDrinking water treatment plant (DWTP) processes generate wastes in the form of residual wastewaters and sludges. The quality of the wastes generated is dependent on the characteristics of the source of raw water. Generally, groundwater contains higher metal(loid) concentrations than surface water due to its contact with rocks and minerals, whereas surface waters contain more organics. The use of raw groundwater may cause a magnification of metal(loid)s such as arsenic (As) and iron (Fe) in residual wastewater from WTPs, making disposal problematic. Therefore, it is necessary to evaluate the quality of residual wastewaters prior to their release to the receptor water. This research evaluated the effectiveness of a Waste Stabilization Pond (WSP) system in treatment of As and Fe in residual wastewaters of a DWTP in southern Saskatchewan, Canada. The WSP system consists of a series of five ponds designed to settle out and oxidize contaminants. Iron and As concentrations across the individual ponds were measured on daily and monthly bases and the effectiveness of the pond system for reducing suspended and dissolved metal(loid)s was evaluated. The concentration of Fe reliably decreased for the first three ponds, before increasing in the final two Ponds. The As concentration generally increased from Ponds 1 through 3, decreased in Pond 4, and increased in Pond 5. Environmental guidelines for As concentrations are typically exceeded in the WSP effluents and individual ponds, while Fe concentrations currently meet guidelines for all ponds in the WSP system.