Recovery potential of aerobic sludge biomass stressed with Cu(II) laden piggery wastewater

Abstract

Piggery wastewater (PWW) contains a variety of pollutants, and lack of treatment infrastructure in piggery farms often results in the discharge of PWW into nearby drains, eventually reaching sewage treatment plants. It may adversely affect the sludge biomass of the treatment plants. This study investigated the effects of prolonged exposure to PWW and copper-laden (40 and 80 mg/L) PWW on the quality of sludge biomass. The results revealed that PWW-exposed reactors experienced a significant decrease in COD removal (65–76% compared to 95% in the control reactor). Additionally, there were changes in sludge characteristics, including a decreased sludge volume index (SVI) and an increased interface settling velocity (ISV). Further addition of PWW+Cu(II) stress significantly reduced COD removal (8–29%), the filamentous index and also lowered cell viability and enzyme activity. However, partial recovery was observed after discontinuing PWW+Cu(II) exposure, particularly at 40 mg/L of Cu(II) concentration. The study is significant for practical wastewater treatment, as it deals with multi-stress conditions caused due to Cu(II) metal laden piggery wastewater. The investigation recommends preliminary tests (microscopic examination and aerobic sludge biomass activity test) and confirmatory tests (cell viability tests and amplified ribosomal DNA restriction analysis) to be used for the evaluation of aerobic sludge biomass quality.