Reactor Performance and Morphology of Aerobic Sludge Biomass in the Presence and Absence of Ni(II) Ion in Feed

Abstract

Heavy metals are frequently encountered in domestic wastewaters (sources being the usage of paints, batteries, electronic goods, etc.). It can get carried away by storm water through municipal sewer systems to the domestic wastewater treatment plants and affecting the biomass. The present work aims to study the impact of nickel [Ni(II)] ion on settling characteristics, metabolic activity and morphology of aerobic sludge biomass in sequential batch reactors (SBRs) in addition to reactor performance. Four SBRs, namely RNi0 (control), RNi5, RNi25 and RNi75, with different concentrations of Ni(II) (0, 5, 25 and 75 mg/L, respectively) in the feed are studied to investigate its impact on aerobic sludge biomass. Reactors are operated in a sequential batch mode with a cycle time of 12 h. At the start of the stressed phase of operation, i.e., the presence of Ni(II) in feed, the COD removal of reactors RNi25 and RNi75 is deteriorated to as low as 50 and 30%, respectively. Settling velocity and compactness of aerobic biomass in the reactors with Ni(II) in feed improved as compared to control. In the recovery phase of operations, when Ni(II) is absent in feed, the reactors show stable performance with nearly 80% COD removal for all the reactors. Notable changes are observed in aerobic biomass morphology and in biomass activity for all the reactors in stressed as well as recovery phases of operations. This study presents results of extensive investigation of aerobic sludge biomass subjected to stressed phase of operation with Ni(II) in the feed and subsequent recovery phase operation with feed without Ni(II).