Acetic acid inhibition of biological phosphorus removal

Abstract

The effects of high acetic acid concentrations on biological phosphorus removal (BPR) in single‐sludge, three‐stage biological nutrient removal systems were studied using two bench‐scale units fed with mixtures of domestic wastewater increments plus increments of either a high acetic acid industrial wastewater or additions of sodium acetate. Incremental additions varying from 25 to 800 mg/L acetic acid delivered to the anaerobic reactor. The systems were maintained at 20°C and operated at a solids retention time of 5 days. The total nominal hydraulic retention time was either 6 or 12 hours, depending on the total chemical oxygen demand of the influent. The results showed that high concentrations of either acetic acid or sodium acetate can cause failure of BPR, with the progression of failure being typical of bacterial washout. The industrial wastewater was considerably more inhibitory to BPR than equivalent amounts of sodium acetate, probably because of other organic chemicals in the industrial wastewater, such as isopropyl alcohol and acetone, although high concentrations of inorganic chemicals such as magnesium and sulfate also were present. Other inorganic chemicals such as nickel, copper, lead, and chromium also were monitored but were present only in trace, nontoxic concentrations.