ACETIC-ACID INHIBITION OF BIOLOGICAL PHOSPHORUS REMOVAL

The effects of high acetic acid concentrations on biological phosphoru s removal (BPR) in single-sludge, three-stage biological nutrient remo val systems were studied using two bench-scale units fed with mixtures of domestic wastewater increments plus increments of either a high ac etic acid industrial wastewater or additions of sodium acetate. Increm ental additions varying from 25 to 800 mg/L acetic acid delivered to t he anaerobic reactor. The systems were maintained at 20 degrees C and operated at a solids retention time of 5 days. The total nominal hydra ulic retention time was either 6 or 12 hours, depending on the total c hemical oxygen demand of the influent. The results showed that high co ncentrations of either acetic acid or sodium acetate can cause failure of BPR, with the progression of failure being typical of bacterial wa shout. The industrial wastewater was considerably more inhibitory to B PR than equivalent amounts of sodium acetate, probably because of othe r organic chemicals in the industrial wastewater, such as isopropyl al cohol and acetone, although high concentrations of inorganic chemicals such as magnesium and sulfate also were present. Other inorganic chem icals such as nickel, copper, lead, and chromium also were monitored b ut were present only in trace, nontoxic concentrations.