Micronutrient supplements to enhance biological wastewater treatment of phosphorus-limited industrial effluent

The chemical oxygen demand (COD) removal and respiration rates of several s amples of activated sludge which were dosed with micronutrient supplements have been compared in this study. Six trace metals and three vitamins were used as chemical additives dosed into the mixed liquor. It was confirmed ex perimentally that a wastewater stream from a chemicals manufacturing plant did not contain a sufficient supply of macro- or micronutrients for efficie nt biological treatment. Some of the supplements increased the metabolic ra te of the sludge while some decreased it, indicating a range of stimulatory and toxic effects; all of the supplements resulted in increased COD remova l rates. Complex interactions between micronutrients that were dosed simult aneously were evident. Control sludge batches (receiving no micronutrient s upplements) attained an average COD removal rate of 1.335 kg COD.kg MLSS-1 d(-1). Dosing micronutrients into the mixed liquor produced COD removal rat es of up to 4.239 kg COD.kg MLSS-1 d(-1). It was concluded that micronutrie nt supplements have the potential to optimize biological treatment of indus trial wastewaters which are nutrient limited or changeable.