Trace metals (K, Fe, Mg, Cu, Ca, Mn, Al, Zn, Mo, Co) and vitamins (biotin, niacin, pyridoxine, lactoflavin, thiamine, pantothenic acid) were tested for enhancing chemical oxygen demand (COD) and toxicity removal in activated sludge treating trade effluent. Rapid respirometry screening indicated that micronutrient addition could not ameliorate macronutrient deficiencies, but could significantly improve the degradation of hard COD in the wastewater (up to 4.24 kg COD/kg MLSS/d, i.e. 320% of the control) with no significant effect on the air requirement of the sludge. Several positive effects led to the conclusion that micronutrients have the potential to optimise the process performance of activated sludge plants treating industrial wastewater. Porous pots were used to further trial eight of the micronutrients. The retention of biomass in the pots was increased in all cases. Improvements in the degradation of COD (up to 260% of the control) were observed while biological oxygen demand (BOD) degradation was not affected. This implied the use of recalcitrant substrate components as a food source. Toxicity tests showed that the effluents from the experimental porous pots were less toxic than the control effluents. The effects of niacin addition in activated sludge treatment of industrial waste at pilot-scale were: improved sludge handling, increased COD, ammonia, suspended solids and phosphorus removal. Several industrialists saw micronutrient addition as a route to successful adaptation of processes to accommodate toxicity– based legislation.

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