Investigations on the biological treatment of mixed petrochemical industrial effluents based on acute toxicity and biodegradation characteristics

Petrochemical wastewater contains various effluents, such as purified terephthalic acid (PTA), polyethylene terephthalate (PET) and polyester (PE) effluents. The effects of mixed petrochemical wastewater on biological processes were investigated by studying their acute toxicity and biodegradation characteristics. The results of combined toxicity assays show that PTA + PET and PTA + PE wastewaters demonstrate an antagonistic effect, while PTA + PET + PE wastewater exhibit a partly additive effect. The results of aerobic biodegradation characteristics and specific oxygen uptake rate assays show that the biodegradation processes of pollutants were inhibited at the initial period and then recovered. On the contrary, there was no significant inhibition effect in the assays of anaerobic biodegradation. The analysis on the relationship of toxicity and biodegradation characteristics show that in aerobic batch assays the inhibition effect is related to the toxicity of wastewater, while anaerobic biodegradation processes were affected by the slowly biodegradable fraction in wastewater.