REMOVAL OF CHLORO AND NITRO AROMATIC WASTE-WATER POLLUTANTS BY OZONATION AND BIOTREATMENT

Synthetic wastewater containing a mixture of 10 different chloro and n itro aromatic pollutants was treated in batch ozonations and in a cont inuous combined ozonation-biodegradation system. The pH dependency of elimination of individual aromatics and of total organic carbon (TOC) was studied in batch ozonations. Experiments at pH 7 showed higher deg radation and elimination rates than those at pH 2 and pH 12. A rapid i ncrease of the dissolved ozone concentration after elimination of the aromatics was observed. This was very useful for on-line control of th e combined process. Ozonation products were shown to be highly biodegr adable through high oxygen uptake rates of biomass. Total mineralizati on of recalcitrant chloro and nitro aromatics was observed in the comb ined ozonation-biotreatment Most significant improvement of ozone effi ciency was obtained by controlling dissolved ozone concentration at op timal levels. A slight further enhancement was observed by recycling t he liquid between the bioreactor and the ozone reactor.