Bioremediation of AOX from pulp and paper industry wastewater and AOX contaminated soils

Abstract

Bleaching of paper pulp with chlorine/ chlorine derivatives leads to formation of severalorganochlorine compounds. These compounds are collectively termed as "Adsorbable OrganicHalides" (AOX). Toxic effects of AOX are well documented. Analysis of various wastewaters,soils irrigated with wastewater and sludge show significant levels of AOX. This is a potentialthreat to the environment. Physical and chemical methods of AOX removal are not economical.Hence, bioremediation technology needs to be developed for effective, ecofriendly andeconomical management of AOX containing waste. With this aim, anaerobic biofilm reactors(7.2L) were developed in our laboratory. Anaerobic cultures degrading chlorophenols wereenriched and a consortium of such enrichments was used as the inoculum for the reactors. Thereactors were fed with nutrient medium and run at 20 days HRT and at 30 °c. Degradation of 2,4dichlorophenol (2,4 DCP) was studied at 100 ppm, 300 ppm and 600 ppm and 96.7, 74.5 and56.8 % dechlorination was observed, respectively. Anaerobic degradation at varyingconcentration of AOX from bleach composite wastewater (BCWW) was studied. Reactors fedwith 12.5, 25, 50 and 75 % BCWW v/v showed 62.9, 56.5, 55.9 and 27.1% AOX degradation,respectively. The results suggest feasibility of treating the BCWW stream separately in anaerobicreactor and then mixing the effluent with composite wastewater. The treatment will ensureprevention of AOX pollution. Fish toxicity bioassays are being carried out to study safe disposalof treated wastewater in natural water bodies. Aerobic cultures degrading different chlorophenolswere isolated. Using a consortium of these cultures bioremediation studies on AOX contaminatedsoils have been initiated.