Bioremediation of soil contaminated with organochlorines of pulp and paper industry wastewater

Abstract

The quality of life on earth is linked inextricably to the overall quality of environment. Due to enormous increase in world population there is a constant increase in demand of land for residential, industrial and agricultural purposes. The ways in which the available resources such as land and water are used show our carelessness and negligence. The past and present activities such as production, use and disposal of hazardous substances have led to the contamination of water and land. Much of the inherited legacy of environmental contamination can be traced back to industrial, municipal and military waste management practices that advocate disposal rather than treatment. Contaminated land is a potential threat to human health. It demands efforts to clean these sites, either as a response to the risk of adverse health or environmental effects caused by contamination or to enable the site to be redeveloped for use. The example of pulp and paper (PAP) industry is amongst the one whose activities result in environmental contamination. This industry requires huge quantity of fresh water, approximately 150-175 m3/ton of pulp produced. It throws almost equal quantity of water as treated effluent in nearby water bodies or the effluent is used for irrigation. The pollution control norms for this industry like in case of many other industries, makes treatment obligatory for wastewater with reference to COD, BOD, TDS, color, etc. In addition it also necessitates removing Adsorbable Organic Halides (AOX) before the wastewater is discharged. AOX is a group of more than 300 different organochlorines and belong to a class of recalcitrant chemicals as they endure for long periods in the ecosystem. Some of the compounds are toxic and show the tendency to bioaccumulate due to their lipophilic nature. Most of these compounds are proven carcinogens (Group 2B) and mutagens and even as Endocrine Disrupting Chemicals (EDCs). It was only recently that the Central Pollution Control Board (CPCB) has included AOX discharge limit as one of the criteria for disposal of PAP industry wastewater, but has not made it mandatory for the industry to completely remove AOX as is the case in USA and some other countries. As per norms, AOX discharge limit was set to 1.0 kg AOX/ton of paper produced from February, 2008. Introduction of AOX discharge limit has made it compulsory for the PAP industry to bring down the AOX level to prescribed limits. Various physico-chemical and biological treatment methods are being developed and attempted but these methods do not necessarily ensure complete removal of AOX from wastewater. Also there are no attempts made to treat soil which has already been contaminated over the years due to AOX discharge.