Investigation of Bacteria and Their Degradation Efficiency Towards Pollution Load from Industrial Effluent

Industrial pollution has continued to be a major factor causing the degradation of the environment around us, affecting the quality of water we use, the air we breathe and the soil we live on. The pulp and paper industry is playing an important role in the economic development of the Indian subcontinent; however, this industry has been categorized among 17th most polluting industries. The pulp and paper mill discharges effluent with a higher biological oxygen demand (BOD), chemical oxygen demand (COD), and recalcitrant organics with intense colour in the form of dissolved lignin and lignin-based compounds and absorbable organic halides (AOX). The colouring body present in the pulp and paper mill effluent is organic in nature and comprised of wood extractives, tannin, lignin and its degradation products formed by the action of chlorine on lignin. It is estimated that 100-120m3 of water is required to produce 1 ton of paper from wood and about 100m3 of waste water is discharged in the form of liquid effluent. One of the major problems is the persistent dark brown colour in the discharged effluent from effluent treatment plant of which the major contributors are lignin and its derivatives. The colour generated from a wood based paper mill normally is in the range of 1200-1500 PCU (Platinum cobalt unit). In view of the stringent legislation imposed by concerned authorities for discharge of effluent, Indian paper industry is making all efforts to reduce and recycle the maximum process water back to the system, so as to discharge minimum quantity of effluent into the recipient bodies. Among various approaches to overcome the problem of colour, bioremediation technique using identified micro-organisms for treatment of paper mill effluent having potential to reduce colour, lignin and other pollutants may prove an effective way to treat the discharged effluent and to make it suitable for recycling back to the process with minimum discharges with a possibility recycling about 50% of the process water back to the system using for the purpose of unbleached pulp washing and pulp dilution. The present paper basically highlights research work on isolation and screening of prominent bacteria having potential to reduce colour, lignin and other pollutants present in paper mill effluent and to develop microbial consortia having capability to treat the paper mill effluent and to achieve prescribed discharged norms in respect of colour and other presented parameters. Sixty eight bacterial colonies were isolated from the soil, sludge and effluent samples collected from wood based paper mill. Primary screening of selected bacterial strains for their lignolytic activity was done on medium supplemented with Gallic acid. Selected strains were acclimatized by sub-culturing on medium with increase in percentage of effluent in the medium. The outlet of primary clarifier (PC outlet) from Effluent treatment plant (ETP) of wood based paper mill was used for present study and decolourization efficiency of individual isolates and combination of isolates were evaluated at laboratory scale by shake flask method. Initially bioremediation experiments were carried out by twelve selected bacterial strains and analysed for various pollutional parameters of interest like colour, lignin, COD and BOD. Five bacterial strains were found to have better decolourization efficiency individually and selected for further study. Experiments were also carried out by inoculating different percentages of bacterial inoculums in wastewater in order to check the effect of concentration of inoculums on reduction of pollutional parameters. 15% bacterial concentration was found most effective for decolourization of effluent. Further bioremediation experiments were continued with consortia of bacterial stains. Combination of isolated bacterial strains showed higher reduction in colour of more than 50%, lignin around 45%, and COD, BOD of approximately 45-50%. Unsterilized conditions were chosen for bioremediation study of paper mill effluent i.e. favourable for further implementation at industrial scale. These results revealed that bacterial consortia proved to be more efficient for the treatment of pulp and paper industry effluent and may be implemented on pilot and mill scale. Keywords— Bioremediation, Lignolytic activity, Bacterial consortia, Effluent, Decolourization