STUDIES ON BIODEGRADATION OF VOLATILE ORGANIC COMPOUNDS

Abstract

Air pollution is a phenomenon by which various pollutants are released into atmosphere. These pollutants may include various chemicals, particulate matter or biological matter and released from sources like motor vehicles, industries, household devices etc. Some of these are highly toxic and pose serious threat to the environment and humans. Among these pollutants volatile organic compounds (VOCs) are one such category of compounds whose accumulation in environment can cause serious health issues for humans. Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air. They are released from vehicle exhaust, paints and coatings, refrigerants and smoking and can pose serious environmental and health issues. Various technologies that are commonly used to reduce their emissions include condensation, scrubbing, incineration, catalytic oxidation and biological treatment. Biological treatment is an economic, efficient, simple, versatile method and releases minimal byproducts. It does not require complex construction facilities and is cheap and reliable. In this process microorganisms are used which oxidize VOCs into carbon dioxide and water In this study biodegradation of volatile organic compounds- toluene and o-xylene was done by using microorganism Psuedomonas putida immobilized on sugarcane bagasse. Immobilized microorganisms were utilized since it results in better removal efficiency than suspended microorganisms. Batch studies were done to study the effect of pH, temperature and initial concentration on individual biodegradation of toluene and o-xylene. Effect of pH and temperature on simultaneous biodegradation of toluene and o-xylene was also studied in batch reactor. Further, air stream containing toluene and o-xylene was treated in a continuous biotrickling filter. This reactor was packed with sugarcane bagasse with Psuedomonas pulida immobilized on it. Also, Scanning Electron Microscope studies of sugarcane bagasse before and after biodegradation confirmed the formation of biofllm on its surface. VIII It Percentage removal in batch studies was found maximum at pH 7 and temperature 30 °C in all cases. It was also found that when initial concentration of substrate was increased it took more time for complete degradation. Also, at higher concentrations percentage removal achieved a less constant value. Biotrickling Filtration suggested that removal efficiency of toluene was higher than that of o-xylene in all three phases. After 42 days of operation of biotrickling filter elimination capacity of toluene was 108 g m 3h while that of o-xylene was 102 gm 3h 1 .