Effect of biosurfactants on the biodegradation of hydrocarbons in waste water

The release of specific industrial wastewaters, including nonbiodegradable and/ortoxic pollutants, to receiving environments is one of the most significant type ofenvironmental pollution by hazardous wastes. Biological treatment of wastewater isoften the most economical alternative when compared with other treatment options.However, industrial effluents are known to contain toxic and/or non-biodegradableorganic substances and conventional biological treatment processes are not efficientin these cases. Thus, they require some enhancements due to the presence ofrefractory or toxic compounds in the wastewaters. For this reason, the use ofsurfactants in the biodegradation of persistent organic pollutants by biologicaltreatment was investigated as an enhancement technique for the biological treatmentprocess.In this study, the effect of biosurfactant on biodegradability of 2,4-dichlorophenol(2,4-DCP) and 4-chlorophenol (4-CP) with using acclimated culture was investigatedby activated sludge bioreactor with changing chlorophenols loading rate and sludgeretention time (SRT), and the effect of biosurfactant on 4-CP degradation inunacclimated culture was studied. Glucose as growth substrate and JBR 425rhamnolipid as biosurfactant were used. Control and test reactors were operatedthrough parallel experiments.During the experimental study, enhanced biodegradation of 2,4-DCP and 4-CP wasobserved in biosurfactant added activated sludge systems (test reactors). Especially,effect of biosurfactant was much higher at lower sludge ages and unacclimatedculture. COD, 2,4-DCP and 4-CP biodegradation rates were much higher inbiosurfactant added systems relative to control reactor. Since biosurfactant existenceattenuated chlorophenol toxicity on the microorganisms, bioactivity of activatedsludge was maintained during operation periods. Also, the presence of biosurfactantstimulated bacterial growth.Keywords: Activated sludge; Bacterial growth; Biodegradation; Biosurfactant; 2,4-Dichlorophenol (2,4-DCP); 4-Chlorophenol (4-CP); Sludge retention time (SRT);Toxicity.