Studies On Isolation, Identification And Characterization Of Bactreia Strains To Degrade Water-Based Detergent Wastewater

Water-based detergent(WBD) is widely used in mechanical, chemical, petroleum, metallurgical industry. Its main ingredient, linear alkylbenzene sulfonate(LAS), as the world’s most highest production-volume anionic surfactant, has been widely used. The LAS in WBD wastewater has the characteristics of high toxicity, persistence in the environment, thus it can cause great harm to the ecological environment and human body. Biodegradation is an important pathway to remove LAS in the environment, and present most of the studies focus on the isolation and degradation mechanism of LAS as the sole carbon source, whereas there are few researchs on the degradation of LAS by co-metabolism mechanism.In order to investigate the characteristics of co-metabolism degradation of LAS. Two strains with high efficiency of degrading LAS, named as L2 and L15, were isolated from activated sludge of aeration tank and the secondary sedimentation pool in Shenzhen sewage treatment plant by selective enrichment method. Based on physiology and 16 S rRNA gene sequence analysis,L2 was determined to Klebsiella sp., while L15 was identified as Enterobacter sp.Different levels of glucose, sucrose, starch, sodium citrate and sodium acetate were employed as co-metabolism substrates to study the degradation efficiency of LAS by the two strains. The results showed that co-metabolism substrates can all promote LAS degradation and glucose has the most notable effect on LAS degradation. Thus, glucose was used as the best carbon source for LAS co-metabolic degradation. The degradation rate of LAS(50mg/L) by L2 was up to 94.2% when glucose was chosen as growth substrate under the conditions as : 30℃, pH 7.5, the mass ratio of glucose and LAS 20:1. The degradation rate of LAS(50mg/L) by L15 was up to 92.2% under the conditions as : 30℃, pH 7.5, the mass ratio of glucose and LAS 16:1. The degradation reaction processes of the two strains are in accordance with the first order kinetic characteristics.The intermediate products sulfophenyl carboxylic acids of LAS were determined by HPLC-MS. Sulfonic acid groups were degraded to SO42- which was detected by Ion chromatography.