Electrical and electronic waste characterization and biodegradation of oil and grease by isolated indigenous bacteria

Abstract

Oil and grease (O&G) are widely used in machine related processes and operations. It provides a fluid layer to separate moving surface of machines, minimizing heat and friction and hindering surface wear under extreme temperature and pressure. Hence electrical and electronic industry (E&E) has the possibility to generate O&G in their E&E effluent. However, the O&G content in E&E effluent became an issue due to factory located in catchment area. Thus it is strictly needed to meet permissible discharge limit of standard A. O&G contamination is hazardous to the aquatic environment as it contains toxic substances that are believed to be carcinogenic, mutational and exert toxic effects. Physical and chemical treatment system are inefficient and costly to remove low concentration of O&G (<10 ppm). Hence, the use of biological treatment to treat wastewater sample contaminated with O&G from E&E industry was investigated. The biodegradation experiment was carried out using Aeromonas hydrophila UTM2 which has been deposited in GenBank with accession number KF049214. The O&G sample screened using GC-MS revealed one of the phenolic compounds which is 2,6-di-tert-butylphenol as one of the components. Hence phenol degradation as representative of O&G derivatives was also carried out. Parameters such as effect of initial phenol concentration, contact time, initial pH, and effect of carbon and nitrogen supplementation on degradation of O&G at 200 rpm, 30oC were studied in batch system. Aeromonas hydrophila UTM2 was chosen for biodegradation study as it showed the higher phenol degradation for phenol concentration of 10 mg/L, 50 mg/L and 100 mg/L. The highest degradation for phenol was 100% and 70.58% when the medium was separately supplemented with glucose (96 hours) and NH4NO3 (120 hours), respectively at initial concentration of 50 mg/L phenol. Complete degradation of O&G using real E&E wastewater was achieved at initial concentration of 5.19 mg/L after 4 hours at pH 7 when the medium was supplemented with tryptone and lactose separately. These optimization parameter for phenol and O&G were applied in real E&E wastewater subjected for phenol and O&G degradation. Complete degradation was achieved for phenol (0.198 mg/L) and O&G (4.88 mg/L) after 2 hours incubation in 1 g/L of tryptone and 1 g/L lactose supplementation at pH 7.0 at 200 rpm and 30oC. Therefore, Aeromonas hydrophila UTM2 can be applied for degradation of low concentrations of O&G found in E&E wastewater.