Biodegradation of Laundry Wastewater Under Aerobic and Anaerobic Conditions: A Kinetic Evaluation Keerthi Katam 1 , Debraj Bhattacharyya 2* ABSTRACT: This research was conducted in a batch mode in a laboratory-scale setup to study (1) the biodegradation of laundry wastewater under aerobic and anaerobic conditions and to quantify the degradation at steady-state in terms of kinetic parameters and (2) the inhibition caused by laundry wastewater on growth-substrate utilization by un-acclimated ethanol- enriched aerobic and anaerobic microbial cultures. The chemical oxygen demand (COD) removal was above 95% under aerobic condition; however, the COD removal varied between 70 and 88% under anaerobic condition. The steady-state kinetic parameters k, K s , Y, l m , and k d were 1.75 d –1 , 21.67 mg COD/L, 0.4 mg volatile suspended solids (VSS)/mg COD, 0.7 d –1 , and 0.06 d –1 respectively under aerobic condition; corresponding values under anaerobic condition were 4.7 d –1 , 173.67 mg COD/ L, 0.06 mg VSS/mg COD, 0.3 d –1 , and 0.04 d –1 . Laundry wastewater caused a competitive inhibition at doses above 200 mg/L under aerobic and anaerobic conditions. Water Environ. Res., 89, 2071 (2017). KEYWORDS: aerobic treatment, anaerobic treatment, biodegradation, inhibition, kinetics, laundry wastewater. doi:10.2175/106143017X14902968254638 Introduction Domestic wastewater consists of two wastewater streams: (1) grey water that originates from kitchen, bathroom, laundry, basins, and others, forms a significant portion of the domestic wastewater, and (2) the sewage (high/moderate strength) that originates from latrines and urinals. The grey water, whose organic strength is significantly less (also less hazardous) can be treated on-site and recycled or reused for irrigation, gardening, and toilet flushing or supplied to industries. Therefore, to design a simple and cost-effective grey water treatment process, characterization of wastewater and laboratory-scale treatment studies are essential prerequisites. Laundry wastewater is an important component of grey water. Laundry wastewater constitutes about 27% of grey water. Laundry detergents are alkaline in nature and have high salt and phosphorus content. These salts can accumulate in soil and can inhibit the growth of plants if laundry wastewater is reused without proper treatment. The surfactant also forms an important component of laundry detergents. This paper describes research, which was conducted to study the aerobic and anaerobic biodegradation of a real laundry wastewater. The scope of the work includes monitoring biodegradation of laundry wastewater under aerobic and anaerobic conditions, evaluating the kinetics of degradation, and studying inhibition caused by laundry wastewater on growth- substrate utilization by un-acclimated ethanol-enriched aerobic and anaerobic microbial culture. Materials and Methods The study was conducted in a Respirometer (Model no: PF8000; RSA, Springdale, Arkansas). The experiment was set up in the Environmental Engineering Laboratory of Indian Institute of Technology Hyderabad, India. Fresh laundry wastewater was obtained from IIT Hyderabad hostels every day. The chemicals used in this study were all analytical grade. An anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was purchased from Sigma-Aldrich. The aerobic culture was collected from a nearby activated sludge process-based Common Effluent Treatment Plant located in Patancheru, Hyderabad, India. The anaerobic sludge was obtained from an upflow anaerobic sludge blanket-based reactor treating domestic wastewater and is situated in Amberpet, Hyderabad, India. Semi-Continuous Study. Five hundred-milliliter Wheaton bottles were used as complete-mix test reactors. The reactors were seeded with aerobic or anaerobic sludge depending on the experimental design. The test bottles were fed with laundry 1 Department of Civil Engineering, Indian Institute of Technology Hyderabad, Kandi, Telangana 502285, India 2* Department of Civil Engineering, Indian Institute of Technology Hyderabad, Kandi, Telangana 502285, India; e-mail: debrajb@iith. ac.in WATER ENVIRONMENT RESEARCH  December 2017 2071