Pak. J. Engg. & Appl. Sci. Vol. 14, Jan., 2014 (p. 27-37) 27 Performance Evaluation of Anaerobic-Aerobic Treatment for the Wastewater of Potato Processing Industry: A Case Study of a Local Chips Factory Sajjad Haydar 1, Ghulam Hussain 2 , Obaidullah Nadeem 3 , Husnain Haider 4 , A.J. Bari 5 and Abdul Hayee 6 1. Institute of Environmental Engineering and Research (IEER), University of Engineering and Technology (UET), Lahore. E-mail: sajjad@uet.edu.pk 2. IEER, UET, Lahore. 3. City and Regional Planning, UET, Lahore. 4. Graduate Research Assistant, University of British Columbia Okanagan, Canada. 5. IEER, UET, Lahore. 6. Graduate Student, IEER, UET, Lahore. Abstract A study was conducted to assess the performance of anaerobic-aerobic treatment system of a local potato processing industry. The wastewater treatment plant (WWTP) consisted of primary treatment, upflow anaerobic sludge blanket (UASB), activated sludge process (ASP) and secondary clarifier. The study analyzed the physical, chemical and biochemical parameters of the influent (raw sewage) as well as the effluent from each component of the plant. Grab wastewater samples were collected on weekly basis and analyzed for the pH, settleable solids (SS), total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD). Study revealed that mean influent wastewater concentrations of TSS, TDS, SS, BOD and COD were 840 mg/L, 2,396 mg/L and 18.7 mL/L, 2,186 mg/L and 3,679 mg/L, respectively. The mean percentage removal efficiency in UASB for TSS, BOD and COD was found to be 56%, 61 % and 51%, respectively. The mean percentage removal efficiency in activated sludge system for TSS, BOD and COD was found to be 70%, 57% and 48%, respectively. The mean percentage removal efficiency of combined anaerobic-aerobic system for TSS, BOD and COD was found to be 93%, 90% and 80%, respectively. The mean effluent concentrations of TSS, BOD and COD were 52 mg/L, 197 mg/L and 784 mg/L, respectively. The effluent from WWTP satisfied NEQS for TSS (200 mg/L) while NEQS for BOD (80 mg/L) and COD (150 mg/L) were not satisfied. Some operational problems, responsible for inadequate efficiencies of the plant components, were identified and solutions were suggested for these problems. Key Words: Industrial wastewater; anaerobic-aerobic treatment; potato processing; UASB; activated sludge 1. Introduction Surface water bodies in developing countries are under serious threat as a result of untreated discharge of effluents from industrial, agricultural, and domestic activities (Kambole, 2003). Pakistan being not an exception, water pollution is the most serious environmental issue due to disposal of liquid waste in surface waters. Among them the most significant are domestic wastewater and industrial effluents. Food processing industry being the second largest industrial sector in Pakistan (GOP, 2004) is among the major polluters of the water bodies. Food handling, processing, packaging and storing leads to an inherent generation of wastewater (Carawan et al, 1979). Large volumes of high strength carbohydrate rich wastewaters (Steven et al, 2005) are produced which are characterized by high biochemical oxygen demand (BOD), chemical oxygen demand (COD), large amounts of total suspended solids (TSS) and various inorganic constituents (Smith, 1976). In addition, the effluents also contain high loads of cleansing, blanching agents, salts and fibers (UNEP, 2004).