ABSTRACT PERFORMANCE OF A WASTEWATER TREATMENT POND SYSTEM WITH MICROFILTRATION Eric Martin The Woodlands Wastewater Treatment Plant (WWWTP) treats wastewater from the Woodlands housing community near Nipomo, California. The treated effluent is recycled for irrigation of a golf course within the community. The treatment facility consists of three facultative ponds in series followed by a microfiltration system and chlorine disinfection. Microfiltration of wastewater pond effluent is a fairly new, and potentially challenging, application of microfiltration. This thesis describes the operating conditions and behavior of the WWWTP pond system followed by a microfiltration system for the purpose of producing recyclable water fit for reuse under the regulations of Title 22. Water quality data were compiled in two ways. Weekly influent and effluent water quality and flow measurements conducted by the WWWTP operators over the course of three years were studied to show the treatment trends of the treatment plant as a whole. In addition, weekly water quality tests were performed on samples of wastewater influent, effluent, and intermediate stages of treatment for 20 weeks and studied to show treatment performance of each individual pond and the microfiltration system. Pond treatment performance was analyzed based on removal of biochemical oxygen demand (BOD) and total suspended solids (TSS) and accumulation of sludge within the pond system. Microfiltration performance was analyzed in terms of meeting the TSS discharge requirement and the membrane fouling rate. The power consumption of the pond system components and the microfiltration system were estimated. The data show that the WWWTP is producing very high quality discharge. Without microfiltration, five-day carbonaceous soluble BOD (csBOD5) averaged 3.0 mg/L and TSS averaged 42.5 mg/L. BOD5 and TSS removal efficiencies were greater than 90%. Microfilter effluent BOD5 and TSS concentrations averaged 3.0 mg/L and 1.6 mg/L, respectively. Total ammonia nitrogen was reduced to 1.61 mg/L. pH remained between 6.5 and 8.5 with few temporary exceptions. The sludge accumulation was at the high end of the range of typical accumulation rates. However, the measured rate is for the first three years of operation and so likely over-estimates the long-term accumulation rate. Although the treatment performance of the WWWTP is excellent, the power consumed was high.