Resource recovery and energy demand reduction of a wastewater treatment plant

The goal of the wastewater treatment industry is evolving from water treatment and protecting public health towards additional goals such as (1) recovering valuable resources, e.g., nutrients and water, (2) recovering chemical and thermal energy, and (3) improving the energy efficiency of the overall process. On this perspective, this dissertation work was carried out with the focus of three major research findings: (1) nutrient recovery from a wastewater treatment plant, (2) removal of a carcinogenic metal (arsenic) from contaminated water, and (3) application of mathematical model to reduce energy demand in wastewater treatment plant. In the case of nutrient recovery research, natural zeolite and modified zeolite (CaO-Z) were used for simultaneous recovery of ammonia and phosphate from belt press filtrate, respectively. Initially, the recovery approach was investigated in the laboratory. Based on the laboratory experiment, the recovery approach was scaled up for bench-scale testing, followed by pilot-scale field testing. It was found that the ammonia-phosphate recovery system of this study can be used to recover more than 88% of ammonia as struvite. Also, about 239 kg struvite could be recovered per 100 m3 of belt press filtrate. In the case of carcinogenic metal removal research, natural zeolite was modified with anhydrous manganese chloride for selective removal of arsenic (III) and arsenic (V). It was found that the modified zeolite (MnO2-Z) can be used to remove at least 40% arsenic regardless of any environmental condition, e.g., pH, initial concentration, and ion species. In the case of optimum pH conditions at pH 9, the modified zeolite can remove almost 99.9% of arsenic (V) at low concentration levels (1 ppb to 25 ppb). In the case of the energy demand reduction research, historical data, and engineering diagrams of Roberto Bustamante Wastewater Treatment Plant were collected to construct a computer-based simulation model of the treatment plant. The computer simulation model was calibration and validated with additional sampling data collected during the summer and winter seasons. Based on the simulation results, it was found that the aeration demand can be reduced by a) modifying primary settling tank scraper design b) adding coagulant at the primary tank, and c) increasing primary settling tank feed flow. If these strategies are implemented at Roberto Bustamante Wastewater Treatment Plant, a yearly aeration energy demand reduction of 2.4 megawatts can be achieved