Over recent decades, environmental regulations on wastewater treatment plants (WWTP) have trended towards increasingly stringent nutrient removal requirements for the protection of local waterways. However, such regulations ignore the other environmental impacts that might accompany the apparent improvements to the WWTP. This PhD thesis used Life Cycle Assessment (LCA) to quantify these environmental trade-offs, and so better inform policy makers on the wider benefits and burdens associated with wastewater treatment. A particular focus was also given to the generation of methane and nitrous oxide in wastewater systems, since the quantification of greenhouse gas (GHG) emissions from WWTPs is presently a substantial area of uncertainty. Rapid changes to the GHG regulatory landscape mean that this level of uncertainty, now represents an unacceptable business risk for many water utilities. Specifically, there were three research objectives of this thesis: Research Objective No.1 – Environmental optimisation of wastewater treatment systems – For typical receiving environments, the optimum wastewater treatment system configuration is not necessarily at the limit of best practice for nutrient removal. The LCA approach to this research objective was divided into two stages. In stage I, a comprehensive desk-top life cycle inventory of ten different wastewater treatment scenarios was completed. The scenarios covered six process configurations and treatment standards ranging from raw sewage to advanced nutrient removal. It was shown that physical infrastructure, chemical usage and operational energy all increased with the level of nutrient removal. These trends represented a trade-off of negative environmental impacts against improved local receiving water quality. In stage II of the LCA, a quantitative life cycle impact assessment of the ten scenarios, referenced against Australian normalisation data, was completed. From a normalised perspective against Australian society, the contribution of WWTPs to headline issues such as global warming and energy consumption was found to be very small. The more prominent environmental impact categories were eutrophication due to nutrient discharge and toxicity issues, due to heavy metals in biosolids. There existed a broader environmental trade-off for nutrient removal, that could only be justified by society and regulators implicitly placing higher value on local water quality, than on other global environmental pressures. In light of this quantitative LCA, regulatory agencies should consider the broader environmental consequences of their policies such as the Queensland Water Quality Guidelines. It is suggested that the scope of WWTP licensing considerations should be widened from a singular focus on water quality objectives, to a more comprehensive LCA-based approach. Research Objective No. 2 – Quantification of nitrous oxide emissions from biological nutrient removal (BNR) wastewater treatment plants – Current GHG assessment methods for wastewater treatment plants are grossly inaccurate because of significant unaccounted N2O emissions. The research for objectives two and three was funded by the Water Services Association of Australia (WSAA), which is the peak body of the Australian urban water industry. Thus, whilst the earlier LCA results suggested that GHG emissions from WWTPs were insignificant from a national perspective, the industry is actually very engaged on this issue from an environmental responsibility and business risk perspective. This PhD study adopted a rigorous mass balance approach to determine N2O-N generation at seven full-scale WWTPs. The results varied considerably in the range 0.006 – 0.253 kgN2O-N generated per kgNdenitrified (average: 0.035 +/- 0.027). These results were generally larger than the current default value assumed in the National Greenhouse and Energy Reporting (Measurement) Technical Guidelines (i.e. 0.01 kg N2O-N.kgN-1denitrified). High N2O-N generation was shown to correspond with elevated bulk NO2--N concentrations in the bioreactor. The results also suggested that WWTPs designed for low effluent TN have lower and less variable N2O generation than plants that only achieve partial denitrification. Research Objective No.3 – Quantification of methane emissions from low-strength wastewater collection systems – Current default GHG assessment methods for sewerage systems are grossly inaccurate because of significant unaccounted CH4 emissions from rising mains. Presently, international GHG guidelines state that “wastewater in closed underground sewers is not believed to be a significant source of methane” (IPCC, 2006). However, the results of this PhD research demonstrated that methane generation in rising main sewers is substantial. It was shown that dissolved methane concentrations were dependent upon pipeline geometry and sewage residence time. Consequently, it was possible to develop a simple, yet robust, theoretical model that predicted methane generation from these two independent parameters. This model provides a practical means for water authorities globally to make an estimate of the currently unaccounted methane emissions from pressurised sewerage systems.

The laboratory-scale University of Cape Town (UCT) process was designed to investigate the effects of changing COD/TP ratios on the performance of biological nutrient removal (BNR) processes. Specific objectives of the research were to investigate the effects of COD/TP ratio on the rates of phosphorus removal, COD removal, nitrogen removal, PHB utilization and oxygen uptake. The system was fed with municipal wastewater and operated at 20° C. The influent COD concentration was held approximately constant while the phosphorus concentration was varied to obtained the desired COD/TP ratio. Once robust enhanced biological phosphorus removal (EBPR) has been established, the COD/TP ratios of 20, 30, 40 and 60 were investigated. The COD/TP ratio of the influent wastewater was observed to have a substantial effect upon the performance of the UCT BNR system. The amount of phosphorus removed by the system and the percent phosphorus in the aerobic zone MLVSS decreased as the COD/TP ratio increased. In addition, the amount of phosphorus released in the anaerobic zone per unit of COD removed in the anaerobic zone increased as the COD/TP ratio decreased. From this research, the amount of anaerobic COD removal required to remove 1 mg/L of phosphorus in the aerobic zone approached a minimum value as the COD/TP ratio decreased. It was also shown that PHB production increased as the COD/TP ratio increased. The highest specific oxygen uptake rate was always observed in the second aerobic reactor and tended to increase as the COD/TP ratio increased. However, the changes in the COD/TP ratio did not significant affect COD removal, nitrogen removal and the observed yield coefficient, but did strongly affect the MLSS concentration. The MLSS concentration at the COD/TP ratio of 60 was only 55% of that at the COD/TP ratio of 20. A high level of anaerobic COD removal, an elevated percent phosphorus in the waste activated sludge (WAS) and a high soluble effluent phosphorus concentration can be used as indicators that the system is operating under COD limiting conditions. Several phenomena were also observed during this research. Firstly, the performance of the UCT BNR system for EBPR was greatly enhanced by reducing the aerobic volume. Secondly, the correlation between non-oxic phosphorus release and the aerobic phosphorus uptake improved when anoxic phosphorus release was taking into consideration. This indicated that the anoxic phosphorus release was not secondary release once the aerobic zone volume was reduced. Finally, no denitrification was observed in the aerobic zone from this study, based on the assumption that 12% of nitrogen was required for bacterial growth. / Master of Science

This research entails the investigation of the effects of a bioaugmentation product from BiOWiSH® called Aqua, referred to as “Aqua” for the remainder of this paper, on the nitrogen removal rate in a membrane aerated bioreactor (MABR). This research was conducted using a MABR design that consisted of a silicone membrane and continuous flow airline with compressed air. The membrane system was designed to supply oxygen, creating an aerated layer at the membrane-biofilm interface and an anoxic layer at the biofilm-water interface. Laboratory experiments were conducted to compare the nitrogen removal rates of natural bacteria alone to natural bacteria paired with Aqua. However, it was not possible to determine if a difference existed between the nitrogen removal rates of the MABR systems with only natural bacteria versus those with natural bacteria augmented with Aqua. The mean nitrogen removal rate observed when the media in the system reached steady state was 0.39 mg-N/L-hr. with a carbon to nitrogen (C: N) ratio of 12:1. The only increase in the nitrogen removal rate observed was when the C: N ratio was doubled to 24:1 and the nitrogen removal rate increased to 0.56 mg-N/L-hr. Although it appeared that the Aqua did not have an influence on the nitrogen removal rate in the MABR systems, many other variables still need to be assessed to reach a conclusion. To improve the efficiency of the system more tubing should be added, or the glucose should be removed from the growth media because the maximum O2 mass transfer rate is only enough O2 for nitrification. The addition of glucose at 12:1 ratio increased the O2 demand in the system to be five times greater than the O2 supplied from the silicone tubing. This research determined that use of trace minerals, Aqua dosing method, and Aqua dosing concentration were not contributing factors in nitrogen removal from growth media under the conditions of this experiment.

Facing the pressure of population growth and global warming, this dissertation provided an array of innovative carbon-efficient wastewater treatment technologies for resource recovery, process intensification, and anammox featured next generation biological nutrient removal (BNR) technologies. These technologies aim to supplant traditional carbon-intensive treatment processes with more sustainable alternatives. To this end, the dissertation first comprehensively reviewed what resources can be recovered from wastewater, and how these valuable resources can contribute to the carbon neutrality in water resource reclamation facilities (WRRFs) and help achieve sustainable society development. Then, the effect of mixed liquor recycle (MLR) configurations on the process intensification through continuous-flow aerobic granulation was explored in plug flow reactors. The results demonstrated that MLR configuration could hinder the sludge granulation, but the hindrance could be alleviated to some extent by its location change. In order to eliminate the energy consuming MLR, endogenous denitrification was taken advantage through a synergistic integration with partial nitrification, partial denitrification anammox (PdNA), and enhanced biological phosphorus removal (EBPR). This idea was tested in a pilot setup treating real primary effluent under highly variable influent conditions and low temperatures. The results showcased substantial carbon savings while meeting the stringent effluent requirements. To take a deeper dive into the PdNA performance and the underlying mechanisms, two parallel pilot-scale moving bed biofilm reactor (MBBR) treatment trains fed with methanol and glycerol, respectively, were operated in a local WRRF. Their efficacies in achieving stringent nutrient removal targets and carbon savings were compared. The impacts of operational conditions on the mechanisms and performance were elucidated. In the culmination of this dissertation, a sidestream process intensification and resource recovery technique, namely thermal hydrolysis pretreatment (THP) enhanced anaerobic digestion (AD), was experimented to compare the efficiencies between thermophilic and mesophilic AD when integrated with THP. To sum up, this dissertation not only advanced our understanding of carbon-efficient wastewater treatment processes but also laid the groundwork for their practical implementation, contributing to the global effort towards sustainability. / Doctor of Philosophy / Wastewater treatment consumes 3-4% of the energy produced in the U.S. and contributes to approximately 1.6% global greenhouse gas emissions. This dissertation aims to advance a series of carbon-efficient technologies specifically tailored for sustainable wastewater treatment. To this end, a variety of valuable resources that can be recovered or reused in wastewater treatment plants was firstly reviewed. Then, an advanced technology that can turn dispersed bacteria into bacteria aggregates was tested with real wastewater in a local wastewater treatment plant. Although these bacteria aggregates allow more wastewater to be treated with less small footprint, which was great, it was realized from this study that the formation of these bacteria aggregates was hindered by the nitrate water recycle which has been commonly practiced for using influent carbon for nitrogen removal. This nitrate water recycle consumed excessive energy for its high flow rate. To save this energy, a novel bioprocessing design was developed to eliminate the need for this nitrate water recycle by using carbon stored in bacterial cells. This new design also incorporated phosphorus recovery capacity and a low carbon nitrogen removal technique into one consolidated system to create an all-in-one solution to meet the stringent wastewater treatment requirement. This low carbon nitrogen removal technique harnessed a special group of bacteria that can use ammonia to reduce nitrite to nitrogen gas. Hence, only minor carbon source needs to be provided to reduce nitrate to nitrite for these bacteria to utilize. Two types of carbon sources, namely methanol and glycerol, were compared in a pilot-scale study to understand their efficiencies in generating nitrite. Results indicated that although both types of carbon sources can work, methanol is better suited for low strength wastewater treatment. These results provided an engineering basis for the full-scale application of the technology in the same wastewater treatment plant where the pilot study was performed. Besides liquid treatment, a carbon efficient solid treatment technology was also studied. The bottleneck constraining the rate of sewage sludge conversion to flammable menthane gas was identified, which provided engineering guidance for the design of the solid treatment process that can destroy more sewage sludge within smaller reactor spaces. In essence, this dissertation offers promising solutions for modern wastewater treatment plants to achieve low carbon wastewater treatment without compromising the treatment performance.

The objective of this research was to design an alternative wastewater treatment system for turkey processing plants to recover energy and reduce N and P to allowable discharge levels. The objective included: 1. Determine the quantity and quality of biogas produced from the turkey processing wastewater (TPW) and COD reduction efficiency. 2. Design a waste treatment system and validate proof of concept for simultaneous P and N removal with a goal of attaining effluent concentrations of 0.1 mg/L and 4 mg/L, for P and N, respectively. A lab-scale complete mixed anaerobic digester was used for turkey processing wastewater (TPW) digestion and biogas recovery running for 6 months. Along with the anaerobic digester, a two-sludge system called A2N-SBR consisting of an anaerobic-anoxic sequencing batch reactor and an attached growth post-nitrification reactor was added for biological nitrogen and phosphorus removal running for 3 months. Biogas production yields of 778 + 89 mL/gVSadded and 951.30 mL/g COD were obtained through anaerobic digestion. Also, an energy balance was conducted on a pilot scale digester for a turkey processing plant with wastewater production of 2160 m3/d and using a combined heat and power (CHP) enginefor conversion of biogas to heat and electricity. Although the biogas yield achieved in a complete mixed reactor was relatively lower than yields obtained in previous studies using reactors such as UASB, still a complete mixed reactor can be a good choice for biogas recovery from TPW and can be used for codigestion with some specific turkey processing byproducts for biogas recovery. Nitrogen and phosphorus removal in the A2N-SBR system were 47% and 75%, respectively, and during the study the nitrogen and phosphorus removal mean concentration in effluent did not meet the nutrient limits specified in the objectives. Average TP and TN in the effluent were 3.2 mg/L and 137 mg/L, respectively. Throughout the study, the nitrification reactor biofilm was not completely developed. Incomplete nitrification and poor settling might be the reasons that quality obtained in effluent was low. To improve the process condition in A2N-SBR, online monitoring of pH, dissolved oxygen (DO) and oxidation reduction potential (ORP) can help to optimize each stage in the SBR and stages duration can be set based on the results. / Master of Science

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The electricity demand of a waste water treatment plants follows the diurnal pattern of society, and this generally leads to higher demand when the market price is high. The possibility to adapt the operation after price variation has been known since long, but few studies have been published. It has been suggested that the influent can be redistributed using an equalization basin, and one study showed 16 % reduction in cost with equalization to constant flow. Oxygen supply by aeration uses the major part of electricity, and adaptation of aeration intensity has also been suggested. However, this requires respect for effluent limits, especially for nitrogen, as larger plants are often equipped with nitrogen removal. In this study, optimal control of aeration was used to evaluate the potential of adapted aeration. Use of an equalization basin was also studied. A reduced version of Benchmark Simulation Model no. 1 was used, with only one basin. Aeration was optimized for minimal cost given a price profile for 24 hours, under a constraint on ammonia discharge. Cost was reduced with 1-2.5 % compared to energy-optimal control. Constant flow equalization showed an energy reduction of 2.5-12 %, and a cost reduction of additionally up to 5 %. Control adapted after price gave another 1-3 % savings. The nitrification process is sensitive to oxygen and ammonia concentration. This makes it difficult to redistribute nitrification over the day, especially with a one basin model. It is therefore motivated to study a model with more basins.

Nitrogen and phosphorus removal is often required before discharge of treated wastewater to sensitive water bodies. Kayseri Wastewater Treatment Plant (KWWTP) is a biological wastewater treatment plant that includes nitrogen and phosphorus removal along with carbon removal. The KWWTP receives both municipal wastewater and industrial wastewaters. In this study, KWWTP was modeled by using a software called GPS-X, which is developed for modeling municipal and industrial wastewaters. The Activated Sludge Model No.2d (ASM2d) developed by the International Association on Water Quality (IAWQ) was used for the simulation of the treatment plant. In this model, carbon oxidation, nitrification, denitrification and biological phosphorus removal are simulated at the same time. During the calibration of the model, initially, sensitivities of the model parameters were analyzed. After sensitivity analysis, dynamic parameter estimation (DPE) was carried out for the optimization of the sensitive parameters. Real plant data obtained from KWWTP were used for DPE. The calibrated model was validated by using different sets of data taken from various seasons after necessary temperature adjustments made on the model. Considerably good fits were obtained for removal of chemical oxygen demand (COD), total suspended solids (TSS) and nitrogen related compounds. However, the results for phosphorus removal were not satisfactory, probably due to lack of information on volatile fatty acids concentration and alkalinity of the influent wastewater.