Algae are a diverse group of simple organisms that lack roots, stems or leaves and are able to use sunlight, carbon dioxide, and nutrients to produce complex compounds, such as carbohydrates, proteins and lipids. These compounds, especially lipids, are highly sought-after by agricultural, nutraceutical and energy interests. Although there is great potential for algae derived biofuels, there are technical and economic challenges associated with their cultivation. Relevant to this dissertation, the environmental impacts associated with algae cultivation can be reduced by using municipal and agricultural wastewaters as a water and nutrient source. This research was divided into three sections to address current challenges in the algal industry and science, technology, engineering and math (STEM) education. The sections were: 1) examination of the growth of indigenous algae on wastewater (centrate) produced from dewatering anaerobically digested municipal sludge, 2) examination of the effect of non-axenic conditions on the growth of three different algal cultures using wastewater from a recirculating aquaculture system (RAS), and 3) using wastewater treatment and algae to increase scientific inquiry in authentic science research with high school students. In the first section, indigenous algae were cultivated on centrate under natural light conditions in a semi-continuous photobioreactor. A non- linear bio-optical model was developed considering Michaelis-Menten photosynthesis-irradiance response. The bio-optical model was applied to fit the cumulative biomass data and had an R-squared value of 0.96. The second section examined the growth and accumulation of storage product. Higher calorific values were observed for all algae cultures when grown under non-axenic conditions, most likely due to significantly higher lipid contents. Significantly higher algal lipid contents under non-axenic conditions may be attributed to the stress of the presence of RAS microorganisms. Finally, having a university-based algal project with involvement of University of South Florida (USF) researchers, teachers and high school (HS) students facilitated increased scientific understanding and skills among HS students. Outcomes included graduate students gaining greater in-depth practical understanding as these students had to learn skills, such as designing a photobioreactor and then immediately had to teach HS students how to construct photobioreactors, design and conduct experiments, and gather scientific data. HS students gained a greater understanding of biological and chemical processes, such as photosynthesis. In addition, they learned important skills, such as calculating means and standard deviations using Excel, orally communicating scientific concepts and preparation of a PowerPoint presentation.

Anaerobic digestion (AD) has been shown to be an effective technique for energy recovery and stabilization of livestock wastes, municipal sludges and industrial wastewaters. However, further treatment is required to remove nitrogen from AD effluents to avoid detriments to surface and ground waters. The high free ammonia (FA) concentrations present in AD effluents can inhibit nitrification processes in conventional biological nitrogen removal (BNR) systems. The overall goal of this research was to develop a process for removal of nitrogen from AD swine waste (ADSW) effluent. The proposed solution was to incorporate particulate chabazite, which has a high cation exchange capacity, into a sequencing batch reactor (SBR) to adsorb ammonium and therefore ease nitrification inhibition. The process developed is called a chabazite-SBR. Three research questions were used to guide this research. First question (Chapter 3): How does chabazite pretreatment with groundwater (GW) affect the kinetics and cation exchange capacity during ammonium (NH4+) uptake? Kinetics and isotherm batch tests were performed with GW pretreated chabazite. In addition, sodium chloride (NaCl), and deionized water (DI) pretreated chabazite was included for comparison because these are typically used pretreatment methods. The Ion Exchange (IX) isotherm model was used to calculate the cation exchange capacity and the pseudo-first and film diffusion kinetics models were applied to quantify the effect of the pretreatment on the reaction rate. Results showed that the exchange capacity was slightly higher for GW pretreated chabazite compared with the other common pretreatment strategies; however, the enhancement was not significantly different. The kinetics of NH4+ uptake during the first four hours of contact was significantly improved by GW pretreatment when compared with other common pretreatment strategies. This was caused by an enhancement in film diffusion mechanisms. The findings of this first part of the research were important because it was shown that NaCl pretreatment is not needed to improve the kinetics and cation exchange capacity of chabazite. Second question (Chapter 4): How does addition of chabazite to ADSW centrate affect nitrification rates? Nitrification batch test with varying NH4+ concentrations were performed to identify the inhibitory NH4+ concentration. Additional nitrification batch tests treating real and synthetic waste with initial NH4+ concentration of 1,000 mg-N L-1 with added zeolite were performed. For the mixed liquor tested in this study, NH4+ concentrations must be maintained below 200 mg-N L-1 to relieve nitrification inhibition. Treatment of ADSW centrate requires a chabazite dose of 150 g L-1 to ease FA inhibition of nitrification. The rate of nitrification increased, by approximately a factor of 3, when chabazite was added to a batch reactor treating high NH4+ strength wastewater. However, Na+ release from the chabazite also plays a role in nitrification inhibition. The findings of this part of the research showed the potential for using chabazite for overcoming FA inhibition of nitrification during treatment of high NH4+ strength wastewater. Third question (Chapter 5): How effective is the chabazite-SBR in removing total nitrogen concentrations from ADSW centrate? A chabazite-SBR was operated for 40 weeks (cycles) to study the TN removal efficiency with varying carbon source. The efficiency of IX was also monitored over time. The chabazite-SBR process achieved stable TN removal from ADSW centrate during the 40 weeks of operation. Simultaneous nitrification-denitrification reduced chemical input requirements. Addition of an external organic carbon source at a rate of 3.2 g-COD g-N-1 resulted in maximum TN removal. An overall TN removal efficiency of 84% was achieved, with specific nitrification and denitrification rates of 0.43 and 1.49 mg-N g-VSS-1 hr-1, respectively. The IX stage of the chabazite-SBR was able to reduce FA concentrations to below the inhibitory level for nitrification inhibition over 40 chabazite-SBR cycles with no loss in IX efficiency over time and no fresh zeolite added to the reactor.

Landfill leachates and thermal hydrolysis pretreated anaerobic digestion centrate can quench UV light at publicly owned treatment works (POTWs). Increased eutrophication, has led to tightening of nutrient discharge limits in some regions of the country. Biologically recalcitrant organic nitrogen, adds to effluent nitrogen making it difficult to meet these requirements. The study aimed at characterizing landfill leachate and centrate fractions to develop an understanding that might help design on-site treatment methods. Leachates varying in on-site treatment and ages were fractionated on basis of hydrophobic nature. Humic substances were the major UV light quenching fractions. Majority of the humic substances were > 1 kDa molecular weight cut off (MWCO) indicating that membrane treatment might be effective for UV quenching substances removal. UV absorbing substances were found to be more bio-refractory than organic carbon. Significant decrease in humic substances with long term landfilling indicated that age was important in determining the potential for leachates to impact the UV disinfection. Organic nitrogen was observed to be hydrophilic in nature (mostly < 1 kDa). Proteins which are easily biodegradable contributed around one-third of the organic nitrogen. For thermal hydrolysis centrate, the optimum treatment depended on particle size and hydrophobic nature. Biological treatment was observed to be more effective for the removal of organic matter and UV254 quenching substances for fractions < 300 kDa. Biological treatment had little impact on organic nitrogen. Coagulation-flocculation is an effective treatment for higher molecular weight (MW) fractions whereas a membrane bioreactor would be more suitable for smaller MW fractions. / Master of Science

Biogas is becoming a more important source of green, renewable energy however, its production results in a liquid wastewater, known as centrate, which must be treated due to its high levels of total dissolved solids (TDS), and chemical oxygen demand (COD). Currently, biogas generation facilities treat centrate using a combination of biological and physical treatments (via a membrane bioreactor (MBR)), which produces a stream known as MBR permeate. While MBR permeate achieves improved quality, MBR usage has several challenges including difficulty of scaling biological processes, and handling capacity limitations. In this study, membrane only treatment of centrate, collected from an operating biogas generation facility, was investigated to determine if similar quality permeates could be obtained without any biological treatments. Single- stage treatment of centrate using either polymeric or ceramic nanofiltration membranes with molecular weight cut offs between 400 and 800 Da, produced a permeate similar to MBR permeate. These membrane types caused average COD rejections of 92% and 90% respectively. However, the permeates from the nanofiltration membranes had very high levels of ammonia, which was not present in the MBR permeate. The ceramic nanofiltration membranes can achieve higher permeate fluxes than the polymeric nanofiltration membranes. Both membrane types experienced significant fouling which was removed using cleaning procedures. Two-stage treatment of centrate using ceramic nanofiltration membranes followed by polymeric reverse osmosis membranes further improved the quality of permeate and achieved COD rejections of 99% overall. While the reverse osmosis membranes did remove some ammonia, the levels were still higher than what was seen in the MBR permeate. The two-stage treatment of centrate can provide the permeate which is closest to the MBR permeate however, further studies are required to address the higher ammonia concentration values. The research shows that only using membranes is a potential treatment pathway for real centrate samples. / Thesis / Master of Applied Science (MASc) / The production of biogas, which is a green, renewable energy source results in a liquid wastewater known as centrate. This wastewater is very dirty and complex and requires treatment as it cannot be dumped and disposed of in its current state. Current treatment methods for centrate use combinations of biological treatment and filtration processes, which has its own challenges due to the complexity of biological treatments. An alternative treatment method for the centrate is nanofiltration membranes which offer the ability to treat large volumes of centrate wastewater without the complexity of relying on biological treatment options. Four different nanofiltration membranes, including two polymeric and two ceramic membranes, were used to treat real industrial wastewater samples of centrate collected from a biogas generation facility. Both types of nanofiltration membranes provided similar quality permeate to the current treatment method of centrate, which uses a combination of biological and physical treatment methods.

A number of innovative nitrogen removal technologies have been developed to address the treatment challenges caused by stringent regulations and increasing chemical and energy cost. A major contributing factor to these challenges is the liquid stream originating from the process of dewatering anaerobically digested solids. This liquid, also knows as centrate, reject water or sludge liquor, can cause an increase of up to 25% in ammonia loading. The recently discovered anaerobic ammonia oxidation (anammox) process is a major breakthrough for treatment of these streams as it has the potential to remove up to 85% of nitrogen load without external carbon source addition. The anammox process is combined with another process that oxidizes half of the ammonia to nitrite (nitritation) in a separate reactor such as in the SHARON process, or in the same reactor such as in the DEaMmONification (DEMON) process. Despite intensive laboratory research for the last 10 years to fully understand these processes, there is still a high level of skepticism surrounding the implementation of full-scale systems. The reason for this skepticism could be due to frequent failures observed in the lab scale systems as well as reported slow bacterial growth. We think that this technology might be used more effectively in the future if process kinetics, inhibition and toxicity can be better understood. This work focused on the DEMON process with a goal to understand the kinetics and inhibition of the system as a whole and the anammox process in particular. A DEMON pilot study was undertaken at the Alexandria Sanitation Authority (ASA) and had several study participants, including ASA, the District of Columbia Water and Sewer Authority (DCWASA), CH2M Hill Inc., Envirosim Ltd, the University of Innsbruck and Virginia Tech. We investigated the growth rate of anammox bacteria within a quasi-optimal environment. Laboratory-scale experiments were conducted to assess anaerobic ammonia oxidation inhibition by nitrite as well as aerobic ammonia oxidation inhibition by compounds present in the DEMON reactor feed, such as a defoaming agent, a sludge conditioning polymer, and residual iron from phosphorus removal practices. The study revealed that the DEMON process can be efficiently controlled to limit nitrite accumulation capable of causing process inhibition. The target ammonium loading rate of 0.5 kg/m3/d was reached, and no upset was noticed for a loading up to 0.80 kg/m3/d with an HRT of 1.7 days. The ammonia removal efficiency reached an average of 76% while total nitrogen removal efficiency had an average of 52%. Most of the process upsets were caused by aerobic ammonia oxidation failure rather than anammox inhibition. Failure in ammonia oxidation affected pH control, a variable which is at the center of the DEMON process control logic. The pilot study is summarized in Chapter 3 of this Dissertation. The low anammox maximum specific growth rate (µmax,An) as well as nitrite inhibition are historically reported to be the major process challenges according to the literature, but the degree to which each contributes to process problems differs widely in the literature. In this study, we estimated µmax,An by using the high F:M protocol commonly used for nitrifying populations. We also studied the effect of both short term and sustained nitrite exposure on anammox activity. In this study, µmax,An was estimated to be 0.017 h-1. The study results also suggest that anammox bacteria can tolerate a spike of nitrite-N at concentrations as high as 400 mg/L as long as this concentration is not sustained. Sustained concentrations above 50 mg/L caused a gradual loss of activity over the long term. Finally, the inhibition of aerobic ammonia oxidizing bacteria (AerAOB) observed in the DEMON reactor was investigated using laboratory experiments and is reported in Chapter 6. AerAOB inhibition was, in most cases, the main reason for process upset. Compounds that were suspected to be the cause of the inhibition were tested. The study noticed that a defoaming agent, polymer and ferrous iron had some inhibiting properties at the concentrations tested. / Ph. D.

Return liquor from thermal hydrolysis process (THP) can significantly add to the nitrogen load of a wastewater treatment plant (WWTP) and introduce UV quenching substances to the wastewater stream when recycled. While there are mature technologies in place to handle the inorganic nitrogen produced due to the thermal pretreatment, organic nitrogen remains a parameter of concern for utilities employing THP pretreatment. The impact of operating conditions of the THP on dissolved organic nitrogen (DON) and UV absorbance in return liquor was investigated. Operating conditions studied were (1) operating temperature (2) solids retention time (SRT) in the anaerobic digester (3) THP flash pressure (4) the effect of co-digestion of sewage sludge with food waste and, (5) polymer conditioning. Operating temperature and polymer dose had the most significant impact on DON and UV quenching. It was found that an increase in operating temperature resulted in an increase in DON, which was primarily contributed by the hydrophilic fraction. An increase in temperature also resulted in increased UV254 absorbance. However, this trend was not linear and the increase was more pronounced when the temperature was increased from 150 C to 170 C. Increasing flash pressure from 25 psi to 45 psi did not have a significant impact on the return liquor. However, increasing the flash pressure to 75 psi increased the DON and UV254 absorbing compounds. Co-digesting the sludge with food waste resulted in a slight increase in DON and a decrease in dissolved organic carbon (DOC) and UV quenching compounds. Increasing the SRT from 10 days to 15 days resulted in a slight decrease in DON but did not have any impact on UV254 absorbance. Overall, it can be concluded that optimizing operating conditions of thermal hydrolysis process can result in decreased DON and UV quenching compounds in the recycle stream. / Master of Science