A Thesis Submitted to the School of Graduate Studies in Partial Fulfilment of the Requirements for the Degree of Master of Science. / Onsite wastewater treatment systems may be improved by altering the design and environmental variables that affect microbial community composition. However, the two most common methods of examining microbial composition through metagenomic sequencing (16S and shotgun sequencing) produce different taxonomic identification results according to microbial community composition and the analytical methods in use. To identify discrepancies between these two sequencing methods, we analyzed the effect of environmental and tank design variables on onsite-wastewater treatment system microbial communities sequenced using both 16S and shotgun sequencing. Shotgun and 16S sequencing produced different results when examining genera-level taxonomic richness, quantifying the effect of system design and environmental variables on community similarity, and identifying differentially abundant taxa between system types. Results were consistent when subjectively examining patterns of community similarity and when examining genera-level taxonomic diversity above 0.1% relative abundance. Identifying methods that produce similar results between 16S and shotgun sequencing supports the reliable analysis of and optimization of OWTS processes. / Thesis / Master of Science (MSc) / Onsite-wastewater treatments systems such as household septic tanks are vital tools for managing wastewater. However, the microbial ecosystem which digests waste within septic tanks contains unknown interactions that can alter the rate of waste digestion. We used two DNA sequencing methods to assess how microbial communities within septic tanks responded to the tank design and surrounding environment. We then compared results produced by the two sequencing methods. The response of microbial communities to tank design and the environment differed between the two methods. However, the two methods both indicated that one system design produced a more variable microbial community.

As societies around the world become increasingly more dependent on fossil based fuels, the need to investigate alternative fuel sources becomes more pressing. Renewable, biomass-based carbon sources obtained from the biosphere can be gasified to produce synthesis gas, which can in turn be fermented to produce fuel-grade ethanol. A byproduct of ethanol production via fermentation is acetic acid. An optimized ethanol fermentation process should produce a wastewater stream containing less than 2 g/L of acetic acid. This is not enough acid to justify recovery of the acid; however it is a high enough concentration that treatment of the stream is required before it can be discharged. The purpose of this research was to convert the acetic acid into biogas, producing a twoold result: removal of the acid from the wastewater stream and the production of methane, which is a valuable source of energy. Microorganisms known as methanogens will consume acetic acid to produce methane and carbon dioxide under anaerobic conditions. The goal of this research was to optimize methane production from the wastewater stream discharged from an ethanol to syngas facility. Sludge containing methanogenic organisms was obtained from the anaerobic digester of a wastewater treatment facility and used as inoculum in batch reactors containing a synthetic acetic acid solution. Variables such as the type and amount of supplied nutrients, acid concentration, pH, cell acclimation, oxygen exposure, headspace gas composition, and agitation rate were examined. The effects of these parameters on the amount of biogas produced and acetic acid degraded were used to evaluate and optimize reactor performance. Additional experimentation further evaluating methanogenesis at low pH was also conducted using a laboratory scale semi-continuous fermentor. Finally, advanced analytical techniques were used to evaluate changes in organism population with respect to changes in reactor operational parameters. The results of this research were used to estimate kinetic parameters, develop different full-scale reactor design models, and estimate the both the cost of wastewater treatment as well as the value of the methane produced.

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Yes / To date, mixing design practice in anaerobic digestion has focussed on biogas production, but no adequate consideration has been given to energy efficiency. A coherent, comprehensive and generalized strategy based on computational fluid dynamics (CFD) modelling is proposed to improve mixing efficiency of a full-scale, unconfined gas-mixed digester for wastewater treatment. The model consists of an Euler-Lagrange (EL) model where biogas bubbles are modelled as the Eulerian dispersed phase, and non-Newtonian sludge as the Lagrangian continuous phase. Robustness tests show that mixing predictions are independent of bubble size. The CFD strategy comprises the assessment of different mixing geometries and a range of input gas flow rates. Quantitative results show that simple retrofitting measures are able to achieve a significant improvement in the degree of mixing with reduced mixing times, and consequently recommendations for best mixing geometry and gas flow rate are given. A generalization to a generic digester is discussed in a form that is readily usable by professionals and consultants.

Phosphorus chemistry controls key aspects of eutrophication, microbial nutrition, corrosion and other environmental processes. It is commonly assumed that phosphorus occurs exclusively as phosphate (+5) in nature. In fact, although phosphate is undoubtedly dominant in many systems, phosphorus compounds with lower oxidation states (reduced phosphorus) can also be present in the environment and could be of practical importance in many circumstances. Most reduced phosphorus compounds are likely to originate in steel-making or thermal phosphorus plants. It was determined that reduced phosphorus would not be detected in routine environmental analyses even if they were present. A new method was developed to detect these compounds, and in a preliminary survey reduced phosphorus was proven to be present in water that contacts corroding iron pipes, steel slag samples, phosphorus plant wastewater, phosphite fertilizers, and in sewage treatment plant effluent. However, no evidence could be obtained for massive bio-reduction of phosphates that has been proposed by some researchers. Given that phosphorus is often a limiting nutrient, and phosphorus compounds sometimes inhibit and sometimes catalyze practically important reactions (e.g. iron corrosion), future work should examine reduced phosphorus occurrence and chemistry in greater detail. / Ph. D.