This thesis explores the treatment of municipal wastewater using pilot-scale raceway ponds and looks specifically at the capability of the raceways in removing BOD and nitrogen. Nine 33 square-meter algal raceway ponds were used to conduct research at the San Luis Obispo Water Resources Recovery Facility. Main objectives of this study were to increase the removal of total ammonia nitrogen (NH3-N plus NH4+-N) from municipal wastewater through increased assimilation and nitrification. Raceway ponds with CO2 addition were operated in series with an intermediate settling step and a total hydraulic retention time (HRT) of 4 days to measure the increase in nitrogen removal through assimilation by two rounds of algae growth. A single round of treatment with a 4 day HRT was also operated and compared to the two rounds. The two rounds of treatment and 1 round of treatment removed on average 36.6 mg-N/L and 35.2 mg-N/L of TAN, with respective standard deviations of 6.3 mg-N/L and 5.3 mg-N/L. No statistical significant difference was found between two treatment methods for TAN (mg-N/L) removal (t = -0.64, DF = 23.3, P =0.28), % TAN removal (t = -1.18, DF = 22.6, P = 0.25), and TAN (mg-N/L) of final effluent (t = 1.11, DF = 23.6, P = 0.28). Raceway ponds were aerated at night to keep nighttime DO from dropping to concentrations inhibitory to nitrification. The rates of nitrification with night aeration were measured. The nitrification rates were compared to a model based on Monod kinetics. The Monod model did not correspond with performance results of ponds.

The economics of microalgal bioproduct commercialization would benefit from increased accumulation of energy storage compounds, such as carbohydrates and lipids, and increased biomass productivity. This thesis explores two adaptive laboratory evolution strategies for improving Scenedesmus obliquus: single UV-mutagenesis and low light cultivation at a high dilution rate to produce cultigens with greater carbohydrate content and iterative UV-mutagenesis and selection under outdoor conditions in a raceway pond at a high dilution rate to increase biomass productivity. Two cultigens were generated with the goal of increased carbohydrate content: K5 and K7. Both were mutagenized for 5 seconds and cultivated in 50-mL Klavins reactors. K5 was maintained at 95 μmol/m2-sec for 16 hours/day, and K7 was maintained at 250 μmol/m2-sec for 6 hours/day. When evaluating the two cultigens in triplicate 800-mL bubble columns against wild-type Scenedesmus obliquus, neither K5 nor K7 demonstrated an increase in carbohydrate content. To increase biomass productivity, Scenedesmus obliquus was iteratively UV-mutagenized (aliquots exposed for 5-60 seconds were combined) and cultivated in a 100-L, 0.5-m2 outdoor raceway pond fed with filtered reclaimed wastewater at a high dilution rate. Three rounds of mutagenesis and selection took place during the spring, summer, and winter months, with the MBE 509 and MBE 510 cultigens being produced after the summer and winter selection rounds, respectively. When evaluated in triplicate 800-mL bubble column reactors: MBE 509 (491 ± 42 mg/L-day, expressed as the mean of the time series ± SD) was 24% more productive than wild-type (397 ± 39 mg/L-day), and MBE 510 (443 ± 26 mg/L-day) was 13% more productive than wild-type (391 ± 9 mg/L-day). When evaluated in replicate 1,350-L, 4.5-m2 raceway ponds, MBE 509 (15.2 ± 2.2 g/m2-day) and MBE 510 (16.1 ± 1.8 g/m2-day) were 5% and 12% more productive than wild-type (14.5 ± 2.4 g/m2-day), respectively. Selection under low light and high dilution did not result in cultigens with higher carbohydrate content relative to wild-type Scenedesmus obliquus, but iterative mutagenesis and selection in an outdoor raceway pond did generate cultigens with higher biomass productivity in both indoor and outdoor environments.

While treating domestic wastewater, algae can be grown and harvested for biofuel production. Water is a vital resource and it is imperative to conserve and reuse as much as possible. Several pilot and lab scale experiments were conducted to further research into a full scale wastewater treatment and biofuel production facility. This thesis will include these topics: nitrogen and phosphorus concentrations of clarified wastewater pond feed, nitrogen and phosphorus transformations by algae, and the potential of algae cell disruption technologies to increase nutrient solubilization. The pilot scale experiments were conducted using nine 33 m2, 0.3 m deep multi-culture raceway algae ponds being continuously mixed. These ponds were setup in triplicates and fed municipal wastewater in the form of primary clarifier effluent. The three experiments conducted using these pilot scale ponds were: grab and 24-hour composite influent comparison, nitrogen and phosphorus of various hydraulic residence times (HRTs), and nitrogen and phosphorus nutrient depletion with water recycle. The grab and 24-hour composite comparison was conducted from July 30 to December 3, 2014 and compared the dissolved reactive phosphorus (DRP) and total ammonia nitrogen (TAN) concentrations of the two sample types. Equations were made to convert from grab to 24-hour concentrations. The sample types for both DRP and TAN were on average within 10% and essentially the same. A comparison of data from ponds operating at different HRTs was collected from October 30 and November 6, 2013 and October 29 and November 5, 2014. There were linear correlations between different HRTs and both soluble nitrogen and DRP. Equations were made to calculate the expected removal of ponds using the HRT. The nutrient depletion with water recycle experiment was conducted during October 15-29, 2015. Soluble nitrogen removal was linear with a rate of 1.5 mg-N/L-day and required 14 days to drop below 5 mg-N/L in the ponds. DRP removal was also linear with a rate of 0.18 mg-P/L-day. The algae cell disruption solubilization experiments were conducted using homogenization, sonication, autoclaving, and boiling pretreatment technologies. Algae harvested from the pilot ponds was anaerobically digested and then aerobically digested in an attempt to reuse nutrients for continued growth. It was found that there was no significant difference between the pretreated and non-pretreated digested samples. Keywords: algae, raceway pond, nutrient transformation, anaerobic digestion, aerobic digestion, assimilation, volatilization, nitrogen, phosphorus, pretreatment of algae, nutrient resolubilization, nutrient solubilization

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Nitrogen removal technologies can help dairy industries meet their nutrient management needs. This thesis investigated two separate treatment technologies for total ammonia nitrogen (TAN) removal: algae raceway ponds and aerated biofilm reactors. Six 1000- liter algae raceway ponds and four 1000-liter tote tanks, each equipped with 10 sheets of nonwoven geotextile (i.e., thermally bonded or needle-punched) biofilm substrate, were used to treat the effluent from a flush dairy in central coastal California (TAN = 251 mg/L, cBOD5 = 204 mg/L). For the algae raceway ponds (TAN loading rate = 7 - 35 g/m³-day among 7-, 10- and 14-day hydraulic residence times (HRT)), first-order removal rate constants (k) were ~0.2 day⁻¹ in the summer and 0.1 - 0.2 day⁻¹ in the winter. Removal rate constants had no correlations (R² < 0.1) with water temperature, weak to moderate (for 7-day ponds, R² = 0.55) correlations with insolation and weak to no correlations with biomass (i.e. volatile solids) concentration. During the winter, low insolation likely inhibited algal photosynthesis and biological TAN treatment. Ponds with 7-day HRT had distinct absence of nitrate and nitrite compared to 10- and 14-day ponds. Net productivities were ~20 g/m²-day in summer and 9 – 11 g/m²-day in winter; gross productivities were 120 – 160 g/m²-day in summer and 77 – 150 g/m²-day in winter. Productivities had no correlations (R² < 0.1) with water temperature and weak to moderate correlations (for 14-day ponds, net productivity R² = 0.56, gross productivity R² = 0.83) with insolation. Analysis of organic compounds in pond effluent showed dissolved volatile solids (~2300 mg/L) were mostly non-biodegradable (~98% of soluble oxygen demand). Dissolved organic nitrogen concentrations in the pond effluent were ~35 mg/L. For the aerated biofilm reactors, tanks with needle-punched geotextiles had greater first- order TAN removal rate constants (0.69 day⁻¹) than tanks with thermally bonded geotextiles (0.23 day⁻¹) while operating in batch mode. Needle-punched geotextile reactor also accumulated sludge faster and had higher attached to water column biomass (i.e. volatile solids) ratios (~0.08 g VS/g VS) than thermally bonded geotextile reactor (~0.04 g VS/g VS). Among the four tanks, mass of attached biomass was 150 – 340 g per tank while mass of biomass in the water column was 3290 – 5430 g per tank. Comparing the two treatment technologies, aerated biofilm reactors (removal = 64 – 77%, k = 0.2 – 0.3 day⁻¹, removal rate = 36 – 43 g-N/m²-day, 16 – 19 g-N/m³-day) had more removal and faster removal rates per square meter of land footprint compared to the algae raceway ponds (removal = 38 – 77%, k = 0.1 – 0.2 day⁻¹, removal rate = 4 – 5 g- N/m²-day, 13 – 17 g-N/m³-day), likely due to direct application of aerators in the reactors.