Efficient and low-energy microalgae harvesting is essential for sustainable biofuel production. Forward osmosis (FO) can provide a potential alternative for algae separation with low energy consumption by using osmotic pressure. In this study, an aquaporin-based polyethersulfone (PES) membrane was evaluated for algae dewatering using FO with three different types of draw solutions (DSs: NaCl, KCl and NH4Cl), and under different cross flow velocities (CFVs). 81% of algae dewatering was achieved with a 29% flux drop. Among three different DSs, although NH4Cl was the best candidate for improved water flux and low reverse salt flux (RSF), it could accelerate cell division, reducing settleability during the FO process. However, RSF originated from NaCl could increase lipid content (~ 49%) in algal biomass probably due to the osmotic imbalance in algal cells. During FO operations, membrane fouling would be an inherent problem against sustainable algae dewatering. In this study, a novel approach was investigated by coupling the FO with an electric field for developing repulsion forces that can prolong the filtration cycle and mitigate foulant attachment. Several electric fields (0.33, 0.13 and 0.03 V mm-1) were applied in continuous and pulsing modes (10sec intervals) to mitigate membrane fouling for effective algae dewatering. The electric field FO configuration used in this study was able to produce 3.8, 2.2 and 2.2 times greater flux at the applied potential of -1.0, -0.4, and -0.1 V, respectively, compared to the control (without an electric field). A high potential of -10 V for 60 sec was applied as an optimal cleaning procedure with a high ability to recover flux (99%). The study also investigated the effect of the electric fields on bulk pH, conductivity, settling velocity, lipid content and microalgal morphology. Overall, this study demonstrates a novel technology for algae dewatering in FO application using the aquaporin-based PES membrane.

Disinfection of potable water supplies is a primary requirement of the United States' Environmental Protection Agency's (USEPA's) Safe Drinking Water Act. The use of chlorine as a disinfectant is widely accepted by water purveyors due to its effectiveness and low cost. However, chlorine reacts with natural organic matter present in water supplies to form suspected carcinogenic disinfection by-products (DBPs). In this work, the formation of the regulated chlorinated by-products total trihalomethanes (TTHMs) and haloacetic acids (HAA5) for eleven Central Florida wells has been investigated. Fluorescence, UV-254, dissolved organic carbon (DOC), specific UV absorbance (SUVA), chlorine decay, and TTHM and HAA5 formation potentials (FPs) were analyzed. Fluorescence results suggested that the highest fraction of organic matter in the wells was in the form of humic acid. TTHM and HAA5 FPs were correlated to UV-254, and to a lesser extent, DOC. TTHM FP results for each well investigated showed 85 to 250 ug/L TTHMs formed with < 0.10 to 1.1 mg/L free chlorine residual after 96 hours of incubation. The highest TTHM-forming wells surpassed the regulatory 80 ug/L maximum contaminant level in less than 10 hours. Granular activated carbon (GAC) in adsorption and biological modes, nanofiltration (membrane softening), ozone oxidation, and aeration with tray, spray, or packed tower technologies were evaluated as treatment alternatives. Conceptual opinions of probable process costs suggest that of the alternative treatment technologies evaluated, recirculating tray aerators were most economical for TTHM reduction at $0.054/Kgal and $0.048/Kgal for a 5 and 10 million gallon per day (MGD) plant, respectively, assuming a 20-year time frame and 8% interest rate. However, ozone could prove useful for HAA5 control at $0.12/Kgal and $0.097/Kgal for a 5 and 10 MGD plant, respectively, assuming a 20-year time frame and 8% interest rate.

As indicated by the National Academy of Engineering, the understanding of nitrogen cycle has been deemed as one of 14 grand challenges in engineering of the 21st century. Due to rapid population growth and urbanization, the stormwater runoff increased in quantity as well as its nutrient concentrations, which may trigger serious environmental issues such as eutrophication in aquatic systems and ecosystem degradation. This study focuses on stormwater and groundwater quality control via Biosorption Activated Media (BAM) which can be applied to enhance the nutrient removal potential as an emerging Best Management Practices (BMPs). BAM was tested in this study with respect to two changing environmental factors including the presence of toxins such as copper and the addition of carbon sources that may affect the removal effectiveness. In addition, the impacts on microbial ecology in BAM within the nitrification and denitrification processes due to those changing environmental conditions were explored through the identification of microbial population dynamics under different environmental conditions. To further enhance the recovery and reuse of the adsorbed ammonia as possible soil amendment or even fertilizer, a new media called Iron Filing Green Environmental Media (IFGEM) was developed based on BAM, with the inclusion of iron filings as a key component for nitrate reduction. The functionality of IFGEM was analyzed through a serious column studies with respect to several key factors, including varying influent nutrient concentrations, pH values, and temperature. The results of the column studies demonstrate promising nutrient removal and recovery potential simultaneously under changing factors.

Methods of optimizing the coagulation, flocculation, sedimentation, and filtration (CSF) process at a conventional surface water treatment plant (WTP) were conducted to investigate opportunities for the reduction of disinfection by-product (DBP) precursor material. The research had two primary components: (1) optimize coagulant dosage and associated operating pH and (2) investigate pretreatment oxidation with chlorine dioxide (ClO2) and potassium permanganate (KMnO4). To accomplish the first component, jar tests were conducted at various pH and aluminum sulfate (alum) dosages to model current and potential treatment conditions during the CSF process at a WTP. Isopleths were developed to examine the removal efficiencies of turbidity and natural organic matter (NOM). NOM is a DBP precursor material and was represented by non-purgeable dissolved organic carbon (DOC) throughout the research. Isopleths indicated that at pH 6.2 and a corresponding alum dosage of 20 mg/L (control condition), turbidity and DOC were reduced by 90 and 35 percent, respectively. However, at pH 5.5 and 30 mg/L alum dosage, turbidity removal decreased to 80 percent whereas, DOC removal improved to 50 percent. Jar testing was conducted to evaluate differences in the use of KMnO4 and ClO2 as a pretreatment chemical to observe the reduction of DBP precursor material (i.e., NOM), dissolved iron, and dissolved manganese. Addition of ClO2 was able to reduce total trihalomethanes and haloacetic acid formation potentials (168-hours) up to 40 percent and 15 percent, respectively, and was dependent on chlorine dioxide generation method, dosage, and raw water characteristics. Chlorine dioxide also was shown to remove iron and manganese at levels greater than 99 percent.

Perfluorinated compounds (PFCs) have been manufactured and used in various industries including food packaging, paintings, and coating industries. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are the most commonly investigated PFCs that have bioaccumulative properties and a strong persistence in environment. Despite the growing interest in using membrane technology to remove PFOA and PFOS from water, little information is available on the impact of natural water matrices on the removal of PFOA and PFOS when using nanofiltration (NF). The presence of natural organic matter (NOM) and cations (Ca2+ and Mg2+) in water matrices and their interactions with the PFCs may significantly impact their removal efficiency. The current study compared the rejection of PFOA and PFOS from laboratory-prepared water (deionized water), surface water and groundwater using a commercial NF membrane (NE 70). Three different experiments were conducted for 20 hours using a bench- scale flat sheet unit. Feed and permeate samples were collected and analyzed to determine the PFOA and PFOS concentrations using liquid chromatography-tandem mass spectrometry (LC/MS-MS). The compound rejections varied from 71 to 80 % for PFOA and 42 to 80 % for PFOS. The results showed increased rejection of PFOA/S in the surface water and groundwaters when compared to the laboratory-prepared water. This is likely due to the presence of NOM and cations in the natural water matrices. The permeate flux declined (12.3-56.2 %) as more cations and NOM were present in the feedwater, suggesting that the increased rejection of PFOS in natural waters may be due to membrane pore blockage.

No description available.

No description available.

Biomass growth of the alga Nannochloropsis oceanica, cultivated outdoors in six pilot-scale raceway ponds, was monitored over the course of 1.5 years, at two different dilution regimes each season, to establish the effects on algal biomass productivity and concentration of dilution rate, pond water temperature, and solar radiation. The 4.5-m2 ponds were located in a mild, mid-latitude, coastal region (central California). Experimental conditions were operated in duplicates or triplicates with a consistent artificial seawater medium, pond depth, pH range, paddle wheel mixing speed, and replete nutrient conditions for the duration of the study. Two cultivation regimes were used to regulate pond biomass concentration: batch growth and a three-times-per-week dilution with a resulting dilution rate of 0.21/d. For the ranges of input variables tested, productivity (g/m2-d) was positively correlated to both pond water temperature and solar radiation. However, the data scatter in the correlations was substantial, indicating the existence of other major influences on productivity. A dilution regime consisting of three dilutions per week and a dilution rate of 0.21/d resulted in the higher productivities compared to batch cultivation for all seasons tested. With high light intensity (200-300 W/m2) and warm water (18.3oC daily average), the highest productivity was 11.4 g/m2-d with a resulting biomass concentration of 0.15-0.20 g/L. With low light intensities (150-200 W/m2) and cool water (16.6oC daily average), the highest productivity was 6.9 g/m2-d with a resulting biomass concentration of 0.10-0.15 g/L.

Shallow, mixed raceway ponds can be used to grow microalgae for the dual purposes of wastewater treatment and biofuel feedstock production. To improve the environmental sustainability of microalgae biofuels and to alleviate resource limitations, nutrients remaining after biofuel production should be recycled for additional cultivation. This thesis considers three topics: wastewater treatment by algae, nitrogen and phosphorus assimilation by algae, and algae cell disruption to facilitate nutrient recovery. The main experimental work was done in pilot raceway ponds growing polycultures of microalgae on clarified municipal wastewater. In addition, two lab-scale pretreatment technologies were tested for their ability to disrupt cells, as indicated by subsequent biomass organic nitrogen and particulate phosphorus degradation during sequential anaerobic and aerobic digestion. The two pretreatment technologies were sonication and high-pressure homogenization. The raceway pond research was conducted at the City of San Luis Obispo Water Resource Recovery Facility (WRRF). Nine 30-m2, 0.3-m deep raceway ponds were operated continuously from March 1, 2013 to August 31, 2014. The ponds were arranged in three sets of triplicates. One set was operated at a 2-day hydraulic residence time (HRT) on clarified wastewater throughout the study. A second set (“Round 1” of ponds-in-series) was operated at a 3-day HRT, also on clarified wastewater. Its effluent was clarified and then discharged into the third set (“Round 2” of ponds-in-series), which initially operated at a 4-day HRT but then later a 3-day HRT. The nutrient removal and assimilation data were compared seasonally—summer (March–October) and winter (November–February). The triplicate raceways operating at a 2-day HRT achieved average total ammonia nitrogen (TAN) removal efficiencies of 11% in the winter and 71% in the summer, while dissolved reactive phosphorus (DRP) removal remained similar throughout seasonality. In the first ponds-in-series experiment (3-day HRT followed by 4-day), average summer TAN removal efficiencies for Round 1 and 2 were 88% and nearly 100%, respectively. Round 1 and 2 average summer DRP removal efficiencies were 29% and 67%, respectively. The first ponds-in-series experiment was not conducted in the winter. In the second experiment, the Round 2 HRT was changed to 3 days. Average TAN removal efficiencies for Round 2 in the winter and summer were 88% and 100%, respectively. DRP removal for Round 2 increased from 38% in the winter to 66% in the summer. Total nitrogen (TN) mass balances on the raceway pond experiments were useful to illustrate the fate of influent nitrogen, including losses. In the first ponds-in-series experiment, 76% of the influent soluble nitrogen was converted to organic nitrogen by assimilation, while 6% of the influent ammonia was lost by volatilization. In the second ponds-in-series experiment, 81% of the influent soluble nitrogen was converted to organic nitrogen by assimilation and only 1% of the influent ammonia was lost by volatilization. The 2-day HRT raceway experiment achieved 41% conversion of influent soluble nitrogen to organic nitrogen by assimilation, with influent ammonia losses of 3% by volatilization. In addition to these pilot-scale raceway pond experiments, laboratory experiments were conducted on re-solubilization of algae biomass nutrients to support additional algae growth. Algae harvested from the pilot ponds was pre-treated with either sonication or high-pressure homogenization. The pretreated biomass was then subjected to anaerobic digestion and then aerobic digestion to increased nitrogen and phosphorus solubilization. The laboratory anaerobic digestion simulated pilot digestion, also conducted at the pilot facility, and the aerobic digestion was meant to simulate further re-solubilization that would occur when algae digestate was returned to the aerobic raceway ponds to promote further algae growth. Neither pre-treatment technologies had a significant impact on degradation of biomass organic nitrogen and particulate phosphorus compared to controls. It was found that simple anaerobic digestion followed by aerobic digestion resolubilized 90% of organic nitrogen and 50% of particulate phosphorus.

The current research was undertaken to evaluate the performance of a top loading vertical flow submerged bed treatment system (TLVFSBTS) treating primary sewage effluent. Both pollutant elimination and microbial processes were measured. The wetland system is located just west of the Hudson River in upstate New York. The system consists of four 232-m2 wetland cells, currently operating in series. Two cells are planted with Phalaris arundineacea and two with Phragmites communis. The data collected were used to evaluate an existing mechanistic compartmental simulation model and to develop an new simulation model for TLVFSBTS wetlands. Treating CBOD5 to permit levels (< 4 mg L-1) was not difficult to accomplish and occurred in the first wetland cell during much of the study period. At no time during the 17-month evaluation period did measurable CBOD5 leave the wetland, although lack of carbon source (CBOD5) for microorganisms in subsequent wetland cells (cells 3 and 4) may have been a limitation for denitrification. Ammonium oxidation in the first wetland cell was greater than in the second wetland cell (70.8% and 39.2%, respectively). Nitrite accumulation in the first wetland cell (2.204 mg L-1 maximum value) appeared to be seasonal, and not directly related to nitrite oxidation. Both nitrite and nitrate leave the wetland system at levels below primary drinking water standards (1 and 10 mg L-1), respectively. The ammonium concentration leaving the system was at or below permit level (2.2 mg L-1) during much of the study period. Nitrification potential and denitrification enzyme activity in the wetland system, especially the first wetland cell, exceeded published values for natural wetlands, tropical soils, and both marine and freshwater sediments. These findings, however, demonstrate the ability of TLVFSBTS wetlands to remove the various nitrogen constituents once the microbial population becomes acclimated to the influent wastewater. The original simulation model evaluated was determined to be inappropriate for TLVFSBTS wetlands. A new TLVFSBTS model was developed, parts of which worked quite well. A computational problem with the chosen simulation software, however, made it impossible to determine the applicability of the current model. Future work will continue to pursue development of the current model, perhaps with different software.