Growth Media and Lipid Determination Comparison of High Rate Algae Ponds Eric Alexander Nicolai The feasibility of algal biofuel production relies on the use of a non-potable water source. Municipal wastewater is nutrient-rich and a cost effective option as a growth media in algae ponds. However, this resource may be too valuable for algal biomass production, as reclaimed wastewater is needed for surface irrigation and groundwater recharge. This thesis compares the performance of 4.2 m2 high rate algal raceway ponds (HRAPs) to 33 m2 HRAPs grown on primary settled wastewater during a media recycling study and a growth media comparison study using wastewater and reclaimed water. The comparative metrics of performance for this study included: pond productivity, settling efficiency, and nutrient removal. This thesis also discusses the variability of algal lipid content from wastewater ponds using three different lipid determination methods. Six 4.2-m2, 0.3 m deep HRAPs were compared to nine 33-m2 HRAPs located at the San Luis Obispo Water Resource Recovery Facility (SLOWRRF). During the media recycling study, the first round of growth (Round 1) included ponds operating at 2-day and 3-day hydraulic retention times (HRTs) for both pond sizes. The pond arrangements for the second round of growth (Round 2) were the same with the exception of no 2-day HRT for the 33-m2 pond set. Net biomass productivity in the 4.2-m2 ponds under predicted the productivity of the 33-m2 ponds. Settling efficiency was comparable between the different rounds of growth for both pond sizes. Total soluble nitrogen removal was predicted using 4.2-m2 ponds. Of the three lipid determination methods, the fatty acid methyl esters (FAMEs) quantification was the most precise between replicates. However, this method determined the lowest lipid content because it quantifies a better representative lipid content by excluding other constituents not relevant to biofuel production.

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Three types of biosolids (lime-stabilized, aerobically digested, and anaerobically digested biosolids) were applied on 0.13-ha test plots on disturbed rangelands in Western Utah at rates of up to twenty times (20X) the estimated N-based agronomic rate. Soil samples at depths up to 1.5 m were collected and analyzed for nitrogen, phosphorus, regulated metals, pH, and electrical conductivity for up to two years after biosolids application. NH4-N at the soil surface (0.2 m) was primarily lost through ammonia volatilization and nitrification. This observation was consistent with reported increases in nitrate (NO3-N) concentrations found within the soil surface on the biosolids-amended sites. A nitrogen mass balance on the surface soil control volume indicated that the nitrogen residual field measurements were significantly higher than the nitrogen level estimated by accounting for nitrogen inputs (biosolids) and outputs (vegetative yield, nitrogen volatilization and nitrate leaching). Biosolids land application led to increases in vegetative growth and dry matter yield when compared to vegetation grown on control plots. Based on the Root Zone Water Quality Model (RZWQM), the model predicted NH4 and NO3 storage values at biosolids-amended sites were significantly different from the field data, which suggests that the model default and limited measured values were inappropriate for a non-irrigated rangeland landscape. The majority of total P and plant available P accumulation was found to occur primarily within the soil surface (0.2 m). Phosphorus soil residual measurements were higher than phosphorus accumulation based on a phosphorus mass balance at soil surface. The phosphorus leachability to ground water at the biosolids-amended treatment sites was low based on the molar ratio of ([P]/([Al]+[Fe])) and the potential formation of calcium phosphate (Ca3(PO4)2). Aerobically digested biosolids appeared to be the optimal biosolids type with regard to minimizing the adverse environmental effects of phosphorus based on the Phosphorus Site Index (PSI). Regulated metal concentrations (As, Cd, Cu, Pb, Mo, Ni, Se, and Zn) were well below the cumulative pollutant loading limits for biosolids-amended soils. Finally, nutrients as well as regulated heavy metals associated with biosolids land application to disturbed rangelands do not pose any significant threat to the environment.

Results from two previous studies conducted at Operable Unit 2 (OU2) of Hill Air Force Base, Utah indicate that the phytovolatilization (volatilization from leaves and trunk) of TCE by indigenous trees as well as soil surface flux may play a significant role in the removal of TCE from shallow groundwater plumes around the base. Previous studies investigated late summer and early autumn TCE leaf volatilization but no attempt was made to examine potential TCE volatilization seasonal variability and the volatilization of TCE directly from tree trunks. Whole tree transpiration rates were also not directly measured. To address those limitations and improve removal estimates, TCE removal via volatilization from leaves and tree trunks at OU2 was measured monthly during a growing season. Sap flow sensors were installed in several representative trees to directly measure transpiration rates. Transpiration rates were estimated between 15 and 160 L/day by sap flow meter data collected in 2007 and 2008. With an average growing season of 150 days, estimated TCE loss to the atmosphere through leaf volatilization was 107 to 211 mg/tree/year. An additional 4.1 mg/tree/year was estimated to volatilize directly from tree trunks. No definite seasonal trends in phytovolatilization were observed. Soil surface flux over 12,200 m2 equated to an overall loss of 390 g/year (180 days per year), with combined losses from all volatilization pathways of a maximum of 424 g/year, assuming an estimated 30 trees. This was one-sixth the removal of the interceptor trench installed in 1997, which is significant considering there was no additional cost for natural attenuation removal. Tree cores, branches, groundwater, precipitation, and nearby canal samples were collected to analyze for stable isotopes of hydrogen and oxygen. Stable isotope results, low summer precipitation, and TCE core sample concentrations suggest that the trees are using shallow groundwater as their primary source of water. There was no indication of any significant yearly or seasonal variability in TCE leaf and trunk volatilization, groundwater concentrations, and groundwater use by trees.

A study reach in a mountain stream highly influenced by groundwater was selected to test common data collection strategies used to characterize and quantify groundwater exchange processes necessary to predict solute transport. The data types collected include: high frequency discharge estimates with the use of rating curves, dilution gauging techniques with instantaneous tracer experiments, groundwater table and stream water surface elevations, vertical head gradients, and hydraulic conductivity estimates. The first two data types were categorized as stream gauging and the remaining three data types as site characterization. The stream gauging data were used to quantify net changes in stream discharge at a reach scale with rating curve predictions and dilution gauging. Each method resulted in opposite net changes at this scale. An error analysis regarding rating curve predictions and dilution gauging suggested that neither method detected groundwater exchange at this scale due to discharge estimates being statistically the same. The error in rating curve predictions was estimated using a 95% joint confidence region of model parameters and the error in dilution gauging was estimated using a first order error analysis. Dilution gauging was also performed at a sub-reach scale to quantify net changes and indicated the groundwater exchange was highly spatially variable, which was not concluded at the reach scale. To quantify a water balance more representative of the exchanges occurring, gross gains and gross losses were quantified by measuring tracer mass recoveries and were found to occur in every sub-reach. However, the error analysis concluded that nearly half of the changes were not significant, which emphasized the importance of quantifying error in stream gauging techniques used to understand surface water-groundwater interactions. The site characterization data were used to test and verify the water balance results by providing information regarding general trends and spatial variability of surface water-groundwater interactions. This study proved that one data type is not adequate to clearly characterize and quantify surface water-groundwater interactions and researchers must exercise caution when interpreting results from different data types at varying spatial scales.

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Stormwater management practices (SMPs) are engineered landscapes that treat runoff by increasing infiltration and retention, reducing the peak flow, and improving water quality. In this study, the mutual impacts of Kd and SMP loading ratio (ratio of contributing to the infiltration area) on SMP performance were assessed by developing a 1-D transport model. After simulation of 20 years of SMP service under baseline salinity conditions, Cl- was the only PTE that showed high mobility and quickly reached the groundwater table, while the other PTEs (e.g., metals) were effectively retarded in the top ~ 60 cm of the fill media. However, experimental batch and column studies showed that in higher salinity conditions, PTE Kd values reduced significantly, resulting in higher PTE mobility. Cation exchange followed by complexation with ligands were the main drivers for lower PTE Kd under high salinity conditions. Such reduced retardation can be alarming because it could readily lead to the overestimation of fill media capability in water quality enhancement. Moreover, columns experiments revealed that cycles of baseline and high salinity conditions cause substantial episodic PTE leachate from the fill media, even for PTEs like Cu and Pb that were not abundant in the fill media. The previously captured PTEs during baseline salinity were desorbed during the periods with high salinity, resulting in leaching. Dynamic transport modeling that included cycles of high and baseline salinity simulated the PTE transport more accurately because it prevented the overestimation of fill media capacity in the high salinity seasons, and it also modeled the substantial episodic leaching. PTE retardation was mainly attributed to the adsorption of metals by the top layers that caused surficial accumulations. Field samples were collected along the gradient of a SMP to study the dynamics of horizontal PTE transport. When compared with coarser particles, the fine particles (d < 10 µm) had two to three times greater PTE Kd values owing to their higher specific surface area and organic content. Fine particles, as vectors for metal transport, were readily resuspended due to runoff flowing over the SMP bed, while resuspension of coarse particles only occurred during the storms with an average intensity of greater than 4.5 mm/hour in the monitored SMP. SMPs may increase the particle and metal loads due to resuspension, imposing a high risk of point source contamination for the downstream water bodies. Also, increasing salinity to environmentally relevant levels resulted in higher stability of fine particles, yet another negative impact of high salinity on SMP performance. In-situ fill media remediation techniques like flushing with cysteine showed promising evidence of cleansing the fill media top layers, which would lower the likelihood of resuspension and redistribution of surficial accumulated PTEs. Well-designed and maintained SMPs may notably reduce the likelihood of surficial resuspension/redistribution via prioritizing infiltration over other forms of the discharge from the SMP as well as decreasing the stream power by adopting measures like appropriate vegetative cover or installing forebays, gabions, and weirs. / Environmental Engineering

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