Browsing by Author "Bott, Charles B."

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    Acid-phase and Two-phase Codigestion of FOG in Municipal Wastewater
    Varin, Ross A. III (Virginia Tech, 2013-06-11)
    Acidogenic codigestion of fats, oils, and greases (FOG) was studied at 37"C using suspended sludge digesters operated as sequencing batch reactors (SBRs). Volatile fatty acid (VFA) production was found to increase with larger FOG loading rates, although this increase was insignificant compared the theoretical VFA production from FOG addition. Long chain fatty acids (LCFAs) were found to have accumulated in the reactor vessel in semi-solid balls that were primarily composed of saturated LCFAs. Adding high FOG loadings to an APD not acclimated to LCFAs allowed for a mass balance calculation and resulted in near complete saturation of unsaturated LCFAs and significant accumulation of LCFA material in the digester, which was found to be mostly 16:0, 18:0, and 18:1. While 18:2 and 18:3 LCFAs were nearly completely removed, 18:0 and 14:0 LCFAs were produced, most likely from the degradation of 18:2 and 18:3 LCFAs. The APD pH was found to have a significant impact on the amount of accumulated LCFA material present, with higher pH levels resulting in less accumulated material. Two-phase codigestion of FOG was also studied using an APD followed by gas-phase (GPD) digesters. The two-phase systems were compared by FOG addition to the APD versus GPD. FOG addition to the APD resulted in 88% destruction of LCFAs, whereas FOG addition to the GPD resulted in 95% destruction of LCFAs. Accumulated LCFAs in the APD receiving FOG were composed mostly of stearic acid (18:0). The low pH of the APD is likely the cause of LCFA accumulation due to saturation of unsaturated LCFAs.
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    Anammox-based Technologies for Sustainable Mainstream Wastewater Treatment: Process Development, Microbial Ecology and Mathematical Modeling
    Li, Xiaojin (Virginia Tech, 2018-03-08)
    The nitritation-anammox process is an efficient and cost-effective approach for biological nitrogen removal, but its application in treating mainstream wastewater remains a great challenge. The key objectives of this dissertation are to develop nitritation-anammox process to treat wastewater with low-nitrogen strength, understand the fundamental microbiology, and optimize its operation through experimental studies and mathematic modeling. Chapter 2 showed that the nitritation-anammox process has been successfully developed in an upflow membrane-aerated biofilm reactor, where pure oxygen was delivered via gas-permeable membrane module. Chapter 3 demonstrated that hybrid anaerobic reactor (HAR) could be an effective pretreatment method to provide a relatively low COD/N ratio for nitritation-anammox reactor. In Chapter 4, a novel mathematical model has been proposed to evaluate the minimum DO requirement for the nitritation-anammox reactor to achieve the maximum TN removal under various COD/N scenarios (controlled by HRTHAR). Chapters 5 and 6 designed an OsAMX system by linking nitritation-anammox to forward osmosis to remove the reverse-fluxed ammonium while using ammonium bicarbonate as a draw solute. The microbial community structures and dynamics, spatial distributions in these bioreactors were characterized by high-throughput sequencing and fluorescent in situ hybridization techniques. The studies in this dissertation have demonstrated that nitritation-anammox process is a promising alternative for sustainable mainstream treatment with the appropriate pretreatment approach and operation optimization.
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    Assessment of a Fixed Media Partial Denitrification/Anammox Process Startup in a Full-Scale Treatment Train
    Wieczorek, Nathan Vincent (Virginia Tech, 2024-04-18)
    Partial denitrification anammox (PdNA) is an emerging wastewater treatment technology with the potential to increase process capacity and save on energy and carbon. PdNA circumvents potential issues with stability of the more familiar mainstream partial nitritation anammox (PNA) process. The PdNA process can be used to effectively remove ammonia, nitrate, and nitrite from mainstream municipal waste streams. To retain slow growing anammox, some sort of retention system is needed with media being a common solution to this problem. PdNA has been successfully implemented in mainstream full-scale systems in sand filters and with moving media. The goal of this study was to assess the denitrifying capabilities, anammox treatment capacity, and effective surface area to volume of two types of fixed media. A nitrifying pilot was set up to assess the effective surface area to volume. To assess the nitrifying and anammox ammonia removal capabilities of the fixed media, a fixed media PdNA system was installed in the second anoxic zone of a full-scale municipal wastewater treatment plant. The fixed media system consisted of three modules of sheets modified to mimic a plug flow system. After accounting for the estimated nitrate removal from mixed liquor, denitrification rates normalized to media surface area were 0.52 +/- 1.9 g/m2-day in the first module, 0.62 +/- 0.91 g/m2-day for the second module, and 0.56 +/- 0.90 g/m2-day for the third module. In ex situ batch testing it was found that maximum ex-situ anammox ammonia removal rates for the
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    Balancing Bromate Formation, Organics Oxidation, and Pathogen Inactivation: The Impact of Bromate Suppression Techniques on Ozonation System Performance in Reuse Waters
    Buehlmann, Peter Hamilton (Virginia Tech, 2019-09-10)
    Ozonation is an integral process in ozone-biofiltration treatment systems and is beginning to be widely adopted worldwide for water reuse applications. Ozone is effective for pathogenic inactivation and organics oxidation: both increasing assimilable organic carbon for biofiltration and eliminating trace organic contaminants which may pose a threat to human health. However, ozone can also form disinfection byproducts such as bromate from the oxidation of naturally occurring anion bromide. Bromate is a known human carcinogen and is regulated by the EU, WHO, and USEPA to a maximum limit of 10µg/L. In waters high in bromide, especially above 100µg/L, bromate formation becomes a major concern. In the secondary wastewater effluent studied, bromide concentration may exceed 500µg/L. Several bromate suppression techniques have been devised in previous work, including free ammonia addition, monochloramination, and the chlorine-ammonia process. While free ammonia addition was not found to adequately reduce bromate formation below the required MCL, monochloramine addition and the chlorine-ammonia process were found to be effective. However, the impact of these chemical suppression techniques on organics oxidation and disinfection has not been fully studied. This study explored the impact of these bromate suppression techniques at a wide range of ozone doses on bromate formation, pathogenic inactivation, ozone-refractory organics oxidation through the surrogate 1,4-dioxane, and N-nitrosodimethylamine (NDMA) formation. Additionally, bromate suppression mechanisms of monochloramine were explored further through a variety of different water quality parameters, such as through hydroxyl radical exposure and ultraviolet absorption spectrum measurements, which were correlated and utilized to develop a hydroxyl radical exposure predictive model.
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    Bioaugmentation and Retention of Anammox Granules to a Mainstream Deammonification Bio-Oxidation Pilot with a Post Polishing Anoxic Partial Denitrification/Anammox Moving Bed Biofilm Reactor
    Campolong, Cody James (Virginia Tech, 2019-03-25)
    The Chesapeake Bay watershed has seen an increase in population, nutrient loading, and stringent effluent limits; therefore, cost-effective technologies must be explored and implemented to intensify the treatment of regional wastewater. This work describes the bioaugmentation and retention of anammox (AMX) granules in a continuous adsorption/bio-oxidation (A/B) mainstream deammonification pilot-scale process treating domestic wastewater. The AMX granules were collected from the underflow of a sidestream DEMON® process. The bioaugmentation rate was based on several factors including full-scale sidestream DEMON® wasting rate and sidestream vs mainstream AMX activity. The retention of bioaugmented AMX granules required a novel settling column at the end of the deammonification step. The settling column was designed to provide a surface overflow rate (SOR) that allowed dense AMX granules to settle into the underflow and less dense floccular biomass to outselect into the overflow. B-Stage was operated to out-select nitrite oxidizing bacteria (NOB) by maintaining an ammonia residual (>2 mg NH4-N/L), a relatively high dissolved oxygen (DO) (>1.5 mg O2/L) concentration, an aggressive solids retention time (SRT) for NOB washout, and intermittent aeration for transient anoxia. AMX activity was not detected in the mainstream at any time. The settling column AMX retention quantification suggested but did not confirm AMX were maintained in the mainstream. NOB were not suppressed during this study and no nitrite accumulation was present in the mainstream process. It was theorized that AMX granules were successfully settled into the settling column underflow and accumulated in the intermittently mixed sidestream biological phosphorus reactor (SBPR) where they disintegrated. This work also describes optimization of carbon addition to an anoxic partial denitrification anammox (PdN/A) moving bed biofilm reactor (MBBR) testing glycerol, acetate, and methanol as carbon sources to maximize total inorganic nitrogen (TIN) removal through the anammox pathway and to minimize effluent TIN. A carbon feeding strategy was developed and was evaluated by the extent of partial denitrification vs full denitrification (partial denitrification efficiency, PdN efficiency). All three carbon sources were capable of high TIN removal, low effluent TIN, and moderate to high PdN efficiency. Average TIN removal for glycerol was 10.0 ± 3.6 mg TIN/L, for acetate it was 8.7 ± 2.9 mg TIN/L, and for methanol it was 11.5 ± 5.6 mg TIN/L. Average effluent TIN for glycerol was 6.0 ± 4.0 mg TIN/L, for acetate it was 5.0 ± 1.1 mg TIN/L, and for methanol it was 4.3 ± 1.5 mg TIN/L. Average PdN efficiency for glycerol was 91.0 ± 9.0%, for acetate it was 88.0 ± 7.7%, and for methanol it was 74.0 ± 8.5%. When PdN efficiency was factored into the cost of each carbon source, methanol was 5.83% cheaper than glycerol per mass TIN removed and 59.0% cheaper than acetate per mass TIN-N removed.
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    Characterizing Kinetic Shifts in Nitrifying, Denitrifying, and Phosphorus Removing Biomass Adapting to Low DO
    Kisling, Tyler Houston (Virginia Tech, 2022-11-03)
    Low dissolved oxygen (DO) biological nutrient removal (BNR) is becoming a viable option to improve the energy efficiency of BNR. To properly model and design BNR processes for low DO operation, it is critical to fully understand how nitrifier, denitrifier, and polyphosphate accumulating organism (PAO) oxygen kinetics adapt in a shift from traditional DO operation (2 mg O2/L or more) to low DO operation. Research characterizing how oxygen kinetics shift over time in activated sludge biomass adapting to low DO is limited. Therefore, a method to characterize oxygen kinetics for nitrifiers, denitrifiers, and PAOs simultaneously is lacking. Here a method was developed to simultaneously measure the oxygen kinetics of nitrifiers, denitrifiers, and PAOs. This method, termed the SND and P-Uptake Oxygen Kinetics test, was able to estimate the ammonia oxidizing bacteria (AOB) oxygen half-saturation coefficient, ammonia maximum removal rate, denitrifier oxygen inhibition coefficient, total inorganic nitrogen (TIN) maximum removal rate, PAO oxygen half-saturation coefficient, phosphorus maximum uptake rate, and a simultaneous nitrification and denitrification (SND) optimum operation point. Three tests were conducted on the Virginia Initiative Plant (VIP) BNR Activated Sludge Pilot while it was operating at a process DO of 2 mg O2/L, and one test while it was operating at 1.5 mg O2/L. The measurements among the three initial tests showed high similarity in their parameter estimates. Estimated oxygen half-saturation and oxygen inhibition coefficients were compared to current suggested ranges and were within the expected magnitudes. At 2 mg O2/L, denitrifier oxygen inhibition coefficients and PAO oxygen half-saturation coefficients were estimated to be remarkably low here, under 0.4 and 0.1 mg O2/L, respectively. AOB oxygen half-saturation coefficients were variable here in the range of 0.62 to 2.57 mg O2/L, seeming to vary with available ammonia concentrations. Upon comparison with a previously developed respirometric test for nitrifier oxygen kinetics, termed the Declining DO test, the AOB oxygen half-saturation coefficient from the SND and P-Uptake Oxygen Kinetics test and the Declining DO test, when both were conducted on the VIP BNR Pilot, showed a similar trend. This provided validation for the AOB oxygen kinetics here and the usefulness of the test developed here. Additionally, measuring and plotting AOB and denitrifier oxygen kinetics together produced an intersection point where ammonia removal rates were equal to TIN removal rates. This intersection point was an optimum point for SND during the conditions of the test. This method can be used to characterize and track oxygen kinetic changes in a BNR system adapting from high to low DO.
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    Characterizing the Drivers of Carbon Use in Post-Anoxic Denitrification
    Bauhs, Kayla Terese (Virginia Tech, 2021-07-26)
    Three of Hampton Roads Sanitation District's (HRSD's) conventional activated sludge Water Resource Recovery Facilities (WRRFs) add methanol for post-anoxic denitrification: the Virginia Initiative Plant (VIP), Nansemond Plant (NP), and Army Base (AB). From 2017-2020, VIP averaged 0.49 ± 0.03 lb COD/lb N removed, while NP and AB averaged 1.48 ± 0.06 and 2.11 ± 0.15 lb COD/lb N, respectively. Significant methanol savings at VIP may result from post-anoxic denitrification using internal carbon that was stored in the anaerobic zone. An investigation into the factors affecting internal carbon-driven (internal C) denitrification was done via a series of batch tests. The capacity for internal C denitrification was demonstrated with sludge from all three WRRFs, despite not necessarily being used full-scale. For each WRRF, an increase in these rates correlated to higher phosphorus uptake rates, suggesting a dependence on the PAO population. Shorter aerobic times and more acetate in the anaerobic stage were shown to increase internal C denitrification rates to varying degrees, and this type of denitrification was only observed for bio-P biomass that was also nitrifying. Beyond internal carbon, other denitrification factors explored include moving the methanol dose point further into the anoxic zone, longer post-anoxic residence times, plug-flow conditions, solids residence time (SRT), and anoxic conditions prior to methanol dosing. Contributions from slowly biodegradable COD were minimal. Understanding the conditions that promote denitrification with internal carbon or other carbon sources would be required for effective strategies to achieve methanol savings at NP and AB that would rival those at VIP.
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    Comparison of Aeration Strategies for Optimization of Nitrogen Removal in an Adsorption/Bio-oxidation (A/B) Process with an Emphasis on Ammonia vs. NOx (AvN) control
    Sadowski, Michael Stuart (Virginia Tech, 2015-12-08)
    Research was performed at a pilot-scale wastewater treatment plant operating an adsorption/bio-oxidation (A/B) process at 20C. The study compared B-Stage performance under DO Control, Ammonia Based Aeration Control (ABAC), and Ammonia vs. NOx (AvN) control. AvN in 1) fully-intermittent and 2) intermittently-aerated MLE configurations was compared to DO Control and ABAC, each with continuous aeration, in an MLE configuration. The study also examined operation of each aeration strategy with two different feed types: A-Stage effluent (ASE) and primary clarifier effluent (PCE). Operating modes were compared on the basis of nitrogen removal performance, COD utilization efficiency for denitrification, and alkalinity consumption. AvN was found to provide comparable nitrogen removal performance to DO Control and ABAC. The highest nitrogen removal performance was seen when operating DO Control (81.4 ± 1.2%) and ABAC (81.1 ± 1.2%) with PCE. High nitrogen removal efficiency (77.5 ± 6.1%) was seen when fully-intermittent AvN operation was fed ASE containing a high particulate COD fraction. A high effluent nitrite accumulation ratio (NAR = NO2-/(NO2-+NO3-)) was seen during this period (46 ± 15%) accompanied by the out-selection of Nitrospira. Feeding effluent from AvN control to an Anammox MBBR improved removal efficiency. Increased soluble COD loading resulted in greater nitrogen removal with strategies operating in an MLE configuration while particulate COD was found to be important for processes where removal was designed to occur in downstream reactors. Efficiency of COD for denitrification was found to vary based on the amount and type of influent COD; however AvN in an MLE configuration was found to use COD more efficiently than fully-intermittent AvN. In either configuration, AvN required less alkalinity addition than DO Control or ABAC. High sCOD concentrations in PCE led to increased nutrient removal as compared to ASE but increased heterotrophic growth and mixed liquor concentrations in the B-Stage making the A-Stage an attractive option for its ability to control the C/N ratio fed to BNR processes.
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    Development of Kinetic Parameterization Methods for Nitrifying Bacteria using Respirometry
    Malin, Kyle George (Virginia Tech, 2022-01-19)
    Understanding how nitrifiers react when exposed to low DO conditions could provide a greater understanding of low DO operations in full-scale biological wastewater treatment. Previous methods to observe nitrifier oxygen kinetics do exist in literature, however they are inefficient and labor intensive. Other more efficient methods require the use of selective inhibitors, which alter the characteristics of the biomass. This study developed a time and labor efficient respirometric method to distinctly measure oxygen half-saturation coefficients for both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) without the use of selective inhibitors. By eliminating the use of inhibitory substances, representative biomass characteristics were maintained throughout the tests. The developed method, called the declining DO method, consisted of using a high-speed dissolved oxygen (DO) probe to measure relative oxygen uptake rates (OUR) within a batch reactor when varying substrates (ammonia and nitrite) were present in excess within the system. A forward model was developed based on Monod kinetics to simultaneously fit Monod curves to the experimental OUR data. These curves were fit by solving for optimum oxygen kinetic parameters representing endogenous respiration, NOB, and AOB. An inverse model using Markov chain Monte Carlo analysis was applied to the results found in the forward model to provide statistical validation of the proposed respirometric method. A separate method, called the substrate utilization rate test, was conducted in parallel with the declining DO tests to compare and verify oxygen half-saturation coefficient results. Parallel tests were conducted using biomass samples from three different Hampton Roads Sanitation District (HRSD) full-scale facilities. Operating conditions between the three HRSD facilities were considered when performing parallel testing, including averages for DO, solids retention time (SRT), and floc size. Average floc size was found to have a significant effect on the observed oxygen half-saturation values. Observed trends for the KO values estimated using the two methods remained consistent throughout all tests, where KO,NOB was always lower than KO,AOB. The comparison of the two methods highlighted some faults associated with the substrate utilization rate test, which is commonly used in literature to observe nitrifier oxygen kinetics. The declining DO method appeared to be more resistant to potential experimental error and required less than half the time compared to the substrate utilization rate test. The development of the declining DO method without the use of selective inhibitors provided a more time and labor efficient technique for estimating apparent KO values for NOB and AOB without sacrificing biomass characteristics representative of the full-scale treatment process. Biomass samples collected from variable treatment process conditions yielded consistent parallel test results, providing further evidence that the proposed declining DO method can be a robust and reliable technique for distinctly measuring apparent oxygen half-saturation values for NOB and AOB.
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    Evaluation of Alternative Electron Donors for Denitifying Moving Bed Biofilm Reactors (MBBRs)
    Bill, Karen Alexandra (Virginia Tech, 2009-05-06)
    Moving bed biofilm reactors (MBBRs) have been used effectively to reach low nutrient levels in northern Europe for nearly 20 years at cold temperatures. A relatively new technology to the US, the MBBR has most typically been used in a post-denitrification configuration with methanol for additional nitrate removal. Methanol has clearly been the most commonly used external carbon source for post-denitrification processes due to low cost and effectiveness. However, with the requirement for more US wastewater treatment plants to reach effluent total nitrogen levels approaching 3 mg/L, alternative electron donors could promote more rapid MBBR startup/acclimation times and increased cold weather denitrification rates. Bench-scale MBBRs evaluating four different electron donor sources, specifically methanol, ethanol, glycerol, and sulfide (added as Na2S), were operated continuously at 12 °C, and performance was monitored by weekly sampling and insitu batch substrate limiting profile testing. Ethanol and glycerol, though visually exhibited much higher biofilm carrier biomass content, performed better than methanol in terms of removal rate (0.9 and 1.0 versus 0.6 g N/m²/day.) Maximum denitrification rate measurements from profile testing suggested that ethanol and glycerol (2.2 and 1.9 g N/m²/day, respectively) exhibited rates that were four times that of methanol (0.49 g N/m²/day.) Sulfide also performed much better than any of the other three electron donors with maximum rates at 3.6 g N/m²/day and with yield (COD/NO₃-N) that was similar to or slightly less than that of methanol. Overall, the yield and carbon utilization rates were much lower than expected for all four electron donors and much lower than previously reported; indicating that there could be advantages for attached growth versus suspended growth processes in terms of carbon utilization rates. The batch limiting NO₃-N and COD profiles were also used to find effective Ks values. These kinetic parameters describe NO₃-N and COD limitations into the biofilm, which affect the overall denitrification rates. Compared to the other electron donors, the maximum rate for methanol was quite low, but the estimated Ks value was also low (0.4 mg/L N). This suggests high NO₃-N affinity and low mass transfer resistance. The other three electron donors estimated higher Ks values, indicating that these biofilms have high diffusion resistance. Biofilm process modeling is more complex than for mechanistic suspended growth, since mass transfer affects substrate to and into the biofilm. Simulating the bench-scale MBBR performance using BioWin 3.0, verified that μmax and boundary layer thickness play key roles in determining rates of substrate utilization. Adjustments in these parameters made it possible to mimic the MBBRs, but it is difficult to determine whether the differences are due to the MBBR process or the model.
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    Evaluation of an Industrial Byproduct Glycol Mixture as a Carbon Source for Denitrification
    Liang, Wei (Virginia Tech, 2013-06-24)
    In order to meet increasingly stringent total nitrogen limits, supplemental carbon must be added to improve the performance of the biological nutrient removal process. An industrial by-product that contained ethylene glycol and propylene glycol was used as a substitute carbon source for methanol in this study. The objectives of this study were to investigate the efficiency of using the glycol mixture as carbon source, including the calculation of denitrification rate and yield at two different initial concentrations of glycols. Possible inhibition effect on nitrification was also investigated. Three SBR reactors were operated by adding methanol, a low dosage of glycol, and a high dosage of glycol into the reactors. The low dosage glycol reactor exhibited the best performance, with the highest denitrification rate of 11.55 mg NOx-N/g MLVSS"h and the lowest yield of 0.21 mg VSS/mg COD. Small nitrite accumulation was observed in the low dosage glycol reactor (COD=185"•15 mg/L), but effluent quality was not influenced. Excess glycol in the reactor caused deteriorated performance. The high dosage glycol reactor (COD=345"•20 mg/L) performed with the lowest denitrfication rate of 8.56 mg NOx-N/g MLVSS"h and the highest yield of 0.55 mg VSS/ mg COD. The reactor with the high dosage of glycol also inhibited the lowest nitrification rate of 1.15 mg NH3-N oxidized/g MLVSS"h, which indicated that excess glycol may cause nitrification inhibition.
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    Evaluation of Bromate Formation and Control using Preformed Monochloramine in Ozonation for Indirect Potable Reuse
    Pearce, Robert Lindsay MacCormack (Virginia Tech, 2018-12-13)
    Ozone is a powerful oxidant and disinfectant used in potable wastewater reuse to destroy specific harmful compounds, including pharmaceuticals, personal care products and endocrine disrupting compounds. Ozonation also increases the biodegradability of recalcitrant organic compounds and inactivates disease-causing microbes. However, bromate, a regulated possible human carcinogen can form when bromide is present due to natural or industrial sources. Pilot-scale testing on wastewater treatment plant effluent with high bromide concentrations showed that the addition of preformed monochloramine could reduce bromate formation by as much as 97%. Monochloramine addition was able to keep concentrations below the U.S. Environmental Protection Agency Maximum Contaminant Level of 10 µg/L while exceeding 3-log or 99.9% virus removal credit. Preforming monochloramine in separate carrier water prior to addition upstream of ozonation eliminated the potential for disinfection byproduct formation when monochloramine is formed in the main water flow. This also allowed for the mechanisms of bromate suppression by monochloramine to be examined without the influence of reactions between chlorine and dissolved organic matter present. This research can help increase the application of ozonation in water reuse.
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    Evaluation of Contaminant Removal Through Soil Aquifer Treatment by a Lab Scale Soil Column Experiment Including a Trace Contaminant Spike Test
    Dziura, Thomas Michael (Virginia Tech, 2020-05-28)
    Soil aquifer treatment (SAT), the removal of contaminants during percolation through soil, is a strategy employed in managed aquifer recharge (MAR), one method of indirect potable water reuse. As part of Hampton Roads Sanitation District's (HRSD) MAR project, The Sustainable Water Initiative for Tomorrow (SWIFT), a soil column study was performed using four columns filled with sand taken from the Potomac Aquifer System (PAS) as well as water from various stages in SWIFT's 1MGD demonstration facility. Two pairs of two columns were operated in series, simulating 3 days and 1 month of travel time through aerobic to anaerobic conditions. During Phase 1 of testing, each pair of columns was fed from different stages in the SWIFT treatment process. During Phase 2 of testing, one set of columns was spiked with a conservative tracer bromide, and several contaminants of emerging concern (CECs). The contaminants monitored during both phases included total organic carbon (TOC), nitrogen species, and the disinfection byproducts bromate and NDMA. During Phase 2 of testing, CECs, iron, arsenic, bromide, and sulfate were monitored in addition to those monitored during Phase 1. About 50% of the TOC was removed within 3 days of travel time, with no additional removal observed in 1 month. Nitrate was conserved in the 3-day columns, but completely removed after 1 month, indicating denitrification. Bromate and NDMA were reduced significantly in the 3-day columns and mostly non-detect in the 1-month effluent. Many of the spiked CECs were reduced significantly in the 3-day column indicating degradation. Three compounds exhibited some retardation through both columns but were not degraded. A few compounds, notably perfluorooctanoic acid (PFOA), showed no retardation or degradation.
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    Evaluation of gasoline-denatured ethanol as a carbon source for wastewater denitrification
    Kazasi, Anna (Virginia Tech, 2011-12-07)
    Methanol (MeOH) is a common external carbon source for wastewater denitrification, because of its low cost and low sludge yield. Ethanol (EtOH), on the other hand, is more expensive, but yields higher denitrification rates. This study introduces gasoline-denatured ethanol (dEtOH), which is now being produced in large quantities for the production of E10 gasoline, as an alternative carbon source. The gasoline added, as the denaturant, is known as "straight-run" gasoline; a lower grade material that contains mostly aliphatic compounds, but lacks the components that normally boost the octane rating, such as benzene, toluene, ethylbenzene and xylenes (BTEX). Herein are presented the results of using dEtOH, EtOH (95.5% ethanol-4.5% water) and MeOH for denitrification in lab-scale, sequencing batch reactors (SBRs). We also focused on the quantification of BTEX present in dEtOH solution and the inhibition potential of these compounds on both nitrification and denitrification. BTEX content in the dEtOH solution had low and consistent concentration. Ethylbenzene and o-xylene were not detected in the reactor. The removal rates of benzene, toluene and m-xylene were 3.1°1.4, 3.4°1.9 and 0.6°0.4 ?g/L·h, respectively. BTEX were not detected in the effluent and did not inhibit nitrification and denitrification. The denaturant did not affect biomass production or the settling properties of the sludge. The yield (COD/NOx-N) and denitrification rates of dEtOH were similar to those of EtOH and higher than those of MeOH. The cost of dEtOH ($0.91//lb NO??-N removed) is slightly higher than that of methanol ($0.74/lb NO??-N removed). Using dEtOH as an external carbon source is, therefore, very promising and utilities will have to decide if it is worth paying a little extra to take advantage of dEtOH's benefits.
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    Evaluation of Glycerol and Waste Alcohol as Supplemental Carbon Sources for Denitrification
    Uprety, Kshitiz (Virginia Tech, 2013-02-27)
    Supplemental carbon has been successfully added and implemented at biological nutrient removal treatment plants all around the world in order to reach low nitrogen discharge limits. Although, methanol has been the most prevalent external electron donor used due to its low cost and effectiveness, many utilities are moving away from it due to cost volatility, safety issues, and hindered performance in cold weather conditions. Many sustainable and alternative sources are being researched, such as glycerin-based products (Rohrbacher et al., 2009), sugar-based waste products (Pretorius et al., 2007), and effluents from food and beverage industries (Swinarski et al., 2009). Four 22-L sequencing batch reactors (SBRs) were utilized to investigate four different supplemental carbon sources: 100% reagent grade methanol, 100% reagent grade glycerol, bio-diesel glycerol waste, and an industrial waste alcohol. These reactors were operated at 20�"C with a 15 day solids retention time. Intensive profiles were carried out three times a week to monitor performance and collect data to calculate COD consumption: nitrate-nitrogen denitrified (C: N) ratios. The glycerol and bio-diesel glycerol waste reactors performed similarly as they both exhibited significant and consistent nitrite accumulation during the entire experiment. Based on reactor restart, nitrite accumulation was evident and significant within two days after startup and consistent for all further operation. Rapid nitrate to nitrite reduction coincident with COD uptake was also observed. The two glycerol reactors demonstrated an increased carbon demand over time. The commonly reported hypothesis that activated sludge transitions from a generalist population of ordinary heterotrophic organisms (OHO) that use substrate, glycerol in this case, less efficiently, producing low yields and slow growth rates, to a specialist population that use glycerol more efficiently, with higher yields and slightly faster growth rates, was verified. This is known as the generalist-specialist theory. While this hypothesis appears to be supported from an overall analysis of the data, the actual mechanism seems to be intracellular glycerol storage coincident with rapid nitrate to nitrite denitrification, followed by slow nitrite reduction to nitrogen gas. This can possibly lead to degradation of the internally stored glycerol in the aerobic zones of the following cycle, implying a significant economic impact with glycerin addition. Although this has not been investigated further, it is believed that the presence of glycogen-accumulating organisms (GAOs) could be responsible for this intracellular storage of glycerol resulting in partial denitrification and accumulation of nitrite. The methanol and waste alcohol reactors also performed similarly to each other and neither of these reactors exhibited any nitrite accumulation upon carbon addition. The specific denitrification rate (SDNR) of the waste alcohol was slightly higher and increased more rapidly than for the methanol reactor. The C: N for these two reactors was comparable, and methanol was close to the expected value of 4.8 g COD utilized/ g nitrate-N denitrified. The C: N for the waste alcohol during steady state operation was somewhat higher than expected. The waste alcohol exhibited an �"alcoholic�" odor upon addition to the reactors during startup, but this issue diminished as the biomass became acclimated to the waste alcohol. Both industrial waste alcohol and glycerol can be considered viable alternatives to methanol; however, glycerol supplementation for denitrification can be problematic. If the glycerol dose is not optimized, then partial denitrification is observed and will lead to nitrite in the effluent, causing an increased chlorine demand for plants applying chlorine for disinfection. This is thought to occur due to energy limitations resulting from carbon storage and thus, using glycerol at treatment plants performing biological phosphorus removal (BPR) or enhanced biological phosphorus removal (EBPR) might see inefficient removal due to selective carbon utilization by polyphosphate-accumulating organisms (PAOs), or due to competition between PAOs and GAOs. Although denitrification of nitrate to nitrite occurs more quickly with prolonged glycerol addition, it also results in an increased carbon demand which causes a significant impact economically.
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    Evaluation of Nitrification Inhibition Using Bench-Scale Rate Measurements, Profile Sampling, and Process Simulation Modeling
    Yi, Phill Hokyung (Virginia Tech, 2010-02-25)
    The Hampton Roads Sanitation District (HRSD) operates thirteen treatment plants in the eastern Virginia area with a combined capacity of 231 million gallons per day (mgd). The Nansemond Treatment Plant (NTP) is one of the larger facilities, and is designed to treat 30 mgd using a 3-stage Virginia Initiative Process (VIP) biological nutrient removal (BNR) process. The majority of the influent is domestic, but there is also a large industrial contribution, particularly from a hog processing facility, landfill leachate, and significant loads from septage and grease deliveries (Bilyk et al, 2008). NTP is currently being upgraded to a 5-stage Bardenpho process to achieve improved total nitrogen (TN) removal. For several years starting in about 2001, NTP has experienced continuous and sporadic nitrification upsets that cannot be explained by plant operations events. Sporadic nitrification upsets are characterized by sharp increases in effluent ammonia and nitrite with decreases in nitrate concentrations due to reduced growth rates in bacteria. The result is reduced overall total nitrogen (TN) removal. Continuous inhibition is evidenced by a previous engineering report by Hazen and Sawyer, P.C. (2007), whereby it was suggested that the ammonia oxidizing bacteria (AOB) maximum specific growth rate (μmax) be reduced from 0.9 to 0.57 days-1. This has significant implications in terms of the required aeration volume for consistent nitrification at cold temperatures. The objective of this project was to determine whether the NTP influent wastewater does in fact exhibit inhibition to ammonia (AOB) and nitrite oxidizing bacteria (NOB), evaluated independently, and to determine the impact on polyphosphate accumulating organism activity (PAO). Because the historical operational experiences and data analysis suggested inhibited AOB and NOB activity, an investigation was initiated targeting the source of that inhibition. After conducting seventeen weeks of batch experiments the source of inhibition was not determined. Batch experiments however, did reveal other possible sources of inhibition including large amounts of chemical toilet waste received at NTP possibly containing quaternary ammonium compounds (QACs). Due to available blower capacity during construction it was planned that nitrification would not be maintained during the fall of 2009. In an effort to stop nitrification, the solids retention time (SRT) was purposely reduced over a period of about one month (as wastewater temperature cooled) until additional blower capacity was available. This provided an opportunity to study baseline nitrification kinetics and determine the potential for continuous inhibition through profile sampling. Simulation modeling of the profile sampling and plant data was performed with Biowin 3.1 (EnviroSim, Ltd.) as a means for comparison and to generate μmax values for AOB to compare with the original design μmax of 0.57-1. Profile sampling was conducted from the primary effluent to the secondary effluent with samples collected along the length of the BNR process. This was being done to address the following issues: • Conduct baseline sampling prior to a more detailed nitrification inhibition study estimated to begin in May 2010, which will include influent sampling and the operation of bench-scale sequencing batch reactors. This will be used to establish "normal" COD, nutrient and DO profiles though the VIP process without (and possibly with) the impact of inhibitory conditions, specifically with respect to N conversions and P release and uptake along the process. • Evaluate the potential for nitrite accumulation in the process and its potential effect on aerobic phosphate uptake by phosphorus accumulating organisms (PAOs). • Evaluate the impact of sporadic ferric chloride addition to the biological process as a means of preventing effluent TP exceedances. • Evaluate the design μmax to the actual observed μmax for AOB through simulation modeling. • Compare modeling and observed profile data for signs of any continuous nitrification inhibition. Experimental results from batch-rate testing confirmed the sporadically inhibitory nature of NTP primary effluent when combined with other stable nitrifying biomasses. Investigation into quaternary ammonium compounds (QACs) which were contained in the chemical toilet waste suggested that QACs at higher concentrations caused some inhibition of NOB activity, but no significant impact on AOB activity. Profile sampling demonstrated no signs of sporadic or continuous nitrification inhibition or impact of nitrite accumulation and ferric chloride addition on biological treatment processes. Modeling of the profile data generated similar profiles; however, there were slight variations as the model predicted nitrification to stop earlier than what was actually observed. From the modeling it was also determined that the maximum specific growth rate (μmax) of ammonia oxidizing bacteria (AOB) was in the range of 0.50 – 60 days-1. This supported batch and profile work that showed NTP PE exhibited some degree of continuous inhibition. Diurnal loadings however, were not accounted for in the modeling which could slightly underestimate the actual AOB μmax value. Several suspected inhibitors were eliminated as potential causes of inhibition, including waste from a hog processing facility, landfill leachate, the addition of ferric chloride, plant internal recycle streams, branches of the collection system, and chemical toilet disinfectants containing QACs. References Bilyk, K., Cubbage, L., Stone, A., Pitt, P., Dano, J., and Balzer, B. 2008. Unlocking the Mystery of Biological Phosphorus Removal Upsets and Inhibited Nitrification at a 30 mgd BNR Facility. Proceedings of the Water Environment Federation Technical Conference and Exposition, 2008. Hazen and Sawyer. 2007. Nansemond Treatment Plant Nutrient Reduction Improvement Technical Memorandum.
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    Evaluation of Nitrification Inhibition Using Sequencing Batch Reactors and BioWin Modeling, and the Effect of Aqueous Film Forming Foam on Biological Nutrient Removal
    Hingley, Daniel McCabe (Virginia Tech, 2011-03-04)
    To evaluate continuous and sporadic nitrification inhibition at the HRSD Nansemond Wastewater Treatment Plant, which has a history of nitrification upsets, continuous sequencing batch reactors (SBRs) were operated to simulate the full-scale plant. Four reactors were operated in this study. One reactor was fed with raw influent (RWI) from the Nansemond Wastewater Treatment Plant (NP). Another was fed with NP primary clarifier influent (PCI), which includes the raw influent, as well as plant recycle streams and truck delivered septage, grease, and chemical toilet waste. The remaining two SBRs were fed with RWI from the VIP Wastewater Treatment Plant, which achieves reliable nitrification year-round. One of these VIP SBRs would remain a control at all times, while the other would be used to evaluate suspected inhibitors to nitrification. The first phase of this project was to determine whether NP was inhibited when compared to VIP, which would be ascertained through a comparison of nitrification performance. The next step was to determine whether the source of inhibition was an industry within the collection system or plant recycles and delivered wastes, which would be ascertained based on comparison of the NR RWI and NP PCI reactor performance. If nitrification performance was comparable between the two SBRs, then it would indicate that the source of inhibition is somewhere within the collection system, whereas if the NP PCI reactor was inhibited when compared to the NP RWI reactor, it would mean that the inhibition is a result of plant recycles or delivered wastes. The next phase would be to determine the specific source by either working back up the collection system or by testing the plant recycles and delivered wastes. After approximately 27 weeks of SBR sampling and monitoring, there was no statistical difference between nitrification rates in reactors A and B, and no signs of nitrification inhibition in either reactor when compared to the VIP control Simulation modeling of reactors A, B, and D (control) was performed with BioWin 3.1 (EnviroSim, Ltd.) as a means for comparison and to ensure reactors were performing as intended. Results suggest that there was some level of continuous inhibition for both NP RWI and PCI reactors, however no sporadic inhibition events were observed. It also appeared that the VIP RWI control reactor experienced some level of continuous nitrification inhibition, although BioWin modeling results indicated that both NP RWI and NP PCI were more inhibitory than VIP RWI. Conclusions drawn from modeling results conflict with those drawn from nitrification rate comparisons. Since solids retention time (SRT) was maintained at exactly 15 days for all reactors, it was assumed that a direct comparison of corrected maximum nitrification rates could be used to compare nitrification performance between SBRs, however the significantly higher influent COD, TKN, and TSS loading to the NP reactors resulted in higher nitrification rates when compared to the VIP RWI control reactors. This was confirmed with BioWin modeling, which also showed consistently higher nitrification rates for NP when compared to VIP RWI, however BioWin also showed that maximum specific growth rates for ammonia-oxidizing bacteria (?maxAOB) in NP RWI and PCI were consistently lower than the ?maxAOB for VIP RWI. This indicates that NP RWI and NP PCI are slightly inhibitory to nitrification, with ?maxAOB values between 0.65 and 0.75 days??, and the fact that both NP RWI and NP PCI are both inhibitory suggests that the source of inhibition is somewhere within the collection system. In a simultaneous study using the reactors fed with raw influent from the VIP Wastewater Treatment Plant, reactor C was spiked with aqueous Film Forming Foam (AFFF) such as that used in methanol feed facility fire suppression systems, while reactor D was left as a control. AFFF was initially added at a concentration of 20 ppm with no effect on either nitrification or denitrification performance. When increased to 40 ppm, the AFFF reactor experienced a complete loss of denitrification, while nitrification rates were not affected when compared with the control reactor. Reactor C took 31 days to fully acclimate to the AFFF feed and fully regain denitrification, and then exhibited no other performance problem throughout this acclimation period. This result was completely unexpected, appears to be repeatable, and is one of very few cases of selective denitrification (and COD uptake) inhibition, as opposed to more commonly observed nitrification inhibition.
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    Evaluation Of Nitrification Kinetics For A 2.0 MGD IFAS Process Demonstration
    Thomas, Wesley Allan (Virginia Tech, 2009-03-30)
    The James River Treatment Plant (JRTP) operated a 2 MGD Integrated Fixed Film Activated Sludge (IFAS) demonstration process from November 2007 to April 2009 to explore IFAS performance and investigate IFAS technology as an option for a full scale plant upgrade in response to stricter nutrient discharge limits in the James River Basin. During the study, nitrification kinetics for both ammonia and nitrite oxidizing bacteria and plastic biofilm carrier biomass content were monitored on a near-weekly basis comparing the IFAS media, the IFAS process mixed liquor, and mixed liquor from the full-scale activated sludge process. Carrier biomass content is variable with respect to temperature and process SRT and relates to the localization of nitrification activity in the IFAS basin. Similar to trends observed for carrier biomass content (Regmi, 2008), ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) activity also shifted from the fixed film to the suspended phase as water temperatures increased and vice versa as the temperature decreased. The data suggest that AOB activity occurs on the surface of the biofilm carriers, while NOB activity remains deeper in the biofilm. During the highest temperatures observed in the IFAS tank, AOB activity on the media contributed as little as 30% of the total nitrification activity in the basin, and after temperatures dropped below 20 °C, AOB activity in the fixed film phase made up 75% of the total activity in the IFAS basin. During the warmest period of the summer, the media still retained more than 60% of the total NOB activity, and more than 90% of the total NOB activity during the period of coldest water temperature. This trend also points out that some AOB and NOB activity remained in the mixed liquor, even during the coldest periods. The retention of nitrification activity in the mixed liquor indicates that the constant sloughing of biomass off of the carriers allowed for autotrophic activity, even during washout conditions. Carrier biomass content and nitrification rates on the IFAS media remained constant along the length of the basin, indicating that the IFAS tank is will mixed with respect to biomass growth, although there was a concentration gradient for soluble species (NH₄-N, NO₂-N, NO₃-N). In addition to the weekly nitrification rate measurements, experiments were also conducted to determine how operational inputs such as dissolved oxygen (DO) and mixing affect the nitrification rates. Mixing intensity had a clear impact on nitrification rates by increasing the velocity gradient in the bulk liquid and decreasing the mass transfer boundary layer mass transfer resistance. At higher mixing intensities, advection through the mass transfer boundary layer increased making substrate more available to the biofilm. The affect of mixing was much more profound at low DO, whereas increased mixing had less effect on nitrification rates at higher bulk liquid DO. DO also affected nitrification rates, such that as DO increased it penetrated deeper into the biofilm increasing the nitrification rate in a linear fashion until the biofilm became saturated. Another aspect of the research was modeling effective half saturation effects for AOB and NOB activity in the fixed film phase. The modeling work demonstrated that KS for AOB activity on the media was similar to accepted suspended growth KS values, while KS for NOB activity on the media was considerably higher than suspended growth KS. This trend indicates that nitrite was not as bioavailable in the biofilm and resists diffusion into the deeper part of the biofilm where NOB activity takes place. KO for both AOB and NOB activity in the biofilm was higher than typical suspended growth values because of boundary layer and biofilm diffusion resistances. In addition, the presence of readily degradable organics did not significantly affect nitrification rates on the media, but did reduce nitrification rates in the mixed liquor. That, combined with low chemical oxygen demand (COD) uptake rates indicates that little heterotrophic activity is occurring on the media.
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    Evaluation of Soil Aquifer Treatment in a Lab Scale Soil Column Experiment
    Pradhan, Prarthana (Virginia Tech, 2018-12-12)
    Soil aquifer treatment (SAT) during managed aquifer recharge has been studied as a method of providing additional environmental barriers to pathogens and contaminants in indirect potable reuse (IPR) applications. A soil column study was conducted by Hampton Roads Sanitation District in order to evaluate the effectiveness of SAT, as a component of its IPR project involving the replenishment of the Potomac Aquifer System (PAS), in providing a sustainable source of drinking water. Four packed soil columns were constructed with sand from the PAS and were designed to simulate the travel time of 3 days and 30 days. The tests conducted aimed at evaluating pathogen removal (MS2, E. coli and Cryptosporidium oocysts); evaluating attenuation of regulated (nitrate, nitrite, bromate, trihalomethane (THM), haloacetic acids (HAA), organic carbon) and unregulated contaminants of concern that affect drinking water quality. Effective pathogen removal was observed with 6 to 7-log removals of MS2 and E. coli and 3 to 5-log removals of microbeads, used as a surrogate for Cryptosporidium. Removal across 3 day columns was comparable to 30-day columns but the potential to achieve higher removal with longer retention time was acknowledged. Nitrate, bromate, THMs and HAAs were completely reduced in 30-day columns. Total organic carbon was removed at 25 – 35% in all four columns. Seven out of the 106 contaminants of emerging concern (CEC) tested were consistently detected in the column feed and effluent at concentrations greater than 100 ng/L; some compounds showed potential for removal while no conclusive results were drawn for the remaining compounds.
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    Hydrocyclone Implementation at Two Wastewater Treatment Facilities To Promote Overall Settling Improvement
    Partin, Allison Kaitlyn (Virginia Tech, 2019-11-11)
    Hydrocyclone density-driven particle separation may offer up improved settling performance for wastewater treatment facilities experiencing poor settleability. Hydrocyclones are fed mixed liquor through the feed inlet and experience a centrifugal motion that separates solids based on density. The variation in hydrocyclone nozzle sizes will report different calculated hydraulic and mass split percentages for the overflow and underflow. Previous research conducted with hydrocyclones have at multiple full-scale facilities used a 10 m3/hr hydrocyclone to promote better settleability as well as aid the formation of aerobic granular sludge (AGS). There has been a multitude of settling improvement experiments and initiatives for full scale wastewater treatment. However, little research has been produced utilizing larger hydrocyclones (20 m3/hr) at a full-scale wastewater treatment facility during continuous operation. Two Hampton Roads Sanitation District (HRSD) plants served as sites for this research: James River (JR) Wastewater Treatment Plant located in Newport News, VA and Urbanna (UB) Wastewater Treatment Plant located in Urbanna, VA. Both treatment facilities have utilized the hydrocyclone for more than two years, to fulfill wasting requirements. The JR plant operates the hydrocyclone continuously for wasting purposes, while UB only uses the hydrocyclone for approximately 30-45 minutes per day. In order to evaluate the effectiveness of the hydrocyclone and its overall impact on settleability at the JR plant, eight hydrocyclones were installed. JR samples were taken from the underflow sample port (representing a mixture of underflow samples representing the number of hydrocyclones operational at the sample time) and overflow samples were taken from the outfall point of a single hydrocyclone. The UB plant only operated one 5 m3/hr hydrocyclone on Treatment Train 1 during wasting operations, while Treatment Train 2 served as the control train for the duration of this research. Hydrocyclone performance at JR was assessed through direct measurement of hydraulic and mass split of the underflow and overflow components, initial settling velocity (ISV), sludge volume index (SVI), and SVI5/SVI30 ratio. UB hydrocyclone and settling performance was measured by ISV, SVI5, SVI30, and SVI5/SVI30 ratios during different comparison experiments: hydrocyclone vs. no hydrocyclone, hydrocyclone vs. polymer addition, and hydrocyclone with polymer addition to Train 1 vs. polymer-only addition to Train 2. Nutrient concentrations from both treatment trains were collected and analyzed to determine any significant changes based on hydrocyclone use. T-test statistical analysis, and a dose response analysis included direct measurements of the ISV, SVI5, SVI30, mass split percentages, along with the effect of polymer with and without the use of a mechanical selector. Hydrocyclone settleability measurements at JR over time revealed a statistically significant positive correlation with the ISV, SVI5, and SVI30 measurements of the aeration effluent. Therefore, the hydrocyclone statistically had a strong impact on three settling parameters that are instrumental in determining overall settling efficiency. Statistically, no strong correlation was determined between the hydrocyclone operation and the total phosphorus (TP) concentration in the secondary effluent, or the ferric addition to the secondary clarifiers. The dose response based on the underflow ISV rate provided understanding of the nozzle comparison and the effect it provided to the underflow sample. Hydrocyclone performance at UB was hindered by the re-seed of Train 1 (inDENSE™) due to over wasting, and most of the data were not representative. Before the re-seed, hydrocyclone performance was improving the overall settleability of the mixed liquor in comparison to Train 2 (Control). All settling parameters measured were in favor of the hydrocyclone operation. After the re-seed the plant mixed liquor changed microbial populations for a brief time and was not representative of the overall treatment efficacy. The hydrocyclone did provide a quicker settling velocity than the polymer addition when the polymer addition was steady, and through both polymeric spikes. Polymeric addition to both trains, while inDENSE™ train still employing the hydrocyclone did not provide any conclusive data as to whether polymer addition with the use of a hydrocyclone was more effective than polymer-only addition. Nutrient profiles from UB did not provide any change in NH4-N, NO3-N, NO2-N, or PO4-P, with the hydrocyclone being operational or not on the secondary clarifier effluent.