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. / Master of Science

Ammonia removal is an important problem that Canadian municipalities are encountering in their wastewater treatment systems due to ammonia’s adverse environmental effects and its increasingly stringent discharge standards. Nitrogen compounds are generally removed from wastewater by a combination of nitrification and denitrification. In full nitrification, ammonia is first biologically oxidized to nitrite, which is then oxidized to nitrate by nitrite-oxidizing bacteria. In denitrification, the resulting nitrate has to be first reduced to nitrite in order to be converted to nitrous oxide, then nitric oxide, and finally to nitrogen gas. Since, nitrite is an intermediary compound in both nitrification and denitrification, it may be more efficient to produce a partial nitrification up to nitrite and then denitrification starting from this nitrite. In this research, EnviroPro Designer was used to simulate, optimize and compare process models for both full nitrification and partial nitrification. The Full System model simulates the traditional full nitrification followed by denitrification. Partial System-1 model simulates the partial nitrification process followed by denitrification directly from nitrite. Partial System-1 significantly reduced the ammonia and domestic waste concentrations in the effluent while achieving 1.5 times faster denitrification rates and utilizing 33% less oxygen. Partial System-1 was further optimized to develop a novel nitrogen removal process, Partial System-3, which incorporated an additional third anoxic stage while the aerobic stage in sludge treatment was removed. Partial System-3 successfully reduced the ammonia and nitrite concentrations in the effluent to values well within the current guidelines while consuming 50% less oxygen than the Full System, which reflected favorably on utility savings. It also showed 2 times faster denitrification rates, and displayed superior domestic waste consumption. Furthermore, the capital and operational costs were less than other nitrogen removal systems investigated in this thesis. The novel Partial System-3 appears to be the best option for removal of nitrogen from medium to high strength wastewater, and further experimental research is required to confirm the kinetic and yield constants assumed in the simulations.

Ammonia removal is an important problem that Canadian municipalities are encountering in their wastewater treatment systems due to ammonia’s adverse environmental effects and its increasingly stringent discharge standards. Nitrogen compounds are generally removed from wastewater by a combination of nitrification and denitrification. In full nitrification, ammonia is first biologically oxidized to nitrite, which is then oxidized to nitrate by nitrite-oxidizing bacteria. In denitrification, the resulting nitrate has to be first reduced to nitrite in order to be converted to nitrous oxide, then nitric oxide, and finally to nitrogen gas. Since, nitrite is an intermediary compound in both nitrification and denitrification, it may be more efficient to produce a partial nitrification up to nitrite and then denitrification starting from this nitrite. In this research, EnviroPro Designer was used to simulate, optimize and compare process models for both full nitrification and partial nitrification. The Full System model simulates the traditional full nitrification followed by denitrification. Partial System-1 model simulates the partial nitrification process followed by denitrification directly from nitrite. Partial System-1 significantly reduced the ammonia and domestic waste concentrations in the effluent while achieving 1.5 times faster denitrification rates and utilizing 33% less oxygen. Partial System-1 was further optimized to develop a novel nitrogen removal process, Partial System-3, which incorporated an additional third anoxic stage while the aerobic stage in sludge treatment was removed. Partial System-3 successfully reduced the ammonia and nitrite concentrations in the effluent to values well within the current guidelines while consuming 50% less oxygen than the Full System, which reflected favorably on utility savings. It also showed 2 times faster denitrification rates, and displayed superior domestic waste consumption. Furthermore, the capital and operational costs were less than other nitrogen removal systems investigated in this thesis. The novel Partial System-3 appears to be the best option for removal of nitrogen from medium to high strength wastewater, and further experimental research is required to confirm the kinetic and yield constants assumed in the simulations.

Thesis (M.Sc. Earth and Ocean Sciences)--University of Waikato, 2007. / Title from PDF cover (viewed March 19, 2008) Includes bibliographical references (p. 97-107)

The purpose of this research was to develop a single sludge multi-environment anoxic/aerobic biological treatment scheme that could achieve oxime degradation and nitrification in the same treatment process. Aerobic and anoxic batch experiments were initially performed to determine degrees of nitrification inhibition caused by three oximes, acetaldehyde oxime (AAO), aldicarb oxime (ADO), and methyl ethyl ketoxime (MEKO), and to investigate the fate of these oximes under anoxic, denitrifying conditions. Results from aerobic batch studies showed that MEKO was the only oxime which caused significant nitrification inhibition at concentrations expected in the industrial client's waste streams. Nitrification rates were reduced by 31% at MEKO concentrations as low as 2 mg/L and were almost completely inhibited above 9 mg/L. Results from anoxic batch studies demonstrated that MEKO was biologically degraded under nitrate limiting conditions, although the microorganism( s) responsible were not explicitly identified. Similar degradation trends were seen for AAO, but at significantly lower rates. ADO, however, appeared to be stable under all anoxic conditions examined. Results from batch studies were utilized to determine operational conditions for a single sludge multi-environment anoxic/anaerobic/aerobic sequencing batch reactor supplied with a synthetic organic wastewater containing up to 40 mgIL MEKO and 56 mgIL AAO. The system was able to achieve complete oxime degradation and nitrification when operated on a one day cycle with a twelve hour anoxic/anaerobic reaction phase and a nitrate:carbon ratio below 0.15 mg N0₃-N/mg TOC. / Master of Science

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

The Walnut Creek Wastewater Treatment Plant in Austin, Texas, has recently experienced increasing influent ammonia concentrations. Nitrification, the biological process used to treat ammonia, consumes alkalinity, which makes it difficult to properly treat ammonia while still maintaining the pH above the required discharge level of pH 6. Operators have looked to the addition of chemicals to supplement alkalinity; one creative alkalinity source was CaCO₃ solids, which are generated by the lime-softening process at Davis Water Treatment Plant. In 2011, the utility began transferring solids to Walnut Creek and immediately noticed improvements in both the nitrification efficiency and the effluent pH. However, undissolved solids accumulated at Walnut Creek and had a detrimental effect on the biosolids treatment efficiency at Hornsby Bend Biosolids Management Plant. Ultimately the costs of the poor biosolids treatment forced the utility to examine an alternative alkalinity source. The objective of this thesis is to help Walnut Creek optimize the use of various alkalinity sources to find a long-term solution that will improve the alkalinity and ammonia balance for adequate nitrification. Analysis of the plant’s influent characteristics suggested that industrial users, especially the semiconductor industry, are major contributors of ammonia and sulfate to the wastewater. A theoretical modeling based on chemical equilibrium predicted that using the CaCO₃ solids would provide a maximum alkalinity benefit of 47 mg/L as CaCO₃. Experimental dissolution jar tests were conducted to verify the model predictions and estimate the kinetics of dissolution. Results from these tests showed no significant dissolution of CaCO₃, and that the solids remained unchanged throughout the test. These results indicate that CaCO₃ solids are not recommended to provide alkalinity at Walnut Creek. Finally, the use of Mg(OH)₂ for alkalinity was employed at Walnut Creek and allowed operators to reduce the blowers that provide aeration. To quantify this observation, bubbling column tests were conducted to measure differences in the oxygen transfer rate at various Mg(OH)₂ concentrations. However experimental results did not match the expectations, so future work is required. / text

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xii, 174 p. : ill., maps. Vita. Includes abstract. Includes bibliographical references.

Graduation date: 1999

Reproduction de : Thèse de doctorat : Biologie : Metz : 1986. / Titre provenant de l'écran-titre. Notes bibliogr.