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Bon Air, VA, United States

Curtis K.,Hampton Roads Sanitation District | Michael Trapp J.,Michael Baker International
Archives of Environmental Contamination and Toxicology | Year: 2016

It is widely understood that stormwater drainage has a significant impact on the health of tidal creek systems via regular inputs of runoff from the surrounding watershed. Due to this hydrologic connection, contamination of the upstream drainage basin will have a direct effect on estuaries and tidal creeks that often act as receiving waters. This study focuses on the importance of drainage basin sediments as they enhance the persistence and transport of the fecal indicator bacteria E. coli within a watershed. Experiments presented use microcosm environments with drainage basin sediments and stormwater to investigate E. coli colonization of stagnant waters and to examine the importance of host sources to bacterial survival. A novel method for establishing microcosms using environmental sediments with in situ bacterial populations and sterile overlying waters is used to examine E. coli colonization of the water column in the absence of flow. Colonization of sterile sediment environments also is examined using two common host sources (human and avian). Each experiment uses sediments of varying grain size and organic content to examine the influence of physical characteristics on bacterial prevalence. Results suggest host source of bacteria may be more important to initial bacterial colonization while physical characteristics of drainage basin sediments better explains extended E. coli persistence. Findings also suggest an indirect control of water column bacterial concentration by sediment type and erodibility. © 2016 Springer Science+Business Media New York

Regmi P.,Old Dominion University | Miller M.W.,Virginia Polytechnic Institute and State University | Holgate B.,Old Dominion University | Bunce R.,Hazen and Sawyer | And 5 more authors.
Water Research | Year: 2014

This work describes the development of an intermittently aerated pilot-scale process (V=0.34m3) operated without oxidized nitrogen recycle and supplemental carbon addition optimized for nitrogen removal via nitritation/denitritation. The aeration pattern was controlled using a novel aeration strategy based on set-points for reactor ammonia, nitrite and nitrate concentrations with the aim of maintaining equal effluent ammonia and nitrate+nitrite (NOx) concentrations. Further, unique operational and process control strategies were developed to facilitate the out-selection of nitrite oxidizing bacteria (NOB) based on optimizing the chemical oxygen demand (COD) input, imposing transient anoxia, aggressive solids retention time (SRT) operation towards ammonia oxidizing bacteria (AOB) washout and high dissolved oxygen (DO) (>1.5mg/L). Sustained nitrite accumulation (NO2-N/NOx-N=0.36±0.27) was observed while AOB activity was greater than NOB activity (AOB: 391±124mgN/L/d, NOB: 233±151mgN/L/d, p<0.001) during the entire study. The reactor demonstrated total inorganic nitrogen (TIN) removal rate of 151±74mgN/L/d at an influent COD/NH4+-N ratio of 10.4±1.9 at 25°C. The TIN removal efficiency was 57±25% within the hydraulic retention time (HRT) of 3h and within an SRT of 4-8 days. Therefore, this pilot-scale study demonstrates that application of the proposed online aeration control is able to out-select NOB in mainstream conditions providing relatively high nitrogen removal without supplemental carbon and alkalinity at a low HRT. © 2014 Elsevier Ltd.

Hampton Roads Sanitation District and D.C. Water & Sewer Authority | Date: 2013-09-13

A reactor and control method thereof for nitrogen removal in wastewater treatment achieves a measured control of maintaining high ammonia oxidizing bacteria (AOB) oxidation rates while achieving nitrite oxidizing bacteria (NOB) repression, using various control strategies, including: 1) ammonia and the use of ammonia setpoints, 2) operational DO and the proper use of DO setpoints, 3) bioaugmentation of a lighter flocculant AOB fraction, and 4) proper implementation of transient anoxia within a wide range of reactor configurations and operating conditions.

Hampton Roads Sanitation District | Date: 2015-07-22

A method and a system as described herein, including a method and system of treating ammonium containing water in a deammonification MBBR process where partial nitritation and anaerobic ammonium oxidation may occur simultaneously in a biofilm, or in an integrated fixed film activated sludge process where partial nitritation takes place in a suspended growth fraction and anaerobic ammonium oxidation occurs in a biofilm. The method and system include controlling airflow to the reactor to achieve a target pH, a target alkalinity, a target specific conductivity, and/or a target ammonium concentration in the reactor or in the effluent.

D.C. Water & Sewer Authority and Hampton Roads Sanitation District | Date: 2013-11-27

A method and a system for selecting and retaining solids with superior settling characteristics, the method comprising feeding wastewater to an input of a processor that carries out a treatment process on the wastewater, outputting processed wastewater at an output of the processor, feeding the processed wastewater to an input of a gravimetric selector that selects solids with superior settling characteristics, and outputting a recycle stream at a first output of the gravimetric selector back to the processor.

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