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1. Sensor‐mediated granular sludge reactor for nitrogen removal and reduced aeration demand using a dilute wastewater

   https://doi.org/10.1002/wer.1296  

   Bekele, Zerihun A. ; Delgado Vela, Jeseth ; Bott, Charles B. ; Love, Nancy G. ( February 2020 , Water Environment Research)

   A sensor‐mediated strategy was applied to a laboratory‐scale granular sludge reactor (GSR) to demonstrate that energy‐efficient inorganic nitrogen removal is possible with a dilute mainstream wastewater. The GSR was fed a dilute wastewater designed to simulate an A‐stage mainstream anaerobic treatment process. DO, pH, and ammonia/nitrate sensors measured water quality as part of a real‐time control strategy that resulted in low‐energy nitrogen removal. At a low COD (0.2 kg m⁻³ day⁻¹) and ammonia (0.1 kg‐N m⁻³ day⁻¹) load, the average degree of ammonia oxidation was 86.2 ± 3.2% and total inorganic nitrogen removal was 56.7 ± 2.9% over the entire reactor operation. Aeration was controlled using a DO setpoint, with and without residual ammonia control. Under both strategies, maintaining a low bulk oxygen level (0.5 mg/L) and alternating aerobic/anoxic cycles resulted in a higher level of nitrite accumulation and supported shortcut inorganic nitrogen removal by suppressing nitrite oxidizing bacteria. Furthermore, coupling a DO setpoint aeration strategy with residual ammonia control resulted in more stable nitritation and improved aeration efficiency. The results show that sensor‐mediated controls, especially coupled with a DO setpoint and residual ammonia controls, are beneficial for maintaining stable aerobic granular sludge.

   Tight sensor‐mediated aeration control is need for better PN/A.

   Low DO intermittent aeration with minimum ammonium residual results in a stable N removal.

   Low DO aeration results in a stable NOB suppression.

   Using sensor‐mediated aeration control in a granular sludge reactor reduces aeration cost.

    

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2. Algal-bacterial shortcut nitrogen removal model with seasonal light variations

   https://doi.org/10.2166/wst.2024.090  

   Iman Shayan, Sahand ; Youssef, Steve ; van der Steen, Peter ; Zhang, Qiong ; Ergas, Sarina J. ( March 2024 , Water Science & Technology)

   The algal–bacterial shortcut nitrogen removal (ABSNR) process can be used to treat high ammonia strength wastewaters without external aeration. However, prior algal–bacterial SNR studies have been conducted under fixed light/dark periods that were not representative of natural light conditions. In this study, laboratory-scale photo-sequencing batch reactors (PSBRs) were used to treat anaerobic digester sidestream under varying light intensities that mimicked summer and winter conditions in Tampa, FL, USA. A dynamic mathematical model was developed for the ABSNR process, which was calibrated and validated using data sets from the laboratory PSBRs. The model elucidated the dynamics of algal and bacterial biomass growth under natural illumination conditions as well as transformation processes for nitrogen species, oxygen, organic and inorganic carbon. A full-scale PSBR with a 1.2 m depth, a 6-day hydraulic retention time (HRT) and a 10-day solids retention time (SRT) was simulated for treatment of anaerobic digester sidestream. The full-scale PSBR could achieve >90% ammonia removal, significantly reducing the nitrogen load to the mainstream wastewater treatment plant (WWTP). The dynamic simulation showed that ABSNR process can help wastewater treatment facilities meet stringent nitrogen removal standards with low energy inputs.

    

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3. A Novel Community Engaged System Thinking Approach to Onsite Wastewater Treatment Management for Nutrient Pollution in the Belizean Cayes

   Delgado, D ; Webb, A ; Prouty, P ; Trotz, M ; Zarger, R ; Ergas, S. ( July 2019 , ACS Fall 2019 National Meeting & Exposition in San Diego, CA, August 25 - 29, 2019)

   A Novel Community Engaged System Thinking Approach to Controlling Nutrient Pollution in the Belize Cayes Nutrient pollution (anthropogenic discharge of nitrogen and phosphate) is a major concern in many parts of the world. Excess nutrient discharge into nutrient limited waters can cause toxic algal blooms that lead to hypoxic zones, fish die-offs, and overgrowth on reefs. This can lead to coral reefs being more vulnerable to global warming and ocean acidification. For coastal communities that depend of fishing and tourism for their livelihood, and for reefs to protect coastlines, these effects can be devastating. A major source of nutrient input into the aquatic environment is poorly treated wastewater from Onsite Wastewater Treatment Systems (OWTS). When properly sited, built, and maintained conventional OWTS are great for removing fats, grease, biological oxygen demand (BOD), and total suspended solids (TSS), but they are rarely designed for nutrient removal and commonly have high nutrient levels in their effluent. This study investigates the factors that influence the performance of OWTS, the Caribbean region’s most common type of treatment technology, in the Belizean Cayes where salt water flushing is common. Using mass-balance-based models for existing and proposed OWTS to predict the system’s performance under various conditions, along with OWTS’ owner, maintainer, and user input, a novel community engaged system thinking approach to controlling nutrient pollution will be developed. Key model performance metrics are concentrations of nitrogen species, BOD, and TSS in the effluent. To demonstrate the model’s utility, a sensitivity analysis was performed for case studies in Belize, estimating the impact on nutrient removal efficiency when changes are made to variables such as number of daily users, idle periods, tank number and volume, oxygen concentration and recirculation. For the systems considered here, strategies such as aeration, increased biodigester tank size, addition of aerobic and anoxic biodigesters, recirculation, addition of a carbon source, ion exchange media is predicted to decrease the effluent nitrogen concentration, and integration of vegetation for nutrient uptake both on land and in the nearshore environment. In a previous case, the addition of an aerator was predicted to decrease the effluent ammonium concentration by 13%, whereas increasing the biodigester tank size would only decrease the effluent ammonium concentration by ~7%. Model results are shared with system manufacturers and operators to prioritize possible modifications, thereby optimizing the use of finite resources, namely time and money, for costly trial-and-error improvement efforts. 

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4. Hybrid Adsorption and Biological Treatment Systems (HABiTS) for Enhanced Nitrogen Removal in Onsite Wastewater Treatment

   Rodriguez-Gonzalez, L. ; Payne, K. ; Anderson, D. ; He, Q. ; Prouty, C. ; Garcia, L. ; Trotz, M. ; Ergas, S. ( October 2018 , 27th Caribbean Water and Wastewater Conference & Exhibition Proceedings)

   Twenty-five United Nations member states in the wider Caribbean region ratified the Cartagena Convention, which covers the marine environment of the Gulf of Mexico, the Caribbean Sea and some parts of the Atlantic Ocean. The Land-Based Sources and Activities protocol (LBS Protocol) of that convention addresses nutrient pollution from sewage discharges, agricultural runoff and other sources. Unfortunately, most Caribbean people use conventional onsite wastewater treatment systems (OWTs), especially septic systems. These systems fail to remove nitrogen effectively, posing a challenge for near shore environments. Passive biological nitrogen removal (BNR) processes have been developed for OWTs that rely on simple packed bed bioreactors, with little energy or chemical inputs and low operations and maintenance (O&M) requirements. This paper provides a case study from Florida on the partnerships and pathways for research to develop an innovative technology, Hybrid Adsorption and Biological Treatment System (HABiTS), for nitrogen reduction in OWTs. HABiTS combine ion exchange materials and BNR to remove nitrogen from septic tank effluent and buffer transient loadings. HABiTS, employs natural zeolite material (e.g. clinoptilolite) and expanded clay in the first stage to achieve both ammonium ion exchange and nitrification. The second stage of HABiTS utilizes tire chips, elemental sulphur pellets and oyster shells for adsorption of nitrate as well as sulphur oxidizing denitrification. Under transient load applications, the nitrogen in excess of the biodegradation capacity during high loading events was partially retained within the ion exchange and adsorption materials and readily available later for the microorganisms during lower loading events. Results from a bench scale bioreactor study with marine wastewater, which is relevant to where seawater is used for toilet flushing, are also presented. Pilot scale tests on the OWT of an engaged stakeholder dependent on the marine environment, would contribute to broader discussions for paradigm shifts for nutrient removal from wastewater. 

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5. Case study: Bioaugmenting the comammox dominated biomass from B‐stage to enhance nitrification in A‐stage at Blue Plains AWWTP

   https://doi.org/10.1002/wer.11005  

   Nguyen Quoc, Bao ; Peng, Bo ; De Clippeleir, Haydee ; Winkler, Mari‐Karoliina H. ( February 2024 , Water Environment Research)

   A comprehensive case study was undertaken at the Blue Plains wastewater treatment plant (WWTP) to explore the bioaugmentation technique of introducing nitrifying sludge into the non‐nitrifying stage over the course of two operational years. This innovative approach involved the return of waste activated sludge (WAS) from the biological nutrient removal (BNR) system to enhance the nitrification in the high carbon removal rate system. Thecompleteammoniaoxidizer (comammox)Nitrospira Nitrosawas identified as the main nitrifier in the system. Bioaugmentation was shown to be successful as nitrifiers returned from BNR were able to increase the nitrifying activity of the high carbon removal rate system. There was a positive correlation between returned sludge from the BNR stage and the specific total kjeldahl nitrogen (TKN) removal rate in A stage. The bioaugmentation process resulted in a remarkable threefold increase in the specific TKN removal rate within the A stage. Result suggested that recycling of WAS is a simple technique to bio‐augment a low SRT system with nitrifiers and add ammonia oxidation to a previously non‐nitrifying stage. The results from this case study hold the potential for applicable implications for other WWTPs that have a similar operational scheme to Blue Plains, allowing them to reuse WAS from the B stage, previously considered waste, to enhance nitrification and thus improving overall nitrogen removal performance.

   Comammox identifying as main nitrifier in the B stage.

   Comammox enriched sludge from B stage successfully bio‐augmented the East side of A stage up to threefold.

   Bioaugmentation of comammox in the West side of A stage was potentially inhibited by the gravity thickened overflow.

   Sludge returned from B stage to A stage can improve nitrification with a very minor retrofits and short startup times.

    

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