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1. Current and future approaches to wet weather flow management: A review

   https://doi.org/10.1002/wer.1506  

   Peters, Paige E. ; Zitomer, Daniel H. ( January 2021 , Water Environment Research)

   Sewers can become hydraulically overburdened during high‐intensity precipitation resulting in untreated water entering receiving streams. Combined (CSOs) and sanitary sewer overflows (SSOs) cause adverse public health and environmental impacts as well as management challenges for many wastewater utilities. This novel review presents information regarding wet weather flow regulation, impacts, and current management methods, and offers ideas for future approaches in the United States. Currently, storage followed by conventional municipal water reclamation facility treatment after precipitation events is often employed. Stand‐alone alternative technologies include high‐rate solids removal, rapid disinfection, filtration, and green infrastructure. However, most current stand‐alone approaches do not address soluble BOD₅or emerging contaminants in stormwater and wastewater. As the needs for wet weather flow management change, future approaches should include a goal of zero overflows and achieve effluent quality as good as or better than conventional treatment. To help achieve zero overflows and complete treatment, the “peaker facility” concept is proposed. The peaker facility often remains idle but treats excess flow when needed. Considering the challenges of remaining idle for long periods, starting up quickly, and handling high flows, chemical oxidation may be an applicable peaker facility component. However, more research and development are needed to determine best practices.

   Combined (CSO) and sanitary sewer overflows (SSOs) pose both environmental and public health risks as untreated water is discharged into lakes and rivers during high‐intensity rain events.

   Current stand‐alone approaches for managing or treating CSOs focus on particulate BOD/COD and solids removal, and do not typically address soluble BOD or emerging contaminants in stormwater and wastewater (including pathogens).

   New wet weather policies and regulations encourage more holistic approaches by wastewater utilities, and future approaches should include a zero‐overflow goal for all CSOs and SSOs.

   To help achieve zero overflows, the concept of the “peaker facility” is proposed.

   Chemical oxidation may be an applicable component of peaker facilities for its short detention time and ability to remove, oxidize, or inactive water impairment‐causing contaminants.

    

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2. Toxicity of azoles towards the anaerobic ammonium oxidation (anammox) process

   https://doi.org/10.1002/jctb.6285  

   Lakhey, Nivrutti ; Li, Guangbin ; Sierra‐Alvarez, Reyes ; Field, Jim A. ( December 2019 , Journal of Chemical Technology & Biotechnology)

   Azoles are an important class of compounds that are widely used as corrosion inhibitors in aircraft de‐icing agents, cooling towers, semiconductor manufacturing and household dishwashing detergents. They also are important moieties in pharmaceutical drugs and fungicides. Azoles are widespread emerging contaminants occurring frequently in water bodies. Azole compounds can potentially cause inhibition towards key biological processes in natural ecosystems and wastewater treatment processes. Of particular concern is the inhibition of azoles to the nitrification process (aerobic oxidation of ammonium). This study investigated the acute toxicity of azole compounds towards the anaerobic ammonia oxidation (anammox) process, which is an important environmental biotechnology gaining traction for nutrient‐nitrogen removal during wastewater treatment. In this study, using batch bioassay techniques, the anammox toxicity of eight commonly occurring azole compounds was evaluated.

   The results show that 1H‐benzotriazole and 5‐methyl‐1H‐benzotriazole had the highest inhibitory effect on the anammox process, causing 50% decrease in anammox activity (IC₅₀) at concentrations of 19.6 and 17.8 mg L⁻¹, respectively. 1H‐imidazole caused less severe toxicity with an IC₅₀of 79.4 mg L⁻¹. The other azole compounds were either nontoxic (1H‐pyrazole, 1H‐1,2,4‐triazole and 1‐methyl‐pyrazole) or at best mildly toxic (1H‐benzotriazole‐5‐carboxylic acid and 3,5‐dimethyl‐1H‐pyrazole) towards the anammox bacteria at the concentrations tested.

   This study showed that most azole compounds tested displayed mild to low or no toxicity towards the anammox bacteria. The anammox bacteria were found to be far less sensitive to azoles compared to nitrifying bacteria. © 2019 Society of Chemical Industry

    

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3. 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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4. Primary sludge fermentate as carbon source for mainstream partial denitrification–anammox (PdNA)

   https://doi.org/10.1002/wer.1492  

   Ali, Priyanka ; Zalivina, Nadezhda ; Le, Tri ; Riffat, Rumana ; Ergas, Sarina ; Wett, Bernhard ; Murthy, Sudhir ; Al‐Omari, Ahmed ; deBarbadillo, Christine ; Bott, Charles ; et al ( January 2021 , Water Environment Research)

   Primary sludge fermentate, a concentrated hydrolyzed wastewater carbon, was evaluated for use as an alternative carbon source for mainstream partial denitrification–anammox (PdNA) in a suspended growth activated sludge process in terms of partial denitrification (PdN) efficiency, PdNA nitrogen removal contributions, and final effluent quality. Fermenter operation at a 2‐day sludge retention time (SRT) resulted in the maximum achievable yield of 0.14 ± 0.05 g sCOD/g VSS without release of excessive ammonia and phosphorus to the system. Based on the results of batch experiments, fermentate addition led to PdN efficiency of 93 ± 14%, which was similar to acetate at a nitrate residual of 2–3 mg N/L. In the pilot‐scale mainstream deammonification reactor, PdN efficiency using fermentate was 49 ± 24%, which was lower than acetate (66 ± 24% during acetate period I and 70 ± 21% during acetate period II), most probably due to lower nitrate and ammonium kinetics in the PdN zone. Methanol cost‐saving potential for the application of PdNA as the main short‐cut nitrogen pathway was estimated to be 30% to 55% depending on the PdN efficiency achieved.

   Primary sludge fermentate was evaluated as an alternative carbon source for mainstream partial denitrification–anammox (PdNA).

   Fermenter operated at a 1 to 2 day SRT resulted in the maximum achievable yield without the release of excessive ammonia and phosphorus to the system.

   Although 93% partial denitrification efficiency was achieved with fermentate in batch experiments, around 49% PdN efficiency was achieved in pilot studies.

   Application of PdNA with fermentate can result in significant methanol cost savings.

    

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5. Phosphorus recovery from wastewater using pyridine‐based ion‐exchange resins: Role of impregnated iron oxide nanoparticles and preloaded Lewis acid (Cu 2+ )

   https://doi.org/10.1002/wer.1469  

   Beaudry, Jeffrey W. ; Sengupta, Sukalyan ( December 2020 , Water Environment Research)

   Inputs of P into receiving water bodies are attracting increasing attention due to the negative effects of eutrophication. Presently available P treatment technologies are unable to achieve strict P discharge limits from wastewater treatment plants (WWTPs) that may be as low as 10 µg/L as P. Moreover, P is a nonrenewable resource and needs to be recycled in a closed‐loop process for environmental sustainability. This article provides details of a process where a pyridine‐based polymeric ion exchanger is modified with a combination of impregnated hydrated ferric oxide (HFO) nanoparticles and a preloaded Lewis acid (Cu²⁺) to effectuate selective P removal from wastewater and its recovery as a solid‐phase fertilizer. Three such ion exchangers were studied: DOW‐HFO, DOW‐Cu, and DOW‐HFO‐Cu. Each of these materials displays selective phosphate affinity over competing anions chloride and sulfate, and also has the ability to be regenerated upon exhaustion to strip off the P in a concentrated solution. The P in concentrated regenerant can be recovered as struvite, MgNH₄PO₄, a slow‐release fertilizer, after addition of MgCl₂and NH₄Cl. Results of equilibrium and kinetic studies and column experiments with synthetic solutions and a real WWTP effluent are discussed.

   Fixed‐bed columns with DOW‐HFO, DOW‐Cu, or DOW‐HFO‐Cu—can selectively remove phosphorus over competing anions.

   Fixed‐bed columns of above‐listed ion exchangers can produce an effluent P < 6 μg/L.

   DOW‐Cu fixed‐bed column ran for ≈500 Bed Volumes before breakthrough when fed Dartmouth WWTP secondary effluent.

   Regeneration of the exhausted DOW‐Cu column resulted in ≈90% recovery of the phosphorus.

   Regenerant solution was used to generate high‐purity crystals of magnesium ammonium phosphate, MgNH₄PO₄(struvite), a slow‐release fertilizer.

    

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