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1. Effects of anaerobic HRT and VFA loading on the kinetics and stoichiometry of enhanced biological phosphorus removal

   https://doi.org/10.1002/wer.1544  

   Coats, Erik R. ; Deyo, Brent ; Brower, Nicole ; Brinkman, Cynthia K. ( March 2021 , Water Environment Research)

   Enhanced biological phosphorus removal (EBPR) can recover significant quantities of wastewater phosphorus. However, this resource recovery process realizes limited use largely due to process stability concerns. The research evaluated the effects of anaerobic HRT (τ_AN) and VFA concentration—critical operational parameters that can be externally controlled—on EBPR performance. Evaluated alone, τ_AN(1–4 h) exhibited no statistical effect on effluent phosphorus. However, PHA increased with VFA loading and biomass accumulated more phosphorus. Regarding resiliency, under increasing VFA loads PAOs hydrolyzed more phosphorus to uptake/catabolize VFAs; moreover, PHA synthesis normalized to VFA loading increased with τ_AN, suggesting fermentation. Kinetically, PAOs exhibited a Monod‐like relationships for qPHA_ANand qVFA_ANas a function of anaerobic P release; additionally, qP_AEexhibited a Monod‐like relationship with end‐anaerobic PHA concentration. A culminating analysis affirmed the relationship between enhanced aerobic P uptake, and net P removal, with a parameter (phosphorus removal propensity factor) that combines influent VFA concentration with τ_AN.

   Evaluated alone τ_ANexhibits no statistical effect on effluent phosphorus in an EBPR configuration.

   Increased PHA synthesis, associated with increased VFAs and/or extended τ_AN,enhances aerobic phosphorus removal.

   PHA synthesis normalized to VFA loading increased with τ_AN, suggesting fermentation in the EBPR anaerobic zone.

   Aerobic phosphorus uptake increases linearly with anaerobic phosphorus release, with the slope exceeding unity.

   Increased VFAs can be substituted for shorter anaerobic HRTs, and vice versa, to enhance EBPR performance.

    

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2. Effects of external recirculation on a two‐stage mainstream anaerobic‐anammox treatment system

   https://doi.org/10.1002/wer.1019  

   Li, Xiaojin ; He, Zhen ( February 2019 , Water Environment Research)

   Nitritation‐anammox treatment can be a potentially energy‐ and resource‐efficient technology for treating mainstream wastewater. However, the issue of nitrate residue from anammox treatment remains to be addressed. Herein, external recirculation of the anammox effluent to a hybrid anaerobic reactor (HAR), which was also to provide a continuous flow with lowCOD/N for the nitritation‐anammox reactor, was employed to decrease the residue compounds. The recirculation ratio of 50% was observed to be the optimal to achieve the best overall performance with potential savings in energy demand. Specifically, in the operation scenario ofR = 50%, the highestCODremoval of ~90% by theHARwas achieved. Meanwhile, the lowestCOD/NH₄⁺‐N ratio of ~2.0 in theHAReffluent ensured the lowest observedNO₃⁻‐N/NH₄⁺‐N ratio of ~14% in the nitritation‐anammox reactor. These results have demonstrated the feasibility of applying external recirculation for nitrate residue removalviadenitrification in the anaerobic pretreatment stage.

   Nitritation‐anammox treatment is an attractive method for mainstream wastewater treatment.

   Nitrate residue from anammox processes contributes to total nitrogen in the final effluent.

   Recirculation of anammox effluent to an anaerobic reactor can decrease nitrate residue.

   A recirculation ratio of 50% results in a low COD/NH₄⁺ratio of 2 that benefits the subsequent anammox.

    

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3. Integrating dairy manure for enhanced resource recovery at a WRRF: Environmental life cycle and pilot‐scale analyses

   https://doi.org/10.1002/wer.1574  

   Bryant, Casey ; Coats, Erik R. ( April 2021 , Water Environment Research)

   The Twin Falls, Idaho wastewater treatment plant (WWTP), currently operates solely to achieve regulatory permit compliance. Research was conducted to evaluate conversion of the WWTP to a water resource recovery facility (WRRF) and to assess the WRRF environmental sustainability; process configurations were evaluated to produce five resources—reclaimed water, biosolids, struvite, biogas, and bioplastics (polyhydroxyalkanoates, PHA). PHA production occurred using fermented dairy manure. State‐of‐the‐art biokinetic modeling, performed using Dynamita's SUMO process model, was coupled with environmental life cycle assessment to quantify environmental sustainability. Results indicate that electricity production via combined heat and power (CHP) was most important in achieving environmental sustainability; energy offset ranged from 43% to 60%, thereby reducing demand for external fossil fuel‐based energy. While struvite production helps maintain a resilient enhanced biological phosphorus removal (EBPR) process, MgO₂production exhibits negative environmental impacts; integration with CHP negates the adverse consequences. Integrating dairy manure to produce bioplastics diversifies the resource recovery portfolio while maintaining WRRF environmental sustainability; pilot‐scale evaluations demonstrated that WRRF effluent quality was not affected by the addition of effluent from PHA production. Collectively, results show that a WRRF integrating dairy manure can yield a diverse portfolio of products while operating in an environmentally sustainable manner.

   Wastewater carbon recovery via anaerobic digestion with combined heat/power production significantly reduces water resource recovery facility (WRRF) environmental emissions.

   Wastewater phosphorus recovery is of value; however, struvite production exhibits negative environmental impacts due to MgO₂production emissions.

   Bioplastics production on imported organic‐rich agri‐food waste can diversify the WRRF portfolio.

   Dairy manure can be successfully integrated into a WRRF for bioplastics production without compromising WRRF performance.

   Diversifying the WRRF products portfolio is a strategy to maximize resource recovery from wastewater while concurrently achieving environmental sustainability.

    

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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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