Abstract
Ion exchange (IEX) processes are a promising alternative to remove and recover nutrients from municipal wastewater. To assess the feasibility and viability of IEX processes for full-scale application, this study aimed at providing an evaluation of performance and economics on upscaling these processes for two different configurations in a 10,000 population equivalent wastewater treatment plant (WWTP) and compared them with a traditional biological nutrient removal (BNR) plant. The IEX processes were designed based on existing pilot-scale data, and after aerobic or anaerobic carbon removal stages. The nutrients were recovered from spent regenerants in the form of (NH4)2SO4 and hydroxyapatite Ca5(PO4)3(OH), allowing regenerant reuse. The 40-year whole life cost (WLC) of IEX coupled with traditional activated sludge processes was estimated to be ~£7.4 M, and WLC of IEX coupled with anaerobic membrane process was estimated to be £6.1 M, which was, respectively, 17% and 27% less than the traditional BNR based WWTP. Furthermore, ~98 tonnes of (NH4)2SO4 and 3.4 tonnes of Ca3(PO4)2 could be recovered annually. The benefits of lower costs, reduction in greenhouse gas emissions and nutrient recovery aligned with circular economy, illustrated that IEX processes are attractive for nutrient removal and recovery from municipal wastewater.
Highlights
Excess nutrients released from wastewater treatment plants (WWTPs) can lead to eutrophication with detrimental effects to the aquatic environment
This study aims at providing an evaluation of performance and economics of ion exchange (IEX) processes as tertiary treatment process, for both ammonia and phosphorus removal and recovery, and by adding hydrated lime, hydroxyapatite Ca5(PO4)3(OH) was recovered with annual production of 3.4 tonnes
Results demonstrate that all the flowsheets investigated, biological nutrient removal (BNR) + Column experiments indicated that adsorption capacity was iron dosing, ASP + IEX and AnMBR + IEX processes could produce the desired effluent quality of COD < 20 mg/L, NaOH required H2SO4 required (NH4)-N < 1 mg/L and PO4-P < 0.5 mg/L
Summary
Excess nutrients released from wastewater treatment plants (WWTPs) can lead to eutrophication with detrimental effects to the aquatic environment. Existing legislation provides stringent control of WWTPs discharges, limiting to 1 mg NH4-N/L and as low as 0.5 mg PO4-P/L1. Nutrients are essential to all life forms, and should be recovered, phosphorus considering the fast depletion of natural reserves[2]. Nutrient recovery can enable alternative revenue streams and is aligned with the delivery of the circular economy[3]. Activated sludge process variations, such as biological nutrient removal (BNR), predominate in WWTPs nowadays[4], ion exchange (IEX) processes are rarely applied in municipal wastewater treatment. Recent advances are tackling these limitations, and IEX processes are being considered for nutrient removal and recovery from municipal wastewater. Recent studies demonstrated that mesolite, a synthetically produced zeolite, has a high capacity for ammonia (NH4-N) adsorption with reported values of 4.6 and 4.9 meq/g, compared with 2.0 meq/g for Clinoptilolite[5]
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