Constructed wetlands for greywater recycle and reuse: A review - PubMed (original) (raw)

Review

Constructed wetlands for greywater recycle and reuse: A review

S Arden et al. Sci Total Environ. 2018.

Abstract

Concern over dwindling water supplies for urban areas as well as environmental degradation from existing urban water systems has motivated research into more resilient and sustainable water supply strategies. Greywater reuse has been suggested as a way to diversify local water supply portfolios while at the same time lessening the burden on existing environments and infrastructure. Constructed wetlands have been proposed as an economically and energetically efficient unit process to treat greywater for reuse purposes, though their ability to consistently meet applicable water quality standards, microbiological in particular, is questionable. We therefore review the existing case study literature to summarize the treatment performance of greywater wetlands in the context of chemical, physical and microbiological water quality standards. Based on a cross-section of different types of wetlands, including surface flow, subsurface flow, vertical and recirculating vertical flow, across a range of operating conditions, we show that although microbiological standards cannot reliably be met, given either sufficient retention time or active recirculation, chemical and physical standards can. We then review existing case study literature for typical water supply disinfection unit processes including chlorination, ozonation and ultraviolet radiation treating either raw or treated greywater specifically. An evaluation of effluent water quality from published wetland case studies and the expected performance from disinfection processes shows that under appropriate conditions these two unit processes together can likely produce effluent of sufficient quality to meet all nonpotable reuse standards. Specifically, we suggest that recycling vertical flow wetlands combined with ultraviolet radiation disinfection and chlorine residual is the best combination to reliably meet the standards.

Keywords: Disinfection; Low energy treatment option; Nonpotable water reuse; Wetland treatment performances; log(10) reduction targets (LRTs).

Copyright © 2018 Elsevier B.V. All rights reserved.

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Figures

Figure 1.

Figure 1.

Effluent concentration data as a function of hydraulic retention time (HRT), including any applicable reuse criteria, for a) biochemical oxygen demand (BOD), b) total suspended solids (TSS) and c) Turbidity. System types include free water surface (FWS), green roof water recycle system (GRW), horizontal subsurface flow (HSSF), recycled vertical flow (RVF), vertical flow (VF) and aerobic plus anaerobic (Aer. + Anaer.). For BOD and TSS, USEPA guidelines for unrestricted reuse are 10 mg/L, for restricted reuse are 30 mg/L. Turbidity guidelines for unrestricted reuse are 2 NTU.

Figure 2.

Figure 2.

Comparison of GW wetland a) biochemical oxygen demand (BOD) and b) total suspended solids (TSS) performance with North American Treatment Wetland Database (NADB) datasets. System types include free water surface (FWS), green roof water recycle system (GRW), horizontal subsurface flow (HSSF), recycled vertical flow (RVF), vertical flow (VF) and aerobic plus anaerobic (Aer. + Anaer.). For BOD and TSS, USEPA guidelines for unrestricted reuse are 10 mg/L, for restricted reuse are 30 mg/L.

Figure 3.

Figure 3.

Log(effluent concentration) of a) total coliform (TC), b) fecal coliform (FC) and c) E. coli as a function of log(influent concentration). *Regression of all system types.

Figure 4.

Figure 4.

Log reductions from GW chlorination studies. Shading indicates influent limited LR and should be interpreted as “greater than”.

Figure 5.

Figure 5.

Log reductions from GW chlorination studies. Shading indicates influent limited LR and should be interpreted as “greater than”.

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