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Floating treatment wetlands as a suitable option for large-scale wastewater treatment

Abstract

In many developing countries, there are limited or insufficient wastewater treatment infrastructures. Floating treatment wetlands (FTWs) can be a cost-effective phytoremediation approach to treat various types of wastewater. The buoyancy of the FTWs is due to air-filled rhizomes and entrapment of gas bubbles by the interwoven roots, which can be supported further by rafts. The performance of full-scale systems for treating genuine wastewater is largely unknown because studies so far have been experimental. Here, we installed full-scale FTWs in stabilization ponds receiving sewage (60%) and industrial (40%) wastewater from Faisalabad, Pakistan, and evaluated their treatment performance over a period of three years. The FTWs promoted a substantial improvement of all recorded water quality indicators and a reduction of heavy metal concentrations in the effluent compared to the influent. The maximum removal capacities of the system were 79% of chemical oxygen demand (COD), 88% of biochemical oxygen demand (BOD) and 65% of total dissolved solids (TDS). The performance was optimal in the second and third years of operation during which about 60 million m3 per year of wastewater was treated at a cost of US$0.00026 per m3. This study demonstrates that FTWs are an appropriate ecotechnology for the large-scale cleanup of sewage and industrial wastewater.

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Fig. 1: Study area and scheme of FTWs.
Fig. 2: af, Installation and temporal growth of FTWs.
Fig. 3: Assessment of physicochemical and biological indicators in influent and effluent.
Fig. 4: Plant growth and development during operation of the FTWs.
Fig. 5: Redundancy analysis reflects seasonal performance of the FTWs.

Data availability

The data that support the findings of this study are available from the corresponding author on reasonable request.

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The code associated with this paper is not available.

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Acknowledgements

The authors would like to thank the Water and Sanitation Agency (WASA), Faisalabad, for providing funding for this study.

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Contributions

M.Af., S.I. and Q.M.K. provided substantial contributions to study conception and analysis design. G.S., R.T., M.A.H., A.J.H. and E.I. contributed to data acquisition. M.Ar., J.A.M. and M.Af. participated in data analysis and interpretation. The article was draughted and revised critically for important intellectual content by M.Ar., J.A.M., E.I. and M.Af. or M.Ar.

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Correspondence to Muhammad Afzal or Muhammad Arslan.

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Afzal, M., Arslan, M., Müller, J.A. et al. Floating treatment wetlands as a suitable option for large-scale wastewater treatment. Nat Sustain 2, 863–871 (2019). https://doi.org/10.1038/s41893-019-0350-y

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