Significance of natural treatment systems to enhance reuse of treated effluent: A critical assessment

This paper summarizes the results of the recently completed India-wide survey of 108 wastewater treatment facilities based on natural treatment systems (NTSs) engaged in wastewater treatment and reuse. During assessment of NTSs, a questionnaire survey was administered for collection of vital data on the shortlisted 41 treatment facilities - especially to obtain insights about the technical, economical and social issues influencing the success and failure of the given facility. Further, five case studies based on the most commonly practiced NTSs were selected for in-depth evaluation and the critical issues including effectiveness of technology and the socioeconomic aspects were studied. The treatment performance of these systems was assessed for one year by collecting primary data during January, June and August corresponding to the three seasons viz. winter, summer and monsoon. The effectiveness of the facilities was assessed in terms of percentage removals as well as the mass removal rate for commonly used parameters. As of today, the total load of sewges including sullages serviced by NTSs in India adds up to be around 1838 million liters a day. The most commonly practiced NTS in India has been the waste stabilization ponds (74 facilities) when compared with the phyto-remediation based systems (19 facilities) followed by the polishing ponds (15 facilities). Among the 41 facilities, nearly 75% facilities were compliant and managed to produce treated sewages suitable for irrigation, discharged into wastewater canals or percolated in the riparian zone of the river. All the five systems that were selected for in-depth evaluation were found compliant during assessment. Also, two facilities (Sewage-fed Aquaculture Karnal and Duckweed Pond Ludhiana) were found to be operating on the public private partnership model and generating revenue for operation and maintenance along with ample benefits to the operating agencies. The study also reveals the associated socioeconomic benefits of various practiced NTSs. Finally, strategies for achieving improved performance of NTSs were articulated - especially focusing the potential for recycling and reusing of treated wastewaters. (C) 2016 Elsevier B.V. All rights reserved.