Post-treatment and reuse of secondary effluents using natural ltreatment systems: the Indian practices

Abstract

Paper summarizes the results of India-wide survey of natural treatment systems (NTSs) for wastewater treatment and reuse. The quality of treated wastewater from different types of NTSs was analyzed for various physico-chemical and bacteriological parameters, and needs for post-treatment were identified. Currently, about 1838 million liters per day (MLD) of wastewater is being treated using NTSs, of which the contributions of polishing ponds, waste stabilization ponds, duckweed ponds, constructed wetlands, and Karnal technology were found to be 53.39, 45.15, 0.13, 0.55, and 0.78%, respectively. Among the NTSs studied, constructed wetland was found most efficient in removal of pollutants including nitrogen, phosphorus, total coliform, and fecal coliform in the range of 76, 61, 99.956, and 99.923%, respectively. Of all types of NTSs, only constructed wetland was found to meet the total coliform count requirements (<1000 per 100 ml). Of all the 108 NTSs in operation, 23 systems are producing treated effluents for irrigation; effluents from 48 systems are being discharged into river or lake, and remaining 38 systems have not found any designated use of treated effluent. The chlorination was the only post-treatment, which is being practiced at only three wastewater treatment facilities. During post-treatment, 1-2 ppm of chlorine is applied to the secondary effluent irrespective of its quality. The treated effluents from different NTSs contain fecal bacteria in the magnitude of 10(3) to 10(5), which may cause the severe health impacts through contamination of groundwater as well as surface water resources.

Sewage-fed aquaculture: a sustainable approach for wastewater treatment and reuse

“…The typical range of removal of organic pollutants, namely BOD 5 and COD was found between 86-94.55 and 72.7-89.2 %, respectively. Likewise, the TKN removal was also found highest in summer as compared with winter and rainy seasons, but their removals were not equally high as in the other natural treatment systems like constructed wetlands (Kumar et al 2015). TKN removals during winter, summer and rainy reason were found to be 7.3, 14.5 and 3.1 %, respectively.…”

“…The broad spectrum of pathogenic micro-organisms, including bacteria, viruses, helminths and protozoa present in wastewater survive in the environment for days, weeks and months in the soil and on crops that come in contact with wastewater. Furthermore, the presence of a high number of faecal bacteria in secondary treated wastewater used for irrigation or discharge into water bodies without any post-treatment (especially disinfection) may cause the most severe problems including groundwater and surface water contaminations (Kumar et al 2015). The crop irrigated with wastewater containing high number of faecal bacteria may also pose the problem of food contamination if the grown vegetables (e.g.…”

“…The direct administration of partially treated or untreated municipal sewage into surface water has deteriorated the water quality of the major rivers of India (Kumar et al 2011;Chaturvedi et al 2014;Kumar et al 2015). Also, Semhi et al (2014) reported that the distribution of certain heavy metals was more available in sewage than in mining zone, justifying the hazards of direct disposal of sewage into the environment.…”

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

“…Typically 1-2 mg/L of chlorine dose is being administered before the effluents are let off for irrigation or gardening or discharged into the legally permitted water bodies (Kumar et al, 2011;Kumar et al, 2012;Kumar et al, 2015a). It was evident from the survey that the secondary treated sewages were typically reused in irrigation (22 facilities) and recharging into lakes or rivers (48 facilities).…”

Disinfection Processes

“…Kumar et al (2015) studied natural treatment systems across India and found that constructed wetlands met total coliform requirements but polishing ponds, waste stabilization ponds, and duckweed ponds did not. A literature review of virus removal in 71 different wastewater treatment pond systems found 1 log removal every 14…”