The purification of the primary treated domestic sewage was performed in the present study through the horizontal sub-surface flow constructed wetland (CW) of 10 × 3.5 m dimension. The study was performed using three setups of CW 1 (Unplanted CW), CW 2 (CW planted with macrophyte Typha latifolia), and CW 3 (CW planted with two species of macrophyte T. latifolia and Commelina benghalensis). The purification experiments were performed by converting one type of CW into the other form sequentially, i.e., CW 1 was built first and after the experiments, it was converted into CW 2 and then CW 3. The CW was filled with a layer of coarse and fine gravel of 70 cm depth as filter media in 1:2 ratio. Each set of wetland was operated for 3 months (12 wk) during which the treatment performance of wetlands for basic physicochemical parameters was evaluated. The CW was operated in continuous mode at an average hydraulic loading rate of 250 L h^− 1 and the treated effluent was analysed twice every week at four different sampling points having hydraulic retention times (HRT) of 12, 24, 36 and 48 h for important sewage quality parameters All the three setups of CW were able to clean the primary treated sewage significantly. Among the three sets of wetlands used, CW 3 was the best performer removing 79, 77, 79, 79, and 78% of biochemical oxygen demand, chemical oxygen demand, nitrate, ammonia, and phosphate respectively in 48 h HRT. Among the three sets of wetlands, the CW 3 removed the highest percent of total coliforms, fecal coliforms, and E. coli as 64, 61 and 52% respectively.

Under the present investigation, vertical subsurface flow constructed wetlands (VSSFCWs) planted with macrophytes treated domestic sewage in an environmentally sustainable manner. Treatment of domestic sewage with wetlands is an alternative method that decreases energy consumption and economic costs involved in the treatment of environmental contaminants. This study evaluates the potential efficiency of VSSFCWs using two different macrophytes, Acorus calamus and Canna indica for the treatment of domestic sewage. To perform this study, two chambers of VSSFCWs of dimensions 2.48 m × 1.24 m × 1.54 m were built. The wetland was fed with the primary treated sewage at a hydraulic loading rate (HLR) of 0.67 m3/h (hours) in a batch flow. Treatment of primary sewage was observed from day 1 to day 6; once a day (i.e. 24 h to 144 h). The treatment of sewage was found to be significant up to day 6 (144 h); beyond this time, no significant removal was observed. The results revealed that both the wetland setups performed significant removal of TDS, BOD5, total nitrogen, and phosphate. The wetland planted with Canna indica was a better performer for the removal of TDS (22.31%), BOD5 (81.79%), total nitrogen (60.37%), and phosphate (80%).

In the present research water quality from nine different sampling points (S1–S9) from the River Ganga at Varanasi was examined for different water quality parameters, and multivariate statistical analyses were carried out. Subsequently, several indices, such as water quality index and Nemerow pollution index (NPI), were calculated. The results indicated that the Ganga River at Varanasi had high levels of coliform concentrations, altered pH, and elevated dissolved oxygen/biochemical oxygen demand and chemical oxygen demand values. The weighted arithmetic water quality index values revealed that sites S8, S9, and S2 were the most polluted and unfit for bathing and drinking. Most of the sampling sites have NPI values greater than 1 for several parameters, indicating high levels of pollution. The study revealed that the water quality is poor for bathing and drinking at most of the sites throughout the year. In addition, the upstream water quality assessment revealed that water quality was good compared with the heavily contaminated downstream region. This knowledge can be useful for environmentalists, policymakers, and water resource managers to develop strategic plans to preserve the cultural and aesthetic worth of the Ganga River in the future.

This study was performed to assess water quality in the Narmada River, the third-longest river in India. Water samples were collected from 6 major sampling stations with 17 sampling points. Nine water quality parameters were analyzed to calculate the water quality index (WQI), followed by multivariate statistical evaluation. The results indicated that water quality in the upper Narmada varied from excellent to very poor – comprising excellent for approximately 12%, good for 17%, poor for 59%, and very poor for 12% of pre-monsoon samples, but excellent for 17%, good for 12%, and poor for 71% of post-monsoon. While the general water quality in the Narmada was poor, anthropogenic inputs such as domestic sewage and agricultural runoff influenced some parameters – e.g. BOD, nitrate, and total coliform. More studies are required for completing water quality evaluation.