– by Shruti Syal
Post-Diwali, mouth clamped with two layers of medical masks, and armed with laboratory paraphernalia, we strutted off to survey a potential site for the implementation of ACWUSTM. We chose a site south of the Noida Toll Bridge for its proximity to one of the four main drains discharging effluents into the Yamuna. Preliminary survey showed that the site had promise: there was a decently-sized wetland just a few hundred metres from a ghastly open drain flowing past an informal settlement.
Trailed at the heel by a throng of neighbourhood kids and teenagers, and a group of excited piglets and their disgruntled guardian, we collected water samples from sites in the drain as well as the adjacent wetland in order to assess the health of the wetland.
Back at the lab, we found that the suspended solids were extremely high for the sewage water downstream of the flow, understandably because of being sampled from a bend in the drain course, where flow was practically non-existent. For the sewage water upstream it was understandably lower because the site upstream was as yet not exposed to the informal settlement’s dumping activities, and yet not below the standard limit for treated wastewater despite the water having been treated.
The trend with regard to oxygen consumption was found to be significant. While it is evident that the oxygen demand for microbial decomposition is extremely high at all sites except the wetland water itself, our results indicated that the wetland water itself demanded far more than that which can allow it to replenish its own oxygen demand. Therefore, using natural wetlands for wastewater treatment would ruin wetland health, so artificial wetlands should be recruited for wastewater treatment. It is common knowledge that Delhi’s few existing water bodies, including the sputtering Yamuna, are seriously oxygen depleted.
This pilot study also helped determine a proper sampling strategy, the number of samples required, the entire array of tests needed in the Indian context, the type of sites where ACWUSTM can be employed, the need to assume treated wastewater as untreated, and the difficulty in using the naturally occurring wetlands for wastewater treatment.
Following this study, it has been planned to consult with ecologists at TERI, Delhi University and Wetlands International South Asia on deciding which sites would respond best to ACWUSTM. Then, the 2-3 finalized sites will be reviewed for their topography and land-use, and water samples collected to analyse a slew of water quality monitoring parameters. Given the picture we have of water quality from these parameters, native vegetation and landscape architecture techniques will be employed to construct an artificial wetland at one site, and implement the ACWUSTM model, which also involves monitoring these variables on the wetland after construction at regular intervals, and maintaining a database of these variables to see the progress of the ACWUSTM model at that site.