— by Shruti Syal
Delhi’s sewage woes are well known. Offensive open drains sullied further by metal contamination, not in the least from the leached constituents of coarse wastes like rubber tires, thermocol packaging material, plastic bags, and glass bottles. And then, there are also herds of both cattle and people indiscriminately using the the water for every discernible purpose.
In Delhi’s case, the pollution is further exacerbated by the 45.6% of Delhi’s population living in informal settlements and without access to infrstructure. With sewage network covering only 53% of current wastewater generation, insufficient wastewater treatment capacity, and the failure of supplementary infrastructure like interceptor drains, it is necessary to also look for decentralized, scalable, low carbon-impact technologies to cope with water treatment demands. Wetlands fit the bill well.
The story of constructed wetlands for reduction of suspended solids, chemical detoxification, increased oxygenation, groundwater recharging, erosion and minor flood control has been told since the 1970s. Their scalability made them widely applicable in all types of sites in North America and England.
In the short term, the constructed wetlands- in addition to extracting solid wastes and toxic chemicals- will strengthen the banks of the river Yamuna, reducing the damage caused by periodic inundation of water overflows, which is a natural floodplain maintenance process. In the long term, ensuring the quality of water entering the river will increase the resilience of the closest water source for the city, whether the water is drawn by the municipal machinery or by individuals in towns and unplanned settlements scattered over the Yamuna floodplain.
Given the rarity and poor health of the few naturally occurring inland wetlands, it is necessary to construct artificial wetlands for the purpose of wastewater treatment. Besides their potential handiness in informal settlements, constructed wetlands can spruce up former industrial sites, fallow areas, and be implemented progressively in DDA neighbourhoods. Already, the Yamuna Biodiversity Park boasts of thriving constructed wetlands, and DDA and INTACH have announced their intention to treat wastewater in constructed wetlands in South Delhi.
As things stand today, STPs are irreplaceable to cope with urban sewage treatment demands. However, the progressive implementation of ACWUSTM at say two dozen sites across Delhi, should the pilot project(s) display promise, can help reduce total dependence on large-scale infrastructure for urban utilities. Landscape architecture magazines are replete with cases of independently constructed eco-efficient homes and community areas all over the Americas and Europe, using constructed wetlands on-site for wastewater treatment. ACWUSTM is an extrapolation of this strategy on a larger scale, and with three purposes in mind: inculcating community stewardship and environmental education, fostering the use of ecological engineering principles to alleviate pressing urban issues, and data collection and management. These are all particularly crucial in developing countries, where inter-agency partnerships have developed between NGOs and educational institutions, and a general environmental consciousness is mounting but has not necessarily acquired the robustness that comes with scientific understanding and management of issues by the entire community.