- Bindal Rao and Rispana, two heavily polluted rivers in Dehradun, show a surge in antibiotic resistance genes in the monsoon when heavy rainfall intensifies river pollution by flushing in more sewage.
- As the rivers are regularly used by locals for irrigation and domestic activities, this increases the chances of direct human contact with antimicrobial-resistant pathogens.
- Researchers call for treating rivers as core urban infrastructure, recommending better sewage and septic-tank waste management, protection from encroachment, and restoration of natural drainage.
In May 2019, Kenyum Bagra, a Ph.D. student from Indian Institute of Technology (IIT), Roorkee, was collecting river water and sediment samples at multiple locations in Uttarakhand, along Bindal Rao and Rispana, two heavily polluted sub-tributaries of the Ganga river, flowing through Dehradun’s densely populated settlements.
While Rispana is a perennial stream, she noted that Bindal, a seasonal river, was dry at upstream locations, as expected at this time before the arrival of the monsoon (between June and September) except near the settlements where there was a slim flow. This flow was the city’s wastewater that drains into the riverbed throughout the year.
Running in parallel, Rispana and Bindal respectively carry almost 10 million litres per day (MLD) and about 18 MLD of municipal wastewater, before joining downstream to form the Suswa river, a polluted river stretch listed under the Namami Gange river restoration programme.
Bagra also noticed that both rivers were being used to dump solid waste. “During my work, I saw solid waste dumped directly into these rivers, as well as dead animals, while children were playing and bathing just downstream,” says Bagra, now an Assistant Professor at IIT-Varanasi.
Based on seasonal (pre-monsoon, monsoon and post-monsoon) and multilocational samplings in 2019, Bagra’s mentor Gargi Singh, Associate Professor, IIT-Roorkee, recently reported that throughout the sampling stretches, these rivers showed widespread faecal and anthropogenic pollution. Monsoon rainfall was also associated with a surge in antibiotic resistance genes (ARG) in both of these rivers. The river sediments were found to contain an elevated level of the ARGs (particularly sulphonamide sul1, sul2, macrolide ermF and tetracycline tetW), even post-monsoon.
“While much has been done for sanitation and sewerage in our country, sewage, seepage from septic tanks, and solid waste still end up in the local rivers that traverse our cities. This is why it was so important for us to follow the urban rivers,” says Gargi.
The research group chose these two rivers because of their unique legacy and contributions to the Dehradun valley. Nidhi Singh, an urban water issues expert from the Centre for Ecology Development and Research (CEDAR), Dehradun, who was not involved in the study, has witnessed changes in these rivers over the years.
“In cities across India, rivers like Bindal and Rispana contribute to drainage, groundwater recharge and flood regulation, while also providing important ecological functions within an increasingly urbanised landscape. So, in many ways, the health of these urban rivers is closely connected to the health and resilience of the city itself,” she says.
When urban rivers turn into drains
According to a 2021 report by the Central Pollution Control Board, there remains a 78.7% gap (22,939 MLD) between sewage generation and installed sewage treatment capacity in India’s towns and cities. Though the gap in treatment capacity is not as high in Uttarakhand, the state’s authorities recently came under scrutiny after untreated sewage was found to be discharged directly into the Ganga from 12 out of 44 sewage treatment plants (STPs).
While one might expect monsoon rains to dilute the contamination by increasing the water volume, the study found the opposite. Presumably drawing in the accumulated solid debris, faecal waste and associated microbes from the city’s streets, drains, overflowing septic tanks and informal dumping sites, the monsoon amplified the noted pollution level by approximately 10 to 1000 times (relative abundance, measured relative to the total bacterial abundance) when compared to pre-monsoon samples.
“Our results show that monsoon rainfall was associated with the mobilisation of faecal pollution and ARGs into the rivers. Surveillance is thus important and should therefore account not only for location, but also for strong seasonal events that may temporarily increase environmental antimicrobial resistance (AMR) levels and potential exposure scenarios,” says microbiologist Uli Klümper, the German collaborator of the study, and a Senior Scientist from Technische Universität Dresden.
As per the study, the contamination level was almost uniform throughout the surveyed river stretch, and no significant difference was detected between samples collected upstream and downstream of STP discharge points. According to the authors, this suggests that the majority of the faecal pollution doesn’t originate from treated effluent from the STP discharge outlets alone, but also from untreated municipal wastewater, which comprises a mixture of domestic wastewaters, hospital effluents, small-scale pharmaceutical and industrial discharges from open drains, informal sewer connections, septic tanks, and diffuse greywater outlets. This sustains the contamination along the entire length of the river.
Beyond clinical settings, accumulated heavy metals in the environment indirectly drive the spread of ARGs by co-selecting for metal resistance genes and ARGs in microbes present in the water, soil and air. The study found severe heavy metal (Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) pollution strongly enriched in sediments compared to water, with peak levels frequently observed downstream of STP discharge points. However, there was no seasonal variation.
Some recent studies have reported that faecal pollution leads to the selection and proliferation of potentially pathogenic metal-resistant microbes in urban rivers like the Ganga and Yamuna, showing significant heavy metal pollution. This study, however, didn’t find any consistent associations between the ten heavy metal concentrations analysed and the elevated ARG level found across either river system. Instead, the strong association of faecal and anthropogenic pollution with ARG level suggests that the overwhelming level of sewage influx makes it the dominant driver and could mask other drivers of antibiotic resistance development in these heavily polluted urban rivers.
“What our rivers are receiving today is far beyond what their natural capacity can assimilate. India is working on the much-needed STPs, but immediate, targeted interventions are also possible to better contain and manage septic-tank waste,” Bagra says.
Urban rivers as conduits of AMR spread and exposure
The Bindal and Rispana rivers flow through populated human settlements, and locals regularly use them for irrigation and domestic activities such as drinking, bathing, and washing. The prevalence of elevated wastewater-associated ARGs in these rivers, as well as monsoon-driven surges, increases the chances of direct human contact with antimicrobial-resistant pathogens. The exposure risk increases during riverbank overflow and floods.
Corresponding author of the study, Gargi, says, “It is deeply concerning because floodwaters, laden with antibiotic-resistant bacteria and potentially other pathogens, can serve as conduits for the transmission of antibiotic-resistant infections in communities affected by flooding and waterlogging. So, in addition to the waterborne, vector-borne, and water-based diseases associated with waterlogging and flooding, our healthcare system and economy are also hit by the antibiotic resistance of these diseases.”
Bagra spent one and a half years at Klümper’s lab in Germany for part of her PhD research. She says, “Working in laboratories in two different countries, and having the opportunity to visit rivers in both places made me appreciate how closely the health of rivers is connected to the communities and environments around them.”
Klümper adds, “I gained a much clearer understanding of the urgency of investigating AMR in Indian urban rivers, where severe pollution and close connections between rivers, wastewater, flooding and human communities can create very different exposure pathways from those typically studied in Germany.”
Bagra notes that river pollution is not only an environmental problem but also a public health and a community problem, and ultimately a One Health problem.
In this context, the proposed Rispana-Bindal elevated road project connecting both rivers over a total stretch of 26 kilometres demands reflection. While this corridor aims to ease traffic in Dehradun, experts are raising concerns about its construction, especially about how it could amplify flood risk.
Nidhi comments, “Before undertaking such large infrastructure projects around these rivers, the utmost priority should be to understand and restore their ecological and hydrological functions by ensuring adequate floodways, preventing further encroachment, managing sewage and solid waste and restoring natural drainage and groundwater recharge areas.”
She adds that the rivers should be treated as critical urban infrastructure in their own right. These functions are just as important for Dehradun’s future as roads and other infrastructure.
She also thinks that the policy approach needs to shift from cleaning the rivers to managing them and ultimately to learning to live with them. “If we continue to treat our rivers as drains, with changing rainfall patterns and more intense rainfall events, these ecological problems will increasingly become an economic, social and public health crisis for the city,” she says.
Stressing the need for more research, Gargi says, “We have been humbled by how little we know about how antibiotic resistance emerges, spreads, and is transmitted through urban areas and communities in India.”
Banner image: Pollution chokes the perennial Rispana river which flows through Dehradun. Image by Kenyum Bagra.
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