The ingenuity of inline chlorination: a cost-effective method ensuring safe and E. coli-free water across Nepal’s Karnali Province

Nepal has abundant water resources. Rivers, streams, and glacial lakes flowing from the Himalayas alone should be enough to meet the nation’s water needs.

However, despite continuous efforts by various agencies, national data shows that only 25% of the country’s population has access to safe drinking water. The government-issued national drinking water quality standards, which outline 19 compulsory parameters for assessing water safety, reveal that Escherichia coli (E. coli) is frequently detected in the nation’s water sources, particularly in hill and mountain regions, while arsenic, iron, and ammonia are more commonly found in the plains or Terai areas. These issues have plagued Karnali Province, Nepal.

Given these challenges, SUSWA embraced a simple and inexpensive technology to address the problem. Aside from strengthening WASH governance and management in the region, the SUSWA team has focused on improving access to safe drinking water. Some applied research and past experience have shown the cost-effectiveness and efficacy of using inline chlorination in water supply schemes, and so we decided to apply it in this context.

Inline chlorination is a simple and affordable water disinfection technique that uses a “chlorine candle” — a type of filter cartridge used in water purification systems often in resource-constrained settings — to mix chlorine with water and achieve the required concentration for safe drinking water.

In this method, mixing occurs through gravity flow, eliminating the need for any external energy source, and chlorine concentration is regulated through a globe valve provided in the system. Currently, two products are available on the market: the Indian-manufacturer PurAll system, which is low-cost and easily available, and Aquatabs, an Irish product known globally for its quality but comparatively more expensive.

In my years as a water resources engineer, I have found integrating inline chlorination in water schemes to be highly suitable to areas such as Karnali, where rural communities, limited infrastructure, and dependence on untreated surface water make simple, low-cost disinfection methods indispensable.

The technology is easy enough to use for community members in Karnali, who do not need technical skills or knowledge to make the system work. Daily operations and maintenance (O&M) consist of simple tasks, which SUSWA trains locals on so that they are self-reliant in O&M even after the project’s completion. For example, replacement of chlorine cartridge, test of residual chlorine and contact private sectors for the required fitting items and chlorine cartridge. 

I am proud to say that SUSWA successfully demonstrated the use of inline chlorination technology in hard-to-reach communities of Karnali. Over 87,000 individuals in the region now benefit from safe drinking water, following the renovation or construction of 180 water supply schemes, each integrated with inline chlorination technology.

The team rolled out capacity-building initiatives designed to teach village maintenance workers, who are also residents, how to work with the system in ensuring water is safely chlorinated, empowering communities to be self-sustaining in the process. Community members share their newfound knowledge with fellow residents by sharing the ideas of fixing chlorine concentration, residual chlorine test process and benefits of use of chlorine. 

The entire project team is proactive in advocating for this smart and simple solution, producing a range of information, education, and communication materials, including leaflets, posters, and videos. These have been developed and shared with communities, government agencies, and sector stakeholders. Beyond Karnali and Nepal, we have also promoted this approach to safe drinking water at global forums.

As the project’s Technical Specialist, I have presented inline chlorination as an appropriate and practical technology to senior personnel of the Department of Water Supply and Sewerage Management and the Ministry of Water Supply. I also had the privilege to share our work in Karnali at World Water Week 2024 in Sweden alongside HELVETAS and Nepal Water for Health to further promote the innovative solutions arising from this project beyond Nepal.

SUSWA’s efforts to promote inline chlorination have been so successful that the Ministry of Water Supply issued a circular mandating a chlorination dosing system in all water supply schemes throughout the country. This means inline chlorination has emerged as one of the top technologies for ensuring safe water and neutralising harmful microorganisms.

Through SUSWA and other similar initiatives I have been a part of, I have seen how adopting inline chlorination is a sustainable and effective solution, particularly for rural and small-scale water supply schemes, allowing individuals in these areas to lead lives of dignity and good health.