Inline chlorination installation
Sustainable WASH for All (SUSWA)
Waterborne diseases remain a major public health challenge in many low- and middle-income countries. A key cause is the contamination of drinking water with human waste, which exposes communities to harmful pathogens and reinforces existing health and economic inequalities.
Globally, unsafe drinking water is one of the leading causes of deaths from diarrhoeal diseases. Limited access to safe-to-drink water, sanitation, and hygiene (WASH) continues to contribute significantly to child mortality rate, with an estimated 43 deaths per 100,000 children under five linked to these conditions.
India faces a similar challenge. Despite large-scale initiatives such as the Jal Jeevan Mission, which has expanded piped water supply networks in rural areas, ensuring the microbiological safety of drinking water remains a critical concern. Inconsistent water treatment, inadequate infrastructure, and limited monitoring of water quality often leave rural and peri-urban communities vulnerable.
As a result, diarrhoeal diseases continue to affect millions of people across the country. They are among the top three causes of death among children under five in India, accounting for an estimated 443,832 deaths annually.
Contaminated water can carry a range of disease-causing organisms, including bacteria such as E. coli, Salmonella, and Shigella, viruses like rotavirus, and parasites such as Giardia. Young children are particularly at risk. According to the National Family Health Survey (NFHS-5), around 9 percent of children aged three to five experienced diarrhoea within a two-week period, underscoring the ongoing risks associated with unsafe drinking water.
Chlorine has been saving lives for more than a century. Since it was first introduced for water treatment in the early 1900s, it has become one of the most widely used and affordable methods for disinfecting drinking water, particularly across countries in the Global South.
Compared with other household water treatment options such as filtration, solar disinfection, or combined flocculation-disinfection, chlorination offers a distinct advantage. It leaves behind a small amount of chlorine in the water, known as a “residual.” This residual continues to protect the water from contamination during storage and handling. This is especially important in many households where water is collected, stored, and used throughout the day. Although some other methods, such as combined flocculation-disinfection, can also provide residual protection, chlorination remains far more affordable and easier to implement.
Introducing inline chlorination
In India, large-scale initiatives like the Jal Jeevan Mission have rapidly expanded piped water supply networks in rural areas. However, maintaining water quality within these systems remains a challenge. In many places, chlorination is done manually, which can lead to irregular dosing and inconsistent disinfection. As a result, microbial contamination can still occur even where piped water infrastructure exists.
To address this issue, Tata Trusts developed an innovative Inline Chlorination (ILC) technology. The system is designed to automatically disinfect water within rural piped networks. It is a gravity-based device that is installed directly into the pipeline and works without electricity or manual intervention. By automatically releasing chlorine as water flows through the system, it ensures continuous and real-time disinfection at a minimal operational cost.
This study examines the design, efficiency, and practical challenges of deploying inline chlorination systems. Based on field evaluations, it presents evidence of how the technology can help improve water safety. By combining public health insights with technological innovation, the study highlights the potential of inline chlorination as a practical solution to reduce the burden of diarrhoeal diseases and support progress towards Sustainable Development Goal 6: Clean Water and Sanitation.
Performance across the distribution network
The inline chlorination system was evaluated by researchers at IIT Guwahati using several key performance indicators. These included residual chlorine levels, improvements in bacteriological water quality, pH stability, turbidity control, system efficiency, and community acceptance. The results showed that free residual chlorine levels remained consistently within the World Health Organisation's recommended range of 0.2–0.5 mg/L, ensuring effective and continuous disinfection of drinking water.
A moderate-to-strong inverse correlation exists between distance and free residual chlorine (FRC) concentration. While a gradual decline in FRC along the pipeline is expected, maintaining levels above 0.2 mg/L across the network is crucial for microbial safety. As water travels from the injection point, the FRC level decreases steadily from 0.5 mg/L near the source to 0.2 mg/L at the 2,000-metre mark. This final measured value aligns with WHO and BIS standards, which mandate a minimum residual of 0.2 mg/L at the farthest point in the network. While the system is functioning effectively, this value sits at the lower safe threshold. Microbial testing confirmed 100% elimination of E. coli and total coliforms, reflecting significant improvements in bacteriological water quality. Furthermore, pH levels remained stable (6.5–8.5) and turbidity stayed below 1 NTU, ensuring optimal chlorine efficacy.
The introduction of the inline chlorination system led to a dramatic improvement in water quality across all tested parameters:
Disinfection Efficiency: Residual chlorine levels increased from 0.00 mg/L to 0.5 mg/L, achieving optimal disinfection within the WHO-recommended range (0.2–0.5 mg/L).
Microbial Safety: Total Coliforms and E. coli, which were previously present in high concentrations (80–120 CFU/100 mL and 40–70 CFU/100 mL, respectively), were completely eliminated. This indicates a 100% microbial removal efficiency.
Physico-chemical Stability: The pH remained stable and well within permissible limits, ensuring that chlorination did not adversely alter the water chemistry.
Improved Clarity: Turbidity was reduced from 1.5 NTU to 0.9 NTU, meeting WHO guidelines for safe drinking water and reflecting improved sediment control.
The system operated efficiently with minimal maintenance issues. Community acceptance was high, with 90% of households reporting satisfaction and a 95% decline in reported waterborne diseases. These findings confirm that ILC technology meets rigorous safety and performance standards, making it highly suitable for scaling up across water supply schemes to ensure long-term public health benefits.
The findings show that the ILC system meets all the key performance criteria, providing safe, chlorinated drinking water while significantly reducing microbial contamination. By improving water quality, the system also contributes to better public health outcomes. These results suggest that the technology can be scaled up and adopted more widely in both rural and urban water supply systems under programmes such as the Jal Jeevan Mission and other safe drinking water initiatives.
One of the main advantages of ILC is its gravity-based design, which helps overcome common challenges in rural areas, such as limited electricity supply and the need for labour-intensive manual dosing. The system also provides residual protection, meaning that a small amount of chlorine remains in the water to guard against recontamination during storage and distribution. This is a benefit that methods such as ultraviolet treatment or boiling do not provide.
The technology is effective against a wide range of bacterial and viral pathogens, and it works well alongside filtration systems used as pre-treatment. However, like most chlorination methods, it has limited effectiveness against certain protozoan cysts. Compared with traditional manual chlorination systems, ILC can reduce operational costs by about 70 percent and eliminate nearly 90 percent of dosing inconsistencies, making water treatment more reliable, particularly in regions with a high disease burden.
While the current evaluation was based on short-term monitoring, long-term observation will be important to track disinfection by-products (DBPs) that may form during chlorination. Future improvements to the system could also include IoT-based sensors, which would allow real-time monitoring and remote data analysis.
Overall, inline chlorination offers a proven, scalable, and cost-effective solution for maintaining water safety across both decentralised and large-scale distribution systems. Its ability to provide continuous disinfection and maintain residual protection makes it an important tool for strengthening modern water management systems.
At the same time, successful implementation requires good system design and regular preventive maintenance to manage chlorine demand effectively. When these conditions are met, ILC systems can play a crucial role in strengthening public health infrastructure.
Integrating inline chlorination into large-scale programmes such as the Jal Jeevan Mission could help prevent more than 136,000 deaths each year, while also generating an estimated $4–6 billion in economic savings by reducing healthcare costs associated with waterborne diseases. In addition, training communities to operate and maintain these systems can improve long-term sustainability, turning local residents from passive beneficiaries into active stewards of water security.
Providing safe drinking water requires both infrastructure and reliable water treatment systems. Inline chlorination demonstrates how simple technological innovations can strengthen rural water supply networks and protect public health.
With proper system design, monitoring, and community engagement, automated chlorination systems could become a key component of rural water management across India.
As the country works toward universal access to safe drinking water, integrating solutions like inline chlorination into national programmes could play an important role in ensuring that the water reaching rural households is not only available, but also safe to drink every day.