Methodology

To compare different centralisation levels and technology types simultaneously, a two-dimensional dynamic cost model was built that allows decision makers to compare the total annual chlorination costs for each possible combination of technology and placement, based on parameters specific to their scheme. The model includes parameters such as the system’s total annual water usage, the number of supplied households, the number of reservoir tanks, reservoir tanks’ distance to the village, and target chlorine concentrations. Interviews with operators (n = 12) and chlorine vendors (n = 3) were conducted to collect market and operational data.

The costs taken into account are the annualised CapEx (capital expenditure) and OpEx (operational expenditure), including chlorine, electricity, labour, and commuting costs for operators. The output of the model is an 8x4 matrix that illustrates the total annual chlorination cost for each possible combination of technology and centralisation level (Table 1).

Key findings

The following results assume an annual water consumption of 125 m³ per household (HH), which is commonly observed across the schemes, along with typical target concentrations (2 mg/L at DC, 1 mg/L at RvT, 0.2 mg/L at HH level), round trip commuting times (1 hour to DC, 30 minutes to RvT), and other cost parameters defined for the Nepal context:

• Aquatabs Flo is a suitable option for isolated (up to three) houses seeking access to safe water.
• The Water Mission in-line chlorinator* appears to be the most financially efficient option for small villages (more than three households) with only one RvT and for systems with fewer than 50 HH in total.
• The injection chlorinator placed at the centralised level outperforms other chlorinators, when there are three RvTs and more than 50 HH in total.
• The injection chlorinator with an injection pump is consistently the most expensive option among the injection chlorinators, but it also enables operators to target a more precise concentration level.
• Manual chlorination performs particularly well for smaller villages with 15 or fewer households. Nevertheless, this chlorination method may be less precise in achieving a specific concentration level and places a significant time and safety burden on the operator.

* The cartridge price was unavailable for the Water Mission in-line chlorinator. Therefore, cost data from a similar project in Uganda were used. This uncertainty may bias the conclusions.

Scenario analysis: Tax exemptions

A scenario analysis was conducted in which chlorination products were exempt from VAT (13%) and import duty (typically at least 20%) for components produced outside Nepal. The analysis shows that these tax exemptions primarily benefit erosion chlorinators, which are foreign-made and use imported chlorine tablets or cartridges, which are more expensive and subject to both taxes. In contrast, injection chlorinators use locally available chlorine (e.g., bleaching powder), which is significantly cheaper and thus less affected by such tax exemptions. This difference is observed because most of the costs for erosion chlorinators are material-related, whereas costs for injection chlorinators using bleaching powder are mainly labour-related.

On average, the injection chlorination option would become 10-18% cheaper with tax exemptions, while erosion chlorination costs would decrease by 18-26% (except for HH level treatment, which becomes cheaper by 32%). The manual chlorination method is barely affected, showing only about a 1% reduction in total cost.

Conclusion

This research project aims to support NGOs, local governments, designers, installation companies, and water users’ committees in decision-making for rural water schemes in Nepal. By modelling annual OpEx and CapEx to develop a two-dimensional cost matrix, this study enables the simultaneous comparison of technologies and placements, a pioneering approach in this field that still requires further validation of costs across diverse contexts and system configurations.

Although developed for rural Nepal, the cost model framework is transferable to other low-income rural contexts. By updating key parameters such as labour costs, chlorine prices, and water demand, practitioners can adapt the model to different geographic and institutional settings, enhancing its usefulness as a global decision-support tool.

Nevertheless, factors beyond finance must also be considered when selecting the optimal chlorination approach. Performance metrics such as treatment efficacy, user acceptance, supply chain and operational reliability, and managerial feasibility play a critical role, as they directly influence sustained system functionality and public health outcomes [2]. Integrating financial assessments with these broader considerations can support more resilient, context-appropriate, and scalable safe water solutions for rural communities.

References

[1] Crider, Y. S., et al., Evaluation of system-level, passive chlorination in gravity-fed piped water systems in rural Nepal, ES&T, 56/19, (2022), 13985–13995

[2] Kunwar, B. M., et al., Chlorination technologies for small piped supplies in Nepal: Practical implementation guide. Sandec Learning Brief, March 2026.