The WHO compendium: Technologies and frameworks for safe drinking-water

Water is a public good, a human right, and a determinant of health and dignity. Yet even today, more than two billion people lack access to safely managed drinking-water. In this context, the World Health Organization’s 2025 “Compendium of Drinking-Water Systems and Technologies from Source to Consumer” marks a critical step forward. It is not merely a manual on treatment or infrastructure; it is a framework for systems thinking—connecting technology, management, and governance within the broader goal of achieving Sustainable Development Goal 6.1: universal and equitable access to safe and affordable drinking-water for all.  

The compendium in context: Translating guidelines into practice

The compendium is anchored in the WHO Guidelines for Drinking-Water Quality (2022), which outline the Framework for Safe Drinking-Water. This framework consists of three interdependent components:

• Health-based targets, established by competent health authorities;

• Well-managed water supply systems, capable of achieving and maintaining those targets; and

• Independent surveillance, ensuring that safety objectives are continuously met.

The publication complements WHO’s Guidelines for Drinking-Water Quality: Small Water Supplies (2024), focusing on contexts where systems are informal, decentralised, or community-managed. It is also conceptually linked to the Compendium of Water Supply Technologies in Emergencies (2021), ensuring coherence between humanitarian and long-term development approaches.

Purpose and methodology

The compendium’s stated objective is to provide foundational, globally applicable knowledge on how different technologies and system configurations can achieve drinking-water safety objectives. It is designed as a decision-support and communication tool for engineers, planners, policy-makers, and practitioners, rather than as a design manual.

Its development methodology, as outlined in Annex 1 of the publication, is based on:

• Review of existing WHO and partner guidance on water safety planning, technology evaluation, and risk management;

• Adaptation of earlier work under the EU Water4India project (FHNW and partners, 2016); and

• Peer review by WHO’s expert network, ensuring technical validity and institutional alignment.

The result is a harmonised document that integrates technical detail, policy relevance, and field applicability.

Structure of the compendium: A systems approach

The compendium is structured in three interlinked parts that together describe how water systems function from catchment to consumer.

Part 1: System Templates

This section presents nine archetypal water supply systems, each associated with a dominant source type or treatment pathway. They are:

• Rainwater harvesting systems

• Centralised surface-water treatment systems

• Decentralised surface-water systems

• Freshwater sources with manual transport and household-level treatment

• Gravity-flow schemes (often in hilly or spring-fed contexts)

• High-quality groundwater systems (requiring minimal treatment)

• Groundwater affected by geogenic contamination (arsenic, fluoride)

• Freshwater affected by anthropogenic contamination (industrial, agricultural pollution)

• Desalination systems for brackish and saline sources

Each template links the six functional groups—source, intake, abstraction, treatment, distribution and transport, and household water treatment & safe storage (often abbreviated as SIATHD)—showing how technologies can be combined into complete systems. The templates are intentionally modular, allowing adaptation to local geography, climate, and governance structures.

For instance, a gravity-fed mountain system may bypass pumping entirely, while a coastal urban settlement may integrate solar desalination and networked distribution. The approach reflects WHO’s principle of context-appropriate technology selection.

Part 2: Technology information sheets

The heart of the compendium is an extensive set of 70+ technology sheets. Each entry follows a standardised structure, describing:

• Function and principle of operation;

• Applicability and scale;

• Operational and maintenance requirements;

• Cost and energy implications;

• Advantages, limitations, and environmental considerations.

Technologies are categorised by functional group, covering:

Source and Intake – roof and surface catchments, protected wells, infiltration galleries, sand dams, and riverbank filtration.
Abstraction – human-powered (rope-and-washer, treadle), solar and electric submersible pumps, hydraulic rams.
Treatment – physical (roughing, rapid sand, slow sand filtration), chemical (coagulation-flocculation, disinfection), and advanced processes (UV, electrochlorination, activated carbon, reverse osmosis, membrane distillation).
Distribution and Transport – piped systems, tanker supply, kiosks, and gravity reservoirs.
Household Water Treatment and Storage (HWTS) – biosand and ceramic filters, boiling, solar disinfection (SODIS), chlorine dosing, and safe containers.

This categorisation provides a menu of technologies that can be combined in system design or service delivery models.

Part 3: Cross-cutting issues

The third section widens the lens to the enabling environment, covering regulation, management, risk governance, gender inclusion, life-cycle costing, and climate resilience. It underscores that sustainable delivery depends on the interplay of institutions, financing, and accountability—not technology alone.

The functional groups explained

Source

The compendium begins at the source, emphasising hydrogeological assessment, water quality monitoring, and protection zones. It differentiates between renewable surface waters and finite groundwater aquifers, guiding users on how to evaluate sustainability through recharge, yield, and quality indicators. Source protection—via fencing, reforestation, or sanitary inspections—is treated as the first barrier in the multiple-barrier framework.

Intake and abstraction

Intake systems vary from simple spring boxes to complex river intakes or boreholes. The compendium catalogues how each can be designed to minimise contamination. Abstraction technologies are compared by depth, discharge, and energy source. The emphasis is on life-cycle cost efficiency and local maintainability—recognising that reliability, not sophistication, determines long-term performance.

For low-income settings, solar PV submersible pumps are highlighted for their declining cost and suitability for off-grid communities. The document also describes manual systems such as India-Mark II handpumps, noting their limitations where aquifer depth exceeds 50 m.

Treatment

This is the most technically dense section, covering processes that together achieve microbial and chemical safety:

• Clarification and filtration: roughing filters, sedimentation tanks, slow sand filters, and pressure filters for turbidity reduction.

• Disinfection: chlorination, electrochlorination, ultraviolet irradiation, ozonation, and solar disinfection.

• Geogenic contaminant removal: adsorption on activated alumina, bone char, or iron oxide media; coagulation and precipitation for arsenic and fluoride.

• Organic and industrial pollutant control: activated carbon and advanced oxidation processes.

• Desalination: reverse osmosis, nanofiltration, and electrodialysis for saline sources.

The compendium quantifies log-reduction values (LRVs) for microbial removal, linking each process to WHO’s microbial health-based targets. It also stresses the multiple-barrier approach: combining processes so that failure of one does not compromise overall safety.

Distribution and transport

The compendium moves beyond treatment to discuss distribution—the often neglected “last mile” where contamination frequently re-enters the system. It explains hydraulic principles for piped networks, storage tank hygiene, and maintenance of residual disinfectant.

In rural and peri-urban areas, where distribution may rely on water vendors or tanker trucks, the guide details sanitary measures and accountability mechanisms to prevent secondary contamination.

Household water treatment and safe storage (HWTS)

Recognising that many communities still depend on water of uncertain quality, the compendium provides evidence-based guidance on point-of-use technologies. It compares the microbial efficacy, affordability, and cultural acceptability of common methods, referencing WHO’s household water treatment evaluation scheme (HWTS-E). By placing HWTS within the system continuum, the compendium ensures that household interventions are not seen as stand-alone or emergency measures, but as part of an integrated service ladder toward safely managed supply.

Risk management and the water safety plan framework

The compendium reinforces WHO’s position that risk management is the cornerstone of water safety. It provides detailed guidance on developing and implementing Water Safety Plans (WSPs)—structured, preventive risk management frameworks that cover:

1. System description and flow mapping;

2. Hazard identification (microbial, chemical, physical);

3. Risk assessment and prioritisation;

4. Control measures and operational monitoring;

5. Management procedures and documentation; and

6. Verification, review, and communication.

The WSP approach shifts focus from compliance-based monitoring to proactive control. It aligns with the International Water Association’s (IWA) risk management standards and is embedded in many national frameworks, including India’s Jal Jeevan Mission (JJM) guidelines for village water safety planning.

The compendium recommends linking WSPs with quantitative microbial risk assessment (QMRA) and sanitary inspection forms for small supplies, providing tools to quantify and manage residual risks.

Governance, regulation, and institutional arrangements

A central message of the compendium is that governance determines sustainability. It classifies management models by ownership and accountability:

• Community-managed systems, common in rural areas, offering local ownership but often limited technical capacity;

• Public utility or municipal systems, with greater scale and financial autonomy but bureaucratic rigidity;

• Public–private partnerships (PPPs), blending efficiency with regulation;

• Self-supply and household systems, relevant in dispersed settlements.

The document discusses how each model influences cost recovery, tariff setting, and maintenance accountability. It also provides guidance on establishing regulatory frameworks that integrate health, environment, and water service authorities. Importantly, the compendium links institutional arrangements to life-cycle costing—emphasising that capital subsidies must be matched by O&M financing and technical support.

Gender, inclusion, and social dimensions

The compendium aligns with WHO’s human-rights-based approach to water, highlighting gender and inclusion as cross-cutting priorities. It recognises that women and marginalised groups often bear the burden of water collection yet are under-represented in decision-making.

Key recommendations include:

• Gender-balanced water committees;

• Inclusion of women in operation and maintenance training;

• Collection of sex-disaggregated data on access and affordability;

• Addressing affordability barriers through progressive tariff design.

By embedding gender in technical guidance, WHO positions social equity as integral to safety and sustainability—not as an add-on.

Climate change, environmental sustainability, and resilience

The compendium explicitly situates water safety within the climate adaptation agenda. Increasing hydrological variability, prolonged droughts, and flooding require that systems be designed for resilience. Recommended approaches include:

• Diversifying sources—rainwater harvesting, managed aquifer recharge, conjunctive use of surface and groundwater;

• Energy-efficient operations—solar pumping, gravity flow, and low-pressure distribution;

• Green infrastructure—wetlands and vegetative buffers for source protection;

• Scenario-based planning—integrating local climate projections into WSPs.

These strategies reinforce the “no-regret” philosophy of adaptation—building flexibility and redundancy into systems irrespective of specific climate outcomes.

Monitoring, data systems, and digital transformation

Modern water safety management depends on data. The compendium promotes the integration of ICTs and smart monitoring tools—low-cost sensors, mobile applications, and cloud-based dashboards—to enhance transparency and accountability. Such tools can automate residual chlorine tracking, enable remote pump control, and link surveillance data to public health monitoring systems. WHO’s guidance here aligns with initiatives like the JMP service ladder and UNICEF–WHO data protocols for SDG 6 reporting.

Practical implications for policy and programmes

The compendium’s significance extends beyond technology selection. It provides a conceptual and operational foundation for national programmes. For example:

• In India’s Jal Jeevan Mission, the six functional groups mirror the steps in village water supply design, from source sustainability to household tap connections. WHO’s frameworks can enhance the programme’s risk management and climate resilience components.

• In African rural water supply, the system templates can help rationalise choices between handpumps, solar-mechanised schemes, and piped networks.

• In Pacific Island States, desalination and rainwater harvesting templates offer guidance for building climate-resilient small systems.

By offering globally applicable principles, the compendium bridges technical disciplines and governance systems, promoting consistency across donor and government interventions.

Institutional capacity and external support

Recognising that many countries face skill and financing deficits, WHO highlights the role of external support mechanisms—technical assistance, training, and knowledge exchange. The compendium’s structure lends itself to modular capacity-building curricula: system mapping, technology assessment, water safety planning, and monitoring. Partnerships with universities, standard-setting bodies, and regional health institutions are encouraged to integrate the compendium into national training frameworks.

The compendium as a policy instrument

Beyond its technical depth, the compendium is a policy instrument. It operationalises international commitments such as:

• UN General Assembly Resolution 64/292 (Right to Water and Sanitation);

• SDG 6.1 and 6.3 (safe water and pollution control);

• The Paris Agreement’s adaptation goals; and

• WHO’s Global Strategy on Health, Environment and Climate Change.

By offering a harmonised taxonomy of technologies and management practices, it provides a common language for regulators, financiers, and implementers to align on safety and sustainability standards.

Conclusion: A living reference for the decade of action

The compendium’s central message is simple yet profound: Safe water cannot be guaranteed by treatment plants alone. It requires a continuum of protection—from catchment to consumer, supported by capable institutions, inclusive governance, and climate-resilient design.

For governments, utilities, and development partners, the compendium provides the scaffolding for the next generation of water safety policies—ones that are technically sound, socially inclusive, and institutionally accountable. 

As the world enters the critical decade for achieving SDG 6, this WHO publication will serve not only as a guide but as a benchmark for integrated water safety planning, ensuring that every drop reaching a household is safe, sustainable, and equitably shared.

Citation: World Health Organization (2025). Compendium of Drinking-Water Systems and Technologies from Source to Consumer. Geneva: WHO. Licence: CC BY-NC-SA 3.0 IGO.