Water Consumption Reduction in Swimming Pools, Barcelona Spain

Compensation

Water savings

Overview

This project aims to transform water management models in swimming pools and spas by implementing an integrated, chemical-free treatment system based on physical and biological processes. The proposal addresses the significant water losses associated with conventional systems, caused by routine draining, regular purging, and bottom cleaning—practices linked to the intensive use of chlorine and other chemical compounds that rapidly degrade water quality.

The proposed technological solution maintains the sanitary and aesthetic quality of pool water through natural purification, microbiological stabilization, and sediment removal processes. This makes full-volume water replacement unnecessary. Rather than discharging water to maintain physicochemical parameters—as is typically done with chlorine—the system maintains constant balance through biofiltration, UV radiation, and recirculation with water recovery. This represents a radical shift in operational logic, where water ceases to be consumed in large volumes and instead is managed in a closed-loop system with minimal external input.

In terms of expected results, the system will generate structural impacts in three key areas:

Environmental: By eliminating the use of chemicals and contaminated water discharges, the flow of pollutants into sewer systems and surface water bodies is interrupted. This protects vulnerable ecosystems and prevents bioaccumulation of compounds such as chloramines and trihalomethanes, commonly released by traditional pools.
Operational: The system significantly reduces the frequency and complexity of maintenance tasks. Draining, weekly purging, and filter backwashing with large volumes of water are no longer required. Instead, operators will work with sensors, remote monitoring, and water-preserving cleaning protocols.
Health and user experience: Users benefit directly from a chlorine-free aquatic environment, free from irritating odors and risks of allergies, skin, or respiratory reactions. This enhances comfort and well-being, positioning the facility as a healthier and more sustainable alternative.

Overall, the system not only saves water but also redefines how this resource is valued and managed. The intervention proves that pools in urban or tourism settings can operate without constant water loss or negative externalities, while still meeting the highest standards for water quality and user safety. This approach aligns with circular economy principles and water stewardship, and can be replicated in both public and private sectors, with strong potential for scalability.

Problem and Causes

Recreational, sports, and therapeutic pools are among the least efficient infrastructures in terms of water use within urban environments. Although not often prioritized in water efficiency plans, their continuous operation results in systematic and largely avoidable consumption, directly impacting potable water networks and wastewater systems.

The core problem lies in the structural water losses caused by:

Intensive use of chemical products: Traditional systems rely on chlorine and similar compounds for disinfection. These chemicals degrade over time and react with organic matter and other pollutants, producing toxic byproducts like chloramines and trihalomethanes, which require partial or full water renewal.

Periodic purging and backwashing: Due to the buildup of dissolved solids and chemical imbalances, traditional pools must frequently purge a significant portion of their volume. These procedures are often manual or semi-automated and are commonly oversized to ensure water quality in the absence of precise measurement.

Bottom cleaning: Essential for sediment removal, bottom cleaning is typically performed using suction systems that discharge water directly into drains without treatment or recovery. This process, often repeated multiple times per week, results in cumulative losses.

Induced evaporation: Water movement, constant heating, and sun exposure often accelerate evaporation. Without proper control, this loss adds to the above, requiring frequent replenishment.

Combined, these factors may lead a medium or large pool to consume between 2 and 5 times its original volume per year, impacting water availability in the watershed, the quality of effluents, and public health due to exposure to chemical residues.

Health Effects

Mitigation Measures and Solutions

The project proposes a comprehensive transformation of water treatment systems in pools, replacing the chemical-based conventional approach with a natural, physical, and biological model. The system operates in situ and eliminates the need for draining or purging. It integrates a set of components that, together, maintain optimal water quality over long periods with minimal intervention:

Active biofiltration: Filters contain biological media designed to host beneficial bacterial colonies that degrade organic compounds and stabilize water chemistry, replacing traditional flocculants and oxidants.

Ultraviolet (UV-C) radiation: High-intensity UV chambers eliminate pathogens and viruses without leaving chemical residues or altering water composition.

Advanced Oxidation Processes (AOP): Depending on system design, technologies combining ozone, peroxides, and UV can be applied to destroy persistent compounds without producing harmful byproducts.

Water recovery and recirculation: Bottom cleaning and filter maintenance are conducted in a closed-loop system that treats and reintegrates water, eliminating drainage discharge and the need for makeup water.

Sensors and digital monitoring: The entire system is controlled by real-time sensors that track pH, ORP, turbidity, temperature, and conductivity, allowing dynamic adjustments and minimizing manual or corrective intervention.

This configuration ensures sustained operational stability, eliminating the need for annual draining, avoiding systematic purging, and minimizing induced evaporation. The result is not only structural water efficiency but also significant improvements in water quality, user experience, and sanitary and environmental safety.

Sustainable Development Goals (SDGs)

SDG 6 – Clean water and sanitation: The solution reduces water use by eliminating unnecessary replacement practices and prevents the discharge of contaminated effluents by eliminating chemical usage. This enhances both water use efficiency and water quality, protecting aquatic ecosystems and sanitation systems.

SDG 11 – Sustainable cities and communities: By converting urban pools into efficient, chemical-free infrastructure, the project reduces environmental impact, improves the urban environment, and promotes healthier, more inclusive, and resilient facilities.

SDG 12 – Responsible consumption and production: The system removes the need to manufacture, transport, and dispose of chemical products, encouraging sustainable operational practices in pool management and reducing hazardous waste associated with conventional systems.

SDG 13 – Climate action: Reductions in water and energy use positively impact the carbon footprint of the facility. Additionally, the system strengthens resilience against drought and water scarcity, improving climate adaptation in vulnerable areas.

SDG 17 – Partnerships for the goals: The project relies on collaboration between operators, technical experts, and traceability platforms to validate results and enable scaling.

Project Information

Country:

Spain

Implementation

The system is implemented through a modular and adaptable approach that allows retrofitting of existing pools or designing new ones with water efficiency and sustainability as core principles. The implementation is structured in three phases:

Technical diagnosis: A thorough assessment of the current system, including pool volume, maintenance frequency, chemical usage, purging patterns, hydraulic infrastructure, water quality, and evaporation rates. This establishes the project baseline.

System installation: Existing filtration systems are replaced or upgraded with biofiltration modules, UV chambers, and advanced oxidation units. Intelligent recirculation pumps, water recovery tanks, and a digital control interface with integrated sensors are added.

Training and monitoring: Facility personnel are trained in operation and maintenance. A continuous monitoring plan is deployed to validate performance using operational and hydrometric indicators. All metrics are traceable and externally auditable, and data can be integrated into reporting platforms

The system is designed for long-term durability, with low-maintenance components, low energy consumption, and high operational stability. Its implementation yields immediate benefits in water savings and water quality, and it can be scaled across facilities without requiring structural redesign.

Understanding the Project

This project aims to transform the operational model of large-volume swimming pools through the incorporation of natural, chemical-free water treatment technologies, with a focus on structurally reducing water consumption. The proposal is framed within the context of increasing pressure on urban and peri-urban water resources, where recreational, sports, and wellness facilities still operate using water-intensive and chlorine-based models that generate considerable environmental and health impacts.

The project is proposed as a replicable pilot in clubs, tourist complexes, spas, and municipal swimming pools, where integrated water treatment systems will be installed. These systems are based on biofiltration, UV-C radiation, advanced oxidation processes, and total water recovery during cleaning operations. The system completely eliminates the use of chlorine and the need for periodic draining, weekly purging, or backwashing with water loss.

Local operating conditions show historically high consumption rates—between two and five times the total pool volume per year—due to maintenance practices involving regular water disposal. Additionally, discharges containing chlorinated compounds place diffuse pressure on sanitation networks and receiving water bodies. Implementing the proposed system will reduce annual water use by up to 95%, eliminate chemical impacts, and enhance operational water resilience.

Initial Assessment

The shared water challenge addressed by this project is the excessive and unaccounted-for water use in the recreational and sports sector, particularly in large pools that follow traditional operation schemes. The diagnosis identifies the following main issues:

High frequency of total or partial water replacement to avoid the buildup of chemical byproducts.
The need for systematic purging and bottom cleaning with direct discharge.
Continuous use of chlorine and other chemicals that generate harmful secondary compounds affecting both health and the environment.
Inability to recover water used for maintenance due to chemical contamination and the absence of a closed-loop system.

From a methodological standpoint, the project applies the VWBA 2.0 framework, with an emphasis on water efficiency, since the primary impact addressed is the relative scarcity and inefficient use of blue water in urban environments. Additionally, the WQBA (Water Quality Benefit Accounting) framework is considered a secondary component, as the elimination of chemicals also improves residual water quality and reduces diffuse pollution.

Key stakeholders include recreational infrastructure managers (clubs, municipalities, tourism operators), environmental and health regulatory bodies, and technical solution providers for water management. From a regulatory perspective, the project aligns with consumption reduction guidelines (SDG 6), discharge regulations (local wastewater standards), and efficiency standards in both public and private operations.

Additionality is guaranteed as this is a non-mandatory intervention that replaces structurally inefficient operational processes. The benefits would not occur without the specific system intervention, and the savings are directly attributable to the actions implemented.

Project Design

The type of intervention is aligned with urban water efficiency, using clean technologies that allow water to be conserved and recovered within the same system. The approach based on grey infrastructure (e.g., additional retention structures) or nature-based solutions (e.g., wetlands) is excluded, since the system is fully self-contained.

The methodological selection follows VWBA 2.0, specifically Method A-2, which is suitable for projects that reduce water use in urban operations by cutting operational consumption, eliminating structural losses, and recovering the resource. As a complementary element, the project may register water quality indicators under the WQBA approach, although quantitative benefits will not be reported under this component.

The baseline is defined using operational records from conventionally managed pools of similar volume, estimating total annual water consumption (replacement + purging + cleaning + evaporation replenishment). This baseline allows the project to establish the differential consumption post-intervention, validated with empirical data during the first year of system operation.

Selected indicators include:

Annual water consumption (m³/year).
Frequency of water replacement and purging.
Physicochemical water parameters (pH, ORP, turbidity).
User satisfaction indicators (absence of chlorine, reduced skin and eye irritation).

Technical additionality is clearly justified, as the proposed system replaces a structurally inefficient practice not mandated by regulation. In other words, without this intervention, pools would continue operating under a loss-and-replacement model. The benefit is therefore direct, attributable, permanent, and measurable.