Closing the loop: Wastewater nutrient recovery as a pillar of sustainable water management

December 8, 2025

Roodeplaat dam is a well-known destination for bird watching, game viewing and a range of water sports including freshwater angling, located about 22km north-east of Pretoria. — Image: © THEGIFT777 | iStock

Everest Group experts guide us through wastewater nutrient recovery as a pillar of sustainable water management

As global populations surge and economies grow, natural environments and their finite resources, such as water, are being polluted. Ensuring safe and sufficient water supply while reducing the negative impact on human health and the environment is becoming more complex due to rising wastewater volumes and nutrient loads. According to the United Nations (UN), globally, an estimated 332 billion cubic meters of domestic wastewater were generated in 2024, of which only 56% was safely treated and discharged.

Similarly, only 22% of the total industrial wastewater was safely treated and discharged. ⁽¹⁾ This implies that a significant amount of wastewater is discharged untreated or inadequately treated, polluting water bodies and exacerbating the release of heavy metals and chemicals. Untreated wastewater fuels eutrophication, including harmful algal blooms (HABs), which deplete oxygen and kill aquatic life. Ineffective treatment practices, ageing infrastructure, and resource constraints further compound these challenges.

The intensifying nutrient challenge

Additionally, the prolonged use of synthetic fertilizers reduces soil organic matter, lowers soil pH, and accelerates soil degradation, threatening global food security and environmental stability. The Food and Agriculture Organization’s (FAO) global cropland nutrient budget data provides precise information on the over- or underuse of nutrients and fertilizers across different regions. The data show that the average global cropland nitrogen (N) use efficiency is surplus, while phosphorus (P) and potassium (K) use efficiencies are in deficit. ⁽²⁾

The results show that excess or insufficient use decreases soil health over time, and imbalanced crop nutrition endangers the productivity and sustainability of agriculture. Nations with excess N levels in waterbodies contribute to HABs and hypoxia (low-oxygen zones), which can lead to dead zones, ecosystem degradation, and the loss of fish populations. Nations with P- and K-deficient soils are subjected to faster soil degradation and will be forced to buy more synthetic fertilizers, which are prone to price fluctuations. Further, microbes break down nitrogen-based synthetic fertilizers to produce nitrous oxide, a greenhouse gas having nearly 300 times the global warming potential of carbon dioxide. ⁽³⁾

Government agencies such as the U.S. Environmental Protection Agency (U.S. EPA) identify vulnerable water bodies to HABs and hypoxia by analyzing nutrient input and testing and validating interventions (e.g., wetland restoration, agricultural practices, nutrient removal technologies) to reduce nutrient loads and thereby reduce HAB/hypoxia risk. The U.S. EPA’s Safe and Sustainable Water Resources (SSWR) research program provides robust research and scientific analysis to support cost-effective nutrient recovery technologies for managing nutrient removal from water bodies. ⁽⁴⁾

As population growth surges, demand for crops with essential nutrients is increasing. This implies a significant increase in fertilizer consumption. Increased and improper use of synthetic fertilizers will, in turn, lead to low-input or nutrient-overload hotspots, resulting in
low-quality crop production while damaging soil health. Identifying sustainable alternatives to synthetic fertilizers is vital to reducing fertilizer costs, strengthening supply chains, and reducing pollution. Thus, considering wastewater as a resource for water reuse, energy, and nutrient recovery through wastewater nutrient recovery (WWNR) techniques represents an increasingly important requirement for sustainable agriculture and water systems. Wastewater can act as a resource rather than an end-of-pipe liability.

The United Nations Environment Programme (UNEP) has convened the Global Partnership on Nutrient Management (GNMP) to bring together governments, scientists, and industries to coordinate nitrogen and phosphorus management worldwide. It addresses the “nutrient challenge” by sharing tools, setting common aims, and supporting national roadmaps that reduce excess nutrients without compromising development, the ideal integration needed to connect wastewater recovery, population growth, agriculture, and environmental protection. ⁽⁵⁾

Technology as the enabler

At the center of this challenge is the largely underused potential of WWNR, a process that recovers essential nutrients (N, P, and K). WWNR is paramount for enabling wastewater reuse, extracting nutrients for fertilizer use, and reducing reliance on synthetic fertilizers derived from fossil fuels. WWNR technologies address both the above-mentioned challenges of ensuring safe water discharge while providing essential macronutrients to the soil to increase crop yield. Further, the WWNR process reduces eutrophication risks, curtails the reliance on phosphate rock mining, and bolsters circular economy strategies, thereby reducing greenhouse gas emissions associated with fertilizer production.

WWNR technologies, such as struvite precipitation (formation of magnesium ammonium phosphate crystals) and algal bioreactors, can capture nutrients from effluents with up to 90% efficiency, generating nutrient-rich fertilizers that compete with synthetic fertilizers in efficacy. Struvite precipitation is commercially proven (Technology Readiness Level (TRL-9)), and algal bioreactors are currently under laboratory testing (TRL-7). The nitrogen (N), phosphorus (P), and potassium (K) fertilizers derived from WWNR technologies have the potential to offset 13% of the global synthetic fertilizer demand in agriculture while improving soil fertility. ⁽⁶⁾

The bioavailability of N, P, and K macronutrients is foundational for chlorophyll synthesis, powering energy transfer, resisting plant diseases, and improving water use, leading to enhanced root development, grain fill, and crop yield stability.

Strategies for effective nutrient management

Implementing effective nutrient management strategies is key to minimizing environmental and human health impacts while maximizing contributions to global sustainable development and poverty reduction. This can be done through the large-scale commercialization of nutrient recovery techniques. For instance, Ostara’s (U.S.-based agriculture company) high-efficiency phosphate fertilizers (struvite) are produced through nutrient recovery solutions that reclaim excess nutrients from municipal and industrial effluents.

Around 62 million pounds of phosphorus and 25 million pounds of nitrogen have been recycled and used to manufacture fertilizer. The fertilizers are 100% plant available and enhance nutrient uptake while eliminating runoff and leaching. ⁽⁷⁾ Other proven technologies include algal bioreactors and enhanced biological phosphorus removal for advanced WWNR methods.

Additional effective strategies include the 4R-Principle, which is based on the concepts of Right source, Right rate, Right time, and Right place, and is implemented through precision agriculture methods such as soil testing, inhibitors, variable-rate technology, and decision tools to improve nutrient-use efficiency and maintain soil pH. ⁽⁸⁾

Several nature-based methods include buffer zones, including constructed and natural wetlands, to recover nutrients before they reach water bodies. Integrated nutrient management techniques blend precision with sustainability, enhancing nutrient recovery while optimizing soil health. Bolstering soil health results in the formation of stable soil aggregates, regulates water flow and aquifer recharge, and minimizes erosion and flooding. Soil aggregates containing clay and humic substances trap suspended solids and adsorb heavy metals and pesticides, thereby preventing toxic chemicals from leaching into the groundwater.

Healthy soils host a diverse array of soil microbes that decompose plant residues, releasing macro- and micronutrients in plant-available forms. Measurement, Reporting, and Verification (MRV) frameworks are key to ensuring regulatory compliance and to validating nutrient recovery performance. Thus, enhancing soil health through WWNR techniques underpins food production, clean water, and climate regulation.

Contribution to Sustainable Development Goals (SDGs)

Nutrient recovery and management underpin global and local sustainable development agendas, intertwining food security with environmental stewardship. Globally, WWNR practices align with several SDGs, such as SDG-6 Clean Water & Sanitation, as lower nutrient discharges protect water quality. WWNR accelerates the efforts to achieve the SDG-6.3 goals of reducing the proportion of untreated wastewater by 50%.

WWNR also aligns with other SDGs such as SDG-12 Responsible Consumption and Production, as recovering N and P nutrients embodies promotion of circular economy practices, SDG-2 Zero Hunger due to the production of crops with high yields and nutrients, and SDG-13/14/15 (Climate action, Life Below Water, and Life on Land) due to less emissions and eutrophication, healthier soils and habitats. ⁽⁹⁾

Singapore’s robust water reuse policy ensures the use of treated municipal water for non-portable industrial reuse through its advanced NEWater process (consisting of microfiltration, reverse osmosis, and ultraviolet (UV) disinfection). The advanced treated water is subject to rigorous water audit procedures and complies with the Singapore Food Agency’s regulations for drinking water quality.⁽¹⁰⁾

Conclusion: A sustainable approach to environmental protection and resource recovery

WWNR techniques offer a sustainable and transformative solution for the circular economy and environmental stewardship. Recovery of valuable nutrients from municipal and industrial wastewater streams closes the nutrient loop, returning essential elements to the soil rather than losing them to waterways, where they can cause eutrophication or HABs. Recovered nutrients, when converted into sustainable fertilizers such as struvite or ammonium salts, enrich soil organic matter and improve microbial activity, thereby strengthening overall soil health. This circular approach reduces reliance on energy-intensive synthetic fertilizers, conserves finite resources such as phosphate rock, and lowers greenhouse gas emissions associated with fertilizer production. Ultimately, integrating WWNR into agricultural and urban systems not only supports resilient food production and soil regeneration but also advances global efforts toward resource-efficient and pollution-free growth.