Using Wastewater in Agriculture: Risks and Rewards

Water is becoming scarce, yet agriculture needs more of it. Globally, farming already consumes about 70% of all freshwater withdrawals, and with food demand projected to grow by at least 50% by 2050, the pressure on water resources will only intensify. In this context, wastewater-once viewed as waste to be disposed of-is emerging as a valuable alternative. But this resource comes with both promise and peril. Understanding the risks and rewards of using wastewater in agriculture is essential for smart, sustainable development in regions facing water stress.

Agriculture as a source of water pollution 🔗

Before discussing wastewater as a solution, it’s important to recognize that agriculture itself is a major contributor to water pollution. According to the U.S. Environmental Protection Agency, agricultural runoff is the leading cause of water quality impacts to rivers and streams in the United States. Each year, approximately 500,000 tons of pesticides, 12 million tons of nitrogen, and 4 million tons of phosphorus fertilizers are applied to crops in the continental United States alone.

These chemicals don’t stay put. Rainfall, irrigation, and snowmelt carry fertilizers and pesticides from fields into streams, rivers, lakes, and groundwater. The U.S. Geological Survey reports that at least one pesticide was found in approximately 94% of water samples and in more than 90% of fish samples taken from streams nationwide. Nearly 60% of shallow wells sampled also contained pesticide residues.

How fertilizers and pesticides contaminate water 🔗

The mechanisms of contamination are straightforward but persistent. Excessive application of agrochemicals leads to nitrogen and phosphorus accumulating in soils. These nutrients then leach downward into groundwater aquifers or wash into surface waters during rain events. Phosphates, while less soluble than nitrates, bind to soil particles and travel through erosion. Animal waste from livestock operations adds another layer of pollution, containing high levels of nutrients, pathogens, and organic matter.

The consequences are severe. Elevated nutrient levels trigger algal blooms in water bodies, which deplete oxygen and create “dead zones” where aquatic life cannot survive. Groundwater contamination from nitrate presents direct health risks to populations relying on wells for drinking water. In areas with vulnerable aquifers, nitrate concentrations may exceed safe drinking water standards, and elevated nitrate levels often indicate the presence of other contaminants like bacteria or pesticides.

This pollution cycle creates a paradox: agriculture needs clean water to thrive, yet modern farming practices often degrade the very water resources it depends on.

Health risks of untreated wastewater irrigation 🔗

Given water scarcity, farmers worldwide increasingly turn to wastewater for irrigation-often out of necessity rather than choice. Research published in Frontiers in Public Health estimates that wastewater is used on roughly 20 million hectares globally, representing about 10% of all irrigated farmland. The majority of this use, particularly in developing countries, involves untreated or partially treated wastewater.

This practice carries significant health hazards. Untreated wastewater contains pathogens-bacteria, viruses, and parasites-that can infect farm workers, their families, and consumers of irrigated produce. A meta-analysis found an overall odds ratio of 1.65 for diarrheal diseases and 5.49 for helminth (parasitic worm) infections among agricultural workers exposed to wastewater irrigation.

Who faces the greatest risks? 🔗

Four distinct groups bear the burden of health risks from wastewater irrigation:

Farm workers and their families face direct exposure through contact with contaminated water and soil. Studies from Vietnam, Ghana, and Mexico document elevated rates of parasitic infections among farmers using wastewater. Working barefoot, touching contaminated soil, and hand-to-mouth contact during work hours are common exposure pathways.

Crop handlers and market workers encounter pathogens through handling produce that has been irrigated with contaminated water. Surface contamination of vegetables is well-documented, and pathogens can even become internalized within plant tissues.

Consumers risk infection when eating raw or undercooked produce. FAO research indicates that fruits and vegetables irrigated with contaminated water have been linked to multiple disease outbreaks, including salmonellosis and gastroenteritis caused by norovirus and pathogenic E. coli.

Nearby residents can be exposed through contaminated groundwater, surface water runoff, or aerosols generated during sprinkler irrigation. Children are particularly vulnerable, with studies showing significantly higher infection rates among children living near wastewater-irrigated fields.

Types of health impacts 🔗

The health consequences of untreated wastewater irrigation are diverse. Diarrheal diseases caused by bacterial and viral pathogens represent the most common acute risk. Recent research in npj Clean Water confirms that wastewater irrigation significantly increases the risk of gastrointestinal and respiratory tract infections for both farmers and consumers.

Parasitic infections-particularly soil-transmitted helminths like Ascaris (roundworm) and hookworm-pose chronic health threats. These parasites can persist in contaminated soils for extended periods. Studies from Ghana found that the incidence of Ascaris infections among farmers exposed to polluted irrigation water was three times higher than among control groups.

Skin infections, including dermatitis and fungal conditions, are also frequently reported among farmers with direct wastewater contact. Research from Vietnam documented significantly elevated odds of skin ailments among workers using wastewater in agriculture and aquaculture.

Wastewater as a valuable resource for agriculture 🔗

Despite the risks, wastewater offers genuine benefits that explain its widespread use. According to FAO, properly managed wastewater can be converted from a burden into an asset. The key lies in balancing the benefits against the risks through appropriate treatment and management practices.

Water security benefits 🔗

In water-scarce regions, wastewater provides a reliable, year-round water supply that doesn’t depend on seasonal rainfall or declining aquifers. Urban areas generate consistent volumes of wastewater that can support peri-urban agriculture. In Jordan, for example, reclaimed water now represents 25% of total water use nationwide. This frees up freshwater resources for drinking and other priority uses.

The availability of wastewater also provides economic security for farmers. Unlike groundwater, which may require expensive pumping, or rainfall, which is unpredictable, wastewater from urban centers is typically accessible at low or no cost.

Nutrient value and improved yields 🔗

Wastewater contains significant concentrations of plant nutrients. FAO estimates that typical domestic wastewater effluent can supply all of the nitrogen and much of the phosphorus and potassium normally required for agricultural crop production. This nutrient content effectively makes wastewater a fertilizer, reducing input costs for farmers and improving crop yields.

When safely used and managed, wastewater irrigation can enhance both water security and food security while improving livelihoods for urban and peri-urban farmers who might otherwise lack access to irrigation water.

Environmental benefits 🔗

Using wastewater for agriculture can also reduce environmental pollution. Rather than discharging nutrient-laden effluent into rivers and coastal waters-where it contributes to eutrophication and dead zones-the nutrients are productively recycled through crops. This approach aligns with circular economy principles and helps close the loop on urban nutrient flows.

Making wastewater safe for agriculture 🔗

The challenge is not whether to use wastewater in agriculture-in many regions, it’s already happening-but how to do so safely. International guidelines, particularly from the World Health Organization and FAO, provide frameworks for managing health risks through multiple barriers.

Treatment approaches 🔗

Wastewater treatment remains the primary defense against health risks. The level of treatment required depends on the intended crop type and irrigation method. Secondary treatment combined with disinfection can significantly reduce pathogen loads. Constructed wetlands offer a cost-effective treatment option for developing countries, as demonstrated in Egypt and Tunisia.

However, treatment alone is rarely sufficient or feasible in resource-constrained settings. This is why a multiple-barrier approach-combining treatment with other protective measures-is essential.

Crop restrictions and irrigation methods 🔗

Restricting which crops can be grown with wastewater is an effective risk reduction strategy. Crops that are eaten raw pose the highest risk, while crops that are cooked, processed, or not for direct human consumption present lower concerns. Some guidelines recommend using lower-quality water only for fodder crops, forestry, or industrial crops.

Irrigation methods matter significantly. Drip irrigation delivers water directly to plant roots, minimizing contact with edible plant parts. Subsurface irrigation reduces exposure further. Sprinkler systems, by contrast, create aerosols that can expose both workers and nearby communities to pathogens.

Post-harvest and hygiene measures 🔗

Cessation of irrigation before harvest allows pathogens to die off on crops and in soil. Studies show measurable reductions in pathogen contamination when irrigation stops days or weeks before harvesting. Post-harvest washing, proper food handling, and cooking further reduce consumer risks.

For farm workers, protective equipment-boots, gloves, and masks-can reduce direct exposure. Education and awareness programs help farmers understand risks and adopt safer practices, though economic constraints often limit the adoption of protective measures.

The path forward for smart regions 🔗

For smart cities and smart villages navigating water scarcity, wastewater reuse in agriculture represents both an opportunity and a responsibility. FAO emphasizes that good management is essential for safe use in agriculture. This requires robust policy frameworks, institutional capacity for monitoring and enforcement, and investment in appropriate treatment infrastructure.

Countries like Israel, Spain, Australia, and the United States demonstrate that planned, controlled wastewater reuse with advanced treatment can be safe and sustainable. In contrast, unplanned use of untreated wastewater-common in many developing regions-perpetuates health risks and environmental degradation.

The goal is to transition from informal, uncontrolled wastewater use to planned, integrated systems that protect human health while delivering the benefits of water and nutrient recycling. This transition requires coordination across water, agriculture, public health, and environmental sectors-a hallmark challenge for smart regional development.

What do you think? As water scarcity intensifies, should more regions invest in wastewater treatment infrastructure for agricultural reuse? How can communities balance the immediate need for irrigation water against long-term health protection, especially in resource-limited settings?

References

1. https://www.epa.gov/nps/nonpoint-source-agriculture
2. https://www.usgs.gov/special-topics/water-science-school/science/pesticides-groundwater
3. https://www.sciencedirect.com/science/article/abs/pii/B9780081030172000064
4. https://www.mda.state.mn.us/groundwater-surface-water-protection-agricultural-chemicals
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC6292135/
6. https://www.fao.org/4/W5367E/w5367e04.htm
7. https://www.nature.com/articles/s41545-025-00438-6
8. https://www.fao.org/newsroom/detail/Exploring-the-use-of-wastewater-in-agriculture/en
9. https://www.fao.org/4/t0551e/t0551e04.htm
10. https://www.fao.org/land-water/water/water-management/wastewater/en/