Land & Water Stories

Wastewater Pollution

Turning a Critical Problem into Opportunity

Sewage pipe with sunset in the background.
Sewage Pipe The Nature Conservancy is committed to a future where aquatic ecosystems are protected from the impacts of wastewater pollution. © Pixabay

Wastewater is a major threat to nature and human health.

Without adequate treatment, wastewater can contribute to habitat loss and extinction. TNC is actively addressing this through innovative science, strategic communications and policy interventions.

A Scary Status Quo

Every day 80% of the world’s wastewater enters our environment completely untreated, jeopardizing nature and public health, with far-reaching consequences for climate resilience, aquatic biodiversity and food and water security and access. Wastewater introduces a toxic cocktail of contaminants that threaten our food and water security as well as marine species. 

What's in wastewater? Pathogens, pharmaceuticals, microplastics, heavy metals, endocrine disruptors and more.

Our existing wastewater treatment systems allow us to “flush it and forget it,” avoiding the complex reality of wastewater pollution. Ignoring this critical issue leads to dangerous consequences, some of which we are already seeing like closed beaches, collapsed fisheries and algal blooms that suffocate aquatic life. 

An open palm dipping fingertips in green sludge producing green fingers.
Eutrophication Excessive nutrients in a lake or other body of water, frequently due to runoff from the land, causes a dense growth of plant life and death of animal life from lack of oxygen. © Michael Meiters/Flickr

TNC’s Solution

TNC scientists and conservation practitioners are addressing the dangerous impacts of wastewater pollution with a whole-system approach.

In addition to TNC’s on-the-ground projects across the globe, our dedicated wastewater pollution program is working across the Pacific to coordinate partners, develop foundational science and find solutions that work.

Eyes on Wastewater

Wastewater can often be a hidden threat. Click through this slideshow to see what's just below the surface.

2 divers inspect the effects of Delray Beach sewage outfall on the coral reef in Florida.
Aerial view of riverine discharges to coastal areas.
Beach closure due to sewage contamination.
Wastewater leading into the ocean.
A water-level image of sewage pollution in Richardson Bay

Strategic Communications & Policy

For too many, wastewater pollution flies under the radar or is simply categorized as someone else’s problem. Cultural taboo, combined with misconceptions about the capacity of oceans and other water systems to absorb wastewater, limits our ability to find and implement solutions. So much of the answer hinges on raising awareness.

It's time the world understood the critical threat wastewater pollution poses to humans and the natural systems we depend on.

That’s why TNC is building awareness and education through partnerships to reach broader audiences and drive campaigns that reduce stigma around wastewater and inspire action. We’re working across sectors to produce and share research, tools, and best practices while highlighting the intersections between wastewater pollution, public health and the environment. 


  • TNC’s collaboration with the Reef Resilience Network provides wastewater pollution training, tools, and learning resources for coral reef practitioners. 
  • Our work alongside partners at the Ocean Sewage Alliance to build a first-of-its-kind knowledge hub and resource library on marine wastewater pollution. 


If the world is to meet the UN's Sustainable Development Goals, we'll need significant policy reform. Many of the world’s wastewater policies and regulations are inadequate and based on outdated science that neither accounts for modern-day stressors nor recognizes the economic opportunity of wastewater resource recovery. TNC is exploring avenues for policy interventions to reduce and mitigate wastewater pollution for human health and environmental protection.

Shoreline along Long Island Sound in Connecticut.
Long Island Sound Shoreline along Long Island Sound in Connecticut. © Rachel Lowenthal/TNC

Coastal Long Island, NY

Nitrogen pollution has had a devastating effect on Long Island’s water quality for decades, causing harmful algal blooms and threatening bivalves, like oysters and mussels, as well as seagrass and salt marsh habitats. TNC’s Long Island team, in collaboration with a myriad of government and private sector partners, knew their restoration work wouldn't be successful without dealing directly with the pollution's source: the island’s half-million septic systems and cesspools. Find out how they worked with policymakers and partners at the federal and local level to secure funding and policy reforms necessary to do just that — from homeowner assistance for upgrading septic systems to building clean water infrastructure across the state that mitigates the effects of wastewater pollution. As of 2024, this coalition continues to work on a major ballot valued at $6B over the next 35 years, to create a county wide water quality restoration act to substantially increase the local funding for clean septic change outs and strategic sewer expansion. This fund would be the key to unlocking federal and state infrastructure funding.

Research & Monitoring

The global scientific community is increasingly recognizing the profound impact that wastewater pollution has on aquatic ecosystems. TNC scientists and field staff are on the front lines monitoring water quality to inform wastewater pollution mitigation and management strategies. 

Studies have linked wastewater pollution to seagrass die-offs, harmful algal bloom events and weakened reefs that can destabilize entire ecosystems. Even coastal wetlands, which naturally absorb nutrients, can become oversaturated when exposed to wastewater pollution over time, making these systems more vulnerable to extreme weather events exacerbated by climate change. 

"Contaminants of emerging concern” (CECs) in wastewater, like PFAS, pharmaceuticals, and other novel chemicals not only threaten drinking water and human health but are also contaminating coastal waters and fisheries. 


TNC’s plan for ocean recovery is expansive. We have a goal of conserving 10 billion acres of ocean worldwide. In order to achieve this goal, we must ensure that wastewater does not threaten the health and quality of the marine waters we protect.

Nature-based Solutions

Nature-based solutions are interventions that harness the power of Earth’s natural features and functions. These can look like dunes and wetlands that insulate coasts from storm surge, or native forest restoration in the face of megafires.

TNC and partners are employing nature-based solutions to address wastewater. One of the most promising solutions our team is studying is constructed wetlands. These are engineered systems designed for wastewater treatment that use natural biological technologies that incorporate wetland vegetation, soils, and microorganisms to remove contaminants.

This can be a cost-effective and sustainable option, and TNC is implementing solutions like these across the globe. From the Dominican Republic to India, our team is demonstrating that constructed wetlands can be an effective, nature-based mitigation strategy to improve water quality and restore wildlife habitat. 

Experimenting with nature-based septic solutions Communities on Cape Cod, MA are facing critical water quality issues due to decades of both wastewater and fertilizer runoff. TNC and our partners are installing innovative, limestone and wood chip-based septic systems that could help filter nitrogen pollution and secure cleaner coastal waters.
An aerial city view of Lake Sembakkam.
Lake Sembakkam in Chennai, India. © Ram Keshav

Constructed Wetlands in Lake Sembakkam

In Chennai, the largest city in India’s southern state of Tamil Nadu, a 100-acre wetland has been restored to protect Lake Sembakkam. Rapid urbanization, including increases in wastewater and stormwater pollution, has caused the lake to degrade over time. This is one of many critical natural wetlands that serve as a lifeline for the city’s people and wildlife—including several rare and threatened species of migratory birds. TNC’s India program helped design and restore these wetlands to support biodiversity and to improve habitat, water quality, groundwater storage and recharge, and recreation landscape. Read more about how these constructed wetlands work and why TNC is expanding the project to the broader system of Chennai’s marshland.

Climate Impacts

Climate change and wastewater pollution are two inextricably linked crises. 

It’s estimated that wastewater treatment plants account for at least 3% of all greenhouse gas emissions, in addition to supplemental emissions from direct discharge into waterways. Beyond the treatment process, wastewater pollution is also a significant threat to some of the key ecosystems we rely on to store carbon, including mangrove forests and seagrass beds. To complicate the matter, the effects of climate change—from sea level rise to the increase in extreme weather events—are overburdening wastewater treatment systems that are already stressed and outdated. 

But if we change the status quo, addressing wastewater pollution can provide multiple avenues for tackling climate change. It starts with implementing treatment options that better protect carbon-storing ecosystems. These options are even more effective when coupled with investment in innovative practices that divert waste into valuable resources, such as reclaimed water, biofuel and fertilizer.

In Florida, TNC and partners have helped pave the way for more widespread reuse of wastewater, helping craft legislation that bans the use of ocean outfalls that discharge treated wastewater directly to the coastal zone within Southeast Florida by 2025, instead encouraging reuse. 

Make Transformative Change Possible.

We depend on nature, and nature depends on those of us who care enough to stand up for it.