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Learn about Small Wastewater Systems

Many small and rural communities, including those in Indian Country and along the U.S.-Mexico border, struggle with aging or inadequate wastewater treatment systems, or do not have access to basic wastewater services. Small communities have 10,000 or fewer people and an average daily wastewater flow of less than 1 million gallons.

Wastewater is water that has been used for various purposes around a community, including sewage, stormwater, and all other water used by residences, businesses, and industry. Wastewater requires treatment before it returns to lakes, rivers, and streams to protect the health of the waterbody and community.

On this page:

Wastewater Treatment Technologies

Decentralized Systems

A decentralized wastewater system treats sewage from homes and businesses near the source where wastewater is generated rather than collecting and transporting waste to a centralized treatment plant. Decentralized systems can provide an effective, low-cost alternative to a centralized system. Centralized systems may be impractical in some situations because of distance, terrain, or other factors.

Decentralized systems play a big role in wastewater treatment in small communities. A variety of decentralized technologies exist, ranging from individual septic systems, to cluster systems that serve multiple properties, to advanced treatment systems that remove pollutants such as nutrients.

Nearly one in four households in the United States depends on an individual septic system or small community cluster system to treat its wastewater.

EPA's Septic (Decentralized/Onsite) Program provides general and technical information, funding sources, training opportunities, guidance, educational outreach materials, and case studies. These resources help homeowners, government officials, and industry professionals design and manage decentralized systems that are cost-effective and meet public health and water quality standards.

Centralized Systems

Centralized systems are public sewer systems. They treat wastewater in a single, centralized location. Sewers collect municipal wastewater from homes, businesses, and industries and deliver it to a treatment plant for processing. After wastewater is treated, it is reused or discharged to surface water or ground water.

Early in the nation’s history, people living in cities and the countryside used cesspools and privies to dispose of domestic wastewater. Cities began to install wastewater collection systems in the late nineteenth century because of increasing awareness of waterborne disease and the popularity of indoor plumbing and flush toilets.

The use of sewage collection systems brought dramatic improvements in public health. Today, approximately 16,000 municipal wastewater treatment facilities operate nationwide serving over 75 percent of the population.

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Small Community Challenges and Needs

Many small communities face significant barriers to building and maintaining effective wastewater treatment services, including:

  • limited financial resources;
  • geographically dispersed populations; and
  • difficulty attracting, training, or retaining system operators.

Some communities face additional barriers:

  • limited managerial capacity;
  • extreme topography and climate; and
  • geographic isolation.

Several reports highlight the challenges and needs facing small and rural communities:

Tribal Communities

Many of the small communities in Indian Country and Alaska Native Villages face obstacles similar to other small communities. These communities are more likely to lack access to wastewater services than other populations in the United States. As of November 2014, 6.1 percent of tribal homes lacked access to safe drinking water services and 5.3 percent of tribal homes lacked access to basic sanitation services.

A lack of clean water infrastructure in tribal communities threatens the health of residents who often rely on local wildlife and fish for food and on the nearest water body for drinking water.

U.S.-Mexico Border Communities

The U.S.-Mexico border region faces similar challenges to other small and rural communities. A significant portion of the border population in small and rural communities experiences high rates of poverty and unemployment and lacks access to basic infrastructure.

This region includes "colonias," which are identifiable communities affected by poverty and lacking the most basic infrastructure such as water, wastewater, and other basic services. Colonias are a subset of the border region’s cultural complexity, where poverty and ethnicity coincide. The majority of the populations are Hispanic and some colonias are located in federally recognized Native American tribal areas. Most lack the capacity to form partnerships and obtain funding.

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