One of the most common forms of pollution control in the United States is wastewater treatment. The basic function of wastewater treatment is to speed up the natural processes by which water is purified.
Every community needs to treat its wastewater because of the serious health problems untreated or inadequately treated wastewater can cause. Although this may seem obvious, untreated wastewater is still the root cause of much environmental damage and human illness, misery, and death around the world.
Sometimes it is useful to reexamine basic ideas like why wastewater treatment is important, especially today when so many communities need to save money and reprioritize their needs and funding for public projects.
What is in wastewater?
Sources of wastewater include homes, farms, hospitals, businesses, and industries. Some older communities have combined sewers that collect both wastewater and storm water runoff from streets, lawns, farms, and other land areas. Wastewater can include debris from streets, pesticides, fertilizers, and wastes from humans and animals. Wastewater from a typical household might include toilet wastes and used water from sinks, baths, showers, washing machines, and dishwashers.
What makes wastewater so dangerous?
Feces and urine from both humans and animals carry many disease-causing organisms. Wastewater from commercial or industrial sources may also contain harmful chemicals and heavy metals known to cause a variety of environmental and health problems. Disease-causing organisms (pathogens) can enter a community’s wastewater system from patients at hospitals or from anyone who is sick or a carrier of a disease. Carriers may not have symptoms or even know they have an illness or disease.
Much of our wastewater, treated or untreated, eventually ends up in our rivers, streams, lakes, and oceans—sometimes via groundwater, the underground water source many citizens access by well to provide drinking water. We often assume that groundwater is pure—and it usually is—but unfortunately, well water contaminated by sewage is a common cause of outbreaks of wastewater-related diseases.
When untreated wastewater reaches water used as a drinking water source for a community, there can be significant health risks. The effectiveness of drinking water treatment can be reduced when water is heavily contaminated. To ensure safe drinking water for their citizens, communities need both effective drinking water and wastewater treatment.
What is wastewater treatment?
Wastewater treatment consists of a combination of processes used in steps to remove, kill, or “inactivate” a large portion of the pollutants and disease-causing organisms that may exist in the wastewater. Most treatment methods include a preliminary step in which the solid materials are filtered out or allowed to settle and separate from the rest of the wastewater. Helpful bacteria grow naturally in the solids or “sludge,” which provide some initial treatment for the sludge and the wastewater that encounters it. The sludge is then treated further by applying lime or chemicals, air drying, heat drying, or composting. For final disposal, it is burned, buried in landfills, used as commercial fertilizer, or may be spread on forested land.
The wastewater receives further treatment often through a combination of filtration and biological and chemical processes. The wastewater is often stored for a period of time to allow further settling and bacterial treatment. If conditions are right, the treated liquid waste stream can be applied to soil, where most of the pollutants are either removed or inactivated by naturally-occurring bacteria present in the soil, adhered to certain materials in the soil, or filtered out before reaching the groundwater.
Otherwise, the wastewater (liquid waste stream) is disinfected and discharged to a nearby body of water. Disinfection is normally the final treatment step for wastewater being discharged near or directly into surface water or for direct groundwater recharge. Chlorine, ozone, ultraviolet light, or other chemical agents inactivate remaining pathogens that manage to survive previous treatment processes. Many states require the removal of excess chlorine before discharge to surface waters by a process called de-chlorination. Alternatives to chlorine disinfection, such as ultraviolet light or ozone, are used in situations where chlorine and chlorine by-products in treated wastewater may be harmful to fish and other aquatic life.
Pollutants, such as heavy metals, chemical compounds, and toxic substances, are more difficult to remove from water and have placed additional burdens on wastewater treatment systems. Rising demands on the water supply only aggravate the problem. The increasing need to reuse water calls for better wastewater treatment. These challenges are being met through better methods of removing pollutants at treatment plants, or through prevention of pollution at the source. Pretreatment of industrial waste, for example, removes many troublesome pollutants at the beginning, not the end, of the pipeline.
However, while wastewater treatment is essential for protecting water quality, it is only one barrier against disease. Additional treatment is usually needed to ensure the water we drink is safe to consume.
Who is responsible for wastewater treatment?
Citizens often don’t realize that ultimate responsibility for protecting their communities from wastewater-related illnesses lies with local governments and community residents. Even though state and federal laws set minimum environmental and health standards, it is usually up to local officials and individual homeowners to ensure that these standards are being met.
Urban areas and communities across the country rely upon a system of collection sewers, pumping stations, and treatment plants. Sewers collect the wastewater from homes, businesses, and industries, and deliver it to wastewater plants for treatment. Most treatment plants are built to clean wastewater for discharge into streams or other receiving waters, some for reuse.
For many small communities, rural areas, or sparsely populated areas, a decentralized approach to the collection, treatment, and dispersal of the wastewater is commonly used and just as effective as large-scale systems at treating wastewater. These types of small-scale or individual systems are often referred to as onsite systems, septic systems, cluster systems, or decentralized systems.
Community Wastewater Treatment
Communities that rely on a network of sewers and a centralized treatment plant to collect, treat, and discharge their wastewater need to make sure that these facilities are being properly operated and maintained. Local governments must make it a priority to monitor treatment plants, be aware of any deficiencies, and ensure that needed improvements are made.
Monitoring may also be done by health departments or state departments of natural resources, environmental protection, or other government agencies. But compliance at inspection time does not guarantee consistent treatment—it is up to communities to protect the health of their residents by making certain that water and wastewater treatment plants stay in compliance.
Another concern for many communities is aging infrastructure and treatment facilities that need to be repaired, replaced, or upgraded. Old sewer collection systems and drinking water distribution lines with cracks or leaks in them can be an additional source of pollution and drinking water contamination.
Some older communities that use the same pipes for sewers and street storm water drains may have problems with flooding and overflows when it rains or when snow melts. Often, untreated wastewater is dumped into nearby lakes, rivers, or oceans. Communities must monitor and control these overflows, or they may need to separate the lines.
Onsite Wastewater Treatment
Many households in small and rural communities use individual onsite treatment systems (i.e., septic systems), to collect, treat, and disperse of their wastewater. These individual systems also need to be monitored and maintained and that responsibility lies with the owner of the system. Onsite systems that are improperly sited, constructed, operated, or maintained can fail and cause several environmental and health problems.
Failing onsite systems can cause untreated sewage to pond on the surface of the ground where it can pose a risk to neighborhood children and animals and provide a breeding place for flies, mosquitoes, and other disease carriers. Groundwater can be polluted by failing onsite wastewater systems, which can contaminate nearby drinking water sources and wells.
It is also extremely important for homeowners to have their well water tested. Outbreaks of waterborne illnesses are frequently traced to contaminated well water. Even well water that looks and tastes fine may contain harmful microorganisms and contaminants from chemical spills, fertilizers, pesticides, and failing wastewater treatment systems. A qualified laboratory can test well water for both bacteria and chemicals.
One way that communities have been working to help ensure that the health of the public is protected is by forming management programs for onsite wastewater treatment systems. The idea behind these programs is to help homeowners by centrally monitoring and managing onsite systems to make sure they always function correctly, and that the health of the community is never at risk. These programs can vary in scope and be organized to fit the needs of individual communities.