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 it 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.
Who is responsible for wastewater treatment?
Americans 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 on a regular basis.
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 many industries, and deliver it to plants for treatment. Most treatment plants were built to clean wastewater for discharge into streams or other receiving waters, or 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.
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. So wastewater can include any debris from streets and waste oils, pesticides, fertilizers, and wastes from humans and animals.
Wastewater from a typical household might include toilet wastes; used water from sinks, baths, showers, washing machines, and dishwashers; and anything else that can be put down the drain or flushed down the toilet.
What makes wastewater so dangerous?
Feces and urine from both humans and animals carry many disease-causing organisms. Wastewater also may contain harmful chemicals and heavy metals known to cause a variety of environmental and health problems. Disease-causing organisms (pathogens) from humans can enter a community’s wastewater from patients at hospitals, or from anyone who is sick or a carrier of disease. Carriers may not have symptoms or even know they have a disease. Animal wastes often enter from farms, meat packing and processing facilities, and from rats and other animals found in or around sewage or sewers.
Much of our wastewater, treated or untreated, eventually ends up in our rivers, streams, lakes, and oceans—sometimes via groundwater, the underground water source we tap for well 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 the community, there can be significant health risks. The effectiveness of drinking water treatment can be reduced when water is heavily contaminated with waste. To ensure safe drinking water, communities need both effective 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 in 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 comes in contact with it. The wastewater receives further treatment often through a combination of filtration and biological and chemical processes. Liquids are often stored for a period of time to allow further settling and bacterial treatment. 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, spread on forested land, or disposed of in the ocean.
Soil can also be used to help treat wastewater. If conditions are right, liquid wastes can be applied to soil, and most of the pollutants are either removed, inactivated by bacteria, adhere to certain materials in the soil, or filtered out before reaching the groundwater. Sand or other media can be used in place of soil in areas where the natural soil or geographical conditions are not suited for this purpose. Disinfection is normally the final treatment step for wastewater being discharged near or directly into surface water or for groundwater recharge. Chlorine, ozone, ultraviolet light, or other chemical agents inactivate many pathogens that manage to survive previous treatment processes. Many states now require the removal of excess chlorine before discharge to surface waters by a process called dechlorination. Alternatives to chlorine disinfection, such as ultraviolet light or ozone, are used in situations where chlorine in treated sewage effluents 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 that water is safe to drink.
Community Treatment Systems
Communities that rely on centralized water and wastewater treatment plants 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. Money must somehow be made available for this purpose.
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 sewers and drinking water 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 may eventually need to separate the lines and the combined sewer overflows and other sewer overflows need to be monitored and controlled.
Onsite Wastewater Treatment Systems
Many households in small and rural communities use individual onsite treatment systems, such as septic systems. These also need to be monitored and maintained. Onsite systems that are improperly sited, constructed, operated, or maintained can fail and failing systems cause a number of 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 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.