Wastewater treatment plants are designed to accept and treat waste water from homes, industries and other institutions. There are different types of waste water treatment facilities: municipal or publicly owned, industrial, institutional, and private waste water treatment facilities.
Municipal or publicly owned treatment works (POTW) are designed to collect and treat waste water from homes served by public sewer. Industrial waste water treatment plants treat process wastewater or storm runoffs within the facilities’ boundary. Institution waste water treatment plants can be government facilities, hospitals, restaurants, and prisons. Private wastewater treatment systems can be for homes not served by public sewers but utilize septic systems to treat wastewater from their homes.
On a side note, it is amazing that many people are not aware of a wastewater treatment plant near their neighborhoods. Reason might be because some wastewater treatment plants are architecturally designed to blend with the neighborhood which they are located. Some cities, towns, and villages have few waste water treatment plants while big cities like New York City have many, about 14 waste water treatment plants.
Under the National Pollution Discharge Elimination System (NPDES), wastewater treatment plants are permitted to discharge their treated effluent to receiving surface water or groundwater. Each delegated state is required to issue a NPDES permit to discharge treated effluent wastewater. The state will set limits for maximum flow and minimum pollutants that can be discharged so that the water quality standards for that surface or ground water are not exceeded.
Waste water treatment follows almost the same treatment profile as the drinking water treatment: screening, primary sedimentation or clarification, aeration, final clarification, disinfection. Some may include a final advanced treatment to remove nitrogen and ammonia.
Contaminants from wastewater treatment plants
Contaminants from WWTP include Biochemical Oxygen Demands (BOD5), Suspended Solids, Fecal Coliform bacteria, Nitrogen, Phosphorus, heavy metals, volatile organic compounds (VOCs) and more.
Although, most treatment plants will effectively treat these pollutants to desired levels, but there have been occasions when inadequately treated waste water has been discharged to receiving water or ground water. When a treatment plant exceeds its capacity to accept waste water during a storm event, flows are throttled upstream of the treatment facilities that results in combined sewer overflows. Also, during a mechanical failure at either the treatment plant or at a satellite facility associated with that treatment plant, raw sewage can be discharged to surface water.
How does this affect my drinking water?
As stated above, storm surge or mechanical failure can affect the effectiveness of wastewater treatment plants. When that happens, harmful pollutants are discharged to surface water and ground water. Some of these discharges may end up near the drinking water intakes, well water, or beaches. Operators of these treatment plants are required by law to notify the public when untreated waste water is being discharged. Chlorides and nitrates in water can be an indication of water contamination by sewage. |
