Virus removal by treatment processes

The most common form of pollution control consists of a system of sewers and waste treatment plants. The sewers collect the wastewater from homes, businesses and industries and deliver it to the plants for treatment to make it fit for discharge into streams, estuaries, or for reuse. During dry weather, when the sewers are handling only the normal amount of wastewater, all of it should be carried to the waste treatment plant. During a storm, when the amount of water in the sewer system is much greater, it may be necessary to allow part of the water—including varying amounts of raw sewage—to bypass directly into the receiving streams. The rest of the wastes are sent to the treatment plant. If part of the increased load of storm water was not diverted, the waste treatment plant would be overloaded and the purifying process would not function properly.