Pollution prevention is the common sense notion of trying to prevent or reduce pollution at the source before it is created. It may include a wide range of activities, programs, and techniques. Elimination or minimization of water pollutants at the source is becoming more important as wastewater treatment plant effluent criteria become more strict. Once a pollutant is discharged into a sewer system, it is diluted by several orders of magnitude and usually much more difficult to remove. Analysis and treatment of these diluted pollutants can be difficult and expensive. Depending on the pollutant's dominant characteristics, it may volatilize into the atmosphere, biodegrade, settle out with the sludge, or pass through into the final effluent.
Pretreatment refers to the treatment of wastewater at industries or commercial establishments before it is discharged to a sewer system. Pretreatment of wastewater reduces the release of conventional and toxic pollutants into the system. Pretreatment processes include physical and chemical treatment and biological treatment. These processes typically result in some type of cross-media transfer of pollutants from wastewater to land or air. For example, chemical or biological processes produce residuals that contain concentrated levels of pollutants removed in treatment. Thermal and biological processes, however, can destroy all or most of some compounds, but others will concentrate in residuals or escape to the atmosphere.
To date, pretreatment has been the main approach used by the federal government to control the discharge of industrial or commercial waste to publicly owned treatment works (POTWs). Environmental Protection Agency (EPA) effluent guidelines are based on the best available control technology. The enforcement of federal pretreatment standards by POTWs has helped reduce the amounts of contaminants, especially metals and some toxic organics, from being discharged to the nation's waterways.
Recycling and reuse involve transformation of potential waste materials into products. Internal recycling and reuse occurs when a material that has served its original purpose and could become a waste is recovered and reused at the site of waste generation; the material is controlled by the waste generator. Internal recycling by industry can involve the installation of closed-loop or in-process recycling systems. Internal recycling takes place in the home when, for example, vegetable wastes are composted rather than disposed as garbage. External recycling and reuse occurs away from the site of waste generation. External recycling is a multiple-step process