Point source water pollution

Point-source water pollution is any discernible, defined, and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, vessel, or other floating craft, from which pollutants are or may be discharged into a river or other surface water body. Non-point-source pollution consists of runoff from irrigated agricultural land. 

Southworth, G.R. 1990. PCB concentrations in stream sunfish (Lepomis auritus and L. macrochirus) in relation to proximity to chronic point sources. Water Air Soil Pollut. 51 287-296. 

Rivers listed in Table 2 and shown in Fig. 3 incorporate a broad range of characteristics, including water discharge, catchment area, land cover, land use, and the number of people hving in the catchment. Land use and population reflect the potential pollution intensity, whereas the percentage of intensively used agricultural land in the catchment or the number of inhabitants per unit water discharge are major pollution stress factors. They also represent important diffuse and point sources of pollution. 

Total Maximum Daily Load (TMDL) Under Section 303(d) of the 1972 Clean Water Act, states, territories, and authorized tribes were required to develop a list of impaired waters. The impaired waters do not meet water quality standards that states, territories, and authorized tribes have set for them, even after point sources of pollution have installed the minimum required levels of pollution control technology. The law requires that these jurisdictions establish priority rankings for waters on the lists and develop TMDLs for these waters. 

M.B. Hocking, D. Hocking, and T.A. Smyth, Fluoride distribution... processes about an industrial point source. Water, Air, Soil Pollut. 14, 133-157, (1980). 

Non-point sources are pollution sources that are rather diffuse in nature. Good examples of this type of pollution are water contamination caused by agricultural runoff or acid rain. Controlling and regulating this type of pollution is much more difficult because you can t identify a particular company or individual as the polluter. In recent years, federal and state agencies have attempted to address non-point source pollution. The Clean Water Action Plan of 1998 was one such attempt that focused on watersheds and runoffs. 

The Water Quality Act of 1987 requires discharge permits for all point sources of pollution. More than 95% of all major facilities now comply with 5-year NPDES permits, which specify the fypes and amounts of pollutants that legally can be discharged. When permits are renewed, they can be modified to reflect more stringent regulations. Violators are subject to enforcement actions by EPA, including criminal prosecution. 

Sources of pollutants are commonly divided into two categories point sources and nonpoint sources. Point sources of pollution refer to discrete, localized, and often readily measurable discharges of chemicals. Examples of point sources are industrial outfall pipes, treated sewage outfalls from wastewater treatment plants, and untreated storm water discharge pipes. A spill of chemicals, due fo an accident on or near a surface water body, can also be regarded as a point source because its initial areal extent is limited. Point sources are often modeled by "plume" or "cloud" models that explicitly consider where and when a chemical release occurs, and then mathematically model the concentration of the chemical as a function of time and location. 

Analysis of Clean Water Act Effluent Guidelines Pollutants. Summary of the Chemicals Regulated by Industrial Point Source Category U.S. EPA, Washiagton, D.C., 40 CFR Parts 400-475, 1991. 

It is also clear that it is difficult to relate cause and effect to any specific chemical since, with the exception of point source effluents, many waterways contain a multitude of chemicals, of which the active endocrine disruptor may not be that which has been measured in the water or tissue. For such reasons, many studies have used in vitro experiments in which isolated tissue, either from a control animal or one captured in a polluted water system, is exposed to a single pollutant in the laboratory. Such experiments have shown significant disruption to testicular activity by a wide range of xenobiotics, including cadmium, lindane, DDT, cythion, hexadrin and PCBs. ... 

---