Return flow

Return flow is surface and subsurface water that leaves the field following application of irrigation water. While irrigation return flows is a point source, they are expressly exempted from permit requirements under the Clean Water Act (P.L. 92-500, as amended).

Return flows generally return to the irrigation centre after a period of about three to four weeks; due to this, the farmers usually need to pour bleach into the water to clean it of any organisms that have entered the stream. If this is not taken care of, diseases such as typhoid or cholera could enter the irrigation and pose a risk of epidemic disease to surrounded towns and cities.

References

This article incorporates public domain material from the Congressional Research Service document "Report for Congress: Agriculture: A Glossary of Terms, Programs, and Laws, 2005 Edition" by Jasper Womach.

Wastewater

Sources of wastewater	Acid mine drainage Ballast water Blackwater (coal) Blackwater (waste) Boiler blowdown Brine Combined sewer Cooling tower Cooling water Greywater Infiltration/Inflow Industrial effluent Ion exchange Leachate Manure Papermaking Produced water Return flow Reverse osmosis Sanitary sewer Sewage Sewage sludge Storm drain Urban runoff

Wastewater quality indicators	Biochemical oxygen demand Chemical oxygen demand Coliform index Dissolved oxygen Heavy metals pH Salinity Temperature Total dissolved solids Total suspended solids Turbidity

Wastewater treatment options	Activated sludge Aerated lagoon Agricultural wastewater treatment API oil-water separator Carbon filtration Chlorination Clarifier Constructed wetland Extended aeration Facultative lagoon Filtration Imhoff tank Industrial wastewater treatment Ion exchange Membrane bioreactor Reverse osmosis Rotating biological contactor Secondary treatment Sedimentation Septic tank Settling basin Sewage sludge treatment Sewage treatment Stabilization pond Trickling filter Ultraviolet germicidal irradiation UASB Wastewater treatment plant

Wastewater disposal options	Combined sewer Evaporation pond Groundwater recharge Infiltration basin Injection well Irrigation Marine dumping Marine outfall Sanitary sewer Septic drain field Sewerage Stabilization pond Storm drain Surface runoff Water reclamation

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