Reverse osmosis is widely used to treat water in industrial and agricultural applications. It effectively removes salts and contaminants from brackish, seawater or wastewater. Reverse osmosis produces a clean stream of high purity water, and as well a smaller stream of waste, referred to as concentrate or brine. Brine is a highly concentrated solution of the salts and contaminants separated from the water with the reverse osmosis membranes.
Brine requires proper disposal, which many times requires permits or other regulatory compliance actions. There are many brine disposal methods available today, which all have different environmental and capital costs. This is a review of common brine disposals methods and a consideration of some of their pros and cons.
Surface Water Discharge
In some instances, brine can be discharged to surface water bodies such as rivers, lakes or reservoirs. This is a low cost solution however it typically must be done in compliance with a facility’s National Pollutant Discharge Elimination System permits.
Brine can be accumulated in a surface impoundment or pond which allows the brine to further concentrate as water evaporates into the atmosphere. There is no federal permit required, however some states may require monitoring.
Brine can sometimes be used as irrigation water.
Deep Well Injection
Brine can be injected into a porous subsurface rock formation. This option is quite costly because of the cost of drilling and maintaining the well. Also an underground Injection Control permit is required and typically includes rigorous site evaluation and monitoring.
Often brine can be disposed of to the local sanitary sewer system. The mingled discharge from the site must often comply with discharge requirements from the sewage plant operator and/or publically owned treatment works.
Brine can also be an effective dust control agent for dryer climates and in summer months. It is applied to roadways or fields by spraying.
Traditionally, road salt is used during the winter months to suppress ice on roads. However, brine can be used for this purpose.