5.4 Alternative Water Resources: Desalination
5.4.8 Brine
Disposing of brine can take multiple forms, however the most common is disposal to the ocean or
surface water streams. This method is a form of dilution based on the volume of discharge relative
to the receiving water body. Surface water disposal can be accomplished by directly dumping brine
into a water body, installing engineering controls such as outfall diffusion devices, or mixing brine
with other less saline waste streams before ultimate discharge. At present, 48% of all desalination
facilities in the United States dispose of their brine to surface water, while 40% dispose of their
water to sewers to be mixed and treated with wastewater (U.S. Bureau of Reclamation 2003).
This disposal method is currently the easiest to design and least expensive option available for
desalination facilities. Unfortunately it exacts heavy costs on the environment. Other methods of
brine disposal include the use of evaporation ponds, injection into confined aquifers via wells,
discharge to saline streams flowing into estuaries, discharge to local wastewater facilities via
sanitary sewers, or injection into saline aquifers via seawater wells.
One of the most significant problems with desalination is finding environmentally sensitive options
for disposal of brine. It can be suggested that the next evolutionary step in the development of
desalination technologies will be to either reduce the amount of brine or find a beneficial use for it.
Listed below are brief descriptions of the currently available methods for disposing of brine:
- Evaporative Ponds – Brine is spread in shallow ponds, where it gradually evaporates. The
residual solids left behind are then disposed of in a landfill or collected for re-use.
- Deep Well Injection – Brine is injected, via wells, into confined, non-potable aquifer
systems or into brackish aquifers occurring along the coast.
- Discharge to Sewer System - Brine is conveyed directly to existing wastewater treatment
facilities.
- Ocean Outfall – Brine is discharged directly to the ocean, where it is diluted by the
surrounding seawater. This dilution can be enhanced through the use of diffusers that
spread the discharge over a wider area, thereby lowering the concentration at any one
location.
- Surface Water Discharge – Discharge is to a stream, river, and/or lake, using the same
dilution concepts as ocean outfall. Surface waters are usually used when the fresh water body is in close proximity to an estuary; however this practice is not necessarily a good
practice.
In Loreto, the existence of the marine park, in addition to the potential environmental impacts to
rare and endangered species and habitats along the coastline, makes brine disposal to the ocean an
unattractive choice. Mexico’s National Protected Area Service (CONANP) has not issued criteria
or standards for intake or discharge in a marine protected area; therefore, it would be unwise to
pursue open water brine discharge as a first option within the boundaries of the Marine Park. |
