Little quantitative data is available on brine discharge in marine water from desalination plants and existing studies are “extremely limited” and have “flaws”, a new report has said.
The new report, Marine Impacts of Seawater Desalination Plants, launched today by the Pacific Institute, examines effects on the marine environment associated with the construction and long-term operation of seawater desalination plants, including withdrawing water from the ocean and discharging the highly concentrated brine.
On the topic of the disposal of “highly concentrated salt brine”, the report said: “Twice as saline as the ocean, the brine is denser than the waters into which it is discharged and tends to sink and slowly spread along the ocean floor, where there is typically little wave energy to mix it.”
It recommended several “proven methods” to disperse brine, such as multi-port diffusers placed on the discharge pipe to promote mixing.
Brine can also be diluted with effluent from a wastewater treatment plant or with cooling water from a power plant or other industrial user, although these approaches have their own drawbacks that must be addressed, the Pacific Institute said.
However, the report also highlighted a lack of data available on brine discharge. It pointed to a study by Roberts et al. (2010) that identified 62 peer- reviewed research articles concerned with brine discharge in marine waters and found that the majority (44%) of articles are discussions or opinion pieces with little quantitative data.
The Pacific Institute went onto say that “studies on the impacts of brine on California biota in particular are “extremely limited, often not peer-reviewed, not readily available, or have flaws in the study design”.
The Key Issues for Seawater Desalination series is an update to the 2006 Pacific Institute report Desalination with a Grain of Salt.
Researchers conducted some 25 one-on-one interviews with industry experts, environmental and community groups, and staff of water agencies and regulatory agencies to identify key outstanding issues for seawater desalination projects in California.
- The new report, Marine Impacts of Seawater Desalination Plants, can be downloaded free of charge from the Pacific Institute website here.