Microbial Communities in the Process and Effluents of Seawater Desalination Plants

Seawater desalination is now being widely regarded as the solution to the ever increasing need for potable water. However, in contrast to the rapid technological developments throughout the desalination process and expanding desalination facilities, not much is known on the environmental and ecological impacts on the marine ecosystem. Specifically, the effects of discharging brine and chemicals, used routinely in the desalination process, have been poorly documented. In this chapter, we summarize the available data examining the impacts of desalination brine and chemicals, such as iron-based coagulants and phosphonate antiscalants, on coastal seawater microbial communities. The data include results from controlled large-scale laboratory experiments and from in situ measurements around desalination plants outfalls. The observed effects could be immediate, on a time scale of several hours, affecting metabolic functions such as primary and bacterial productivity, and on longer temporal scales of days to weeks, influencing community composition and structure. The specific changes depend predominantly on plant location, capacity, chemical utilization, and discharge technologies (open versus submerged outfalls). We conclude with gaps in knowledge and recommendations for SWRO plant operations.