How can we tap the ocean’s limitless supply of water and support thriving ecosystems?
Fresh water has become scarcer around the world, and as drought increases and water demand grows, seawater desalination may be key to the very survivial of many economies and communities near the ocean.
The impact of desalination on nearby marine ecosystems may be a cause for concern if not thoughtfully developed. Open-ocean intake systems can harm fish and other marine life, and leftover brine with a high saline load can be damaging to ecosystems on the ocean floor near the outfall.
Other processes have specific impacts: Reverse osmosis seawater desalination is energy-efficient, yet chemicals are used during pretreatment and to address biofouling of reverse-osmosis membranes. Thermal desalination can cause heat pollution in receiving water bodies.
While desalination can cause ecological change, location and designs informed by environmental impact studies can establish a healthy relationship between marine life and desalination.
Velocity-cap intakes, subsurface intakes, and travelling screens can minimize the number of fish harmed, and environmental restoration and restocking can help where impacts are severe. Impacts on marine life communities on the ocean floor can also be addressed by locating diffuser systems based on current and flow modeling.
Environmentally Responsible Desalination
During development of a desalination plant at Point Fortin, Trinidad, design and siting considerations were only part of the effort to preserve marine ecosystems.
The island needed a reliable source of fresh water for a community that had long suffered from sporadic water service, sometimes only one or two days a week. And, the plant needed to allow nearby marine ecosystems to flourish. According to a report from the Zofness Sustainable Infrastructure Program at Harvard’s Graduate School of Design:
[T]he Point Fortin plant showcased an impressive goal of maintaining marine biology intact and preserves marine habitats, species, and non-living natural systems. It does this by measuring baseline data of all natural habitats before construction of the plant and receiving third-party recommendations to mitigate any negative effects it has on the surrounding environment. Another great aspect was the project’s choice of site, which was in a previously developed and polluted space with scrap metal and trash. With the development of the plant, this site was renovated and cleaned. […] The project avoids development in a site of high ecological value or adverse geology.
Two independent firms have been engaged to test water quality in Guapo Bay, approximately a kilometer from shore, to monitor the effects of brine discharge. If the effluent fluctuates in salinity, temperature, or alkalinity, adjustments are made.
Marine biologists are contracted to track marine life and plan improvements to species health near the plant, and the project has improved species biodiversity by preserving bottom-dwelling marine life, which in-turn supports larger marine organisms.
Protecting Marine Health
With populations growing and precipitation becoming less dependable, the choice for coastal regions and islands soon may be “how” desalination will be implemented, not “if” it will be.
At Seven Seas, we believe there is no better catalyst for collective action than aligned interests. Performance-based Water-as-a-Service® BOO and BOOT financing structures can find common ground among parties to provide water services that lower costs and protect the vital ocean ecosystems that coastal communities need.