Impacts of Desalination Brine Discharge on Benthic Ecosystems.

Seawater reverse osmosis (SWRO) desalination facilities produce freshwater and, at the same time, discharge hypersaline brine that often includes various chemical additives such as antiscalants and coagulants. This dense brine can sink to the sea bottom and creep over the seabed, reaching up to 5 km from the discharge point. Previous reviews have discussed the effects of SWRO desalination brine on various marine ecosystems, yet little attention has been paid to the impacts on benthic habitats. This review comprehensibly discusses the effects of SWRO brine discharge on marine benthic fauna and flora. We review previous studies that indicated a suite of impacts by SWRO brine on benthic organisms, including bacteria, seagrasses, polychaetes, and corals. The effects within the discharge mixing zones range from impaired activities and morphological deformations to changes in the community composition. Recent modeling work demonstrated that brine could spread over the seabed, beyond the mixing zone, for up to several tens of kilometers and impair nutrient fluxes from the sediment to the water column. We also provide a possible perspective on brine's impact on the biogeochemical process within the mixing zone subsurface. Desalination brine can infiltrate into the sandy bottom around the discharge area due to gravity currents. Accumulation of brine and associated chemical additives, such as polyphosphonate-based antiscalants and ferric-based coagulants in the porewater, may change the redox zones and, hence, impact biogeochemical processes in sediments. With the demand for drinking water escalating worldwide, the volumes of brine discharge are predicted to triple during the current century. Future efforts should focus on the development and operation of viable technologies to minimize the volumes of brine discharged into marine environments, along with a change to environmentally friendly additives. However, the application of these technologies should be partly subsidized by governmental stakeholders to safeguard coastal ecosystems around desalination facilities.

海水反渗透（SWRO）海水淡化设施生产淡水，同时排放高盐度卤水，其中通常包含各种化学添加剂，如阻垢剂和混凝剂。这种浓稠的卤水会沉到海底并在海床上蔓延，最远可达排放点5公里处。先前的综述已经讨论了海水反渗透海水淡化卤水对各种海洋生态系统的影响，但对底栖生境的影响关注甚少。本综述全面讨论了海水反渗透卤水排放对海洋底栖动植物的影响。我们回顾了先前的研究，这些研究表明海水反渗透卤水对底栖生物，包括细菌、海草、多毛类动物和珊瑚，产生了一系列影响。在排放混合区内的影响包括活动受损、形态畸形以及群落组成的变化。近期的模拟研究表明，卤水可能会在海床上扩散，超出混合区，最远可达数十公里，并损害从沉积物到水柱的营养通量。我们还对卤水在混合区地下对生物地球化学过程的影响提供了一种可能的观点。由于重力流，海水淡化卤水会渗入排放区周围的沙质底部。卤水中的化学添加剂，如基于多磷酸盐的阻垢剂和基于铁的混凝剂在孔隙水中的积累，可能会改变氧化还原区域，从而影响沉积物中的生物地球化学过程。随着全球对饮用水需求的不断增加，预计本世纪卤水排放量将增加两倍。未来的工作应侧重于开发和运营可行的技术，以尽量减少排放到海洋环境中的卤水量，同时改用环保型添加剂。然而，这些技术的应用应由政府利益相关者提供部分补贴，以保护海水淡化设施周围的沿海生态系统。