Study on the Impact of the Brine Discharge from the Desalination Plant on Marine Ecological Environment

Abstract

In order to understand the impact of brine discharge from seawater desalination plants on marine ecological environment, the seawater quality, phytoplankton and zooplankton were investigated and monitored in the waters adjacent to Qingdao Baifa seawater desalination plant for four seasons in 2021, and the seawater quality environment and marine ecological environment were evaluated by improved Nemerow index and biodiversity index respectively. The results show that, except inorganic nitrogen and inorganic phosphorus, all the other water quality monitoring indicators meet the fourth class seawater quality standard in the Standard for Seawater Quality (GB3097-1997), and some monitoring indicators reach the first class or the second class seawater standard. The pollution of inorganic nitrogen and phosphorus is not obviously related to the discharge of brine discharge. The improved Nemerow index evaluation shows that the seawater in the brine discharge area is in a relatively clean state. A total of 49 species of phytoplankton belonging to 31 genera were identified in four seasons of the year, including 44 species of bacillari-ophyta belonging to 26 genera and 5 species of pyrrophyta belonging to 5 genera. In the whole year, the phytoplankton cell abundance at each station ranged from 0.54 to 6496.00 × 10 4 cell/m 3 , with an average of 1082.62 × 10 4 cell/m 3 , and the peak of phytoplankton cell abundance appeared in September. The main dominant species are Chaetoceros , Eucampia zodiacus , Skeletonema cos-tatum , Coscinodiscus sp., and Nitzschia spp. A total of 20 adult Zooplankton species were identified in four quarterly surveys throughout the year, including 15 species of Arthropod, 2 species of coelenterates, only 1 species of Protozoa, chaetognatha, and planktonic cysts, and 10 species of planktonic larvae. The abundance of zooplankton at each station was between 5 and 145 ind./m 3 , with an average of 85 ind./m 3 , and the biomass was between 2.5 and 610 mg/m 3 , with an average of 44 mg/m 3 . The main dominant species of Zooplankton community are Acartia hongi , Tortanus derjugini , Tortanus spinicaudatus , Oithona brevicornis , Oikopleura dioica , and Nauplii larva . The species, quantity, dominant species have not undergone significant changes, and the biological community structure is relatively stable. In the short term, the discharge of concentrated seawater from the desalination plant has not had an impact on the ecological environment of the surrounding sea areas.