Impacts Of Drainage From Seawater Flue Gas Desulfurization System In Coal-fired Power Plant On Eco-environment In Surrounding Sea Area

To study the long-term potential environmental impacts of the drainage from theSeawater Flue Gas Desulfurization System (SFGDS) of Huadian Qingdao Power Ltd.,samples were collected from fourteen sampling stations, including two in the outfallsof the1#and3#aeration tanks, and twelve in the desulfurization drain outfallstowards the Haibo River and the adjacent sea area on December27th,2011, June5th,2012, and December26th,2012. The surface water, surface sediment, and marineorganisms samples were collected following the Specification for oceanographicsurvey (GB12673-2007). And subsequently, the physicochemical analysis, the speciesidentification, and the statistic of species abundance and biomass were performedfollowing the specification for marine monitoring (GB17378-2007). Accordingly, theimpacts of the characteristic pollutants in the drainage from the studied company wereanalysized on the marine eco-environment. The main results are as follows:(1) Characteristic pollutants in drainage from the SFGDSThe DO and pH significantly decreased, and COD, temperature, inorganicnitrogen, active phosphate, Cu, and Pb significantly increased in the drainage of the1#and3#aeration tanks compared with corresponding intake water, where theincrease of temperature could be attributed to the cooling process of the power plant.Consequently, DO, pH, COD, temperature, inorganic nitrogen, active phosphate, Cu,and Pb were the characteristic pollutants of the drainage from the SFGDS.(2) The impact of the drainage from the SFGDS on the marine water quality insurrounding sea areaThe characteristic pollutants including pH, DO, temperature, COD, inorganicnitrogen, and active phosphate varied significantly within400meters downstream the desulfurization outfalls, while no significant changes were observed above700meters.And no significant changes of Cu or Pb occurred at any diffusion distance. Therefore,the drainage from SFGDS could affect the distribution levels of the pH, DO, COD,inorganic nitrogen and active phosphate in the seawater within400metersdownstream from the desulfurization outfalls, and had no effects on the water qualitybeyond700meters.The decrease of pH could be mainly attributed to the release of H+in sea wateraccompanied by the absorption of SO2, and deduced subsequent descent of the pH by0.2-2.2in the seawater within400meters downstream from the desulfurizationoutfalls. And consequently, the seawater quantity failed to meet the standard of therespective marine functional zone. The decline of DO would be due to the SO32-residues in the drainage. The temperature rise was mainly influenced by the coolingprocess of the power plant unit rather than the desulfurization process. The pollutionloads of COD, N, and P would not be significantly increased by the desulfurizationdrainage.(3) The impacts of the drainage from the SFGDS on the surface sediment insurrounding sea areaAccording to the investigation, slight differences of the levels of the heavymetals in the surface sediment were observed at different stations adjacent to thedesulfurization outfalls, and all of them well reached the standard of respectivemarine functional zone. The ecological risk of these heavy metals was assessedemploying the potential ecological risk index methods. And accordingly, the Erivalues of Cr, Cu, Zn, As, Pb, Cd were all less than40and the RI value whichcharacterized the integrated potential ecological hazard of the six metals was farbelow150, which presented low risk to marine organisms. In comparison with thehistoric pollution status, the concentrations, Erivalues, and RI value of the heavymetals in the surface sediment did descend in the study sea area. In conclusion, thedrainage from the SFGDS presented little or no ecological risk to the marineorganisms.(4) The impacts of the drainage from the SFGDS on the marine biological community in the surrounding sea area4phylums of phytoplanktons,6categories of zooplankton, and8phylums ofmacrozoobenthos were collected in the sea area near the desulfurization outfalls,which involving74,42, and106species, respectively and dominated byBacillariophyta, Copepods, and Polychaetes, respectively. The community structurewas generally stable with a high level biodiversity in most cases, except for twostations (7#、12#), where the Shannon-Wiener indices were bellow1.0and the Pielouindices were below0.3in the summer of2012. The pH of several stations was lowerthan6.5, and the temperature rise was above2℃within400meters downstream theoutfalls, which presented potential detrimental affects on marine species along withthe biological community structure. However, in consideration of the variation of thecommunity indices in multiple stations, the Shannon-Wiener indices, Pielou indices,and Margalef indices distributed homogeneously, there was no significant increase ordecrease tendency. Additionally, no significant differences were observed between thestations within400meters downstream the outfalls and those in Jiaozhou Bay ascontrol, which revealed little or no adverse effects on the marine biologicalcommunity by the changes of the characteristic pollutants within400metersdownstream the desulfurization outfalls due to the drainage from SFGDS.