Study On The Effect Of Brine On Typical Phytoplanktons In Jiaozhou Bay And The Environmental Capacity

With the implementation of the sustainable development strategy, the concern about the impact on the environment from the seawater desalination is more and more, seawater desalination is an effective solution to the problem of water shortage, at the same time, the process also has adverse effect on the environment, the discharging of brine is an important issue to be resolved.In this thesis, the" four-in-one" integrated experimental method, which includes field investigation, laboratory test, field test and numerical simulation is adopted, on the basis of analyzing the the main components in brine discharged from Huaou seawater desalination plant in Qingdao, the no-detected effective concentration (NDEC) of brine on the typical phytop;ankton in Jiaozhou Bay is estimated through the laboratory and on-site simulation experiment, with the inputting conditions of existing desalination volume and the volume planning in 2010, the distribution and change of the salinity in the bay were simulated combining the salinity diffusion model, sequentially, the environmental capacity of brine in Jiaozhou Bay is estimated. The research will give some necessary scientific foundation to the scale and position of the seawater desalination plant. Main achievements are described as follows:1 The nature of brine discharged from Huaou seawater desalination plant in Qingdao is analysed, and the effect of brine on the growth of the dominant phytoplankton species in Jiaozhou Bay is also studied in the laboratory and on-site, at the same time, NDEC of brine on the phytoplankton community is determined with the No-detected effective concentration model.(1) In brine discharged from Huaou seawater desalination plant, the salinity is up to 50.0, about 20.0 higher than the original seawater; the content of the suspended particulate matter is more than two times of the seawater; pH is 7.45, 0.69 lower than the original seawater; In addition, the concentrations of DTN and DTP are respectively 3.3 and 16.2 times of the seawater, while the contents of NH3-N, NO3-N, NO2-N, PO4-P and SiO3-Si are respectively 6.7, 1.6, 5.7, 7.9, 3.6 times compared with the original seawater; The concentration of the heavy metals in brine is significantly increasing, Mn, Hg, Ni, Cu and Cd are respectively 2.1, 2.8, 3.7, 2.5 and 1.5 times of seawater, Cr and Pb respectively reach 0.42 and 0.13μg/L, while they are not detected in the seawater.(2) The results about the ecological effects of brine show that, to Skeletonema costatum, Chaetoceros debilis and Pseudo-nitzschia pungens, besides high salinity, other factors in brine may affect their growth, but to Prorocentrum micans t, the high salinity is the main reason which affects its growth.(3) NDEC of brine on the phytoplankton community is determined with the No-detected effective concentration model based on the laboratory and on-site experiment results, initially NDEC of brine on the phytoplankton community in the Jiaozhou Bay is estimated to be 37.1.2 The salinity diffusion model in the Jiaozhou Bay is set up based on the POM model. With the inputting conditions, the distribution and changes of the salinity in the bay are simulated. The results show that, brine discharged from the desalination plants will have only a little effect on the distribution of average salinity in the whole bay in 2010, but it will lead to a marked increasing in salinity near the area of the desalination plants.(1) Due to the effect of the rainfall, in winter, the average salinity of the bay is the highest, and following are spring and autumn, in summer the average salinity is the lowest; The average salinity increased slightly than before in the different seasons in 2008, the increasing range is 0.0003~0.0013, and the increasing range is 0.0183~0.0229 in 2010, much more than the increasing in 2008.(2) The seawater area with the salinity above 32.0 are respectively 0.04, 0.04, 0.00 and 0.04km2 in spring, summer, autumn and winter in 2008, which in 2010 are 0.37, 0.21, 0.21 and 0.33km2, more than five times the same period in 2008, and in 2010, the seawater area with the salinity above 33.0 turns up, respectively are 0.08, 0.12, 0.08 and 0.12km2 in spring, summer, autumn and winter.(3) The highest salinitys near the Huaou seawater desalination plant respectively reach 32.4626, 32.1613, 31.9469 and 32.6664 in spring, summer, autumn and winter in 2008, slightly higher than the highest salinity in the same period without brine discharging. in 2010, the highest salinity respectively are 39.5799, 39.1602, 37.5569 and 39.9239, above 20% higher than non-brine discharging and the highest salinity in 2008, and the highest salinity in the four seasons in 2010 are all higher than 37.1, which is the no-detected effective concentration of brine on the phytoplankton community in the Bay, this may be have significantly typical of inhibitory effect on the growth of the phytoplankton in Jiaozhou Bay, and will affect the marine environment.3 Based on the salinity diffusion model, under the desalination planning conditions, the environmental capacity of brine discharged from seawater desalination plants in Jiaozhou Bay is calculated by optimal discharge flux method, which is 6.7×108m3?a-1, the allocated capacity of brine in Qingdao Power plant is the most, which accounts for about 42.8%, and following are the allocated capacities of brine in Huaou seawater desalination plant, which accounts for about 31.3%, and the Petrochemical plant in Qingdao allocated capacity of brine is the least, which only accounts for about 25.9%; Base on the eleven brine discharge sites, under the conditions of the optimal layout of brine around Jiaozhou Bay, the environmental capacity of brine discharged from seawater desalination plants in Jiaozhou Bay is about 8.8×108m3·a-1. Comparing with the allocated capacity of brine in eleven discharge sites, the allocated capacity of brine in Tuandao discharge site is the most, which accounts for about 17.8%, and following are the allocated capacities of brine in Huaou seawater desalination plant, Licun River, Dagu River, Qingdao Power plant, the Petrochemical plant in Qingdao, Moshui River, Banqiaofang River, Yang River and Loushan River discharge sites, which account for about 14.7%, 12.9%, 12.8%, 10.8%, 10.3%, 8.2%, 7.2%, 4.0% and 1.2%, and the allocated capacity of brine in Baisha River discharge site is the least, which only accounts for about 0.2%. Under the allocated capacity loads of brine through the eleven brine discharge sites, the salinity diffusion model could calculate the environmental capacity of brine and the results are logical.