Research On The Impact Of Thermal Power Plant To Groundwater Environment During Operating Period

Water resource has the double attribute of resource and environment, which is also an important support to ecological system. At the same time, as a strategically economic resource, water resource is an organic part of comprehensive national strength, which is closely linked with national economic and social stability. As an important component of water resources, groundwater resource accounts for a third of the water resources quantity and has now become a major source of drinking water for cities, industry and agriculture. With the rapid development of industrialization and urbanization in our country in recent years and the growth of population, the imbalance between supply and demand for water resources highlights and has the tendency to intensify. Human exploiting groundwater and discharging sewage in unreasonable way, has caused many environmental geological problems. The impact of human activities on groundwater environment has increasingly strengthened, and the problem of groundwater pollution is becoming more and more serious.Electric power industry is the foundation of the national economic and social development, and has made outstanding contributions to national economic and social development. Although in recent years, nuclear power, wind power and solar power have improved on the proportion of electricity supply in our country, and at the same time geothermal power is also on the way, but the endowment of rich coal resources determines that thermal power in our electric power industry will also be in the dominant position. However, if environmental protection measures are not executed well,or in some accident cases, the construction and operation of thermal power plants will have lots of adverse influence on atmospheric environment and groundwater environment.The article relies on the "Replacing small units with large ones " project of thermal power plant of Beijing Energy Investment Holding Co., Ltd.(hereinafter referred to as “BEIH”) in economic development zone of QinHuangDao. Based on the work such as data collection, indoor and field test, the outdoor investigation and monitoring, the article researched and analyzed the possible impact on groundwater environment during the operating period. Main achievements and conclusions are as follows:(1) Based on collecting data and field experiment investigation in the study area, the basic geomorphic features, the geological condition, hydrogeological condition, and natural flow field of groundwater and the present situation of water quality were found out. The main landscape is stacking plains and low hills, the main water-bearing rock groups are composed of the quaternary holocene and the upper pleistocene series of strata, and the groundwater chemical category is quaternary unconsolidated rock pore water and weathering crevice water, giving priority to pore water. The embedded depth of groundwater table changes between 6.2 and 9.0 meters, and that is about one meter in the ash field. The lithology of aquifer mainly consists of the coarse sand and gravel. The water content, conductivity, permeability are good, and the groundwater is abundant. Groundwater chemical types in the study area is complex, but the water is fresh, with the value of PH between 6.4 to 8.4, belonging to neutral-weak alkaline water and groundwater salinity less than 1g/L.(2) There are four possible accident conditions, they are if the underground pipeline of the diesel ignition system damaged, if diesel oil tank leaked suddenly, if bottom of the waste water pool of desulfurization system was broken and if seepage prevention layer in the ash field was broken.And meanwhile the pollution factors were determined.(3) Based on the work such as data collection, indoor and field test, the outdoor investigation and monitoring, the groundwater flow model and the solute transport model were established by applying the numerical simulation method, to predict and evaluate the possible impact on the local groundwater environment under the four accident conditions above.(4) The simulation results are as follows: The first case: if the underground pipeline of diesel ignition system leaks by accident, the concentration of the petroleum pollutant is higher than the detection limit but not excessive after 7300 days, and it is lower than the detection limit after 10950 days, indicating that it has some effect on the groundwater environment. The second case: if the diesel tank leaks suddenly with the bottom impermeable layer effective, the concentration of petroleum pollutant is below the detection limit after 1000 days, indicating that it has a small influence on the aquifer. But if the impermeable layer fails, the concentration of petroleum pollutant will always overweight in the prediction period, showing that it has great influence on the aquifer. So it is needed to increase the seepage control facilities to reduce the influence on the groundwater environment. The third case: if wastewater pool in desulfurization wastewater treatment plant leaks by accident, SO42– will be below the detection limit after 3650 days in the prediction period, but no violation will occur in the whole prediction period. And the concentration of Cl– will be below the detection limit, after 7300 days, but no violation will occur in the whole prediction period. It indicates that the case has a relatively smaller effect on the aquifer. The forth case: if seepage prevention layer in the grey field fails, the pollutants will Migrate down in the groundwater, the influence scope will increase gradually, and F- overweight in the prediction period, showing that the case has a large effect on the aquifer. Although the incidence of accident above is small, but the monitoring program must be strict with, and the seepage prevention measures and emergency measures must be taken, so that the impact on the environment can effectively reduce to the range acceptable.