Research On The Water Quality Constraints Of Ground Water Heat Pumps

Shallow geothermal energy has broad prospect for development and utilization, while ground water heat pumps(GWHP) is an important way to achieve it. Looking at the results of previous studies, there are few ones on the impact of ground water quality which produced by the operation of water source heat pumps.The paper chose four representative projects of ground water heat pumps for research in Anhui Province. Water quality was evaluated and hydrochemical type was analyzed on the basis of hydrometeorological, geological, hydrogeological information and water quality data. Then, Jingxian County was chosen as the research object, with ground water flow and water quality numerical simulation model established by GMS software, and then simulation factors were selected to predict scientific affection of ground water quality on this area as the run of ground water heat pumps. Conclusions are listed as follow:(1) On the basis of ground water quality data, evaluation factors were selected and water quality evaluation was carried out, results show that the run of the system has little effect on water quality category of the project in Tianchang and Chizhou City.While, in Jingxian County, due to a substantial increase of the Fe-content in system operation, water quality deteriorates from class I to class V. In Lixin County, due to a significant reduction of the F-content, water quality changes from the class V to class I.(2) Based on Piper-diagram drawn by RockWare AqQA, the hydrochemical type analysis in each research area shows that, there is almost none influence for the operation of ground water heat pumps on ground water hydrochemical type in the aera of Jingxian County, Lixin County and Tianchang City,of which hydrochemical type is separately HCO3-Ca, HC03-Na and HCO3-Ca·Mg, which is consistent with the regional hydrogeological conditions. While in the area of Chizhou City, due to a substantial increase of SO42-, the hydrochemical type changes from HCO3-Ca to SO4-Ca. (3) According to hydrogeological conditions of Jingxian County, hydrogeological conceptual model was established. On the basis of water quality data, numerical simulation model of ground water flow is established by GMS. The paper chose the period from January 1,2013 to December 31,2013 for recognition, and the one from January 1,2014 to December 31,2014 as the validation period, and then calibrated hydrogeological parameters of the area. The water level of observation wells fit well, showing that the numerical simulation model can reflect the basic characteristics of the regional ground water flow field well. Based on this, ground water quality numerical simulation model can be established with simulation factors selected, and then the concentration variation trend of these factors which changed under the operating conditions of ground water heat pumps can be analyzed. The results show that the run of the system has little effect on water quality of the research area.