摘要
再生水回灌是一个世界性的尝试,实践经验表明:将符合水质要求的再生水回灌地下含水层,可以有效地增加地下水资源的存储量,并可以较好地利用含水层的储水空间,起到年度和年际间的调节作用。但是,限于经济和技术原因,回灌水中盐分难以得到有效去除,将会影响到供水安全问题,必须引起足够的重视。
本次研究根据前期工程地质勘察及研究区土壤样品采集分析,选取北京市顺义潮白河再生水受水区三种典型代表性土壤介质(砾石含砂、细砂、粉质粘土)作为研究对象,并采用受水区再生水进行淋溶模拟试验。
实际河水淋溶单一介质模拟柱试验的测试结果分析表明,在三种典型土壤介质中,阳离子交换吸附作用主要体现为K-Ca之间的交换,且粉质粘土柱中阳离子离子交换作用较砾石含砂柱和细砂柱更为显著。另外,柱试验结果还表明,随着土壤介质中粘粒含量及总有机碳含量的增加,和阳离子交换容量及粘土矿物总量的上升,典型介质淋溶模拟柱试验中阳离子交换作用达到平衡时所需要的时间也就越长,分别约为砾石含砂72天、细砂80天和粉质粘土86天。定量结果计算也证明了上述结论,粉质粘土介质的各阴阳离子本底含量最高,单位质量粉质粘土介质总硬度及溶解性总固体(TDS)的贡献量最大,分别为57.67mg·100g~(-1)和69.52 mg·100g~(-1)。
实际河水淋溶组合介质模拟柱试验的测试结果分析表明,在组合介质模拟柱中,阳离子交换吸附作用依然主要体现为K-Ca之间的交换,且组合柱中砾石含砂段阳离子交换方向主要是水中钙离子交换土壤介质中的钾离子,而细砂段与粉质粘土段中,阳离子交换方向则主要是水中钾离子交换土壤介质中的钙离子。其次,组合柱出水水质中总硬度和TDS有降低的总趋势,二者分别降低了4.69mg/L和17.64mg/L,推测这与年后试验环境温度值的降低、进水水化学类型的变化(由年前重碳酸钠型水变为年后重碳酸钠钙型水)及淋溶模拟柱试验本身阳离子交换作用处于临界状态等因素存在一定的关系;另外,实际河水淋溶组合柱各过渡段对总硬度及TDS浓度变化的贡献要大于各单一介质段对其的贡献。
Groundwater recharge with reclaimed water is a world-wide attempt, the experience shows that: the reclaimed water recharge to groundwater aquifer is an effective way to increase the storage capacity of groundwater resources, and can be a better use of aquifer storage space, and play a regulation function of a year and between inter- annual. However, because of the limited of economic and technical, salt difficult to be effectively removed from the reclaimed water. it will affect the water supply security, must be given due consideration, therefore, it must be given due consideration.
According to engineering geologic investigation and soil sample test analysis, selects reclaimed water of Chao-bai River in Beijing Shun-yi to take three kind of typical representative soil medium (sandy gravel, fine sand, silty clay) as the object of study, and uses the reclaimed water of Chao-bai river to carry on the leaching simulation test.
The actual river-water leaching single-medium simulation column test results shows that, the cation exchange adsorption mainly manifests is between the K-Ca exchange, and in the silty clay column, the cation exchange function compares the sandy gravel column and the fine sand column is more remarkable. Moreover, the column test result also indicated that, along with clay content and total organic compounds (TOC) increase, with cation exchange capacity (CEC) and total amount of clay minerals rise, in the typical medium leaching simulation column experiment, the cation exchange function's equilibrium time is also longer, respectively is 72 days for the sandy gravel、80 days for the fine sand and 86 days for the silty clay. The quantificational result computation has also proven the above conclusion, the background value of various anions and cations concentration of the silty clay medium is highest, and the contribution quantity of the total hardness of the unit mass silty clay medium and the total dissolved solids (TDS) is biggest, respectively is 57.67mg·100g~(-1) and 69.52 mg·100g~(-1).
The actual river-water leaching combination-medium simulation column test results shows that, in the combination-medium simulation column, the cation exchange adsorption also mainly manifests is between the K-Ca exchange, and in the layer of sandy gravel of the combination-medium column, the direction of cation exchange mainly is calcium ion in the water exchange to the potassium ion in the soil-medium, but in the layer of fine sand and silty clay of the combination-medium column, the direction of cation exchange mainly is potassium ion in the water exchange to the calcium ion in the soil-medium. Second, total hardness and TDS of effluent water quality are the general trend of lower in the combination-medium column, respectively decreased by 4.69mg/L and 17.64mg/L, this phenomenon is speculated the reason is that the lower temperature of test ambient、the changes of enter water chemistry type (from water chemistry type of HCO3-Na change ioto water chemistry type of HCO3-Na、Ca) and the function of cation exchange of its own in leaching simulation column test is in a critical state and so on. Moreover, the contribution rate of the transition layers of the actual river-water leaching combination-medium column for the total hardness and the total dissolved solids (TDS) is bigger than the contribution rate of the layers of the single-medium.
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