三级处理水中DOM在土壤含水层处理过程中的富集转化

Accumulation and Transformation of Dissolved Organic Matter in Tertiary Effluent during Soil Aquifer Treatment

在实验室研究了城市污水处理厂三级处理水中溶解性有机物(DOM)在模拟土壤含水层处理(SAT)土壤柱中的富集及转化.利用XAD-8/XAD-4树脂,将原状土、SAT土壤柱中不同深度土壤DOM分级为疏水性有机酸(HPO-A)、疏水性中性有机物(HPO-N)、过渡亲水性有机酸(TPI-A)、过渡亲水性中性有机物(TPI-N)和亲水性有机物(HPI).SAT对三级处理水中DOM的去除主要表现在土壤吸附及土壤生物降解两个方面,其中微生物对DOM的降解作用主要发生在土壤柱顶部0—0.50m段(尤其是0—0.25m段),而土壤对DOM的吸附作用则贯穿于整个土壤柱.三级处理水中HPO-A、HPO-N及TPI-A在土壤柱上部(特别是土壤柱0—0.50m)大量吸附而富集,表层生物对该组分相对较低的降解使得其在土壤柱0—0.25m段达到吸附饱和,并均于0.25m处达到最大;而TPI-N及HPI由于较易于生物降解,故其DOC在土壤柱顶部达到最高.三级处理水回灌过程中土壤DOM及其分级组分三氯甲烷生成势(THMFP)、紫外254nm处吸光度(UV-254)和比三氯甲烷生成势(STHMFP)均出现增长,其中HPO-A、HPO-N及TPI-A增幅相对较大;但各组分10%—30%的STHMFP增幅与其对应的THMFP及UV-254相比增幅较小.FT-IR结果表明三级处理水在SAT处理过程中改变了土壤DOM结构.

A laboratory-scale soil column had been set up to investigate the accumulation and transformation of dissolved organic matter （DOM） in the tertiary effluent during soil aquifer treatment （SAT）. Using XAD resins, extractable DOM in the soils was fractionated into five classes ： hydrophobic acid （ HPO-A）, hydrophobic neutral （ HPO-N）, transphilic acid （ TPI- A）, transphilic neutral （TPI-N）, and hydrophilic fraction （HPI）. The results indicated that high DOC removal efficiency of the SAT system was ascribed to both adsorption and biological degradation within the soil column, in which biological degradation mainly occurred within the top 0. 50m of surface soil and the adsorptions within the entire soil column. Overall, the highest DOC concentrations of HPO-A, TPI-A and HPO-N were observed at the depth of 0. 25m of the soil column, whereas that of the TPI-N and HPI were obtained at the top of the column. The results indicated that the adsorption of HPO-A, TPI-A and HPO-N by the top soil （0--0. 25m） was saturated as a result of the significant accumulation and the relatively lower bio-degradation ability, whilst the biodegradation mechanism of the top soil was effective for the removal of TPI-N and HPI. The trihalomethane formation potential （THMFP） and UV-254 of DOM fractions for the soil samples increased significantly during the SAT treatment, especially for HPO-A, TPI-A and TPI-N. Although 10%--30% increases of specific THMFP （STHMFP） were observed for the DOM fractions as a result of the SAT treatment, the increase of STHMFP was relatively lower as compared with the corresponding increase of THMFP and UV-254. In addition, the Fourier-transform infrared （FF-IR） results showed that the structure of soil DOM fractions was changed during the SAT treatment.