Removal Of Dissolved Organic Matter In Secondary Effluent During Slag Modified Sat

Inadequate water supply and water quality deterioration represent serious contemporary concerns for municipalities, industries, agriculture, and the envi-ronment in many parts of the world. As a wastewater treatment system, Soil aquifer treatment (SAT) process has a great advantage. Dissolved organic matter (DOM) is the important precursors of the disinfection by-products in chlorination. In recent years, it is widespread concerned by researchers at home and abroad. Due to the complexity of the structure of DOM, it is difficult to analyse DOM by conventional methods. In this study, XAD resin is used to separate different components of DOM. According to the different adsorption characteristics, DOM is divided into five different substances: Hydrophobic acids (HPO-A), Hydrophobic neutral (HPO-N), Transphilic acids (TPI-A), Transphilic neutral (TPI-N), Hydrophilic fraction (HPI). The adsorption capacity of SAT system for hydrophobic and high molecular weight material is not good enough. Coal slag was used to improve the efficiency of SAT system. Dissolved organic carbon (DOC), UV absorbance at 254 nm (UV-254), trihalomethane formation potential (THMFP), trihalomethane formation activity (STHMFP), the excitation-emission fluorescence spectra and IR spectra were used to investigate the removal of DOM in the slag modified SAT system. Besides, health risk assessment of the recycled water was carried out. In order to compare with the slag modified SAT system, activated carbon (GAC) adsorption system was combined with the SAT system (GAC+SAT), in which the removal of DOM was investigated.GAC adsorption experiment results showed that GAC played an important role in the removal of large molecules materials. The UV-254 removal rate of HPO-A fraction by GAC was greater than the SAT system. GAC system combined with the traditional SAT system had excellent removal rate to HPI fraction, proved that HPI components were more likely to be biodegradabled. The preferential adsorption of macromolecules by GAC and biological degrada-tion of microorganism in soil were the the reason of high efficiency of GAC+SAT system.Slag adsorption experiments showed that particle size was closely related with the removal of DOM, acidic conditions favored the adsorption reaction of slag and the temperature had a positive effect on the adsorption of DOM. The DOC, UV-254 of DOM was substantially removed by slag modified SAT system, especially the HPO-A fraction. Slag modified SAT system also had good treatment effect on HPI fraction. HPO-A and HPI fractions were the major contribution components of aromatic material in Secondary effluent. Therefore, the effective removal of HPI and HPO-A fractions was important to the control of water quality. The efficient removal of THMFP proved that utilize slag to modify SAT system is meaningful. The EEM spectra and IR spectra showed that the slag did affect the activity of soil microorganism, but not very strong. Maintain soil layer in the slag modified SAT system was necessary. The HPI removal by slag modified SAT system was not as good as GAC + SAT system. To some extent, The slag could affect the microorganism in soil columns. Keep the upper 25 cm of the soil layer in the modified system to maintain a good biodegradability was necessary.The health risk assessment of slag modified SAT effluent revealed that the cancer risk and non-cancer risk of the effluent were in an acceptable range for potable reuse. For non-potable reuse, the cancer risk and non-cancer risk were also lower than the control values. And cancer risk was much higher than non-cancer risk.