Pure nano-Al13 and aggregates at various concentrations were prepared to examine the particle size effect of coagulation with inorganic polymer flocculant.The property and stability of various species formed were characterized using Infrared,27Al-NMR,photo correlation spectroscopy(PCS),and Ferron assay.Results showed that concentration and temperature exhibited different roles on the stability of Al13.The quantity of Alb species analyzed by ferron assay in the initial aging period corresponded well with that of Al13,which has been confirmed in a dimension range of 1-2 nm by PCS.Al13 solutions at high concentrations(0.5-2.11 mol/L) were observed to undergo further aggregation with aging.The aggregates with a wide particle size distribution would contribute to the disappeared/decreased Al13 basis on the 27Al-NMR spectrum,whereas a part of Al13 would still remain as Alb.At low concentrations,Al13 solution was quite stable at normal temperature,but lost its stability quickly when heating to 90°C.
High performance size exclusion chromatography (HPSEC) is used in water quality research primarily to determine the molecular weight distribution of the dissolved organic matter (DOM), but by applying peak fitting to the chromatogram, this technique can also be used as a tool to model and predict DOM removal. Six low specific UV absorbance (SUVA) source waters were treated using coagulation with alum and both the source and treated water samples were analysed using HPSEC. By comparing the molecular weight profiles of the source and treated waters, it was established that several DOM components were not effectively removed by alum coagulation even after high dosage alum treatment. A peak-fitting technique was applied based on the concept of linking the character (molecular weight profile) of the recalcitrant organics in the treated water with those of the source water. This was then applied to predict DOM treatability by determining the areas of the peaks which were assigned to removable organics from the source water molecular weight profile after peak fitting, and this technique quantified the removable and non-removable organics. The prediction was compared with the actual dissolved organic carbon (DOC) removal determined from jar testing and showed good agreement, with variance between 2% and 10%. This confirmed that this prediction approach, which was originally developed for high SUVA waters, can also be applied successfully to predict DOC removal in low SUVA waters.
Linan XingRolando FabrisW.K.ChowJohn van LeeuwenMary DrikasDongsheng Wang
Correlations between raw water characteristics and pH after enhanced coagulation to maximize dissolved organic matter(DOM) removal using four typical coagulants(FeCl3,Al2(SO4)3,polyaluminum chloride(PACl) and high performance polyaluminum chloride(HPAC)) without pH control were investigated.These correlations were analyzed on the basis of the raw water quality and the chemical and physical fractionations of DOM of thirteen Chinese source waters over three seasons.It was found that the final pH after enhanced coagulation for each of the four coagulants was in?uenced by the content of removable DOM(i.e.hydrophobic and higher apparent molecular weight(AMW) DOM),the alkalinity and the initial pH of raw water.A set of feed-forward semi-empirical models relating the final pH after enhanced coagulation for each of the four coagulants with the raw water characteristics were developed and optimized based on correlation analysis.The established models were preliminarily validated for prediction purposes,and it was found that the deviation between the predicted data and actual data was low.This result demonstrated the potential for the application of these models in practical operation of drinking water treatment plants.
Jiankun XieDongsheng WangJohn van LeeuwenYanmei ZhaoLinan XingChristopher W. K. Chow
Eight typical drinking water supplies in China were selected in this study.Both source and tap water were used to investigate the occurrence of chlorinated disinfection byproducts(DBPs),and seasonal variation in the concentrations of trihalomethanes(THMs) of seven water sources was compared.The results showed that the pollution level for source water in China,as shown by DBP formation potential,was low.The most encountered DBPs were chloroform,dichloroacetic acid,trichloroacetic acid,and chlorodibromoacetic acid.The concentration of every THMs and haloacetic acid(HAA) compound was under the limit of standards for drinking water quality.The highest total THMs concentrations were detected in spring.
Wenbo LiuYanmei ZhaoChristopher WK ChowDongsheng Wang
Raw water from the Songhua River was treated by four types of coagulants, ferric chloride(FeCl3), aluminum sulfate(Al2(SO4)3),polyaluminum chloride(PACl) and composite polyaluminum(HPAC), in order to remove dissolved organic matter(DOM). Considering the disinfection byproduct(DBP) precursor treatability, DOM was divided into five chemical fractions based on resin adsorption.Trihalomethane formation potential(THMFP) and haloacetic acid formation potential(HAAFP) were measured for each fraction. The results showed that hydrophobic acids(HoA), hydrophilic matter(HiM) and hydrophobic neutral(HoN) were the dominant fractions.Although both HoN and HoA were the main THM precursors, the contribution for THMFP changed after coagulation. Additionally,HoA and HiM were the main HAA precursors, while the contribution of HoN to HAAFP significantly increased after coagulation.HoM was more easily removed than HiM, no matter which coagulant was used, especially under enhanced coagulation conditions.DOC removal was highest for enhanced coagulation using FeCl3 while DBPFP was lowest using PACl. This could indicate that not all DOC fractions contained the precursors of DBPs. Reduction of THMFP and HAAFP by PACl under enhanced coagulation could reach51% and 59% respectively.
Yanmei ZhaoFeng XiaoDongsheng WangMingquan YanZhe Bi
