Abstract
The removal of natural organic matter (NOM) from surface water sources was evaluated by a pilot ultrafiltration plant through 3 different treatment processes: UF, PAC/UF and PAC/C-S/UF. For UF, the ultrafiltration plant was used as the only treatment. For PAC/UF, tests were performed with powdered activated carbon (PAC) as pre-treatment to the ultrafiltration membrane. For the PAC/C-S/UF hybrid treatment process, adsorption with PAC and coagulation-sedimentation with aluminum sulphate as a coagulant was used as pre-treatment. The results indicated that the best hybrid treatment process was PAC/C-S/UF, since it maintained a stable transmembrane pressure (TMP) of around 0.5 bar in the operating time, while in the this process the flow remained constant at about 227 L/(m2h). In addition, with this process, the highest removal efficiencies were obtained for the NOM parameters evaluated. Coagulation pre-treatment improved the removal of NOM in comparison with PAC and UF as the only treatment. The results showed that both hydrophobic and hydrophilic organic compounds could be removed by the action of the coagulant. When further comparing the increased removal rates of the hydrophobic material (HoM) and hydrophilic material (HiM) fractions, it was observed that the hydrophobic organic chromophores could be removed by coagulation more easily than the hydrophilic organic chromophore compounds. The molecular weight distribution (MWD) was evaluated, indicating that the PAC/C-S/UF treatment successfully removed medium-high molecular weight (MW) compounds (> 1701 Da), but the removal efficiency of medium-low MW compounds (≤ 1701 Da) began to decrease as the compounds had lower MW.DOI: http://dx.doi.org/10.5755/j01.erem.72.3.12906
Highlights
Natural water sources mostly contain natural organic matter (NOM) and organic matter from wastewater
The results showed that the organic matter removal performance improved substantially in the powdered activated carbon (PAC)/UF and PAC/C-S/UF processes compared with UF without pre-treatment
The results of the PAC/UF and UF processes had similar low Dissolved organic carbon (DOC) removal efficiencies of about 13%, indicating that the dissolved organic material present in the raw water passes through the UF membrane pores
Summary
Natural water sources mostly contain natural organic matter (NOM) and organic matter from wastewater. The nature of the organic compounds of NOM may vary with climatic changes like heavy rains, floods and droughts (Sharp et al, 2006). Floods and droughts have the largest impact on the availability and quality of water. These climatic changes are some of the reasons for the increase in the total amount of NOM in the water (Evans et al, 2005). NOM interferes with the removal of many pollutants, including metals. It is responsible for clogging membranes, contributes to corrosion and acts as a substrate for bacterial growth in distribution systems. It is the largest contributor to the formation of disinfection by-products (DBPs)
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