EFFECTS OF NATURAL ORGANIC MATTER ON CONTAMINANT REMOVAL BY SUPERFINE POWDERED ACTIVATED CARBON COUPLED WITH MICROFILTRATION MEMBRANES

Hybrid activated carbon/membrane systems are used in drinking water treatment for their significant capability of removing synthetic organic contaminants (SOCs) or taste-and-odor compounds along with particles. Preliminary data showed that decreasing the carbon particle size and creating superfine powdered activated carbon (S-PAC) removed phenanthrene and atrazine better than adsorbents with larger particle size in the presence of competitive adsorbents like natural organic matter (NOM). NOM is present in all natural water from degradation of terrestrial biomass which leaches from soil into a water source. Water treatment facilities target the removal of NOM because they are precursors to disinfection by-products formed as a result of chlorination. The thesis addresses the effects of NOM on contaminant removal through different treatment techniques. The effect of NOM in the coupled S-PAC/microfiltration membrane process was investigated further in the study. Atrazine and carbamazepine were applied in the experiments as the SOCs. Filtered Edisto River water (about 4 mg/L dissolved organic carbon (DOC)) was applied in bench-scale membrane tests. Results indicated that the S-PAC had a better removal efficiency of both atrazine and carbamazepine than powdered activated carbon (PAC). In the presence of NOM, the dominance of S-PAC removal efficiency was more apparent than in deionized water. Flux measurements in deionized water showed that S-PAC caused about 50 percent flux decline; however, when NOM was present the flux decreased much further. NOM proved to be the main culprit in membrane fouling, not S-PAC. Instead of increasing the pore blockage, S-PAC actually decreased the fouling compared to NOM alone. Thus, this evidence helped alleviate some initial worries about the small particles in S-PAC being detrimental to membrane systems. The results indicated that S-PAC may be applied in full-scale membrane plants and will perform better than conventional PAC. NOM concentration was varied and pH value was adjusted. Since the adsorption of contaminant decrease more rapidly on PAC when NOM concentration increases, the external sites and conformation on S-PAC may be more favorable for the SOCs. At low pH, carboxyl groups of NOM will be protonated that results in larger complexes that are easy to on adsorbents and harder to block the membrane