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Coagulation combined with ultrafiltration (UF) is an effective drinking water treatment process. However, inefficient removal of natural organic matter (NOM) and membrane fouling problems, especially those initiated by the adhesion of biopolymers, greatly restrict the practical application of the UF process. Here, we investigated a biologically enhanced coagulation–ultrafiltration (CUF) process treating samples of a natural surface water, which demonstrated a superior NOM removal and antifouling performance. The membrane flux (under 1.0 bar constant pressure) of the biologically enhanced CUF [using polyaluminum chloride (PACl)] process scheme was approximately 4.4 and 8.4 times higher than that of a conventional CUF and direct UF process, respectively, and PACl was found to perform better than AlCl3. Characterization of the NOM showed that the biological pretreatment combined with the coagulation process significantly contributed to the reduction of hydrophobicity, aromaticity, and molecular weight of the dissolved organics. Analyses of biopolymers showed that the combined process can remove over 99% of the biopolymers (represented by proteins and polysaccharides), which are considered to be the main cause of membrane fouling. Results of X-ray photoelectron spectroscopy and FTIR analyses further elucidated the transformation and reduction of biopolymers during the combined process. With respect to the disinfection byproduct formation potential (DBP-FP), the results showed that the conventional CUF process had a limited impact on the DBP-FP, while the biologically enhanced CUF process had a substantial impact consistent with meeting the current EPA DBP standards. Overall, this study has highlighted the potential advantages of using a biologically enhanced CUF process for producing higher quality drinking water with a simultaneous low membrane fouling propensity.

Interactions of purified Aldrich humic acid (PAHA) with the protein lysozyme (LSZ) are studied with dynamic light scattering and isothermal titration calorimetry by mixing LSZ and PAHA at various mass ratios. In solution LSZ is positive and PAHA is negative at the investigated pH values. Up to moderate KCl concentrations no aggregation occurs for LSZ and for PAHA aggregated particles with an average radius of 80 nm are present Complexation of PAHA with LSZ starts as soon as PAHA is added to LSZ and is followed by aggregation when the isoelectric-point (IEP) of the complexes is approached. Aggregation is gradual for 50 mM KCl and sudden for low KCl concentrations. The aggregate size is at its maximum at the IEP of the complexes. At mass ratios beyond the IEP the aggregates partially disaggregate. Positively charged complexes of PAHA and LSZ, formed in the absence of salt, strongly aggregate upon salt addition. Mixing of LSZ and PAHA is initially enthalpically driven. Near the IEP complexation and aggregation are due to hydrophobic forces (structural reorganization) and counterion release. The observations are relevant for other HA-protein systems when the protein is positively charged.

In this study, chitosan was successfully grafted onto the top surface of a bromomethylated poly(phenylene oxide) (BPPO) ultrafiltration membrane without pretreating the membrane at harsh conditions and/or using other cross linkers. Due to the grafting of polar groups of chitosari onto the membrane top surface, the hydrophilicity of the membrane top surface and the polar component of the total surface energy are improved compared to the pristine BPPO membrane. Theoretical calculation shows that the polar component of surface energy is a major contributor to the reduction in interfacial free energy of the membrane surface and interaction strength between foulants and membrane surface Therefore, the foulants adsorbed onto the top surface of chitosan/BPPO composite membranes are much easier to desorb during the cleanning process and as a result, a higher flux recovery was obtained compared to the pristine BPPO membrane, Moreover, due to the antibacterial nature of chitosan, such composite membranes show a better antibacterial property and the antibacterial rate was improved by 70% in comparion with pristine BPPO membrane.

Marine emissions of dimethyl sulfide (DMS) to the atmosphere play a fundamental role in the global sulfur (5) cycle and have important consequences for the Earth's radiative balance. In the ocean, DMS is mainly produced by marine algae and bacteria via cleavage of the precursor compound dimethylsulfoniopropionate (DMSP). Here, we studied the reaction between DMS and the strong oxidant hypobromous acid (HOBr), which is also produced by marine algae. Further, reactions between DMS oxidation products and HOBr were studied. The second-order rate constants were determined in competition kinetic experiments using sulfite as a competitor. In addition, we developed a new HPLC-ICP-MS/MS method to identify and quantify the oxidation products of DMS and related compounds. We found that HOBr reacts very fast with DMS to dimethyl sulfoxide (DMSO), with a second-order rate constant of 1.6 X 10(9) M-1 s(-1), while the subsequent oxidation of DMSO to dimethyl sulfone (DMSO2) is much slower (0.4 M-1 s(-1)). Concentrations of DMSP, DMSO2, and methanesulfonic acid (MSA) did not decrease when exposed to excess concentrations of HOBr, implying that these S-containing compounds are not or only slightly reactive toward HOBr. A quantitative comparison of known DMS sinks shows that HOBr may be an important, hitherto neglected sink for marine DMS that needs to be considered in ocean-atmosphere chemistry models.