School of Sustainable Engineering and the Built Environment, Arizona State University , Tempe, Arizona 85287, United States.
Environ Sci Technol. 2014 Jul 1;48(13):7349-56. doi: 10.1021/es500435e. Epub 2014 Jun 18.
Membrane fouling is a major challenge in water and wastewater treatment. Recent observations that ozone mitigates membrane fouling during filtration of secondary effluent prompted this study into the impact of preozonation on membrane fouling caused by biogenic colloids. The focus of this study was on liposomes, synthetic vesicles composed of (phospho)lipid bilayers, which are representative of the diverse cellular vesicles present in all biologically impacted waters. The overarching hypothesis was that these biologically produced, nonrigid or "soft" colloids (e.g., vesicles) present in wastewater give rise to unique fouling behavior that can be mitigated by preozonation. Using dead-end ultrafiltration (UF) and batch ozonation tests, the key findings of this study were (1) liposomes fouled UF membranes faster (4-13 times membrane cake resistance (RC) per mgC filtered) than polysaccharides, fatty acids, and NOM on a DOC-normalized basis; (2) based on the estimated carbon distribution of secondary effluent, liposome-like biogenic nanomaterials could be responsible for 20-60% of fouling during UF; and (3) preozonation reduces liposomal fouling during UF, likely due to the disruption of the liposome structure through cleavage of the fatty acid tails at carbon-carbon double bonds.
膜污染是水处理和废水处理的一个主要挑战。最近的观察表明，臭氧在过滤二级出水时可以减轻膜污染，这促使人们研究预臭氧化对生物胶体引起的膜污染的影响。本研究的重点是脂质体，由（磷酸）脂质双层组成的合成囊泡，它们是所有受生物影响的水中存在的各种细胞囊泡的代表。主要假设是，这些生物产生的、非刚性或“软”胶体（例如囊泡）在废水中存在，会导致独特的污染行为，可以通过预臭氧化来减轻。通过死端超滤（UF）和分批臭氧化试验，本研究的主要发现是：(1)与多糖、脂肪酸和 NOM 相比，脂质体在 DOC 归一化基础上更快地污染 UF 膜（每过滤 1mgC 的膜饼阻力 (RC) 增加 4-13 倍）；(2)根据二级出水的估计碳分布，类脂体状生物纳米材料可能占 UF 过程中 20-60%的污染；(3)预臭氧化可减少 UF 过程中的脂质体污染，这可能是由于脂肪酸尾部在碳-碳双键处的断裂而破坏了脂质体结构。
