Ceramic membrane fouling caused by recycling biological activated carbon filter backwash water: Effective backwash with ozone micro-nano bubbles.

The widespread use of ceramic membranes in wastewater recycling is still hampered by membrane fouling problems. Frequent chemical cleaning increases operating and maintenance costs. This work proposes ozone micro-nano-bubble (O-MNB) backwash as a new backwashing method to control the ceramic membrane fouling.

Adsorption of perfluoroalkyl acids on granular activated carbon supported chitosan: Role of nanobubbles.

The safety threat posed by Perfluoroalkyl acids (PFAAs) in drinking water is a growing concern. In this study, we loaded chitosan (CS) on granular activated carbon (GAC) to adsorb PFAAs, and we explored the role of nanobubbles in the adsorption process through experiments and density functional theory (DFT) calculations. Compared with GAC, we found that the use of the composite adsorbent (CS/GAC) enhanced the removal rate of perfluorooctanoic acid by 136% with the assistance of nanobubbles.

Effects of pipe materials on the characteristic recognition, disinfection byproduct formation, and toxicity risk of pipe wall biofilms during chlorination in water supply pipelines.

There are growing concerns over the contributions of biofilms to disinfection byproduct (DBP) formation in engineered water systems (EWSs). Three kinds of water supply pipes, ductile iron (DI), cement-lined stainless steel (SS) and polyethylene (PE) pipes, were selected for the experiment conducted in this study. Based on test results, the three pipe biofilms showed relatively obvious differences in growth, morphological characteristics, organic components and bacterial diversity.

Elevated risk of haloacetonitrile formation during post-chlorination when applying sulfite/UV advanced reduction technology to eliminate bromate.

The formation of haloacetonitriles (HANs) during chlorination after sulfite/ultraviolet (UV) treatment of bromate (BrO) in the presence of amino acids (AAs) was investigated. During sulfite/UV treatment, the primary species hydrated electrons (e) and hydrogen atom radicals (H) dominated the reduction of BrO to bromide (Br), whereas the sulfite anion radicals (SO) and H degraded AAs to produce the intermediates HN=C(CH)-COOH, CH-CH=NH, and CH-C≡N via α‑hydrogen abstraction and NH-hydrogen abstraction mechanisms. During post-chlorination, Br was converted to HBrO/BrO-, and the HN=C(CH)-COOH, CH-CH=NH, and CH-C≡N groups featured higher bromine utilization factor (BUF) and chlorine utilization factor (CUF) values than AAs, enhancing the formation of dibromoacetonitrile (DBAN) and dichloroacetonitrile (DCAN).

UV/Chlorination of sulfamethazine (SMZ) and other prescription drugs: kinetics, transformation products and insights into the combined toxicological assessment.

The UV/chlorination of three prescription drugs, sulfamethazine (SMZ), gemfibrozil (GEM) and antipyrine (ANT) were studied by the investigation of kinetics, transformation products and combined toxicological assessment. The degradation followed pseudo-first-order kinetics, with half-lives significantly affected by chlorine dosage, without being greatly influenced by pH value and bromide concentration. Based on the Frontier Orbital Theory, the structures of products by hydroxylation or chlorine substitution were proposed and the transformation pathways were introduced, with two, two and one never-before-reported products identified for SMZ, GEM and ANT, respectively.