Drinking water distribution system (DWDS) necessitates sustainable, durable, and nonpolluting materials for enhanced water quality of the end-users. Stainless steel (SS) is gaining momentum in DWDS, particularly in end-point distribution facilities such as secondary water storage tanks, pumps, and household water pipes due to its high chemical stability and robust mechanical strength. However, SS’s susceptibility to corrosion in given defect areas is of great concern, and there is a lack of fundamental insight on SS corrosion from an interdisciplinary perspective of materials science and environmental science. Herein, the SS corrosion in the DWDS environment is critically assessed, encompassing the basic science of SS corrosion occurrence, its cascading influence on water quality, and anticorrosion strategies. Electrochemical corrosion mechanisms of SS corrosion are specifically differentiated, particularly those initiated at given SS defects, including welding points, grain boundaries, and areas with tensile stress. It is shown that SS corrosion influences water quality by destroying the Cr-rich passive film and releasing Cr, Fe, and other heavy metals from the corrosion scale. The critical factors influencing SS corrosion are subsequently identified, namely, SS elemental composition, SS manufacturing process (e.g., heat-affected zone, stress concentration), and water condition in DWDS (e.g., chlorine, oxygen, sulfate, hydraulic shock, pH). Corresponding strategies are elucidated to facilitate the anticorrosion resistance of SS and improve the water quality, including SS alloying enhancement, SS dispersion strengthening, SS surface treatment/modification, and tuning water condition in DWDS. Overall, this review highlights the importance of controlling SS corrosion, which could provide guidance on the rational design and utilization of SS in DWDS to enhance the ultimate water quality of the end-users and the overall resilience of the DWDS.

The extracellular polymeric substances (EPS) from activated sludge played significant roles in the removal of nanoparticles from wastewater. A series of batch experiments were carried out to determine the adsorption mechanism of three nano-Ag by activated sludge, as well as the contributions of EPS fractions including dissolved EPS (DEPS), loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS). The results demonstrated that the adsorption of nano-Ag by sludge biomass agreed with pseudo-second-order kinetic reaction model and Freundlich isotherm model. About 26.0-41.2% of nano-Ag was trapped by the bound EPS (BEPS) matrix of activated sludge (especially LB-EPS) and 42.5-52.6% of them was adsorbed onto the inner cells after the adsorption. Moreover, the interaction energy contributions of EPS fractions followed the order of EDE > 0 > ETB > ELB, suggesting DEPS in wastewater went against the removal of nano-Ag due to steric repulsion while LB-EPS and TB-EPS were positive to nano-Ag adsorption by modifying biomass surface and providing extensive binding sites. Besides, EPS fractions played significant roles in the adsorption of nano-Ag with low initial concentrations but had limited effect at high concentrations. Overall, this study investigated the effect of EPS fractions on the adsorption behaviors of nano-Ag by activated sludge biomass, which is meaningful to understand the removal mechanism of nanoparticles in sewage and the potential role of EPS fractions.

Dissolved black carbon (DBC), widely found in soil and water environments is likely to affect the transport of nanoplastics in aquatic environments. The aggregation and deposition behaviors of fresh and aged polystyrene nanoplastics (PSs) with and without DBC in NaCl solution were investigated by time-resolved dynamic light scattering (DLS) and quartz crystal microbalance with dissipation monitoring equipment (QCM-D) techniques. The results suggest that DBC can screen the surface charges of PSs by interacting with PSs through hydrogen bonding, hydrophobic interactions and π-π interactions, although they were negatively charged. DBC promoted the aggregation of PSs under relatively low ionic strengths, and it minimally affected the stability of PSs under high ionic strength. Deposition experiments showed that both DBC in salt solution and DBC adsorption on silica surface facilitated the deposition of fresh PSs while HA inhibited both deposition processes. After aging, PSs were more stable, and the effects of DBC and HA were weakened. This study investigated the influence mechanism of DBC on the aggregation and deposition behaviors, which provides new insights into the stability and transport of PSs in complex aquatic environments.

A novel advanced oxidation process, combined zero-valent iron and sulfite (Fe⁰/sulfite) system containing oxygen, was firstly developed to efficiently degrade organic pollutants at weak acidic and neutral conditions by selecting X-3B as a target compound. The removal of X-3B was attributed to the formed reactive radicals, such as SO₄ ^-, SO₅ ^- and HO^[rad], in the Fe⁰/sulfite system, and SO₄ ^- was evidenced as the principal reactive species. The quite low removal efficiency of X-3B (less than 5%) after reaction for 90 min with purging nitrogen gas suggests oxygen to be an essential factor for producing SO₄ ^- in the system. Optimal dosages of Fe⁰ and sulfite were suggested to be 0.5 mM and 1.0 mM, respectively, in the system as both the two chemicals would scavenge the reactive radicals at overdosing. The presence of 2 mM bicarbonate significantly inhibited the removal of X-3B from 74.1% to 37.5% in the system. Halide ions inhibited the removal of X-3B following a trend that Cl⁻ <Br⁻ <I⁻. HSO₃ ⁻, being effective in complexion of Fe(II) and transferring Fe(III) to Fe(II), is the main species during pHs 4–6, which results in the good reuse of Fe⁰ and the highest removal efficiency of X-3B at weak acidic condition. Fe⁰/sulfite system was also evidenced to be effective in the treatment of actual textile effluents along with improving biodegradability, and the removal of nitrobenzene, methylparaben, bisphenol A, imipramine and amitriptyline. Overall, this study provided a cheap and easy operational advanced oxidation process in treatment of aqueous organic pollutants.

Cyanobacteria blooms in source waters have become a worldwide issue for drinking water production. UV-activated persulfate (UV/PS) technology was firstly applied to remove cultivated Microcystis aeruginosa (M. aeruginosa) in bench scale. The presence of persulfate significantly enhanced both cytoclasis and algal organic matter mineralization compared with UV-C inactivation alone. Around 98.2% of algal cells were removed after UV/PS process treatment for 2 h at a dosage of PS being 1500 mg/L (approximately 6 mM). Both sulfate and hydroxyl radicals were proven to contribute to the removal of algae and the loss of cell integrity. The cultivated M. aeruginosa in death growth phase were found to be more vulnerable to UV/PS treatment than those growing in log phase, thus a significant lower dosage of PS is needed to achieve the desired removal efficiency. This study suggested a novel application of UV/PS process in the removal of algae in source waters due to the high degradation efficiency of both algal cells and their derived organic matter.