Service-lines as major contributor to water quality deterioration at customer ends

Atomistic understanding of Ti3C2 MXene membrane performance for separation of nitrate ions from aqueous solutions

Water desalination, which is a reliable method for providing drinking water and a suitable solution, as well as the membrane filtration method in wastewater treatment, has increased significantly in recent years. In this research, the separation of nitrite and nitrate ions from aqueous solutions was done using the MXene membrane of the Ti3C2 type using molecular dynamics simulation. In this study, various parameters, such as pore size MXene structure, characteristics of cavities, applied pressure, and flux were investigated. To investigate the removal of toxic pollutants from water, water flux, potential mean force, distribution of water molecules, and density were investigated. The results showed that the amount of penetration through the membrane increased with the increase in pressure. It was observed that by applying pressure to the system, the number of water molecules accumulated in front of the membrane decreases because they quickly pass through the membrane, which indicates the positive effect of increasing pressure on the separation rate of molecules. The permeability of this membrane was several times higher than the existing membranes in the industry. So that Mexene membranes, which consist of at least two layers, can repel ions with 100 % success.

Protecting against micropollutants in water storage tanks using in-situ TiO2 coated quartz optical fibers

Photocatalyst-coated optical fibers (P-OFs) using UV-A LEDs offer a highly promising solution for the degradation of micropollutants within municipal, reuse, industrial or home distribution systems, by integrating P-OFs into water storage tanks. P-OFs have photocatalysts attached to bundles of optical fibers, enabling their direct deployment within tanks. This eliminates the necessity for photocatalyst slurries, which would require additional membrane or separation systems. However, a current limitation of P-OFs is light management, specifically light oversaturation of the coated photocatalysts and short light transmission distances along fibers. This study overcomes this limitation and reveals strategies to improve the light dissipation uniformity along P-OFs, and demonstrates the performance of P-OFs on degrading a model micropollutant, carbamazepine (CBZ). Key tunable variables of fibers and light emission conditions, including photocatalyst coating patchiness (p), minimum light incident angles (θm), radiant flux launched to fibers (Φi), and fiber diameters (D), were modeled to establish their relationships with the light dissipation uniformity in TiO2-coated quartz optical fibers (TiO2-QOFs). We then validated modeling insights by conducting experiments to examine how these variables influence the generation of evanescent waves which are localized energy on fiber surfaces, leading to either photocatalyst activation or the recapture of unused light back into fibers. We observed substantial enhancements in evanescent waves generation by decreasing p and increasing θm, resulting in uniform light dissipation which reduces light oversaturation and improves light transmission distances. Moreover, these optimizations led to a remarkable three-fold improvement in CBZ degradation rates and a 65% reduction in energy consumption. Such improvement substantially reduces the capital and operational cost and enhances practicality of energy-efficient photocatalysis without additional chemical oxidants for micropollutant degradation in water storage tanks.

Bacterial communities of planktonic bacteria and mature biofilm in service lines and premise plumbing of a Megacity: Composition, Diversity, and influencing factors

Although simulated studies have provided valuable knowledge regarding the communities of planktonic bacteria and biofilms, the lack of systematic field studies have hampered the understanding of microbiology in real-world service lines and premise plumbing. In this study, the bacterial communities of water and biofilm were explored, with a special focus on the lifetime development of biofilm communities and their key influencing factors. The 16S rRNA gene sequencing results showed that both the planktonic bacteria and biofilm were dominated by Proteobacteria. Among the 15,084 observed amplicon sequence variants (ASVs), the 33 core ASVs covered 72.8 %, while the 12 shared core ASVs accounted for 62.2 % of the total sequences. Remarkably, it was found that the species richness and diversity of biofilm communities correlated with pipe age. The relative abundance of ASV2 (f_Sphingomonadaceae) was lower for pipe ages 40-50 years (7.9 %) than for pipe ages 10-20 years (59.3 %), while the relative abundance of ASV10 (f_Hyphomonadaceae) was higher for pipe ages 40-50 years (19.5 %) than its presence at pipe ages 20-30 years (1.9 %). The community of the premise plumbing biofilm had significantly higher species richness and diversity than that of the service line, while the steel-plastics composite pipe interior lined with polyethylene (S-PE) harbored significantly more diverse biofilm than the galvanized steel pipes (S-Zn). Interestingly, S-PE was enriched with ASV27 (g_Mycobacterium), while S-Zn pipes were enriched with ASV13 (g_Pseudomonas). Moreover, the network analysis showed that five rare ASVs, not core ASVs, were keystone members in biofilm communities, indicating the importance of rare members in the function and stability of biofilm communities. This manuscript provides novel insights into real-world service lines and premise plumbing microbiology, regarding lifetime dynamics (pipe age 10-50 years), and the influences of pipe types (premise plumbing vs. service line) and pipe materials (S-Zn vs. S-PE).