Synergistic effects of trace sulfadiazine and corrosion scales on disinfection by-product formation in bulk water of cast iron pipe.

The effects of trace sulfadiazine (SDZ) and cast-iron corrosion scales on the disinfection by-product (DBP) formation in drinking water distribution systems (DWDSs) were investigated. The results show that under the synergistic effect of trace SDZ (10 µg/L) and magnetite (Fe3O4), higher DBP concentration occurred in the bulk water with the transmission and distribution of the drinking water. Microbial metabolism-related substances, one of the important DBP precursors, increased under the SDZ/Fe3O4 condition. It was found that Fe3O4 induced a faster microbial extracellular electron transport (EET) pathway, resulting in a higher microbial regrowth activity. On the other hand, the rate of chlorine consumption was quite high, and the enhanced microbial EET based on Fe3O4 eliminated the need for microorganisms to secrete excessive extracellular polymeric substances (EPS). More importantly, EPS could be continuously secreted due to the higher microbial activity. Finally, high reactivity between EPS and chlorine disinfectant resulted in the continuous formation of DBPs, higher chlorine consumption, and lower EPS content. Therefore, more attention should be paid to the trace antibiotics polluted water sources and cast-iron corrosion scale composition in the future. This study reveals the synergistic effects of trace antibiotics and corrosion scales on the DBP formation in DWDSs, which has important theoretical significance for the DBP control of tap water.

Self-purification of actual wastewater via microbial-synergy driving of catalyst-surface microelectronic field: A pilot-scale study.

High energy consumption is impedimental for eliminating refractory organics in wastewater by current technologies. Herein, we develop an efficient self-purification process for actual non-biodegradable dyeing wastewater at pilot scale, using N-doped graphene-like (CN) complexed Cu-Al2O3 supported Al2O3 ceramics (HCLL-S8-M) fixed-bed reactor without additional input. About 36% chemical oxygen demand removal was achieved within 20 min empty bed retention time and maintained stability for almost one year. The HCLL-S8-M structure feature and its interface on microbial community structure, functions, and metabolic pathways were analyzed by density-functional theory calculation, X-ray photoelectron spectroscopy, multiomics analysis of metagenome, macrotranscriptome and macroproteome. On the surface of HCLL-S8-M, a strong microelectronic field (MEF) was formed by the electron-rich/poor area due to Cu-π interaction from the complexation between phenolic hydroxy of CN and Cu species, driving the electrons of the adsorbed dye pollutants to the microorganisms through extracellular polymeric substance and the direct transfer of extracellular electrons, causing their degradation into CO2 and intermediates, which was degraded partly via intracellular metabolism. The lower energy feeding for the microbiome produced less adenosine triphosphate, resulting in little sludge throughout reaction. The MEF from electronic polarization is greatly potential to develop low-energy wastewater treatment technology.

Trace Iron as single-electron shuttle for interdependent activation of peroxydisulfate and HSO3-/O2 enables accelerated generation of radicals.

The generation of reactive oxygen species generally requires initiators in various environmental remediation processes, which necessitates high dosage of activators and downstream treatment for eliminating the accumulation of deactivated catalysts. Herein, a coupled process was constructed using trace iron for simultaneously activating HSO3-/O2 system and peroxydisulfate (PDS) oxidation system, where the iron ions (2 mg/L) transferred single-electron from the former system to the latter due to the moderate redox potential (Fe3+/Fe2+, +0.77 V) between the potentials of SO3·-/HSO3- (+0.63 V) and PDS/SO4·- (+2.01 V). Hence, the phenol degradation quickly occurred at a first-order kinetic constant of k1=0.223 min-1 due to the accelerated generation of sulfate radical (SO4·-) and hydroxyl radical (·OH) in the process. The k1 value was almost 6-fold of that in the deoxygenated condition (0.040 min-1). Density function theory reveals that the single electron shuttle spatially separates the electron-donating activation of HSO3- and electron-accepting activation of PDS, while avoiding the "mutual-annihilation" of HSO3- and S2O82- via direct two-electron transfer. Finally, utilizing the in-situ generated electron-shuttle (dissolved iron from cast iron pipe), the HSO3-/PDS reagent could efficiently inactivate the chlorine-resistant pathogens and inhibits biofilm regrowth inside the distribution systems at regular intervals or infectious disease outbreak in a neighborhood.

[Synergistic Control of Nitrogenous Disinfection By-products and Opportunistic Pathogens in Drinking Water by Iron-Modified Quartz Sand Filtration].

The main function of quartz sand in drinking water treatment has been to remove turbidity, while the microbial effect of its solid-liquid interface has been ignored. In order to solve the limitations of control of the disinfection by-products (DBPs) and opportunistic pathogens (OPs) in common quartz sand, the common quartz sand was modified to iron sand. The maximum DBPs formation potential of typical nitrogenous disinfection by-products (N-DBPs) and carbonaceous disinfection by-products was determined using gas chromatography-ECD. Compared with those of sand, the inhibition effects of halonitromethanes, haloacetamides, and haloacetonitriles by the Fe-sand were increased by 51.51%, 43.66%, and 90.6%, respectively. In addition, the gene copy numbers of Hartmanella vermiformis, Legionella spp., Mycobacterium spp., M. avium, and Naegleria spp. were detected via quantitative qPCR, and the results indicated that the Fe-sand did have a similar significant inhibitory effect on OPs. The Fe-sand had limited ability to enhance the removal of NOM. However, the Fe-sand effectively inhibited the continuous contribution of biofilm to N-DBPs and opportunistic pathogens. The distribution of biofilms on the surface of the Fe-sand filter media was uniform, not likely to fall off, and more stable; however, the suspended biofilms in the effluent were more difficult to aggregate. In addition, the α-helix of the secondary structure in the extracellular protein disappeared in the effluent of the Fe-sand. Therefore, the whole suspended biofilm was easily penetrated by chlorine. The Fe-sand solid-liquid interface did significantly change the microbial community structure and suspended biofilm characteristics, which provides a new concept to ensure the safety of drinking water quality and plays a good theoretical supporting role in the improvement and transformation of the existing process in drinking water treatment plants.

Contribution of extracellular polymeric substances and microbial community on the safety of drinking water quality: By mean of Cu/activated carbon biofiltration.

Change in water quality was investigated with laboratory-scale ozone-biological activated carbon filters using copper-modified granular activated carbon (Cu/GAC) and unmodified granular activated carbon (GAC). In the first seven days of the experimental period, Cu/GAC removed organic matter more efficiently owing to its enhanced adsorption capacity. As the running time increased, the amount of disinfection by-products (DBPs), dissolved organic carbon, and extracellular polymeric substances (EPS) increased sharply in the effluent of the Cu/GAC filter (CCW). More importantly, the EPS suspended in the CCW exhibited weaker flocculating efficiency and hydrophobicity, causing more active chemical reactions between chlorine and EPS substances. The copper species significantly limited the microbial biomass (0.01 nmol/L adenosine triphosphate) but stimulated the secretion of significant amounts of EPS by microorganisms for self-protection. Furthermore, the microbial community in the bulk water was successfully shaped by Cu/GAC, resulting in a continuous supply of EPS-derived DBP precursors and a sharp rise in chlorine consumption in the downstream drinking water distribution. Therefore, use of modified GAC materials, similar to Cu/GAC, as carrier materials for biological activated carbon (BAC) treatment remains controversial, despite enhanced pollutant adsorption capacity. This is the first study to reveal the mechanism of BAC-modified materials for water quality stability. The study potentially contributes to a comprehensive understanding of the effects of biofilm transformation and microbial community succession on drinking water quality. These results showed that tap water safety risks could be reduced by improving BAC pretreatment in drinking water treatment plants.

Effects of cast iron pipe corrosion on nitrogenous disinfection by-products formation in drinking water distribution systems via interaction among iron particles, biofilms, and chlorine.

The effects of cast iron pipe corrosion on nitrogenous disinfection by-products formation (N-DBPs) in drinking water distribution systems (DWDSs) were investigated. The results verified that in the effluent of corroded DWDSs simulated by annular reactors with corroded cast iron coupons, typical N-DBPs, including haloacetamides, halonitromethanes, and haloacetonitriles, increased significantly compared with the influent of DWDSs. In addition, more dissolved organic carbon, adenosine triphosphate, and iron particles were simultaneously detected in the bulk water of corroded DWDSs, thereby indicating that abundant iron particles acted as a "protective umbrella" for microorganisms. Under the condition of corroded DWDSs, the extracellular polymeric substances gradually exhibited distinct characteristics, including a higher content and lower flocculation efficiency, thereby resulting in a large supply of N-DBPs precursors. Corroded cast iron pipes, equivalent to a unique microbial interface, induced completely distinct microbial community structures and metabolic functions in DWDSs, thereby enhancing the formation of N-DBPs. This is the first study to successfully reveal the interactions among iron particles, biofilms, and chlorine in DWDSs, which may help to fully understand the biofilm transformation and microbial community succession in DWDSs.

A human cell panel for evaluating safe application of nano-ZrO2/polymer composite in water remediation.

Nanomaterials, such as ZrO2 nanoparticles (ZrO2 NPs), are very effective in water remediation. However, the safety issues related to nanoparticle release and toxicity to humans remain to be resolved. Here we evaluated the cytotoxicity of ZrO2 NPs and their adducts with pollutants using a human cell panel containing stomach, intestine, liver and kidney cells. We found that different pollutants or ZrO2NP/pollutant adducts targeted cells from different organs, suggesting the necessity of a cell panel to model oral exposures. The cooperation of ZrO2 NPs and pollutants was quite complex, consisting of synergistic, antagonistic, or additive effects. For example, ZrO2 NPs enhanced the cytotoxicity of Pb2+ in GES-1 cells and of Pb2+, Cd2+ in FHC cells, while alleviating the toxicity of Pb2+ and As (III) in HepG2 and Hek293 cells. Our results also indicated that even concentrations of pollutants that meet the national standard, the ZrO2 NPs concentration should be kept below 17 µg/mL to avoid ZrO2 NP/pollutant adduct synergistic toxicity.

Characterization of bacterial community and iron corrosion in drinking water distribution systems with O3-biological activated carbon treatment.

Bacterial community structure and iron corrosion were investigated for simulated drinking water distribution systems (DWDSs) composed of annular reactors incorporating three different treatments: ozone, biologically activated carbon and chlorination (O3-BAC-Cl2); ozone and chlorination (O3-Cl2); or chlorination alone (Cl2). The lowest corrosion rate and iron release, along with more Fe3O4 formation, occurred in DWDSs with O3-BAC-Cl2 compared to those without a BAC filter. It was verified that O3-BAC influenced the bacterial community greatly to promote the relative advantage of nitrate-reducing bacteria (NRB) in DWDSs. Moreover, the advantaged NRB induced active Fe(III) reduction coupled to Fe(II) oxidation, enhancing Fe3O4 formation and inhibiting corrosion. In addition, O3-BAC pretreatment could reduce high-molecular-weight fractions of dissolved organic carbon effectively to promote iron particle aggregation and inhibit further iron release. Our findings indicated that the O3-BAC treatment, besides removing organic pollutants in water, was also a good approach for controlling cast iron corrosion and iron release in DWDSs.