In this study, the responses of activities and communities of nitrifying bacteria to toxic hexavalent chromium (Cr(VI)) in activated sludge were investigated in sequencing batch reactors (SBRs). The shock loading concentrations of Cr(VI) were 1, 5, 8, 10 and 20 mg Cr(VI) L⁻¹ for five identical SBRs. The results showed that Cr(VI) resulted in more serious inhibition on nitrification than on COD removal. The activities of nitrifying bacteria (i.e. ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB)) were inhibited by greater than 5 mg Cr(VI) L⁻¹. With 10 and 20 mg Cr(VI) L⁻¹ loadings, the deterioration of nitrification was very significant in the Cr(VI) loading and subsequent recovery cycles. A loading of less than 10 mg Cr(VI) L⁻¹ caused few changes in communities of nitrifying bacteria. Higher loading of 10 and 20 mg Cr(VI) L⁻¹ reduced the densities of some nitrifying bacteria and changed the community structure of nitrifying bacteria. Twelve AOB and eight NOB species were identified by cloning and sequencing analyses. During the whole experiments period, Nitrosomonas sp. and Nitrobacter sp. were the major detected AOB and NOB species, respectively. New species of Nitrosospira sp. appeared in the recovery phase.

The adhesion of deleterious bacteria on titanium substrates not only causes economic losses but also endangers human life and health. The study is expected to address the challenging issues of using ZnO as an antibacterial material, including low bactericidal efficiency without lighting, susceptibility to ZnO cluster formation, and easy adhesion of bacteria to its surface. It is proposed that the prepared ZnO nanorod arrays with a hexagonal wurtzite structure on the surface of titanium-based materials can address the issue of ZnO cluster formation. Remarkably, a mere 3.49 g cm⁻² of decorated Ag/AgCl achieves over 99% sterilization efficiency without lighting. The incorporation of FAS (1H,1H,2H,2H-perfluorodecyltrimethoxysilane) molecules with low surface energy enables the prepared Ti@ZnO@Ag/AgCl@FAS to attain a Cassie–Baxter wetting state, thereby imparting exceptional bacterial anti-adhesion properties exceeding 99.50%. Furthermore, antibacterial and anti-adhesion models have been proposed to elucidate the underlying mechanisms. This innovative approach is anticipated to be adaptable for application across various material substrates, which opens up a new avenue for the application of the antibacterial and bacterial anti-adhesion properties on the surface of ZnO materials.

In recent years, the biological toxicity of oxide copper nanoparticles (CuO NPs) to microorganisms has received some attentions. The toxicity mechanism of CuO NPs can be concluded as follows: (1) CuO NPs facilitate more rapid dissolution of ions than equivalent bulk material, which potentially leading to increased toxicity of CuO NPs; (2) CuO NPs can generate reactive oxygen species (ROS), and potentially disturb the functioning of protein, enzymes and DNA; (3) CuO NPs have high capacity to adsorb biomolecules and interact with biological receptors, they can reach sub-cellular locations leading to potentially higher localized concentrations of ions once those particles start to dissolve or degrade in situ. Ammonia-oxidizing bacteria (AOB) are the main functional bacteria for biological nitrogen removal in the environment. It has been reported that CuO NPs can change the community structures of AOB, however, the toxicity mechanism of CuO NPs to AOB in cytological level is rarely reported. This review aims to evaluate the current understanding of CuO NPs toxicity to microorganisms, as well as to provide a set of pointers and guidelines for future studies to access the toxicity mechanism of CuO NPs to AOB.

This study investigates the dual catalytic inhibition mechanisms of chlorobenzene (CBz) formation during combustion using N- and S-modified layered double hydroxides (LDHs). The metal hydroxide layers in these LDHs primarily suppress lower-chlorinated CBzs (e.g., trichlorobenzene-dichlorobenzene) under inert conditions by inhibiting direct chlorination, achieving inhibition rates above 80%. In contrast, N/S functional groups, particularly thioacetamide, enhance catalytic inhibition efficiency under air, increasing it from 17.8% to 77.3% in the solid phase by controlling catalytic chlorination and limiting highly chlorinated CBzs (e.g., pentachlorobenzene–hexachlorobenzene). These findings highlight the complementary roles of metal hydroxide layers and N/S functional groups in reducing CBz formation, offering insights for developing efficient, multifunctional inhibitors for waste incineration pollution control. While promising, the scaling up of the application of LDH-based inhibitors may face challenges related to synthesis complexity and cost, requiring further research to provide a theoretical foundation for their large-scale application.

This study systematically investigated the performance and microbial response of a two-stage partial denitrification/anammox (PD/A) system treating printed circuit board (PCB) wastewater. The front-end partial denitrification reactor was intended to function as a biobarrier to mitigate toxicity and protect downstream anammox activity. However, sustained exposure to PCB wastewater severely inhibited its performance, reducing the NO2--N accumulation rate (SNO2’) by 67% and shifted metabolic pathways toward complete denitrification. As a result, severe NO2--N deficiency impaired anammox bacteria (AnAOB), decreasing their nitrogen removal contribution from 57.60% to negligible levels. High-throughput sequencing analysis revealed significant microbial community restructuring, marked by the enrichment of the sulfide-oxidizing genus Thiobacillus from 0.10% to 15.57%, confirming S2- as a critical toxic agent. Further microbial profiling demonstrated functional divergence between nirS-and nirK-type denitrifiers under stress. Although partial denitrification activity recovered after PCB withdrawal, the system did not essentially restore its PD/A synergistic function as Phase I due to AnAOB exhibited persistent suppression of key functional genes and compromised metabolic connectivity. These findings underscore that the dual inhibition from toxic wastewater constituents and NO2--N scarcity constitutes the major bottleneck for implementing the PD/A process in treating such industrial effluents.