Joint effect of triclosan and copper nanoparticles on wastewater biological nutrient removal

Triclosan in contact with activated sludge and its impact on phosphate removal and microbial community

Triclosan (TCS) is applied in a wide range of pharmaceutical and personal care products to prevent or reduce bacterial growth. In this study, the effects of TCS on phosphate removal and bacterial community shifts of activated sludge, especially on functional bacteria variation, were investigated. Compared with the control group (R-control), the treatment group (R-TCS) with 100 μg/L TCS inhibited the microbial growth. In addition, the phosphorus removal efficiency of PO₄^3--P and total phosphorus removal rates declined by 15.99% and 7.81%, respectively. Proteobacteria gradually dominated the microorganisms. The growths of Proteobacteria and Bacteroidetes were inhibited when 150 μg/L of TCS was added. Moreover, the differences in the microbial community structures of the R-control and R-TCS groups gradually expanded, no obvious difference was observed in the final stage, and the interrelationships of microbes in the latter weakened. The long-term addition of TCS impairs the growth of polyphosphate-accumulating organisms (PAOs).

Effects of heavy metals and metal (oxide) nanoparticles on enhanced biological phosphorus removal

With the rapid growth of economics and nanotechnology, a significant portion of the anthropogenic emissions of heavy metals and nanoparticles (NPs) enters wastewater streams and discharges to wastewater treatment plants, thereby potentially posing a risk to the bacteria that facilitate the successful operation of the enhanced biological phosphorus (P) removal (EBPR) process. Although some efforts have been made to obtain detailed insights into the effects of heavy metals and metal (oxide) nanoparticles [Me(O)NPs], many unanswered questions remain. One question is whether the toxicity of Me(O)NPs originates from the released metal ions. This review aims to holistically evaluate the effects of heavy metals and Me(O)NPs. The interactions among extracellular polymeric substances, P, and heavy metals [Me(O)NPs] are presented and discussed for the first time. The potential mechanisms of the toxicity of heavy metals [Me(O)NPs] are summarized. Additionally, mathematical models of the toxicity and removal of P, heavy metals, and Me(O)NPs are overviewed. Finally, knowledge gaps and opportunities for further study are discussed to pave the way for fully understanding the inhibition of heavy metals [Me(O)NPs] and for reducing their inhibitory effect to maximize the reliability of the EBPR process.

Green synthesis of Ag/ZnO microplates by doping Ag ions on basic zinc carbonate for fast photocatalytic degradation of dyes

The Ag/ZnO microplates, composed by various nanoparticles, were facilely synthesized by calcination of the precursor obtained by ion exchanging between zinc carbonate hydroxide [Zn₂(OH)₂CO₃] and silver nitrate (AgNO₃) in a short time. The structures of ZnO and Ag/ZnO were characterized carefully by a series of methods and so on. Especially, the results from the UV-Vis-NIR diffuse reflectance and PL spectra confirmed that the presence of metallic Ag led to the fact that the adsorption of visible light and an increase of separation of electrons and holes in the Ag/ZnO composite. The photocatalytic activities of the Ag/ZnO were 1.5 and nearly 5 times higher that of ZnO for removal of RhB and MB, respectively. We proposed a possible mechanism to explain the enhanced photocatalytic degradation over Ag/ZnO under UV light irradiation. Finally, this work could provide a simple example for the synthesis of metal-semiconductor composite as well as their applications.

Simultaneous removal of mixed contaminants triclosan and copper by green synthesized bimetallic iron/nickel nanoparticles

The mixed contamination of environmental matrices by antibacterial agents and heavy metals has attracted much attention worldwide due to the complex nature of their environmental interactions and their potential toxicity. In this work, green synthesized bimetallic iron/nickel nanoparticles (Fe/Ni NPs) was used to simultaneously remove triclosan (TCS) and copper (Cu (II)) under optimal experimental conditions with removal efficiencies of 75.8 and 44.1% respectively. However, in a mixed contaminant system the removal efficiencies of TCS and Cu (II) were lower than when TCS (85.8%) and Cu (II) (52.5%) were removed separately, suggesting that there was competitive relationship between the two contaminants and Fe/Ni NPs used for remediation. SEM-EDS, XRD and FTIR all indicated that both TCS and Cu (II) were adsorbed onto Fe/Ni NPs. Furthermore, while XPS showed that Cu (II) was reduced to Cu⁰, GC-MS analysis showed that TCS also underwent degradation with 2,7/2,8-Cl₂DD as the major intermediate. The adsorption of both contaminants fit well a pseudo second order kinetic model (R²>0.998) and the Freundlich isotherm (R²>0.905). Whereas the reduction kinetics obeyed a pseudo first order model. Thus, overall the removal of TCS and Cu (II) involved a combination of both adsorption and reduction. Finally, a removal mechanism for triclosan and Cu (II) was proposed. Overall, Fe/Ni NPs have the potential to practically coinstantaneously remove both TCS and Cu (II) from aqueous solution under a wide range of conditions.