ABSTRACT
The wide use of ZnO and CuO nanoparticles in research, medicine, industry, and other fields has raised concerns about their biosafety. It is therefore unavoidable to be discharged into the sewage treatment system. Due to the unique physical and chemical properties of ZnO NPs and CuO NPs, it may be toxic to the members of the microbial community and their growth and metabolism, which in turn affects the stable operation of sewage nitrogen removal. This study summarizes the toxicity mechanism of two typical metal oxide nanoparticles (ZnO NPs and CuO NPs) to nitrogen removal microorganisms in sewage treatment systems. Furthermore, the factors affecting the cytotoxicity of metal oxide nanoparticles (MONPs) are summarized. This review aims to provide a theoretical basis and support for the future mitigating and emergent treatment of the adverse effects of nanoparticles on sewage treatment systems.
Subject(s)
Wastewater/toxicity , Sewage/chemistry , Zinc Oxide/chemistry , Waste Disposal, Fluid , Nanoparticles/chemistry , Metal Nanoparticles/chemistry , Nitrogen/metabolism , Water PurificationABSTRACT
Resource utilization is an effective way to cope with the rapid increase of kitchen waste and excess sludge, and volatile fatty acids produced by anaerobic fermentation is an important way of recycling organic waste. However, the single substrate limits the efficient production of volatile fatty acids. In recent years, volatile fatty acids produced by anaerobic co-fermentation using different substrates has been widely studied and applied. In this paper, we analyze the characteristics of fermentation to produce acid using kitchen waste and excess sludge alone or mixture. Influences of environmental factors and microbial community structure on the type and yield of volatile fatty acids in the anaerobic fermentation system are discussed in detail. Moreover, we propose future research directions, to provide a reference for recycling kitchen waste and excess sludge.
Subject(s)
Anaerobiosis , Bioreactors , Fatty Acids, Volatile , Fermentation , Hydrogen-Ion Concentration , Microbiota , Organic Chemicals , SewageABSTRACT
Nitrite is a by-product of the nitrogen cycle. The excessive nitrite not only constrains growth and metabolism of bacteria, but also impairs health of humans and aquatic organisms. On the other hand, the continuous maintaining of nitrite accumulation could achieve the shortcut nitrification process, and reduce energy consumption of biological nitrogen removal to save cost. This article reviews the biological processes and causes of nitrite accumulation in the water environment, and summarizes the factors that affect the accumulation of nitrite, to provide reference for wastewater treatments, including improving the nitrogen removal efficiency, reducing operating costs, decreasing discharge of sewage and nitrite nitrogen in natural water.
ABSTRACT
Phosphatases play a key role not only in cell physiological functions of an organism, but also in host-pathogen interactions. Many studies demonstrated that some Gram-negative pathogenic bacteria could evade host immunity and promote pathogenicity by injecting phosphatases into host cells through type III secretion system. However, there were few reports about pathogenic fungi evading the immunity of hosts. Our researches indicated that the entomogenic fungus Metarhizium anisopliae could dephosphorylate the signal transduction substance of locust humoral immunity specifically in vitro by secreting extracellular protein tyrosine phosphatase, which implied that the fungus might interfere with the immune defense of locust. To provide reference for further studies of the functions of phosphatases, we reviewed the types of phosphatases and their roles in pathogen infection.