查看更多>>摘要：The present study investigated the odor emission potential of activated sludge through comprehensive assessment for physicochemical properties and bacterial profile of sludge. Three types of sludges from wastewater treatment plants treating slaughterhouse (SWTP), meat processing (MWTP) and domestic wastewater (DWTP) were used based on distinct morphological features which were speculated to impact odor generation. Total element S in the SWTP sludge with relatively more disintegrated cellular debris exhibited higher level than that in the MWTP and DWTP sludge, while the emitted odorants (hydrogen sulfide and methyl mercaptan) showed the opposite patterns (i.e., the lowest level for the SWTP sludge). Nitrifying bacteria was only detected in the SWTP sludge, which was well in line with abundant nitrate in the corresponding aeration tank. Principal component analysis indicated that the potential of the odor emission from the sludge had strong correlations with dehydrogenase activity, and nitrate, which implies that these parameters may serve as referring indices for evaluating the potential of odor emission of sludge or treated product.
查看更多>>摘要：Quorum-quenching (QQ) has become an attractive strategy for the mitigation of membrane biofouling known as biocake or biofilm. In this study, a QQ system, which exploited two QQ bacteria (Serratia sp. Z4 and Klebsiella sp. Q2) and gamma-caprolactone (GCL), was established and used to effectively mitigate biofouling. This system could delay the increase in transmembrane pressure by half during a 40-day operation in a continuous membrane bioreactor (MBR) with low effluent chemical oxygen demand and ammonium nitrogen. GCL improved the biofouling-mitigation ability of the QQ bacteria without stimulating bacterial growth. The reduction in soluble microbial products was consistent with the delay in transmembrane pressure increase. Furthermore, soluble microbial products (SMP) in the reactors were significantly influenced by the QQ system, suggesting that SMP was important for the occurrence of biofouling. Microbial community analysis showed that the relative abundance of some main genera was not greatly influenced by the QQ system. The two most abundant genera of quorum sensing (QS)-related bacteria found in the sludge mixture were Alicycliphilus and Thauera. The results indicated that a QQ strategy based on the disturbance of QS among the microbes should be effective for biofouling mitigation in MBR.
查看更多>>摘要：The water associated with cultural heritage materials is the most important factor before initiation microbial colonization and subsequent biodeterioration processes to occur. Since moisture or water in such materials is the key to life, a more refined characterization of water is needed to advance the basic understanding of the fundamental mechanisms, especially for the accurate assessment of bio-susceptibility or bio-receptibility of different materials. Water can be categorized to free, gravitational, capillary, and hygroscopic to account for the physical states and sorption strength with the materials. Material porosity or water-holding capacity are fundamental criteria used in characterization of various types of materials on a common ground and basis, but pore connectivity has been largely ignored and must be addressed to establish the methods for assessment and also its relationship to bio-colonization and biodeterioration. When a threshold value of water in the relevant physical categories is available, microbial life can colonize and establish colonies as biofilms on materials surfaces to carry out the biochemical reactions leading to biodeterioration, from appearance of discoloration to physical damage of the materials. Microbial destruction of inorganic materials is mainly carried out by the biochemical reactions through carbon, nitrogen and sulfur cycles. Among material porosity characteristics, available water and microorganisms, mobility and movement of soluble salts under wet and dry cycles have significant impact on the durability of materials. Uptake of soluble salts and supersaturated salts in water into materials can result in crystallization and mineral formation under evaporation condition to initiate the internal stress and cracks, which eventually result in surface delamination and damage. From an architecture design point of view, it is clear that management of water is a basic and important strategy to prevent development of microbial issues in the long-term protection of cultural heritage.
查看更多>>摘要：Marine biofilms formed on submerged substrates are important sources of biofouling. Despite extensive studies dedicated to the surface-biofilm bacteria, few studies focused exclusively on the colonization characteristics of pioneer surface-associated eukaryotes (PSE) in biofilms on composite surfaces. Given this, the colonization dynamics of the biofilm-forming PSE on different carbon nanotubes (CNTs)-filled polydimethylsiloxane (PDMS) composites were investigated via 18S rRNA gene sequencing. Diverse PSE with differential taxonomic compositions, structures and diversity characteristics were colonized on different CNTs/PDMS composites, and their colonization was greatly influenced after CNTs incorporation in PDMS. Bacillariophyta, Annelida and Arthropoda were the core phyla, taking 44.17% of the total; Aphelochaeta, Navicula and Pseudovorticella were the dominant genera, taking 38% of the total. These dominant taxa showed different sensitivities to the CNT incorporation. Some dominant PSE involved multiple biosynthesis and degradation pathways (e.g. Nucleoside and Nucleotide Biosynthesis, Amino Acid Biosynthesis and Fatty Acid and Lipid Degradation), and two key functional modules (Module 50 and Module 88) related to the initial colonization of Navicula were excavated via the correlation network analysis. Our study revealed the potential mechanisms on how different CNTs/PDMS composites influenced the colonization dynamics of PSE and provided fundamental guidance for future development of the anti-biofouling materials.
NSTL
Elsevier