Insights into the effects of single and combined divalent copper and humic acid on the performance, microbial community and enzymatic activity of activated sludge from sequencing batch reactor

Sponge iron enriches autotrophic/aerobic denitrifying bacteria to enhance denitrification in sequencing batch reactor

Sponge iron (SFe) coupled with a sludge system has great potential for improving biological denitrification; however, the underlying mechanism is not yet fully understood. In this study, the denitrification performance and microbial characteristics of ordinary sludge and SFe-sludge systems were investigated. Overall, the SFe-sludge reactor had faster ammonium degradation rate (94.0 %) and less nitrate accumulation (1.5-53.3 times lower) than ordinary reactor during the complete operation cycle of sequencing batch reactors. The addition of SFe increased the activities of nitrate and nitrite reductases. The total relative abundance of autotrophic denitrifying bacteria (Acidovorax, Arenimonas, etc.) in the SFe-sludge system after 38 days of operation was found to be 10.6 % higher than that in the ordinary sludge reactor. The aerobic denitrifying bacteria (Dokdonella, Phaeodactylibacter, etc.) was 5.3 % higher than ordinary sludge. The SFe-sludge system improved denitrification by enriching autotrophic/aerobic denitrifying bacteria in low carbon-to-nitrogen ratio wastewater treatment.

Combined Effects of Tetracycline and Copper Ion on Microorganisms During the Biological Phosphorus Removal

Tetracycline and copper ion are common pollutants in wastewater, and the effects of mixed pollutants on microorganisms in wastewater biological treatment have been less studied. In order to reveal the effects of mixed pollutants of tetracycline and copper ion on the microorganisms during the biological phosphorus removal, three ratios of tetracycline and copper ions were designed by the direct equipartition ray method. The relative abundance and diversity of microbial community were investigated, and the microbial interactions were revealed through microbiological methods. The results demonstrated that, for three different ratios, the inhibitory effect of specific phosphorus uptake rate became more significant with the increase of the tetracycline-copper ions concentration and the reaction time. The microbial community decreased with the increase of the proportion of tetracycline in different ratios. The relative abundance of Acinetobacter decreased with the increase of the proportion of tetracycline, while the relative abundance of Ca.Competibacter was higher under the conditions of low mixtures concentrations. Positive interactions and symbiotic relationships among microorganisms were predominant for three different ratios. However, as the proportion of tetracycline increased, the community structure of microorganisms shifted from phosphate-accumulating organisms to glycogen accumulating organisms and denitrifying bacteria. This study can provide a reference for the effect of mixed pollutants on microorganisms and the mechanism of wastewater treatment.

Characterization of the microbial community and prediction of metabolic functions in an anaerobic/oxic system with magnetic micropolystyrene as a biocarrier

Polystyrene (PS) and magnetic polystyrene (MPS) materials have been used extensively in wastewater treatment. In this research, a 55-day anaerobic/oxic process was carried out to evaluate the effects of PS and MPS on microorganisms under aerobic and anaerobic conditions. Scanning electron microscopy results revealed differences in the entanglement state of the sludge with the biocarrier due to differences in surface morphology. High-throughput sequencing analysis showed that the microbial communities differed considerably in the presence of PS and MPS addition under both aerobic and anaerobic conditions. The highest abundance and diversity were observed in the PS reactor, with 929 observed species and a PD_whole_tree index of 91.58 under anaerobic conditions. MPS promoted the enrichment of bacteria related to nitrogen recycling such as Nitrospirota which increased from 1.13% in the seeding sludge to 3.48% and 10.07% in the aerobic reactors with PS and MPS, respectively. Moreover, advanced analysis showed that PS inhibited many microbial functions (e.g., protein export, nitrogen metabolism), and MPS alleviated this inhibition. This study provides significant insights into the microbial effects of PS and MPS and may shed light on biocarrier selection in future studies.

Enhancement of biological nitrogen removal performance from low C/N municipal wastewater using novel carriers based on the nano-Fe3O4

The aim of this work was to study the effects of the magnetic microparticles (MMP) on nitrogen removal under low C/N conditions. A 30-day anaerobic/oxic progress illustrated that nitrification and denitrification were promoted in the presence of MMP. MMP could facilitate the production of extracellular polymeric substances (EPS) and act as pH buffering in aerobic conditions. The high-throughput sequencing displayed that, compared with the sludge without MMP, the relative abundance of Dokdonella and Comamonas which are capable of both nitrifying and denitrifying were 8.7% and 1.29% higher in anaerobic sludge and 7.11% and 0.97% higher in aerobic sludge with MMP, respectively. The relative abundance of Pseudomonas with the excellent capability of EPS secretion was also observed 4.33 times higher than that without MMP in the aerobic sludge. Based on the superior performance above, MMP is a promising additive to enhance nitrogen removal efficiency for low C/N wastewater.

Effects of combined 4-chlorophenol and Cu2+ on functional genes for nitrogen and phosphorus removal and heavy metal resistance genes in sequencing batch bioreactors

The effects of combined 4-chlorophenol (4-CP) and Cu²⁺ on microbial community structures, functional genes for nitrogen and phosphorus removal, and heavy metal resistance genes (HMRGs) were explored in wastewater treatment using sequencing batch bioreactors (SBRs). Compared to influent 4-CP (2.3-4.5 mg/L), the removal of pollutants including chemical oxygen demands (COD), NH₄⁺-N, PO₄^3--P, and 4-CP was inhibited under Cu²⁺ stress (5 mg/L). The effects of Cu²⁺ on microbial community structures were more significant than those of 4-CP with respect to operational time, while the dominant function from gene information was not affected with or without influent 4-CP and Cu²⁺ via sequencing analysis. The influent 4-CP and Cu²⁺ largely influenced the dynamic changes of functional genes and HMRGs, and the abundance of partial HMRGs was correlated to the functional genes and dominant genera. This study provides insights into the treatment of combined chlorophenols and Cu²⁺ in wastewater.

Constructed microalgal-bacterial symbiotic (MBS) system: Classification, performance, partnerships and perspectives

The microalgal-bacterial symbiotic (MBS) system shows great advantages in the synchronous implementation of wastewater treatment and nutrient recovery. To enhance the understanding of different MBS systems, this review summarizes reported MBS systems and proposes three patterns according to the living state of microalgae and bacteria. They are free microalgal-bacterial (FMB) system, attached microalgal-bacterial (AMB) system and bioflocculated microalgal-bacterial (BMB) system. Compared with the other two patterns, BMB system shows the advantages of microalgal biomass harvesting and application. To further understand the microalgal-bacterial partnerships in the bioflocculation of BMB system, this review discusses bioflocs characteristics, extracellular polymeric substances (EPS) properties and production, and the effect of microalgae/bacteria ratio and microalgal strains on the formation of bioflocculation. Microalgal biomass production and application are important for BMB system development in the future. Food processing wastewater characterized by high biodegradability and low toxicity should be conducive for microalgal cultivation. In addition, exogenous addition of functional bacteria for nutrient removal and bioflocculation formation would be a crucial research direction to facilitate the large-scale application of BMB system.

Response of extracellular polymeric substances and microbial community structures on resistance genes expression in wastewater treatment containing copper oxide nanoparticles and humic acid

The extracellular polymeric substances (EPS) and microbial community structures were investigated in wastewater treatment containing copper oxide nanoparticles (CuO NPs) (reactor R1) and CuO NPs and humic acid (HA) (reactor R2) using both sequencing batch bioreactors (SBRs), and their response on resistance genes expression was analyzed. The removal of influent chemical oxygen demands (COD) and NH₄⁺-N was moderately influenced under CuO NPs (5 mg/L) stress, while the function of HA (10 mg/L) was not reflected. However, the EPS production and microbial community were affected by the HA addition. The expression of different antibiotic resistance genes (ARGs), metal-resistance genes (MRGs), and intI1 was related to the primary compositions of polysaccharides and proteins in EPS and different microbial communities at the genus level. Furthermore, the expression of resistance genes was not stimulated under CuO NPs stress, and supplying HA was suggested to reduce their expression in wastewater treatment.

Interactions between Humic Substances and Microorganisms and Their Implications for Nature-like Bioremediation Technologies

The state of the art of the reported data on interactions between microorganisms and HSs is presented herein. The properties of HSs are discussed in terms of microbial utilization, degradation, and transformation. The data on biologically active individual compounds found in HSs are summarized. Bacteria of the phylum Proteobacteria and fungi of the phyla Basidiomycota and Ascomycota were found to be the main HS degraders, while Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes were found to be the predominant phyla in humic-reducing microorganisms (HRMs). Some promising aspects of interactions between microorganisms and HSs are discussed as a feasible basis for nature-like biotechnologies, including the production of enzymes capable of catalyzing the oxidative binding of organic pollutants to HSs, while electron shuttling through the utilization of HSs by HRMs as electron shuttles may be used for the enhancement of organic pollutant biodegradation or lowering bioavailability of some metals. Utilization of HSs by HRMs as terminal electron acceptors may suppress electron transfer to CO2, reducing the formation of CH4 in temporarily anoxic systems. The data reported so far are mostly related to the use of HSs as redox compounds. HSs are capable of altering the composition of the microbial community, and there are environmental conditions that determine the efficiency of HSs. To facilitate the development of HS-based technologies, complex studies addressing these factors are in demand.