A full-scale integrated-bioreactor with two zones treating odours from sludge thickening tank and dewatering house： performance and microbial characteristics

A full-scale integrated-bioreactor consisting of a suspended zone and an immobilized zone was employed to treat the ordours emitted from a wastewater treatment plant. The inlet concentrations of H,S and NH3 were 1.6-38.6 mg.m-3 and 0.1 6.7 mg.m-3 respectively, while the steady-state outlet concentrations were reduced to 0-2.8mg.m - for H2S and 0-0.5mg.m for NH3. BothH2SandNH3 were eliminated effectively by the integrated-bioreactor. The removal efficiencies of H2S and NH3 differed between the two zones. Four species of microorganisms related to the degradation of H2S and NH3 were isolated. The characteristics and distributions of the microbes in the bioreactor depended on the inlet concentration of substrates and the micro-environmental conditions in the individual zones. Product analysis indicated that most of the H2S was oxidized into sulfate in the immobilized zone but was dissolved into the liquid phase in the suspended zone. A large amount of NH3 was converted into nitrate and nitrite by nitration in the suspended zone, whereas only a small amount of NH3 was transferred to the aqueous phase mainly by absorption or chemical neutralization in the immobilized zone. Different microbial populations dominated the individual zones, and the major biodegradation products varied accordingly.

Microbial Activity Indices: Sensitive Soil Quality Indicators for Trace Metal Stress

Physicochemical properties, total and DTPA （diethylenetriaminepentaacetic acid）-extractable Cu, Zn, Pb and Cd contents, microbial biomass carbon （C） content and the organic C mineralization rate of the soils in a long-term trace metal-contaminated paddy region of Guangdong, China were determined to assess the sensitivity of microbial indices to moderately metal-contaminated paddy soils. The mean contents of total Cu, Zn, Pb and Cd were 251, 250, 171, and 2.4 mg kg^-1 respectively. DTPA-extractable metals were correlated positively and significantly with total metals, CEC, and organic C （except for DTPA-extractable Cd）, while they were negatively and highly significantly correlated with pH, totall Fe and Mn. Metal stress resulted in relatively low ratios of microbial biomass C to organic C and in remarkable inhibition of the microbial metabolic quotient and C mineralization rate, which eventually led to increases in soil organic C and C/N. Moreover, microbial respiratory activity showed a stronger correlation to DTPA-extractable metals than to total metal content. Likewise, in the acid paddy soils some “linked” microbial activity indices, such as metabolic quotient and ratios of basal respiration to organic C, especially during initial incubation, were found to be more sensitive indicators of soil trace metal contamination than microbial biomass C or basal respiration alone.

Aggregate-associated changes in nutrient properties,microbial community and functions in a greenhouse vegetable field based on an eight-year fertilization experiment of China

Soil aggregation,microbial community,and functions(i.e.,extracellular enzyme activities;EEAs)are critical factors affecting soil C dynamics and nutrient cycling.We assessed soil aggregate distribution,stability,nutrients,and microbial characteristics within>2,0.25-2,0.053-0.25,and<0.053 mm aggregates,based on an eight-year field experiment in a greenhouse vegetable field in China.The field experiment includes four treatments:100%N fertilizer(CF),50%substitution of N frtilizer with manure(M),straw(S),and manure plus straw(MS).The amounts of nutrient(N,P20,and K20)input were equal in each treatment.Results showed higher values of mean weight diameter in organic amended soils(M,MS,and S,2.43-2.97)vs.CF-amended soils(1.99).Relative to CF treatment,organic amendments had positive effects on nutrient(i.e.,available N,P,and soil organic C(SOC))conditions,microbial(e.g,bacterial and fungal)growth,and EEAs in the>0.053 mm aggregates,but not in the<0.053 mm aggregates.The 0.25-0.053 mm aggregates exhibited better nutrient conditions and hydrolytic activity,while the<0.053 mm aggregates had poor nutrient conditions and higher oxidative activity among aggregates,per SOC,available N,available P,and a series of enzyme activities.These results indicated that the 0.25-0.053 mm(<0.053 mm)aggregates provide suitable microhabitats for hydrolytic(oxidative)activity.Interestingly,we found that hydrolytic and oxidative activities were mainly impacted by fertilization(58.5%,P<0.01)and aggregate fractions(50.5%,P<0.01),respectively.The hydrolytic and oxidative activities were significantly(P<0.01)associated with nutrients(SOC and available N)and pH,electrical conductivity,respectively.Furthermore,SOC,available N,and available P closely(P<0.05)afected microbial communities within>0.25,0.25-0.053,and<0.053 mm aggregates,respectively.These findings provide several insights into microbial characteristics within aggregates under dfferent frilization modes in the greenhouse vegetable production system in China.

Evolution of urban black and odorous water:The characteristics of microbial community and driving-factors

Urban black blooms that are primarily caused by organic carbon are deleterious environmental problems.However,detailed studies on the microbial characteristics that form urban black blooms are lacking.In this study,we observed the composition,diversity,and function of bacterial community in the overlying water and sediments during the occurrence and remediation of urban black blooms using high-throughput 16S rRNA gene amplicon sequencing analysis.First,we found that pivotal consortia in the overlying water increased significantly during the formation of black blooms,including the genera Acidovorax,Brevundimonas,Pusillimonas,and Burkholderiales involved in the degradation of refractory organics,as well as the genera Desulfovibrio,Dechloromonas,and Rhizobium related to the production of black and odorous substances.An RDA analysis revealed that chemical oxygen demand,dissolved oxygen,and oxidation reduction potential were related to the changes in microbial community composition.Furthermore,aeration was found to accelerate the removal of ammonia nitrogen and enhance the function of microbial community by stimulating the growth of order Planktomycetes during the remediation of black blooms,but aeration substantially damaged the microbial diversity and richness.Therefore,the health of the aquatic ecosystem should be comprehensively considered when aeration is applied to restore polluted waterbodies.Notably,we observed a large number of pathogenic bacteria in urban black blooms,which emphasizes the importance of treating domestic sewage so that it is harmless.Together,these findings provide new insights and a basis to prevent and manage urban black blooms.

Response of soil microbial activities and ammonia oxidation potential to environmental factors in a typical antimony mining area

Mining,smelting and tailing deposition activities can cause metal(loid)contamination in surrounding soils,threatening ecosystems and human health.Microbial indicators are sensitive to environmental factors and have a crucial role in soil ecological risk assessment.Xikuangshan,the largest active antimony(Sb)mine in the world,was taken as the research area.The soil properties,metal(loid)contents and microbial characteristics were investigated and their internal response relationships were explored by multivariate statistical analysis.The assessment of the single pollution index and Nemerow synthetic pollution index(PN)showed that the soils were mainly polluted by Sb,followed by Cd and As,in which sampling site S1 had a slight metal(loid)pollution and the other sampling sites suffered from severe synthetic metal(loid)pollution.The microbial characteristics were dissimilar among sampling points at different locations from the mining area according to hierarchical cluster analysis.The correlation analysis indicated that fluorescein diacetate hydrolase,acid phosphatase,soil basal respiration andmicrobial biomass carbonwere negatively correlatedwith PN,indicating their sensitivity to combined metal(loid)contamination;that dehydrogenase was positively correlated with pH;and that urease,potential ammonia oxidation and abundance of ammonia-oxidizing bacteria and archaea were correlated with N(nitrogen)contents.However,β-glucosidase activity had no significant correlations with physicochemical properties and metal(loid)contents.Principal components analysis suggested bioavailable Sb and pH were the dominant factors of soil environment in Xikuangshan Sb mining area.Our results can provide a theoretical basis for ecological risk assessment of contaminated soil.

Optimization of the methane production in batch anaerobic digestion of maize straw by adjustment of total solid and substrate-to-inoculum ratio based on kinetics

Anaerobic digestion(AD)operating under conditions of organic overload stress typically exacerbates the potential for process instability,thereby resulting in significant economic and ecological ramifications.In this investigation,an augmented substrate-to-inoculum ratio(S/I)along with varying total solid content(TS)levels was employed to replicate diverse organic loadings,utilizing maize straw and cattle manure.The findings reveal that a moderate augmentation in S/I and TS proves advantageous in augmenting methane yield,while an excessive substrate loading diminishes methane yield,hampers the kinetics of methane production,and even induces severe process instability.Kinetic study also displayed the variation of the model parameters for the first-order model,the modified Gompertze model,and the transfer function model.Both the modified Gompertze model and transfer function model exhibited the same environmental stress trend.Thus,both the increase in particulate content and the increase in S/I had a substantial effect on the substrate conversion rate to methane.Microbial analysis demonstrates the dominant influence of Firmicutes and Methanosarcina under different organic loading stresses.From both a kinetic and a microbiological point of view,this work provides novel insights into the fundamental processes that regulate anaerobic digestion(AD)under varying loading stress.Furthermore,it has significant implications for improving the operating efficiency of AD,which is a significant benefit.

Comparison of the removal of monovalent and divalent cations in the microbial desalination cell

Microbial desalination cell （MDC） is a promis- ing technology to desalinate water and generate electrical power simultaneously. The objectives of this study were to investigate the desalination performance of monovalent and divalent cations in the MDC, and discuss the effect of ion characteristics, ion concentrations, and electrical characteristics. Mixed salt solutions of NaC1, MgC12, KC1, and CaC12 with the same concentration were used in the desalination chamber to study removal of cations. Results showed that in the mixed salt solutions, the electrodialysis desalination rates of cations were： Ca2＋ 〉 Mg2＋ 〉 Na＋ 〉 K＋. Higher ionic charges and smaller hydrated ionic radii resulted in higher desalination rates of the cations, in which the ionic charge was more important than the hydrated ionic radius. Mixed solutions of NaC1 and MgC12 with different concentrations were used in the desalination chamber to study the effect of ion concentra- tions. Results showed that when ion concentrations ofNa＋ were one-fifth to five times of Mg2~, ion concentration influenced the dialysis more profoundly than electrodia- lysis. With the current densities below a certain value, charge transfer efficiencies became very low and the dialysis was the main process responsible for the desalination. And the phosphate transfer from the anode chamber and potassium transfer from the cathode chamber could balance 1%-3% of the charge transfer in the MDC.

Evaluation of Beauveria bassiana （Hyphomycetes） isolates as potential agents for control of Dendroctonus valens

The red turpentine beetle （RTB）, Dendroctonus valens LeConte, as a destructive invasive pest, has become one of the most economically important forest pest in China. Effective control measures are desperately needed. Entomopathogenic fungi, such as Beauveria bassiana, have shown great potential for the management of some bark beetle species. In this study, 12 isolates of B. bassiana from bark beetle were examined for biological characteristics and virulence, to assess their potential as biocontrol agents for RTB. There were significant differences （at P = 0.05） in colony growth rate, conidial yield, conidial germination, tolerance to UV light and extracellular proteases activity among the tested B. bassiana isolates. Isolates, including Bbl801, Bb1906, Bb789 and Bb773, exhibited the best characteristics, because they have faster hyphal growth rate, higher spore production and faster spore germination, higher UV tolerance and protease （Prl） production. The results of a pathogenicity test ofB. bassiana on RTB larvae showed that most isolates of B. bassiana have demonstrated high efficacy and the highest virulent isolate was Bb 1801, which killed 100% of the treated insects and had a median lethal time （LT50） of 4.60 days at a concentration of 1 ×107 conidia/mL. Therefore, isolate Bb1801 has a great potential for sustainable control of RTB in the forest. The correlation between biological characteristics and virulence of the fungal isolates is discussed and the possibility of combination of entomopathogenic fungi with semiochemicals, as one of the promising strategy for RTB control, is considered.