Goodeipsen9264

The effective inhibition of nitrite oxidizing bacteria (NOB) is the key to realizing satisfactory nitrite accumulation and achieving effective nitritation. In order to explore the selective effect of hydroxylamine (NH2 OH) on ammonia oxidizing bacteria (AOB) and NOB, a sequencing batch reactor (SBR) with the operation mode of anaerobic/aerobic/anoxia (A/O/A) was used to observe the start-up of nitritation at different concentrations and frequencies of NH2 OH. The results showed that when 5 mg·L-1 of NH2 OH was added once every 2 cycles, the nitrite accumulation rate (NAR) increased from 0.1% to 57.4% in 6 days, and was maintained at (62.0±4.6)% until the end of the trials. In the typical cycle on day 6, the NN4+-N dropped from 26.05 mg·L-1 to 8.06 mg·L-1, thus producing 9.02 mg·L-1 of NO2--N and 6.70 mg·L-1 of NO3--N. Meanwhile, the ratio of the maximum activity of AOB (rAOB) to NOB (rNOB) increased from 1.05 on day 1 to 4.22 on day 9. Moreover, qPCR results indicated that the abundance of AOB and NOB decreased to 30.2% and 19.1%, respectively, on day 9 in comparison to the original sample. The results indicate that the selective effect of AOB and NOB based on NH2 OH is expected to provide a feasible application for the rapid start-up nitritation of municipal wastewater.The tetracycline (TC) antibiotic has been widely found in different environmental matrices. The tetracycline resistant bacterium (TRB) of Shigella flexneri was screened and purified from activated sludge, and was then used to study the impact of TC stress on the gene abundances and expression levels of TC resistance genes (TC-ARGs), including tetC, tetO, and tetX, which were respectively quantified by quantitative PCR and reverse transcriptional PCR. Correlations between the TC concentration and gene abundances of TC-ARGs and their expression levels were discussed. The results showed that TC stress had an inhibiting effect on the growth of Shigella flexneri during the entire culture cycle (24 h) and that the growth rate of the bacterial concentration decreased with increasing TC concentration. However, less impact on the gene abundance of TC-ARGs was found. TC stress could promote the expression of TC-ARGs in Shigella flexneri, and the expression levels of tetC, tetO, and tetX genes first increased and then decreased. The correlation results indicated that no significant correlation was observed between the TC concentration and gene abundances of TC-ARGs and their expression levels. Nevertheless, the gene abundances of tetC and tetO were significantly correlated with their expression levels, thus indicating that they can be used to evaluate and assess expression levels to a certain extent.In order to explore the conjugation of genes encoding extended-spectrum β-lactamase (ESBL), ESBL-expressing P. aeruginosa and E.coli strains isolated from the wastewater of major hospitals in Singapore were used as donors. gfp-tagged E.coli SCC1 strains resistant to chloramphenicol (CHL) were chosen as recipients. Using response surface analysis, we detected and analyzed the induction of conjugal transfer under single-exposure and co-exposure of tetracycline (TC), sulfamethoxazole (SMZ), and ceftazidime (CAZ) at sublethal concentrations. It was found that the ESBL plasmid could be conjugal transferred from P. aeruginosa and E.coli strains to the recipient E.coli SCC1 strains at an average frequency of 0.0015 and 0.0042, respectively, without stress from inducing antibiotics, thus showing a low fitness cost and higher conjugal frequency between E.coli strains under the exposure of sub-MIC antibiotics. A significant conjugation between E.coli strains occurred under the single-exposure or co-exposure of a TC concentration of less then 0.03 mg·L-1 and a CAZ concentration of less then 0.002 mg·L-1, as inhibited by a sub-MIC level of TC. The conjugation between P. aeruginosa and E.coli strains was stimulated under the exposure of TC and CAZ with concentrations 5-times larger than the MIC, while no significant induction was detected from the sub-MIC antibiotics.A laboratory-scale anaerobic membrane bioreactor (AnMBR) was used for the co-digestion of sewage sludge and food waste to investigate its organic matter removal characteristics, biogas production performance, and microbial community composition. The results showed that the degradation rate of volatile solids (VS) increased from 17.5% for a single digestion to 40% for the total digestion, and that the COD removal was 95.3% when the organic loading rate (OLR) was stabilized at 0.59-0.64 kg·(m3·d)-1. Selleckchem CID44216842 The solids content of the digested sludge increased by a factor of 3.9. The final CH4 content was 60% and the CH4 yield was 78.7 mL·g-1 of CODadded. The transmembrane pressure (TMP) and average flux were maintained at between -3.1 and -2.7 kPa and 0.106 L·(m2·h)-1, respectively, and membrane fouling was not serious. According to an analysis of the microbial diversity using 16S rRNA, the anaerobic bacterium in the AnMBR were mainly phylum Proteobacteria, Bacteroidetes, and Cloacimonetes, and the dominant methanogens included the Methanobacterium family, Methanosaeta genus, and Methanolinea genus. This study provides a strong theoretical basis for research into the stability and performance of AnMBRs for the co-treatment of sludge and other high-solid waste streams, and provided an effective solution for biomass resource utilization and the energy crisis.Ammonia inhibition is an important factor impacting methane production efficiency during the anaerobic digestion of high-solid organic wastes. This study investigated the effect of micro-sized zero-valent iron (m-ZVI) on the anaerobic digestion of excess sewage sludge and thermal hydrolyzed sludge using batch mode experiments. The effect of m-ZVI on ammonia inhibition mitigation was also studied. Results showed that the kinetic characteristics of the methane production rate, lag phase, and methane production potential of the anaerobic digestion of excess sludge and thermal hydrolyzed sludge were not impacted by the addition of m-ZVI at a dosage of 4 g·L-1 and 10 g·L-1. However, during the inhibited anaerobic digestion process with a high ammonia concentration, the addition of 4 g·L-1 and 10 g·L-1 of m-ZVI was able to shorten the lag phase from 18.61 d (the control) to 17.22 d and 16.18 d, respectively. Moreover, the maximum methane production rate (based on the VS) increased from 6.34 mL·(d·g)-1(the control) to 7.84 mL·(d·g)-1 (4 g·L-1 m-ZVI) and 7.39 mL·(d·g)-1 (10 g·L-1 m-ZVI). The pH buffer system was not influenced by the chemical reaction of m-ZVI in the anaerobic digestion, although the relative abundance of the dominant methanogenic archaea (Methanosarcina) improved greatly from 30.71% (the control) to 53.50% (4 g·L-1 m-ZVI) and 60.30% (10 g·L-1 m-ZVI) at 27 d. This study proved that m-ZVI was incapable of improving the methane production potential of sewage sludge, while the mitigation of ammonia inhibition during anaerobic digestion was enhanced by the stimulating effect on methanogenic archaea.Phosphorus is a non-renewable resource. The recovery of phosphorus from excess sludge by the struvite precipitation process has been applied on a full-scale. However, different sludge pretreatment methods have been used to release carbon, nitrogen, and phosphate from excess sludge, which could affect the subsequent struvite precipitation process. In this study, the decision-level analytical structure of the 3-layer and 6-index was constructed to evaluate the effects of six excess sludge treatment processes on struvite recovery. According to the preference ranking organization method for the enrichment of evaluations Ⅱ (PROMETHEEⅡ) decision-making analysis, enzymatic hydrolysis or enzymatic hydrolysis-anaerobic fermentation was the better sludge treatment choice for struvite recovery under the "product quality" priority case, while thermal hydrolysis or thermal hydrolysis-anaerobic fermentation could be better under the "time and economy" priority case. This study provides a recommendation for the selection and design of excess sludge treatment for struvite recovery.To explore the feasibility of the rapid start-up of partial denitrification and the stable accumulation of NO2--N in different waste sludge sources, three identical SBR reactors (S1, S2, and S3) were inoculated respectively with sludge discharged from a laboratory municipal wastewater denitrifying phosphorus removal system, surplus sludge from a municipal wastewater treatment plant, and river sediment sludge. The characteristics of the partial denitrification start-up and NO2--N accumulation were compared, and the partial denitrification activity of the system or NO3--N→NO2--N transformation performance were investigated by analyzing the characteristics of the functional bacteria genera of the reactor from the perspective of microbiology. The results showed that all three SBR partial denitrification reactors could be launched successfully in a short time with sodium acetate as the sole carbon source, under a high alkalinity, and by using a suitable COD/NO3--N ratio. The average NO3--N→NO2--N transformation ratio of the system was ranked asS1 > S2 > S3 (75.92% > 73.36% > 69.90%). It was found that S1 and S2 had different degrees of partial denitrification performance deterioration under a continuous low temperature, but that S3 could maintain a good NO2--N accumulation performance. High throughput sequencing showed that Proteobacteria and Bacteroidetes were dominant in the partial denitrification system, and that the abundance of Thauera was significantly different in the three PD reactorsS3 > S1 > S2 (25.09% > 4.71% > 3.60%), thus indicating that S3 had stable and efficient NO2--N accumulation performance and that a high abundance of Thauera might play a significant role in maintaining low temperature partial denitrification activity.In this study, three SBR reactors R1, R2, and R3 were set up and operated using (A/O)3-SBR gradient aeration, (A/O)3-SBR constant aeration, and the conventional (A/O)-SBR mode, respectively. The nutrient removal performance and aerobic granular sludge characteristics under these aeration modes were explored using real municipal wastewater as the influent matrix. The experimental results revealed that for the R1, R2, and R3 particles during the stable period, the average removal rate of COD was 88.68%, 89.05%, and 88.96%, respectively, the average removal rate of TN was 76.97%, 71.99%, and 64.92%, respectively, the average removal rate of TP was 96.28%, 85.05%, and 78.97%, respectively, and the proportion of denitrifying phosphorus accumulating bacteria to phosphorus accumulating bacteria was 25.52%, 19.60%, and 12.77%, respectively. The results showed that the operation mode of anaerobic, aerobic, and anoxic was more conducive to the enrichment of denitrifying phosphorus accumulating bacteria (DPAOs), and thatively, at the time of particle stabilization, which revealed that the mode of intermittent gradient aeration was beneficial to stimulate the secretion of EPS. This was especially the case for the secretion of PN, which increased the PN/PS value, enhanced the cell hydrophobicity, and made the particles dense and stable.