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It is a well-established fact that aerobic denitrifying strains are profoundly affected by antibiotics, but bacterium performing simultaneous aerobic denitrification and antibiotic degradation is hardly reported. Here, a typical aerobic denitrifying bacterium Pseudomonas aeruginosa PCN-2 was discovered to be capable of sulfamethoxazole (SMX) degradation. The results showed that nitrate removal efficiency was decreased from 100% to 88.12%, but the resistance of strain PCN-2 to SMX stress was enhanced with the increment of SMX concentration from 0 to 100 mg/L. Transcriptome analysis revealed that the down-regulation of energy metabolism pathways rather than the denitrifying functional genes was responsible for the suppressed nitrogen removal, while the up-regulation of antibiotic resistance pathways (e.g., biofilm formation, multi-drug efflux system, and quorum sensing) ensured the survival of bacterium and the carrying out of aerobic denitrification. Intriguingly, strain PCN-2 could degrade SMX during aerobic denitrification. Seven metabolites were identified by the UHPLC-MS, and three degradation pathways (which includes a new pathway that has never been reported) was proposed combined with the expressions of drug metabolic genes (e.g., cytP450, FMN, ALDH and NAT). This work provides a mechanistic understanding of the metabolic adaption of strain PCN-2 under SMX stress, which provided a broader idea for the treatment of SMX-containing wastewater.

Aerobic denitrification has been proved to be profoundly affected by temperature and antibiotics, but little is known about how aerobic denitrifiers respond to temperature and antibiotic stress. In this study, the nitrate reduction performance and the intracellular metabolism by a psychrotolerant aerobic denitrifying bacteria, named Pseudomonas psychrophila RNC-1, were systematically investigated at different temperatures (10 °C, 20 °C, 30 °C) and different sulfamethoxazole (SMX) concentrations (0 mg/L, 0.1 mg/L, 0.5 mg/L, 1.0 mg/L, and 5.0 mg/L). The results showed that strain RNC-1 performed satisfactory nitrate removal at 10 °C and 20 °C, but its growth was significantly inhibited at 30 °C. Nitrate removal by strain RNC-1 was slightly promoted in the presence of 0.5 mg/L SMX, whereas it was significantly suppressed with 5.0 mg/L SMX. Nitrogen balance analysis indicated that assimilatory nitrate reduction and dissimilatory aerobic denitrification jointly dominated in the nitrate removal process of strain RNC-1, in which the inhibition effected on assimilation process was much higher than that on the aerobic denitrification process under SMX exposure. Further transcriptomics and proteomics analysis revealed that the psychrotolerant mechanism of strain RNC-1 could be attributed to the up-regulation of RNA translation, energy metabolism, ABC transporters and the over-expression of cold shock proteins, while the down-regulation of oxidative phosphorylation pathway was the primary reason for the deteriorative cell growth at 30 °C. The promotion of nitrate reduction with 0.5 mg/L SMX was related to the up-regulation of amino acid metabolism pathways, while the down-regulation of folate cycle, glycolysis/gluconeogenesis and bacterial chemotaxis pathways were responsible for the inhibition effect at 5.0 mg/L SMX. This work provides a mechanistic understanding of the metabolic adaption of strain RNC-1 under different stress, which is of significance for its application in nitrogen contaminated wastewater treatment processes.

The proper choice of dissolved oxygen (DO) is important in aerobic treatment. In this paper, a multi-stage vertical variable diameter membrane bioreactor was developed to treat pharmaceutical wastewater containing 6-APA and ceftriaxone sodium. In the 180 days of operation, the performance of COD, BOD5, 6-APA, ceftriaxone sodium removal, sludge index, and microbial enzyme activity under different DOs (from 0.5 to 6.0 mg/L) were investigated. The results showed that the optimal range of DO was 1.5–2.1 mg/L, and the highest removal rates of COD and BOD5 were observed 87.3%±2.4% and 95.3%±1.8%, the corresponding effluent COD and BOD5 were 189 mg/L and 24 mg/L, respectively. To reduce the energy consumption and ensure stability of DO in the reactor, a control strategy based on an improved differential evolution BP fuzzy neural network was built and found that the performance and cost of the controlled DO were improved effectively than that of uncontrolled DO.

This paper focused on the feasibility and performance of an up-flow anaerobic bio-electrochemical system (UBES) for treating sulfamethoxazole (SMX) antibiotic wastewater at different COD loading rates (LRs) from 2.02 ± 0.13 to 6.09 ± 0.14 kgCOD/(m3·d). Open-circuit UBES had a lower average COD removal rate of 62.4 ± 4.7% in Run2, and the accumulation of volatile fatty acid (VFA) was occurred. However, closed-circuit UBES can alleviate the accumulation of VFA (which was decreased from 720.4 to 102.4 mg/L), the highest average COD, SMX removal rates were 85.7 ± 3.2% and 73.7 ± 2.0%, respectively. The closed-circuit UBES can withstand more than 3 times LR than open-circuit UBES, which proved that the ability of microorganisms to resist toxic substance stress was strengthened. And the mathematical models for pollutants removal rate were established and well interpreted the results, which also can guide the operation of UBES.

Low-flush toilets have received increasing attention in relation to the water crisis in water-scarce regions because the vacuum flushing system (VFS) can reduce the amount of water required for flushing by approximately 80%. However, low-flush toilet wastewater exhibits the characteristics of high pollutant concentrations and cannot be directly discharged into urban pipe networks; therefore, decentralized wastewater treatment is necessary. Traditional control process (mainly consisting of hydrolysis acidification tank (HAT), anaerobic-anoxic–oxic (AAO) tank, coagulation sedimentation filtration tank and UV disinfection) was unsatisfactory for treating this type of wastewater. Therefore, a newly designed integrated biological-electrocatalytic (AAIE) process (mainly consisting of anaerobic baffled reactor (ABR), alternating internal circulation activated sludge process (AICS), and electrocatalytic oxidation (EC)) was introduced. ABR achieved large amounts of organic matter removal, the organic biodegradation kinetics revealed that the maximum specific degradation rate of the ABR was 0.050 to 0.082 d−1; AICS further removed COD and nitrogen, the denitrification rate and growth rate of nitrifying bacteria in the AICS were in the range of 0.079–0.121 kg/(kg·d) and 0.32–1.54 d−1, respectively. The temperature and organic loading rate were identified as two key parameters for ABR and AICS to remove pollutants, therefore, EC was the guarantee to make the effluent quality met the directly discharge standard of China (GB 18918-2002), especially in winter. The results showed that the AAIE process presented COD, colority, ammonia and total nitrogen removal rates of 98.5 ± 0.7%, 98.8 ± 0.6%, 97.0 ± 0.4% and 93.4 ± 2.6%, respectively, which were considerably higher than those of the control process. Furthermore, the economic analysis indicated that the AAIE process was feasible and may help to pave the way for wide application of biological-electrocatalytic processes for highly concentrated toilet wastewater treatment.

Owing to the low biodegradation and highly recalcitrant nature of pesticide wastewater, the conventional anaerobic treatment process is often limited with low organic removal efficiency. In this study, based on the existing wastewater treatment system of a pesticide production company, a pilot-scale original combined system (hydrolysis/acidification-based processes) and a pilot-scale enhanced combined system (electrochemical-assisted hydrolysis/acidification-based processes) were designed and operated in parallel to explore the feasibility and economics of pesticide wastewater treatment. The average effluent BOD5/COD ratio in the electrochemical-assisted hydrolysis/acidification reactor increased from 0.19 ± 0.02 to 0.30 ± 0.05, which was 16.3% greater than that of the original hydrolytic/acidification reactor. In addition, the maximum difference in effluent COD between the two-stage anaerobic process and original up-flow anaerobic sludge blanket reactor reached 5696 mg/L. Meanwhile, the optimum compliance rates of COD and BOD5 in the biological contact oxidation pool of the enhanced combined system were 85.7% and 100.0%, respectively, which proved that most of the effluent could meet the reception standard of an urban wastewater treatment plant (COD ≤ 300 mg/L; BOD5 ≤ 250 mg/L). Although the investment cost of the enhanced combined system was slightly higher than that of the original combined system, the operating cost of the enhanced combined system can achieve a cost reduction rate of 14.1% with a payback period of 10 y.

In this study, a lab-scale multiple draft tubes airlift loop membrane bioreactor (Mt-ALMBR) was used for treating acidic 7-amino cephalosporanic acid (7-ACA) wastewater under different pHs (3.54–6.20) and hydraulic retention time (HRT) (48 h, 36 h, 24 h and 16 h). During about 200 days operation, under HRT of 48 h and pH condition about 6.0, the optimum average COD and BOD5 removal rates were reach to 84.4 ± 2.1% and 94.9 ± 0.8%, and the highest 7-ACA removal rate also observed as 77.6%. Biodegradation, membrane rejection, hydrolysis and sludge adsorption were the four main pathways of 7-ACA removal. With the increase of pH, biodegradation, membrane rejection and hydrolysis had significant positive impacts on 7-ACA removal, while adsorption had a negative impact. Moreover, mathematical models for 7-ACA removal rate and pH were calculated to guide the operation of Mt-ALMBR. Biodegradation was the main pathway to remove 7-ACA when pH was >4.17.

In this study, the performance and removal mechanisms of a novel lab-scale multiple draft tubes airlift loop membrane bioreactor (Mt-ALMBR) for treating high-strength ampicillin pharmaceutical wastewater under different temperatures (7 °C, 16 °C, 24 °C, 36 °C, 48 °C) were investigated. During 150 days operation, the optimal average chemical oxygen demand (COD) and ampicillin removal rates were 98.2 ± 0.2% (36 °C) and 63.2 ± 5.6% (7 °C), respectively. The main mechanisms of pollutants removal were membrane removal (7 ~ 16 °C) and bioreactor removal (16 ~ 48 °C). Adsorption and membrane rejection were main pathways at low temperature, as temperature increased, hydrolysis and biodegradation gradually occupied a dominant position. Meanwhile, the optimum temperature ranges for activated sludge microorganisms were 16 °C ~ 36 °C, the corresponding β-lactamase at 36 °C was the highest activity value among all the set temperature values. Experimental results showed that temperature had a significant impact on the removal rate, the optimum temperature range was proposed to be at 24 ~ 36 °C. The half-life ( t 1 2 ) of ampicillin drastically decreased from 330.0 d to 2.1 d when the temperature was increased from 7 °C to 48 °C. And the maximum adsorption capacity K f at the adsorption temperatures of 7, 16, 24, 36 and 48 °C was 0.1284, 0.2169, 0.0645, 0.1502 and 0.1524 mg/g, respectively. The values of Δ G ° were all negative, proving that the adsorption process of the ampicillin belonged to a spontaneous physical adsorption. In addition, autoregressive integrated moving average (ARIMA) and mathematical fitting models were developed and well simulated the performance of Mt-ALMBR to treat the ampicillin wastewater. These results suggest that Mt-ALMBR holds great potential for application in ampicillin pharmaceutical wastewater treatment.

This paper focused on the performance of an up-flow bio-electrochemical system (UBES) for treating the β-lactams pharmaceutical wastewater under different hydraulic retention time (HRT). UBES is added a bio-electrochemical system below the three-phase separator based on up-flow anaerobic sludge blanket (UASB). Comparisons of chemical oxygen demand (COD) removal, accumulation of volatile fatty acid (VFA) and biogas production were investigated during the 316-day operation time, which was divided into five parts with HRT of 96 h, 72 h, 48 h, 36 h and 20 h, respectively. The average COD removal efficiency of UBES could reach 45.3 ± 7.5%, 72.2 ± 3.5%, 86.2 ± 1.4%, 75.9 ± 1.8% and 64.9 ± 2.0%, which were 2.4%, 6.1%, 6.4%, 10.2%, 8.7% more than those of UASB under different HRTs, respectively. Biogas production as well as methane production of UBES were significantly higher than UASB during the whole changing HRT process, the maximum methane yield of UBES was 0.31 ± 0.07 L/gCODremoved. Accumulation of VFA in UBES was discovered to be lighter than UASB, the minimum average VFA in UBES was 131.9 ± 18.5 mg/L, which was obtained at HRT of 48 h. These results proved that UBES can slow down the inhibition of VFA on methanogens to make sure a good performance on COD removal and biogas production than UASB. Moreover, the relationships between methane production and VFA, biogas production and COD consumption were analyzed. A cost and benefit were analyzed for evaluating the potential of UBES in practical applications compared with UASB. Finally, radial basis function neural network (RBFNN) model was developed and fitted well with the experimental data, which can be employed to predict the effluent quality of the UBES and UASB.