Zhaobo Chen

Effect of the high cross flow velocity on performance of a pilot-scale anaerobic membrane bioreactor for treating antibiotic solvent wastewater

The effect of high cross flow velocity (CFV) on the operational efficiency of a pilot-scale anaerobic membrane bioreactor (AnMBR) treating antibiotic solvent effluents was explored. The average of total Chemical Oxygen Demand (COD) and tetrahydrofuran (THF) removal efficiencies during four Runs were 96.5% and 98.7%. Meanwhile, biological removal contributions were 74.3% and 78%, the rest part was attributed by the physical removal process of the membrane block, VFA (Volatile Fatty Acids) and alpha value (VFA/alkalinity) increased with the increase of CFV, resulted alkalinity decreased. Biomass concentration mixed liquid suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) as well as the polysaccharide increased smoothly in the suspended sludge with the CFV increasing, and the protein content decreased gradually. However, the concentration of biomass, polysaccharide and protein presented opposite trends in the attached sludge of the membrane. The results indicated that AnMBR can effectively treat the antibiotic solvent wastewater under high CFV.

Performance evaluation and microbial community dynamics in a novel AnMBR for treating antibiotic solvent wastewater

This study aims at evaluating the performance and microbial community dynamics of anaerobic membrane bioreactor (AnMBR) treating antibiotic solvent wastewater at improved influent quality period. The whole process was divided into five phases according to the influent COD concentration with a fluctuated volume loading rate (VLR) ranging from 3.9 to 12.7kgCOD/(m3·d). After 249days of operation, the average COD and THF removal efficiency were 93.6% and 98.7%, respectively. The accumulation of VFA, relatively low pH, decline of biogas production and methane content were discovered at higher VLR (>10kgCOD/(m3·d)). Methanomicrobiales are the major population throughout the whole running period. Methanosaetaceae showed a minor relative abundance compared both of them, while Methanobacteriales remained a minimum value. Results showed that the reactor performed an excellent pollutants removal effect because of the function of membranes even at high VLR conditions.

Performance and extracellular polymers substance analysis of a pilot scale anaerobic membrane bioreactor for treating tetrahydrofuran pharmaceutical wastewater at different HRTs

Tetrahydrofuran (THF) is one of the most representative characteristics of pollutant in pharmaceutical industry usually has high biological toxicity, making it difficult to treat. In this study, a pilot scale anaerobic membrane bioreactor (AnMBR) was employed to treat THF pharmaceutical wastewater under different hydraulic retention time (HRT). During the 80-day operating time, chemical oxygen demand (COD) and THF removal efficiencies reached 95.3% and 98.5% when HRT was above 24h. Mixed liquid suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) in the attached sludge on membrane surface showed a trend of rising on first 28days (48h-36h) and then decreasing. Protein is the major component of extracellular polymeric substances (EPS) independent of changes in HRT. The study concludes that THF pharmaceutical wastewater can be effectively remedied in the AnMBR system at low HRT.

Effect of organic loading rate on the removal of DMF, MC and IPA by a pilot-scale AnMBR for treating chemical synthesis-based antibiotic solvent wastewater

This study focuses on the effects of organic loading rate (OLR) on the removal of N,N-Dimethylformamide(DMF), m-Cresol (MC) and isopropyl alcohol (IPA) by a pilot-scale anaerobic membrane bioreactor (AnMBR) for treating chemical synthesis-based antibiotic solvent wastewater at period of improved influent COD concentration with decreased HRT. The whole process was divided into five stages in terms of the variation of OLR ranging from 3.9 to 12.7 kg COD/(m3·d). During 249 days of operating time, the average DMF, MC, IPA removal efficiency were 96.9%,98.2% and 96.4%, respectively. Cake layer was accumulated on the membrane surface acted as a dynamic secondary biofilm which lead to the increase of physical removal rate. In addition, mathematical statistical models was built on the linear regression techniques for exploring the inner relationship between EPS and the performance of the AnMBR.

The performance and membrane fouling rate of a pilot-scale anaerobic membrane bioreactor for treating antibiotic solvent wastewater under different cross flow velocity

The performance of a pilot-scale anaerobic membrane bioreactor (AnMBR) for treating antibiotic solvent wastewater under different cross flow velocities (CFV) was investigated. Effects of mixed liquid suspended solids (MLSS), colloid total organic carbon (TOC) and CFV on membrane fouling rate (RMF) were also explored in this paper. Throughout 341 days of experiment, the average total removal rate of N, N-Dimethylformamide (DMF) was 98.5% which hardly affected by the variation of CFV, and the compliance rate of DMF was 92% according to the Chinese standard (<25 mg/L). However, the relevant high total removal rate of M-cresol (MC) was achieved as 97.5%, the content of effluent failed to meet the national level emission standard (<0.1 mg/L). The biogas yield and the methane content of the biogas increased gradually with the increase of CFV, and the average methane content were over 70%. There were four kinds of methanogens in AnMBR, Methanosaeta spp was the largest methanogenic community, with an area of 45-70% of the archae. There was a linear relationship between colloid TOC and RMF at different MLSS concentrations. Then a universal mathematical model for the changes of RMF with influence factors was established. The result showed that model well fitted the laboratory data. It is suggested that the model proposed could reflect and manage the membrane fouling of AnMBR treating antibiotic solvent wastewater.

Performance and methane fermentation characteristics of a pilot scale anaerobic membrane bioreactor (AnMBR) for treating pharmaceutical wastewater containing m-cresol (MC) and iso-propyl alcohol (IPA)

In this study, a pilot scale anaerobic membrane bioreactor (AnMBR) was operated for 80 days to treat pharmaceutical wastewater containing m-cresol (MC) and iso-propyl alcohol (IPA). The aim of the study is to investigate the performance and methane fermentation characteristics of AnMBR at different hydraulic retention time (HRT) (48, 36, 24, 18 and 12 h). The average total removal efficiencies of MC and IPA were 95%, 96% during the 80 days, which demonstrated that the AnMBR system performed well in the MC and IPA removal. The major volatile fatty acid (VFA) was found to be acetic acid, propionic acid, butyric acid, besides, the VFA accumulated apparently when HRT decreased to 12 h. The decrease of HRT led to an increase of relative abundance of methanosarcina from 13 to 33% and a decrease in biogas yield from 0.19 to 0.05 L/gCODremoval. The biogas production was found to increase dramatically at HRT of 36 h. The trend of methane content kept stable at this stage with the average value of 78.5% which higher than other HRTs. The investigation of methanogen community showed that methanosarcinaceae was always dominant acetoclastic methanogens and methanomicrobiales was the dominant hydrogen utilizers throughout the operational period. When the HRT dropped to 12 h, the growth of the methanosarcinaceae and methanomicrobiales was observed, the amount of the methanosarcinaceae and methanomicrobiales sharply increased. After the overall research, HRT of 36 h was chosen as the most suitable operating condition due to the comprehensively preferable performance and more economical.

Performance and kinetic model of degradation on treating pharmaceutical solvent wastewater at psychrophilic condition by a pilot-scale anaerobic membrane bioreactor

A pilot-scale anaerobic membrane bioreactor (AnMBR) was operated for 435 days in this study, aiming to treat pharmaceutical solvent wastewater containing m-Cresol (MC), isopropanol (IPA) and N,N-Dimethylformamide (DMF) pollutants at different temperatures of 35 ± 3 °C, 25 ± 3 °C, 15 ± 3 °C and 25 ± 3 °C, respectively. The reactor reached average total removal efficiencies of about 96%, 97.2% and 98% of MC, IPA and DMF at psychrophilic condition (15 ± 3 °C). Higher physical removal rate was obtained at 15 ± 3 °C due to the important contribution of membrane filtration. At this stage, the biogas production, methane content and specific methanogenic activity and extracellular polymeric substances of suspended sludge were observed with the lowest level. Moreover, the kinetic models for solvent degradation were established at different temperatures, results showed the smaller maximum specific substrate degradation rate of MC and IPA, besides, the lowest degradation rate of three solvents were obtained at 15 ± 3 °C.