Jianbo Guo

Study on a novel non-dissolved redox mediator catalyzing biological denitrification (RMBDN) technology

There are little literatures about the accelerating effect of redox mediators on the denitrification processes. In this paper, a novel non-dissolved redox mediator catalyzing biological denitrification (RMBDN) technology was first explored, and the accelerating effect of redox mediator on the denitrification processes was conducted with immobilized anthraquinone. Anthraquinone as a redox mediator was able to increase the denitrification rate, and was immobilized by entrapment in calcium alginate (CA). The results suggested that the artificial redox mediator anthraquinone was found to be capable of raising about 2-fold denitrification rate, and the stabilized oxidation-reduction potential (ORP) values with anthraquinone immobilization beads were lower around 20mV than the control without anthraquinone immobilization beads. The results of repeated-batch operations shown that anthraquinone immobilization beads appeared to exhibit good reusability. The study explored a great improvement of the redox mediator application and the new bio-treatment concept for the denitrification processes.

Reduction of Cr(VI) by Escherichia coli BL21 in the presence of redox mediators

Anthraquinone-2,7-disulfonate (2,7-AQDS), anthraquinone-1-sulfonate (α-AQS), anthraquinone-2-sulfonate (AQS), anthraquinone-2,6-disulfonate (AQDS) and anthraquinone-1,5-disulfonate (1,5-AQDS) were selected as redox mediators for Cr(VI) reduction by Escherichia coli BL21. In the presence of 0.8mmoll(-1) AQS, the Cr(VI) reduction efficiency was 98.5% in 7.5h, whereas it was only 21-34% in the absence of a mediator or in the presence of α-AQS, 1,5-AQDS, AQDS, 2,7-AQDS. A linear correlation, k=0.768C(AQS)+1.5531 (R(2)=0.9935), was found for the reaction constant, k (mg Cr(VI) g(-1) dry cell weight h(-1)) and the AQS concentration (C(AQS)). The Arrhenius equation described the Cr(VI) reduction in the tested temperature range, and the pre-exponential factor A was 13.249mg Cr(VI) g(-1) dry cell weight h(-1),and the activation energy Ea was 28.01kJmol(-1). Glucose was the best carbon sources, and the optimum pH was 6.0. The Cr(VI) reduction rate obtained with AQS is a significant improvement over low conventional anaerobic reduction rates.

Insight into biological phosphate recovery from sewage

The worlds increasing population means that more food production is required. A more sustainable supply of fertilizers mainly consisting of phosphate is needed. Due to the rising consumption of scarce resources and limited natural supply of phosphate, the recovery of phosphate and their re-use has potentially high market value. Sewage has high potential to recover a large amount of phosphate in a circular economy approach. This paper focuses on utilization of biological process integrated with various subsequent processes to concentrate and recycle phosphate which are derived from liquid and sludge phases. The phosphate accumulation and recovery are discussed in terms of mechanism and governing parameters, recovery efficiency, application at plant-scale and economy.

Study the catalyzing mechanism of dissolved redox mediators on bio-denitrification by metabolic inhibitors

The effect of dissolved redox mediators on denitrification by Paracoccus versutus sp. GW1 were studied with α-AQS, AQS, 1,5-AQDS, AQDS and 2,7-AQDS. AQDS presented the best catalytic effect which increased denitrification rate by 1.5-fold with 0.17 mmol L(-1). Denitrification rate was found to be pseudo-zero order with 0-0.32 mmol L(-1) AQDS (k=19.874C AQDS+10.301 (R(2)=0.9984)). The accelerating mechanism for respiratory chain was also explored by using metabolic inhibitors. Addition of AQDS eased the inhibitions of rotenone, dicumarol, sodium azide on respiratory chain, and enhanced the nitrite accumulation during bio-denitrification process. AQDS exhibited slight catalytic effect on nitrite denitrification. These results allowed us to deduce the accelerating site of AQDS on the denitrification respiratory chain. Increased nitrate denitrification by AQDS might mainly attribute to the accelerated electrons transfer from NADH to nitrate reductase via complex I and ubiquinone/ubiqunol. This study provided further understanding of the mechanism of redox mediators on denitrification.

Rapid start-up of the anammox process: Effects of five different sludge extracellular polymeric substances on the activity of anammox bacteria.

This study investigated the rapid start-up of the anaerobic ammonium oxidation (anammox) strategy by inoculating different biomass ratios of denitrifying granular sludge and anammox bacteria. The results demonstrated that two reactors (R1 and R2) were rapidly and successfully started-up on days 25 and 28, respectively, with nitrogen removal rates (NRRs) of 0.70kg/(m(3)·d) and 0.72kg/(m(3)·d) at biomass ratios of 10:1 (R1) and 50:1 (R2). The explanation for rapid start-up was found by examining the effect of five different sludge extracellular polymeric substances (EPS) on the activity of anammox bacteria in the batch experiments. Batch experiments results first demonstrated that the denitrification sludge EPS (DS-EPS) enhanced the anammox bacteria activity the most, and NO2(-)-N, NH4(+)-N removal rates were 1.88- and 1.53-fold higher than the control with optimal DS-EPS volume of 10mL. The rapid start-up strategy makes possible the application of anammox to practical engineering.

Effective and characteristics of anthraquinone-2,6-disulfonate (AQDS) on denitrification by Paracoccus versutus sp.GW1

The effects of anthraquinone-2,6-disulfonate (AQDS) on microbial populations and the biocatalysing characteristics of AQDS on denitrifying strain GW1 are discussed. The results showed that microbial population abundances were 30, 6, 12 and 18% during the different periods (1st, 5th, 10th and 20th days). Strain GW1 utilized AQDS as an electron acceptor in the respiration chain and reduced AQDS to hydroquinone (QH2). The nitrate removal efficiency of strain GW1 was increased 1.14–1.63 fold with 0.04–0.32 mmol/L AQDS. A linear correlation was found between the nitrate removal reaction constant (where VSS is volatile suspended solids) and AQDS concentration (CAQDS), which was k=19.332 CAQDS+11.115(R2=0.9749). The stabilized oxidation–reduction potential (ORP) values with AQDS were lower 22–92 mv than the control during the denitrification process. The concentration of nitrite sequentially accumulated up to around 250 mg/L when nitrate have removed completely. The results suggested that AQDS as redox mediator was capable of biocatalysing the nitrate and nitrite removal rate.

Development of bioreactor systems with functional bio-carrier modified by disperse turquoise blue S-GL for disperse scarlet S-BWFL decolorization

The effect of redox mediator has been studied in details in the bio-decolorization processes, but there are little literatures about bioreactor systems with functional bio-carrier modified by redox mediator. Two different bioreactor configurations (bioreactor R1 with functional bio-carrier modified by disperse turquoise blue S-GL (as redox mediator) and bioreactor R2 with non-modified bio-carrier) were designed and tested for disperse scarlet S-BWFL decolorization by Halomonas sp. GYW (EF188281) in this study. Influencing factors such as co-substrate, temperature and pH were optimized through batch experiments. Compared to bioreactor R2, bioreactor R1 exhibited good decolorization efficiency and performance ability for the disperse scarlet S-BWFL decolorization, which showed higher decolorization efficiency (over 96% color removal with 0.8 g L(-1) dye concentration) and less hydraulic retention time to attain the same decolorization efficiency. The combinational technology of redox mediator and bio-carrier was a new bio-treatment concept and a great improvement for the application of redox mediator.

Decolorization and Degradation of Azo Dyes by Redox Mediator System with Bacteria

Azo dyes are the largest and the most diverse group of synthetic dyes widely used in many industries, which are generally recalcitrant to biodegradation due to their xenobiotic nature. The effective treatment of azo dye wastewaters has been a big challenge, and up to now there is no single and economically attractive treatment that can effectively decolorize dyes. However, notable achievements have been conducted to explore the accelerating effects of different redox mediators during the anaerobic decolorization and degradation of azo dyes over the last two decades. The accumulated evidence suggest that redox mediators play a major role of electron shuttles in the reductive decolorization of azo dyes, both by chemical and biological mechanisms. This review is focused on the bacterial decolorization and degradation of azo dyes catalyzed by redox mediators and the further investigation to enhance the applicability of redox mediators on the bio-transformation of azo dyes.

Redox activity and accelerating capacity of model redox mediators during biodenitrification

The aim of this study was to analyse different model redox mediatiors: anthraquinone-2,7-disulphonate (2,7-AQDS), anthraquinone-1-sulphonate (α-AQS), anthraquinone-2-sulphonate (AQS) and anthraquinone-2,6-disulphonate (AQDS), with regard to the structure–activity relationship indicated by their cyclic voltammograms, their chemical structure, their oxidation–reduction potential and their capacity to accelerate the denitrification reaction during denitrification. Compared to the control, the nitrate removal after 21 h of denitrification was enhanced by a factor of 1.94, 1.56, 1.56 and 1.3 by 2,7-AQDS, AQDS, AQS and α-AQS, respectively. The ranking of the mediators based on their reduction potential ( ) was 2,7-AQDS > AQDS ≥ AQS > α-AQS. was positively correlated with accelerating the denitrification in experiments using 0.024 mmol·L−1 redox mediator, 360 mg L−1 NO3−–N and 5.0 g L−1 of dry cell weight. Practical computational approaches (the frontier orbital theory and the atoms-in-molecules theory) and inductive and resonance effects were also used to explain and assess how the molecular structure and stability of the redox mediators affect the accelerating capacity during denitrification.

Rapid start-up of denitrifying granular sludge by dosing with semi-starvation fluctuation C/N ratio strategy

This study cultivated denitrifying granular sludge in three UASB reactors by the semi-starvation fluctuation C/N ratio strategy (reactor 1 (R1): constant C/N ratio; R2: regular fluctuation C/N ratio; and R3: semi-starvation fluctuation C/N ratio (SSF)). Microbial aggregates appeared in R1, R2 and R3 on days 28, 14 and 6, respectively. Compared with the results in R1 and R2, the guanosine tetraphosphate (ppGpp) concentration was highest, the acyl homoserine lactones (AHLs) concentration quickly reached a certain threshold, and more protein (PN) of extracellular polymeric substances (EPS) secretion resulted in the rapid formation of denitrifying granular sludge in R3. The SSF strategy enhances microbial diversity, and denitrifying granular sludge has a better nitrogen removal performance. The result demonstrates that ppGpp, AHLs, EPS and the denitrifying sludge granulation process are associated. A mechanism for denitrifying sludge granulation with SSF strategy was proposed from the aspect of quorum sensing (QS).