Junguo He

Anaerobic biohydrogen production from monosaccharides by a mixed microbial community culture.

Monosaccharides (e.g. glucose and fructose) are produced from the hydrolyzation of macromolecules, such as starch, cellulose, hemicellulose and lignin, which are abundant in various industrial wastewaters. The elucidation of anaerobic activated sludge microbial community utilizing monosaccharides will lay an important foundation for the industrialization of biohydrogen production. In this study, the hydrogen production by a mixed microbial culture on four monosaccharides (glucose, fructose, galactose and arabinose) was investigated in a batch cultures. The mixed microbial culture was obtained from anaerobic activated sludge in a continuous stirred-tank reactor (CSTR) after 29 days of acclimatization. The results indicated that glucose had the highest specific hydrogen production rate of 358 mL/g.g mixed liquid volatile suspended solid (MLVSS), while arabinose had the lowest hydrogen production rate of 28 mL/g.gMLVSS. Glucose also possessed the highest specific conversion rate to hydrogen of 82 mL/g glucose, while fructose had the highest specific conversion rate to liquid product of 443 mg/g fructose. Arabinose had the lowest conversion rates to both liquid products and hydrogen. Metabolic pathways and fermentation products were the major reasons for the difference in hydrogen production from these four monosaccharides. The complex fermentation pathways of arabinose reduced its hydrogen production efficiency and a long acclimation period (over 68 h) was required before the anaerobic activated sludge could effectively utilize arabinose in batch cultures.

Hydrogen-producing capability of anaerobic activated sludge in three types of fermentations in a continuous stirred-tank reactor

A continuous stirred-tank reactor was used as an anaerobic sludge system and the hydrogen production capabilities of three typical fermentations, in terms of specific hydrogen production rates, were investigated under the same hydraulic retention times (8 h) and influent chemical oxygen demand (5000 mg/L) at 35 degrees C. The reactor was continuously fed with diluted molasses, while the pH and oxidation reduction potential in the reactor were regulated to control the type of fermentation. The specific hydrogen production rate of the anaerobic sludge reached 2.96 mol/kg mixed liquid volatile suspended solid (MLVSS)/day, (mol x kg MLVSS(-1) d(-1)), in ethanol-type fermentation, while 0.57 mol x kg MLVSS(-1) d(-1) in butyric acid-type fermentation, and 0.022 mol x kg MLVSS(-1) d(-1) in propionic acid-type fermentation. The hydrogen production capability of ethanol-type fermentation was 4.11 times greater than that of butyric acid-type fermentation and 148 times that of propionic acid-type fermentation.

Assessment of the effects of dry anaerobic co- digestion of cow dung with waste water sludge on biogas yield and biodegradability

Dry anaerobic digestion has been treated as feasible process for potential renewable energy recovery with nutrient-rich fertilizer and sustainable solid waste management. Dry methane fermentation of undiluted cow manure (CM), waste water sludge (WWS) and their mixtures into different ratios were conducted at 35°C in the laboratory-scale single-stage batch reactors for 63 days. The specific biogas production obtained for the CM/WWS ratios of 1:0, 4:1, 3:2, 2:3, 1:4 and 0:1 were 56.94, 58.51, 61.64, 63.12, 59.30 and 55.39 L/kg, with methane yield were 32.01, 33.14, 35.31, 36.91, 34.76 and 32.63 L/kg respectively. The experimental results showed that the co-digestion with CM/WWS ratio of 2:3 obtained highest total biogas production of 63.12 L/kg, methane yield of 0.328 m3/kgVS and total solid (TS), volatile solids (VS), chemical oxygen demand (COD), total organic carbon (TOC) reductions of 34.24, 54.80, 55.22 and 70.71% compared to the other co-digestion ratios and single digestions. It was also revealed that co-digestion resulted in 3.11-13.99% higher methane gas yields, due to synergistic effect. The synergistic effect is mainly attributed to more balanced nutrients and increased buffering capacity. n n xa0 n n Key words:xa0Dry anaerobic digestion process, co-digestion, specific energy production, methane.

Role of aeration intensity on performance and microbial community profiles in a sequencing batch reaction kettle (SBRK) for wastewater nutrients rapid removal.

A lab-scale SBRK was operated to investigate the effects of aeration intensity on the system performance and microbial community dynamics within it. Results showed that the sewage nutrients was removed rapidly (just about 3-6h) with the aeration intensity increasing from 0 to 0.6MPa. Average effluent parameters were: COD below 50mg/L, NH4(+)-N less than 1mg/L, 1.5-4.5mg/L for nitrate and TP below 0.5mg/L. The highest community similarity and diversity emerged simultaneously with the aeration pressure rising from 0.2 to 0.4MPa, which was regarded as the optimal aeration intensity range. Microbial community shifted obviously and the function species of Comamonadaceae, Dechloromonas, Flavobacterium and Nitrospira dominated in the corresponding communities. RDA indicated that aeration intensity was the main factor for regulating system communities to optimize the system performance. It inferred that high aeration pressure played a key role on sewage nutrients rapid removal.

Role of N-acyl-homoserine lactone (AHL) based quorum sensing on biofilm formation on packing media in wastewater treatment process

Quorum sensing (QS) signaling has been extensively studied in granules and single species populations. However, the knowledge regarding QS in biofilm formation on packing media has neither been experimentally explored nor theoretically addressed. We performed a long-term study to investigate the links between QS, organization and composition of complex microbial communities when biofilm developed on packing media. Three distinct phases were defined according to the weight of the biofilm and the removal rate of COD and ammonia nitrogen. Four kinds of N-acyl-homoserine-lactone (AHL) were found to be regularly and positively correlated with biofilm in growth stage (activation phase) (p < 0.01), while the correlation was not significant in other phases. Total AHL level was also closely related to the productions of extracellular polymeric substance (EPS), especially in polysaccharide. Sequence analysis results revealed that community structure changed with growth of biofilm, and top 34 most abundant community members had a significant correlation with AHLs production. Notably, biofilm and production of EPS, as well as community structure changed after dosing with nanomolar level of exogenous AHL in stable and mature biofilm, but this change was not a signal concentration-dependent manner. This study provides a foundation for investigation of QS effect on biofilm formation on packing media in many natural and engineered ecosystems, where it coordinates community behavior.

Microbial community related to lysozyme digestion process for boosting waste activated sludge biodegradability

Waste activated sludge from a lab-scale sequencing batch reactor was used to investigate the potential relation of microbial community with lysozyme digestion process for sludge solubilization. The results showed the microbial community shifted conspicuously as sludge suffered lysozyme digestion. Soluble protein and polysaccharide kept an increasing trend in solution followed with succession of microbial community. The rise of lysozyme dosage augmented the dissimilarity among communities in various digested sludge. A negative relationship presented between community diversity and lysozyme digestion process under various lysozyme/TS from 0 to 240min (correlation coefficient R(2) exceeded 0.9). Pareto-Lorenz curves demonstrated that microbial community tended to be even with sludge disintegration process by lysozyme. Finally, with diversity (H) decrease and community distribution getting even, the SCOD/TCOD increased steadily in solution which suggested the sludge with high community diversity and uneven population distribution might have tremendous potential for improving their biodegradability by lysozyme digestion.

Biofouling control by biostimulation of quorum-quenching bacteria in a membrane bioreactor for wastewater treatment.

Bacterial quorum quenching (QQ) has been shown to be effective in controlling biofouling in membrane bioreactors (MBRs) for wastewater treatment. However, the encapsulation of a sufficient level of QQ bacteria is complicated and difficult. In plant research, gamma‐caprolactone (GCL), which is structurally similar to the quorum signal, N‐acyl homoserine lactone (AHL), was successfully used to specifically stimulate AHL‐degrading bacteria (biostimulation) in hydroponic systems to control blackleg and soft rot diseases in potato. In this study, the feasibility of enriching QQ bacteria from activated sludge by GCL was examined, and the effect of biostimulation on biofouling control in MBR treating domestic wastewater was investigated. The results showed that after enrichment with GCL, activated sludge could effectively degrade AHLs, and a QQ gene (qsdA) was augmented. The proposed biostimulation QQ strategy, by introducing and continuously dosing GCL, could significantly increase QQ activity, decrease AHL, control the secretion of extracellular polymeric substances (EPS), and thus, effectively control biofouling in an MBR. This biostimulation QQ strategy provides a more convenient option for biofouling control in MBR applications. Biotechnol. Bioeng. 2016;113: 2624–2632.

Biofilm activity and sludge characteristics affected by exogenous N-acyl homoserine lactones in biofilm reactors

This study verified the effect of N-acyl homoserine lactone (AHL) concentrations on mature biofilm systems. Three concentrations of an AHL mixture were used in the batch test. Introducing of 5nM AHLs significantly increased biofilm activity and increased sludge characteristics, which resulted in better pollutant removal performance, whereas exogenous 50nM and 500nM AHLs limited pollutant removal, especially COD and nitrogen removal. To further identify how exogenous signal molecular affects biofilm system nitrogen removal, analyzing of nitrifying bacteria through real-time polymerase chain reaction (RT-PCR) revealed that these additional signal molecules affect nitrifying to total bacteria ratio. In addition, the running state of the system was stable during 15days of operation without an AHL dose, which suggests that the changes in the system due to AHL are irreversible.

Removal of heavy metals with sequential sludge washing techniques using saponin: optimization conditions, kinetics, removal effectiveness, binding intensity, mobility and mechanism

Testing of sequential sludge washing in triplicate using typical biosurfactant saponin was conducted to remove heavy metals. The aim of the testing was to improve efficiency and reduce mobility of heavy metals. Different washing conditions such as concentration, contact time, liquid/solid ratio and pH were optimized. The heavy metal desorption performances were investigated strictly and the experimental data fitted the pseudo-second order equation very well. A sequential washing step and heavy metal mobilization was investigated, and the results demonstrated that the total content and fractions of the heavy metals reached remarkable extraction efficiencies, after three washings, Cr obtained the highest extraction efficiency (65.00%), and the Pb exchangeable fraction acquired the highest extraction efficiency (85.00%). Also, the heavy metal binding intensity and mobility were investigated, and the results indicated that the heavy metal binding intensity (IR) increased after washing, conversely, the mobility (MF) decreased, due to the weak fractions extracted by saponin. The toxicity characteristic leaching procedure (TCLP) indicated that heavy metals have more stable fractions in the after washing sludge. SEM, FTIR and XRD revealed that mechanism of saponin enhanced heavy metal extraction from the sludge, elucidated that carboxyl and hydroxyl were the main functional groups. This study indicated that the saponin may be a replacement for organic acids, inorganic acids and less environmentally friendly refractory chelators in the extraction of heavy metals from the sludge.

Removal of heavy metal from sludge by the combined application of a biodegradable biosurfactant and complexing agent in enhanced electrokinetic treatment

In this work, the heavy metal removal potentiality of an electrokinetic (EK) decontamination treatment enhanced by a biodegradable complexing agent Tetrasodium of N, N-bis (carboxymethyl) glutamic acid (GLDA) also in combination with a biodegradable biosurfactant (rhamnolipid) was investigated to decontaminate heavy metals from the sludge. The main results explored that the nature of sludge and their interactions with different improving agents significantly influenced the electrokinetic removal processes. A general increase of pH values from anode to cathode in the sludge-cell was observed due to the strong buffering capacity of carbonates. Compared with the deionized water, the use of GLDA as an electrolyte, Cu, Zn, Cr, Pb, Ni and Mn removal efficiencies were 53.2xa0±xa03.12%, 67.4xa0±xa03.45%, 59.2xa0±xa04.78%, 45.4xa0±xa04.15%, 72.8xa0±xa03.68% and 45.0xa0±xa04.85%, respectively, whereas a further improvement heavy metals removal efficiencies (Cu, Zn, Cr, Pb, Ni and Mn removal efficiencies were 64.8xa0±xa02.34%, 56.8xa0±xa04.12%, 49.4xa0±xa04.45%, 46.6xa0±xa02.35%, 60.4xa0±xa03.45% and 69.6xa0±xa03.54%, respectively) were achieved by repalcing rhamnolipid as the electrolyte. Significantly higher removal efficiencies (Cu, Zn, Cr, Pb, Ni and Mn removal efficiencies were 70.6xa0±xa03.41%, 82.2xa0±xa05.21%, 89.0xa0±xa03.34%, 60.0xa0±xa04.67%, 88.4xa0±xa04.43% and 70.0xa0±xa03.51%, respectively) were obtained by the simultaneous use of GLDA and rhamnolipid due to their synergic action in electrokinetic process.