Maoan Du

Removal of phenols, thiocyanate and ammonium from coal gasification wastewater using moving bed biofilm reactor

A laboratory-scale moving bed biofilm reactor (MBBR) with a volume of 4 L was used to study the biodegradation of coal gasification wastewater. Maximum removal efficiencies of 81%, 89%, 94% and 93% were obtained for COD, phenols, SCN(-) and NH(4)(+)-N, respectively. NO(2)(-)-N accumulation induced increase of effluent COD concentration when the hydraulic residence time (HRT) decreased. Phenols removal was not affected when the HRT decreased from 48 to 32 h. Effluent SCN(-) and NH(4)(+)-N concentration increased with the decrease of the HRT, and decreased gradually when the HRT returned to 48 h. Batch experiments were carried out to study performance of the suspended and attached growth biomass in the MBBR.

Aerobic denitrification by novel isolated strain using NO―2—N as nitrogen source

Biological denitrification reaction can be achieved under aerobic environment. Few aerobic denitrifiers using nitrite as sole nitrogen source were identified. Using nitrite as the sole nitrogen source, this work assessed the denitrification activity of yy7, an aerobic heterotrophic denitrifier identified as Pseudomonas sp. (94% similarity) by 16S rRNA sequencing analysis. The logistic equation describes the cell growth curve, yielding a generation time of 2.9h at an initial 18 mg l(-1)NO(-)₂-N. Reduction of NO(-)₂-N was primarily achieved during its logarithmic growth phase, and was accompanied by an increase in suspension pH and near complete consumption of dissolved oxygen. Three genes relating to nirK, norB, and nosZ were noted to involve in isolate strain. Isolate yy7 can survive and remove up to 40 mg l(-1)NO(-)₂-N and, hence, can be applied as an effective aerobic denitrifier during simultaneous nitrification and denitrification via nitrite processes.

Electrokinetic remediation and microbial community shift of β-cyclodextrin-dissolved petroleum hydrocarbon-contaminated soil

Electrokinetic (EK) migration of β-cyclodextrin (β-CD), which is inclusive of total petroleum hydrocarbon (TPH), is an economically beneficial and environmentally friendly remediation process for oil-contaminated soils. Remediation studies of oil-contaminated soils generally prepared samples using particular TPHs. This study investigates the removal of TPHs from, and electromigration of microbial cells in field samples via EK remediation. Both TPH content and soil respiration declined after the EK remediation process. The strains in the original soil sample included Bacillus sp., Sporosarcina sp., Beta proteobacterium, Streptomyces sp., Pontibacter sp., Azorhizobium sp., Taxeobacter sp., and Williamsia sp. Electromigration of microbial cells reduced the biodiversity of the microbial community in soil following EK remediation. At 200xa0Vu2009m−1 for 10xa0days, 36% TPH was removed, with a small population of microbial cells flushed out, demonstrating that EK remediation is effective for the present oil-contaminated soils collected in field.

Continuous volatile fatty acid production from waste activated sludge hydrolyzed at pH 12.

This study adopted rapid alkaline treatment at pH 12 to hydrolyze 66% of total chemical oxygen demands. Then the hydrolyzed liquor was fermented in a continuous-flow stirred reactor to produce volatile fatty acids (VFAs) at 8-h hydraulic retention time and at 35 °C. The maximum VFA productivity reached 365 mg VFAs g(-1) volatile suspended solids in a 45-d operation, with most produced VFAs being acetate and propionate, principally produced by protein degradation. The Bacteroidia, ε-proteobacteria and the Clostridia were identified to be the classes correlating with the fermentation processes. The fermented liquor was applied to denitrifying phosphorus removal process as alternative carbon source after excess phosphorus and nitrogen being recycled via struvite precipitation. Fermented liquors from alkaline hydrolysis-acid fermentation on waste activated sludge are a potential renewable resource for applications that need organic carbons.

Enhanced production of volatile fatty acids (VFAs) from sewage sludge by β-cyclodextrin

Organic matter in sewage sludge can be converted into volatile fatty acids (VFAs) as renewable carbon sources. This work for the first time demonstrates that β-cyclodextrin (β-CD) molecules enhance sludge hydrolysis for production of VFAs. With 0.2gβ-CDg(-1) dried solids (DSs), the increment rate for VFAs peaked at 4200gg(-1)DSsg(-1) β-CD, with acetate and propionate as the predominant VFAs. Compositional and microbial community analyses confirm that the β-CD molecules break a cells membrane, such that it releases intracellular substances. Although β-CD molecules inhibited activities of methanogens, they did not impair those of acid-forming bacteria, thereby demonstrating that β-CD-assisted VFAs are renewable organic carbon sources, except in anaerobic digestion processes.

Improved volatile fatty acids production from proteins of sewage sludge with anthraquinone-2,6-disulfonate (AQDS) under anaerobic condition

Organic matters in sewage sludge can be converted into volatile fatty acids (VFAs) as renewable carbon sources. This work for the first time applied anthraquinone-2,6-disulfonate (AQDS) for enhancing VFA production from sewage sludge. With 0.066 or 0.33 g AQDS g(-1) dried solids (DS), the yields for VFAs peak at 403 or 563 mg l(-1), 1.9- or 2.7-fold to the control. The accumulated VFAs were principally composed of acetate and propionate. The AQDS enhances degradation rates of model proteins (bovine serum albumin), but had little enhancement on that of model polysaccharides (dextrans). The acidification step is proposed the rate-limiting step for VFA production from sewage sludge, in which the AQDS molecules shuttle electrons to accelerate the redox reactions associated with amino acid degradation. Methanogenic activities are inhibited in the presence of AQDS. The AQDS-assisted VFAs are renewable organic carbon sources, although their direct use for anaerobic digestion is not advised.

Effect of nitrate concentration on performance of pre-denitrification moving bed biofilm reactor system in treating coal gasification wastewater

Abstract An anoxic moving bed biofilm reactor (ANMBBR) followed by an aerobic moving bed biofilm reactor (AEMBBR) operated as pre-denitrification system was used to investigate the effect of different influent NO3 −-N concentrations on performance of the pre-denitrification system in treating real coal gasification wastewater. Influent NO3 −-N concentration was controlled at 50, 100, 200, and 400u2009mg/L during the experiments. Evolution of COD and phenols in the effluent of the ANMBBR and AEMBBR, and performance of nitrification in the AEMBBR with different influent NO3 −-N concentrations were studied. Almost complete denitrification was achieved when influent NO3 −-N concentration was 100u2009mg/L. NO3 −-N and NO2 −-N accumulated in the effluent of the ANMBBR with influent NO3 −-N concentrations of 200 and 400u2009mg/L. NO3 −-N concentration of 400u2009mg/L facilitated high NH4 +-N removal efficiency in the AEMBBR when influent NH4 +-N concentration was around 165u2009mg/L. The ratio of CODconsumed/NO3 −-Nconsumed along w...

Succession of bacterial community in anaerobic–anoxic–aerobic (A2O) bioreactor using sludge fermentation liquid as carbon source

AbstractTo analyze the effect of sludge fermentation liquid on succession of bacterial community as carbon source, a three-month-long experiment was conducted in anaerobic–anoxic–aerobic process at room temperature. Experimental results showed that the removal efficiencies of total nitrogen and total phosphorus were improved to 84.7 and 94.3% from 64.5 and 54.2% at flow ratio of fermentation liquid and municipal wastewater, 1:35. Meanwhile, the principal component analysis demonstrated that significant shifts of bacterial community were observed with fermentation liquid addition. In particular, fermentation liquid appeared to be selective for the phosphorus-removal bacteria Gammaproteobacteria, denitrifying bacteria Comamonas sp., nitrogen-removal bacteria Betaproteobacteria, and denitrifying phosphate accumulating organisms Sphingobacterium, indicating simultaneous nitrification and denitrification, and denitrifying dephosphatation might be present after fermentation liquid addition.

Characteristics of flocs formed by polyaluminum chloride during flocculation after floc recycling and breakage

AbstractThe formation and the size distribution of the flocs were studied using a floc imaging system, and the relationship between breakage/regrowth of flocs from coagulation and flocculation with polyaluminum chloride and flocculation by floc recycling was investigated, from which it was found that both the processes exhibited similar performance in adsorption/charge neutralization zones; however, there were significant differences in restabilization and sweep coagulation zones. In adsorption/charge neutralization zones, the size distribution of flocs shifted toward flocs growth during the two processes. At the coagulant dosage of less than 0.010u2009mmolu2009L−1, the residual turbidity and the particle number frequency of small flocs decreased, and both increased at the coagulant dosage of more than 0.010u2009mmolu2009L−1. In restabilization and sweep coagulation zones, the floc size distribution shifted toward floc withering. Residual turbidity deterioration occurred after the breakage/regrowth of flocs, which was re...

Two-stage mesophilic anaerobic digestion from waste activated sludge enhanced by low-temperature thermal hydrolysis

AbstractTwo-stage mesophilic anaerobic digestion of waste activated sludge was conducted to enhance methane production by low-temperature thermal hydrolysis. Two steady stages were evaluated: the first acidogenic stage was operated at sludge retention times of 2xa0d, and the second methanogenic stage was controlled at hydraulic retention times of 8xa0d. Thermal hydrolysis results showed that more chemical oxygen demand, proteins and carbohydrates were released from sludge as temperature increased from 50 to 120°C. Protein-like substances were major components from three-dimensional (3D) excitation–emission matrix analysis, and their fluorescence intensities were matched with temperatures. Sludge extracellular structure was disintegrated from scanning electron microscope analysis when the temperature was beyond 80°C. The volatile fatty acids (VFAs) and methane production had positive relation to the soluble organic matters after low-temperature hydrolysis. About 100°C was the suitable temperature for sludge di...