Long-Fei Ren

Effect of zero-valent iron on the start-up performance of anaerobic ammonium oxidation (anammox) process

The long start-up time of anaerobic ammonium oxidation (anammox) process hinders the widespread application of anammox technology in practical wastewater treatment when anammox seed sludge is not available. Meanwhile, the production of nitrate cannot meet the increasingly more strict discharge standards. To combine the chemical nitrate reduction to ammonium with biological nitrogen removal, two anammox upflow anaerobic sludge blanket reactors packed with different types of zero-valent iron (ZVI), microscale ZVI (mZVI) and nanoscale ZVI (nZVI), were developed to accelerate the start-up of anammox process. The results revealed that anammox start-up time shortened from 126 to 105 and 84xa0days with the addition of mZVI and nZVI. The nitrogen removal performance was also improved remarkably by adding ZVI, especially in the start-up stage. The value of dissolved oxygen showed that ZVI could be regarded as a useful deoxidant to create anaerobic condition for the proliferation of anammox bacteria. ZVI was favorable for the secretion of EPS, which would represent the activity of anammox bacteria. The result of real-time quantitative PCR (qPCR) further confirmed that the proliferation of anammox bacteria was enhanced by ZVI.

Phenol biodegradation and microbial community dynamics in extractive membrane bioreactor (EMBR) for phenol-laden saline wastewater

An extractive membrane bioreactor (EMBR) for phenol-laden saline wastewater was set up in this study to investigate the variations of phenol removal, extracellular polymeric substance (EPS) release and microbial community dynamics. The gradual release of phenol and the total separation of salt were achieved by silicon rubber tube membrane. Only phenol (55.6-273.9mg/L) was extracted into microorganism unit from wastewaters containing 1.0-5.0g/L phenol and 35.0g/L NaCl. After 82d of EMBR operation, maximal 273.9mg/L of phenol was removed in EMBR. Low concentration of phenol in wastewater (2.5g/L) played a favorable effect on the microbial community structure, community and dynamics. The enumeration of Proteobacteria (30,499 sequences) significantly increased with more released EPS (82.82mg/gSS) to absorb and degrade phenol, compared to the virgin data without phenol addition. However, high concentration of phenol showed adverse effects on EPS release, microbial abundance and biodiversity.

Enhancement of anammox performance in a novel non-woven fabric membrane bioreactor (nMBR)

To reduce operating costs and membrane fouling of conventional membrane bioreactors (cMBR), a novel MBR using a non-woven fabric membrane (nMBR) was constructed and the performance of the two MBRs was compared for anaerobic ammonium oxidation (anammox) cultivation. The results showed that the start-up period for the nMBR (44 days) was notably shorter than that for the cMBR (56 days), meanwhile the nMBR achieved a 2-times higher nitrogen removal rate (231.5 mg N per L per d) compared to the cMBR (112.3 mg N per L per d). Illumina MiSeq sequencing showed that Candidatus Kuenenia and Candidatus Jettenia were the main distinguished anammox bacteria. FISH analysis revealed that anammox bacteria predominated in both reactors, especially in the nMBR (58%) corresponding to a qPCR analysis of 1.07 × 109 copies per mL (day 120). N2O emission analysis confirmed the advantage of the nMBR in N2O reduction to reduce the influence of greenhouse gas emission while treating identical nitrogen. These results clearly demonstrated that nMBRs could be a prospective choice for anammox start-up and performance enhancement.

Novel zero-valent iron-assembled reactor for strengthening anammox performance under low temperature

To further expand the application of anammox biotechnology, a novel zero-valent iron-assembled upflow anaerobic sludge bed reactor was employed to strengthen anammox performance under low temperature and shock load. Packed with sponge iron and polyester sponge, this novel reactor could speed up the recovery of anammox activity in 12xa0days and improve the adaptability of anammox bacteria at the temperature of 10–15xa0°C. The high nitrogen loading rate of 1109.2xa0mg N/L/day could be adapted in 27xa0days and the new nitrogen pathway under the effect of sponge iron was clarified by batch experiment. Moreover, the real-time quantitative PCR analysis and Illumina MiSeq sequencing verified the dominant status of Candidatus Kuenenia stuttgartiensis and planctomycete KSU-1, as well as demonstrated the positive role of sponge iron on anammox microorganisms’ proliferation. The findings might be beneficial to popularize anammox-related processes in municipal and industrial wastewater engineering.

Bioremediation of wastewaters with decabromodiphenyl ether by anaerobic granular sludge

Facilities adopting anaerobic granular sludge are widely used for the treatment of high strength wastewater, and hence collect many polybrominated diphenyl ethers (PBDEs), especially decabromodiphenyl ether (BDE-209). We initiated a detailed investigation to gain insight into the bioremoval of BDE-209 by anaerobic granules. Influenced by solution pH, ionic strength and temperature, the equilibrium time was ∼6 h and the biosorption amount increased from 0.099 to 1.25 mg/g suspended sludge with the increase of BDE-209 concentrations. Kinetic studies indicate that BDE-209 biosorption on anaerobic granules follows the pseudo second-order kinetic model. Isotherm analysis exhibits that the Langmuir model fits the data at low temperature, while the Freundlich model is appropriate at room temperature. Thermodynamic analysis shows that biosorption followed an endothermic path and was nonspontaneous with negative value of ΔG0. XPS and FTIR spectra confirmed that oxygen and nitrogen atoms notably contributed to BDE-209 binding.

Phenol separation from phenol-laden saline wastewater by membrane aromatic recovery system-like membrane contactor using superhydrophobic/organophilic electrospun PDMS/PMMA membrane

Phenol recovery from phenol-laden saline wastewater plays an important role in the waste reclamation and pollution control. A membrane aromatic recovery system-like membrane contactor (MARS-like membrane contactor) was set up in this study using electrospun polydimethylsiloxane/polymethyl methacrylate (PDMS/PMMA) membrane with 0.0048u202fm2 effective area to separate phenol from saline wastewater. Phenol and water contact angles of 0° and 162° were achieved on this membrane surface simultaneously, indicating its potential in the separation of phenol and water-soluble salt. Feed solution (500u202fmL) of 0.90u202fL/h and receiving solution (500u202fmL) of 1.26u202fL/h were investigated to be the optimum conditions for phenol separation, which corresponds to the employed Reynolds number of 14.6 and 20.5. During 108-h continuous separation for feed solution (2.0u202fg/L phenol, 10.0u202fg/L NaCl) under room temperature (20u202f°C), 42.6% of phenol was recycled in receiving solution with a salt rejection of 99.95%. Meanwhile, the mean phenol mass transfer coefficient (Kov) was 6.7u202f×u202f10-7u202fmu202fs-1. As a membrane-based process, though the permeated phenol increased with the increase of phenol concentration in feed solution, the phenol recovery ratio was determined by the membrane properties rather than the pollutant concentrations. Phenol was found to permeate this membrane via adsorption, diffusion and desorption, and therefore, the membrane fouling generated from pore blockage in other membrane separation processes was totally avoided.

Bacterial community evolutions driven by organic matter and powder activated carbon in simultaneous anammox and denitrification (SAD) process

A distinct shift of bacterial community driven by organic matter (OM) and powder activated carbon (PAC) was discovered in the simultaneous anammox and denitrification (SAD) process which was operated in an anti-fouling submerged anaerobic membrane bio-reactor. Based on anammox performance, optimal OM dose (50u202fmg/L) was advised to start up SAD process successfully. The results of qPCR and high throughput sequencing analysis indicated that OM played a key role in microbial community evolutions, impelling denitrifiers to challenge anammoxs dominance. The addition of PAC not only mitigated the membrane fouling, but also stimulated the enrichment of denitrifiers, accounting for the predominant phylum changing from Planctomycetes to Proteobacteria in SAD process. Functional genes forecasts based on KEGG database and COG database showed that the expressions of full denitrification functional genes were highly promoted in RC, which demonstrated the enhanced full denitrification pathway driven by OM and PAC under low COD/N value (0.11).

The effect of magnetite on the start-up and N2O emission reduction of the anammox process

In order to observe the effect of magnetite during anammox start-up and stabilization stages, a novel up-flow anaerobic sludge blanket reactor using magnetite as a functional bio-carrier was designed and operated. Continuous experiments indicated that magnetite could shorten the endogenous denitrification stage and improve the nitrogen removal rate. The nitrogen removal performance increased from −0.06 to 1.17 kg N per m3 per d of R1 and from −0.08 to 1.18 kg N per m3 per d of R0 (as control reactor) on day 150. Analysis of variance (ANOVA) results of NRR during days 90–150 showed that R1 was statistically different from R0 (p = 0.045 < 0.05). The corresponding quantitative polymerase chain reaction results of nirS and nirK, fluorescence in situ hybridization results and Illumina MiSeq sequencing showed that proliferation of the anammox bacteria was promoted by magnetite with an increase of the nitrogen loading rate. The reduced N2O emission (25.06 ± 15.27 μmol L−1) combined with the reduced nosZ qPCR results (2.26 ± 0.029 × 106 copies per ng) revealed that this magnetite–anammox reactor also can serve as an ideal alternative for N2O emission reduction in ammonium-rich wastewater treatment.

Microbial dynamics of biofilm and suspended flocs in anammox membrane bioreactor: The effect of non-woven fabric membrane

Membrane bioreactor with non-woven fabric membranes (NWMBR) is developing into a suitable method for anaerobic ammonium oxidation (anammox). As a carrier, non-woven fabric membrane divided total biomass into biofilm and suspended flocs gradually. Total nitrogen removal efficiency was maintained around 82.6% under nitrogen loading rate of 567.4mgN/L/d after 260days operation. Second-order substrate removal and Stover-Kincannon models were successfully used to simulate the nitrogen removal performance in NWMBR. High-throughput sequence was employed to elucidate the underlying microbial community dynamics. Candidatus Brocadia, Kuenenia, Jettenia were detected to affirm the dominant status of anammox microorganisms and 98.2% of anammox microorganisms distributed in biofilm. In addition, abundances of functional genes (hzs, nirK) in biofilm and suspended flocs were assessed by quantitative PCR to further investigate the coexistence of anammox and other microorganisms. Potential nitrogen removal pathways were established according to relevant nitrogen removal performance and microbial community.

Changes in degrading ability, populations and metabolism of microbes in activated sludge in the treatment of phenol wastewater

Herein, changes in the degrading ability, populations and metabolism of microbes in activated sludge exposed to 60–350 mg L−1 phenol are thoroughly investigated. A phenol degradation experiment is conducted using activated sludge as inoculum over 140 days. The results suggest that the sludge efficiently degrades 250 mg L−1 phenol; however, it is unable to remove 350 mg L−1 phenol completely in two days, which might be caused by the decreased activities of catechol 1,2 dioxygenase (C12O) and catechol 2,3 dioxygenase (C23O). The specific oxygen uptake rate (SOUR) of the sludge and extracellular polymeric substances (EPS) generation are inhibited at the beginning of phenol degradation and then increase with phenol loading. A large amount of humic acid (HA) is produced during the degradation of 350 mg L−1 phenol due to cell decomposition. Illumina-MiSeq sequencing indicates that denitrifiers are competitive clusters at high phenol concentrations. The present study provides a comprehensive understanding of mechanisms of microbial responses to toxic compounds.