Biomedical subjects

Hanchang Shi

Publications and source records attributed to Hanchang Shi.

11 recordsLinked to original sources

PubMed2004

Enhancement of 2,4-dichlorophenol degradation in conventional activated sludge systems bioaugmented with mixed special culture.

Efficient and reliable removal of recalcitrant compounds, which are present in wastewater intermittently, is critically important to prevent toxicity discharge and system upset, especially for those biotreatment systems with poor anti-shock loading capacity such as conventional activated sludge (CAS) systems. In this study, 2,4-dichlorophenol (2,4-DCP) was chosen as a model recalcitrant substance. 2,4-DCP degrading mixed culture was bioaugmented to a CAS system in terms of enhancing 2,4-DCP removal and maintaining system stability under shock loading conditions. The effects of bioaugmentation on the performance of CAS systems after single inoculation were investigated under long-term continuous operation, during which four times shock loading occurred. Results showed that the two bioaugmented CAS systems, which were inoculated with 5% and 15% 2,4-DCP degrading mixed culture, respectively, demonstrated and maintained stronger ability to degrade 2,4-DCP than the non-supplemented control one during the first three shock loading periods within the first month after the first inoculation. For the fourth 2,4-DCP shock loading which occurred 100 days after inoculation, the advantages demonstrated by the bioaugmented systems were greatly reduced compared to those of the previous three runs. In addition, ribosomal intergenic spacer analysis method was used to track the supplemented special culture and assay the effect of bioaugmentation on the changes of microbial community structure.

Anthelmintics↗

PubMed2003

Biodegradation of 2,4-dichlorophenol in sequencing batch reactors augmented with immobilized mixed culture.

2,4-Dichlorophenol (2,4-DCP) degrading mixed culture was immobilized in polyvinyl alcohol jel beads and supplemented to sequencing batch reactors (SBR) to treat 2,4-DCP containing wastewater. Impacts of bioaugmentation level on the performance of bioaugmented systems were studied. Results show that inoculum size affected the start-up time of the SBR systems. For the non-augmented SBR system, nine days was needed for the system to start-up, whereas it only took six, four, three and two days for the SBRs with 1.9%, 3.7%, 5.6% and 9.3% immobilized culture, respectively. In addition, bioaugmented SBR systems demonstrated stronger capacity to cope with high 2,4-DCP shock loading than the control system. The control SBR failed to treat 2,4-DCP at 166 mg/l in influent, while the SBR with 1.9% inoculation could successfully cope with 2,4-DCP at 166 mg/l, but failed at 250 mg/l, and the SBR with 3.7%, 5.6% and 9.3% immobilized culture could successfully degrade 250 mg/l 2,4-DCP in feed. Furthermore, the contributions to the removal of 2,4-DCP by the introduced and indigenous culture in an augmented SBR system at various operation stages were investigated. It was found that augmented culture played the primary role in degrading 2,4-DCP at the beginning of system start-up, but after one-month operation, both the indigenous and the introduced culture posed strong ability to degrade 2,4-DCP.

Anthelmintics↗

PubMed2003

[Effects of phenol presence on the biodegradation of 2,4-dichlorophenol in a bioaugmented system].

Special culture for 2,4-Dichlorophenol(2,4-DCP) degradation were supplemented to an activated sludge system and the effects of the presence of phenol at various concentration on the removal of 2,4-DCP were studied. In addition, the changes of the removal rate of 2,4-DCP and phenol under the long existence of phenol was investigated in semicontinuous test. Results show than the presence of phenol at the concentration of 10 mg/L, 50 mg/L, 100 mg/L and 300 mg/L inhibit the biodegradation of 2,4-DCP and the inhibition increased with increasing of phenol concentration. 2, 4-DCP biodegradation rate declined with the run of semi-continuous test, while the biodegradation rate of phenol was much faster than the first run.

Bacteria↗

PubMed2003

[Observation and comparison on microstructure of immobilized Aerobacillus fusiformis under wastewater treatment].

Aiming at printing ink wastewater, a strain of bacterium was isolated from activated sludge, and identified as Aerobacillus fusiformis. The Aerobacillus fusiformis was respectively immobilized in calcium alginate gel, polyvinyl alcohol (PVA) and microporous ceramics and their microstructure were observed by scanning electron microscope (SEM). It was found that calcium alginate gel might dissolve in the wastewater, and the activity was restricted as cells wrapped in PVA, so the COD removal ratio was low. The method of immobilized cells using microporous ceramics is simple and COD removal efficiency can be achieved. In addition, the immobilized bacterium could not be separated easily from the ceramics in the wastewater.

Alginates↗

PubMed2003

[Rural sewage treatment performance of constructed wetlands with different depths].

The treatment performance, for low concentration rural sewage, through constructed wetlands of different depths(60 cm and 40 cm), was comparatively investigated by using pilot-scale apparatus in Lake Dian-chi area, Yunnan province, China. The experiment results showed, under a high hydraulic loading rate of 30 cm/d, that the removal efficiencies of COD, total nitrogen, ammonia-nitrogen and total phosphorus in the constructed wetland of 60 cm depth were 66.4%, 57.7%, 78.7% and 63.2%, respectively, and were 63.8%, 59.1%, 82.1% and 61.3% in the 40 cm depth, respectively. The removal efficiencies of COD and total phosphorus in the constructed wetland of 60 cm depths were higher than those in the 40 cm depth, but the nitrogen removal efficiency in the latter was higher than that in the former. Nitrogen and phosphorus removal mechanisms were studied. The results showed that nitrogen removal through nitrification/denitrification and the phosphorus removal through absorb and sedimentation were their main removal mechanisms. The nitrogen and phosphorus removed by plant harvesting were amounting to 10% and 9% of input TN and TP, respectively, which was also an important removal pathway for nitrogen and phosphorus.

Bacteria↗

PubMed2002

Relationship between structures of substituted indolic compounds and their degradation by marine anaerobic microorganisms.

Degradation of selected indolic compounds including indole, 1-methylindole, 2-methylindole, and 3-methylindole was assessed under methanogenic and sulfate-reducing conditions using the serum-bottle anaerobic technique and marine sediment from Victoria Harbour, Hong Kong as an inoculum. Our results showed that indole degradation was achieved in 28 days by a methanogenic consortium and 35 days by a sulfate-reducing consortium. During degradation under both conditions, two intermediates were isolated, purified and identified as oxindole and isatin (indole-2,3-dione) suggesting that both methanogenic and sulfate-reducing bacteria use an identical degradation pathway. Degradation processes followed two steps of oxidation accomplished by hydroxylation and then dehydrogenation at 2- and then 3-position sequentially prior to the cleavage of the pyrrole ring between 2- and 3-positions. However, none of 1-methylindole or 2-methylindole was degraded under any conditions. 3-Methylindole (3-methyl-1H-indole, skatole) was transformed under methanogenic conditions and mineralized only under sulfate-reducing conditions. It is clear that methyl substitution on 1- or 2-position inhibits the initial attack by hydroxylation enzymes making them more persistent in the environment and posing longer toxic impact.

Bacteria, Anaerobic↗

PubMed2002

[Mechanisms of separating lignin from black liquid by inorganic microfiltration].

The effects of rejection to lignin from black liquid were carried out by inorganic membranes which had pore size 50 nm, 0.2 micron and 0.8 micron, respectively. The results show that MF membranes can effectively separate lignin from black liquid. The flux of 0.2 micron alpha-Al2O3 and ZrO2 membranes were larger than the flux of 50 nm and 0.8 micron membranes. The flux of each membrane drops deeply as the SS concentration increased under the conditions of low SS in black liquid. However, the flux dropping had the linear relationship with SS concentration when it was high. 2 g/L polyethylene glycol 4000 solution can not affect the fluxes of 0.2 micron and 50 nm membranes, effectively, instead of decreasing the flux of 0.8 micron membrane about 60%. 2 g/L polyethylene glycol 20,000 solution can sharply decrease the flux of each membrane. Reason that provoke flux decreasing and change the rejective ability was the cake formation on the surface membrane and the lignin aggregation.

Filtration↗

PubMed2002

[Non-woven fabric media for wastewater treatment and mechanism].

Non-woven fabric was adopted as a new kind of suspended media. Adapting condition and operation parameters and biodegradation mechanism using non-woven fabric media in wastewater treatment were studied. The result of experiment shows that different CODCr volumetric load should take different media volume. When CODCr volume load was lower than 1.2 kg/(m3.d), the volume ratio of media to reactor should be 20%; the CODCr volume load between 1.2-2.0 kg/(m3.d), the volume radio of media to reactor 38%; the CODCr volume load was larger 2.0 kg/(m3.d), the volume radio of media to reactor 29%. The result of the model shows that the biodegradation rule of pollutant can be described by the format of Monod Equation.

Bedding and Linens↗

PubMed2002

[Treatment of a 2,4-dichlorophenol contaminated wastewater in an air-lift inner-loop bioreactor].

An air lift inner-loop bioreactor packed with honeycomb-like ceramic carrier was immobilized with a 2,4-Dichlorophenol-degrading pure culture and was investigated to degrade 2,4-Dichlorophenol and phenol. In fed-batch operation mode, 2,4-DCP biodegradation rate increased with run numbers and followed zero-order kinetics model when it existed alone, but when 2,4-DCP was present in the mixture with phenol, phenol degradation rate had an apparent trend to increase whereas 2,4-DCP removal rate became slower and slower. In continuous operation, 2,4-DCP at the concentration ranged from 6.9 to 102.4 mg/L could be degraded well at the dilution rate of 0.16 h-1 and the average removal percentage was 96.5%. Carbon sources changed from 2,4-DCP to acetate sodium and peptone in the course of operation for 12 days did not cause the bacteria loss the DCP-degrading ability.

Biodegradation, Environmental↗

PubMed2002

[Studies on ceramic dual function membrane bioreactor for wastewater treatment].

A new bioreactor including ceramic dual function membrane, filtration and aeration, was developed and used for wastewater treatment. The turbidity of effluent by the ceramic membrane was comparable to that of 4-24 hours by sedimentation. Aeration and filtration could be switched constantly to the ceramic membrane in the bioreactor and the clogging of ceramic membrane could be well prevented. The wastewater was treated in batch and continues operation modes respectively and the experimental results showed that the COD loading was 1.1 kg/(m3.d) and 1.5 kg/(m3.d) respectively.

Bioreactors↗

PubMed2002

[Pilot study on subsurface wastewater infiltration system applied in rural sewage treatment].

A pilot plant of subsurface wastewater infiltration system (SWIS) filled with red clay was tested to treat rural sewage with hydraulic loading of 2 cm/d. The experiment results showed that average removal rates of COD, NH4(+)-N, total phosphorus, and total nitrogen were 84.7%, 70.0%, 98.0% and 77.7%, with average effluent concentrations of COD, NH4(+)-N, total phosphorus, and total nitrogen being 11.7 mg/L, 4.0 mg/L, 0.04 mg/L and 4.7 mg/L respectively, which met the standard for water reuse issued by the Ministry of Construction of China. Nitrogen removal mechanism analysis revealed that nitrogen in the influent was mainly eliminated through biological removal via nitrification/denitrification processes. In the pilot system, denitrification was well proceeded but nitrification was not satisfactory. How to improve nitrification performance through change of soil environment was the key to enhance nitrogen removal rate. The measurement results of redox potential in the filled soil showed that reductive property of soil was main hindrance to nitrification process.

Filtration↗