Biomedical subjects

W J Ng

Publications and source records attributed to W J Ng.

24 records · Page 2Linked to original sources

PubMed2002

Packed bed columns for high rate nitrogen and carbon removals.

Two packed bed column (PB) systems, namely anoxic-anoxic and anoxic-oxic were investigated for treatment of wastewater containing high concentrations of nitrogen (N) and COD. The anoxic-anoxic PB removal rates 6.70 kg N/m3 x d and 26.02 kg COD/m3 x d, respectively. The responding removal rates of the anoxic-oxic PB system were 7.41 kg N/m3 and 28.00 kg COD/m3 x d, respectively. The N and COD removal efficiencies of anoxic anoxic PB system were in the range of 99.2-100% and 97.2-98.8%, respectively. The corresponding removal efficiencies of anoxic-oxic PB system were 97.5-100% and 98.6-99.4%, respectively. These findings showed that a PB system consisting of anoxic-oxic columns in series has a high capacity to remove nitrogenous and carbonaceous compounds even though the influent to the anoxic stage was oxygenated. Better system stability in terms of denitrification was, however, obtained with the anoxic-anoxic system.

Bioreactors↗

PubMed2002

Toxicity assays to determine the start-up strategy for an anaerobic sequencing batch reactor (anSBR).

Addition of glucose as the co-substrate and the use of a water-based polymer to enhance granulation were studied with the aim of shortening the start-up period of an anSBR (anerobic sequencing batch reactor) for high-strength industrial wastewater treatment. An initial start-up feed composition consisting of 70% sucrose and 30% industrial wastewater was favorable to reduce the start-up time. Increase in the average particle size and reduction in settled supernatant turbidity was observed with increased water-based polymer addition up to a concentration of 0.1 m/L. Polymer dosages above 0.1 ml/L were undesirable as big and "flaky" flocs were formed which prevented the flocs from settling quickly. Addition of 0.005 ml/L to 0.1 ml/L polymer to the mixed liquor had no observable adverse effects on the anaerobic biomass metabolism. Instead, the addition of the polymer appeared to improve biogas production and had an overall positive effect on anSBR performance treating the industrial wastewater.

Bacteria, Anaerobic↗

PubMed2001

Fermentation of starch for enhanced alkaline protease production by constructing an alkalophilic Bacillus pumilus strain.

A new engineering strain, Bacillus pumilus c172-14 (pBX 96), was obtained by introducing the pBX 96 plasmid, which carries the alpha-amylase amy gene, into the host strain of alkalophilic Bacillus pumilus c172 via transformation. The newly constructed strain was found to express the amy gene and could use starch instead of glucose or starch hydrolysate as carbon source for its fermentation of alkaline protease. The pBX 96 plasmid in the new host was found to be segregationally and structurally stable. The expression of amy gene did not affect the host strain's resistance to bacteriophages. Moreover, the level of alkaline protease was improved significantly compared with the parent strain. The constructed strain gave a maximum alkaline protease activity of 14,014 U/ml in shaking flask after 48 h cultivation when growing in a medium containing 6% corn meal, 4% soybean flour, 0.4% Na2HPO4, 0.03% KH2PO4, 0.02% MgCl2, 0.3% CaCl2, 0.25% Na2CO3, 0.1% glucose, and 20 microg/ml kanamycin (pH 7.0). The optimal pH value and temperature of the alkaline protease were 11.0 and 40 degrees C, respectively. This enzyme was stable over a pH range of 8-11. Its residual activity remained at 100% when treated under a temperature of less than 45 degrees C for 30 min. The corresponding residual activity reduced to 65% of its optimal value at 60 degrees C for 30 min. The alkaline protease was a kind of serine protease, which was demonstrated by the complete inactivation by PMSF (1 mM). This newly constructed strain will be useful in the alkaline protease industry.

Bacillus↗

PubMed2001

Denitrifying phosphorus removal by anaerobic/anoxic sequencing batch reactor.

Denitrifying phosphorus removal was verified in a laboratory anaerobic/anoxic Sequencing Batch Reactor (A/A SBR) for a period of 18 months. The results obtained demonstrated the ability of the anaerobic/anoxic strategy to enrich the growth of denitrifying phosphorus bacteria (DPB) capable of taking up phosphate under anoxic conditions by using nitrate as the electron acceptor. Phosphorus removal efficiency ranging from 40-100% could be attained in an A/A SBR system. Simultaneous anoxic phosphate uptake and biological denitrification under anaerobic/anoxic condition occurred in this system. Batch tests showed, however, that simultaneous presence of carbon and nitrate would be detrimental to denitrifying phosphorus removal. Results of bacteria studies suggested that three denitrifying isolates had aerobic phosphorus removing ability.

Anaerobiosis↗

PubMed2001

The effects of water reclamation technologies on biological stability of industrial water.

A modified Assimilable Organic Carbon (AOC) procedure was adopted in conjunction with Heterotrophic Plate Count (HPC) method to assess the effect of Single Effect Distillation (SED) and Reverse Osmosis (RO) lab-scale systems on the biological stability of industrial water. Industrial water was collected from a local Industrial Water Works, pre-treated with alum coagulation and cartridge filtration, before being subjected to advanced water treatment. The results obtained in this study indicated that AOCs in the SED product water were in the range of 70-80 micrograms acetate-C/L, while those in the RO product water ranged from 30-40 micrograms acetate-C/L in the 15-min permeate to 55-65 micrograms acetate-C/L in the 3-hr permeate. The above findings suggested that product water of both systems were potentially biologically unstable and would likely lead to bacteria regrowth during its distribution and storage. Removal efficiencies of lab-scale RO and SED systems on AOC were as high as 90%, dependent on the concentration of AOC-NOX in the industrial water. The RO system had much higher organic removal efficiencies in terms of AOC and DOC than the SED system. Organics removed from both feed waters were found to be concentrated in the brine water and rejected water in SED and RO systems respectively.

Conservation of Natural Resources↗

PubMedDate not supplied

Monitoring of bacterial morphology for controlling filamentous overgrowth in an ultracompact biofilm reactor.

This research was part of a study of filamentous growth and control in an ultracompact biofilm reactor (UCBR). Morphologies of biofilm and filamentous bacteria in the UCBR were investigated. Ethanol was used as a substrate and sodium hypochlorite was applied as a toxicant to control filamentous growth. The results indicated that factors such as chemical oxygen demand, surface loading rate, pH, and dissolved oxygen could initiate filamentous overgrowth in the UCBR. Different biofilm and filamentous morphologies in the UCBR were observed under different operational conditions. Chlorination was an effective approach to control filamentous growth during and after biofilm formation. Proper chlorine dosing had no effect on biofilm, but killed filaments. Overdose of chlorine damaged biofilm and caused adverse effects such as low treatment efficiency, media clogging and washout, and biofilm color change in the reactor. Frequent monitoring of the morphologies of filaments and biofilm was needed during chlorination to prevent chlorine overdose.

Bacteria↗