Biomedical subjects

Gayle Newcombe

Publications and source records attributed to Gayle Newcombe.

8 recordsLinked to original sources

PubMed2006

Biodegradation rates of 2-methylisoborneol (MIB) and geosmin through sand filters and in bioreactors.

Taste and odour (T&O) causing compounds, in particular, 2-methylisoborneol (MIB) and geosmin, are a problem for water authorities as they are recalcitrant to conventional water treatment. In this study, biological sand filtration was shown to be an effective process for the complete removal of MIB and geosmin, with removal shown to be predominantly through biodegradation. In addition, MIB and geosmin were also effectively degraded in batch bioreactor experiments using biofilm sourced from one of the sand filters as the microbial inoculum. The biodegradation of MIB and geosmin was determined to be a pseudo-first-order reaction with rate constants ranging between 0.10 and 0.58 d(-1) in the bioreactor experiments. Rate constants were shown to be dependent upon the initial concentration of the microbial inoculum but not the initial concentration of MIB and geosmin when target concentrations of 200 and 50 ng l(-1) were used. Furthermore, rate constants were shown to increase upon re-exposure of the biofilm to both T&O compounds. Enrichment cultures with subsequent community profile analysis using 16S rRNA-directed PCR-DGGE identified four bacteria most likely involved in the biodegradation of geosmin within the sand filters and bioreactors. These included a Pseudomonas sp., Alphaproteobacterium, Sphingomonas sp. and an Acidobacteriaceae member.

Bacteria↗

PubMed2006

Decrease in toxicity of microcystins LA and LR in drinking water by ozonation.

Unchlorinated treated waters from two Australian reservoirs were spiked with microcystin-LA and -LR extracted from a toxic scum of Microcystis aeruginosa. The two waters had considerably different water quality and therefore ozone demands. The spiked sample waters were ozonated using the batch method of ozonation at a range of doses and the samples were analysed for toxins using high-performance liquid chromatography (HPLC). The toxin content of the samples was also determined using a protein phosphatase type 2A inhibition assay (PP2A) and toxicity via the standard mouse bioassay. The HPLC results correlated well with the PP2A results and toxicity tests for both waters. A loss of both toxins and toxicity was observed with increasing ozone dose, resulting in a complete loss of toxicity for both waters once an ozone residual had been achieved. At this ozone residual no toxin was detected using HPLC. The results indicate that microcystins are not transformed into toxic by-products.

Animals↗

PubMed2006

Differences in the chlorine reactivity of four microcystin analogues.

The presence of microcystin toxins in drinking water is highly undesirable as they have the potential to adversely affect human health. Consequently, effective removal of these toxins from water is a major goal for water authorities. In this study, four microcystin analogues were chlorinated in two treated waters, and two of the analogues were chlorinated in deionised water. The oxidation of the microcystins was related to the chlorine exposure (CT) of the sample waters with the ease of oxidation following the trend: microcystin-YR > microcystin-RR > microcystin-LR > or = microcystin-LA. This trend was in agreement with published data on model compounds and free amino acids. Values of CT of up to 25 mg min L(-1) were required for oxidation of all microcystin analogues to below the World Health Organization guideline value of 1.0 microg L(-1). Results from this study indicate that for some water resources it is important to determine the speciation of the microcystin analogues to optimise chlorination practices.

Chlorine↗

PubMed2006

Bacterial degradation of microcystin toxins within a biologically active sand filter.

Microcystin toxins are a problem for water authorities as they are recalcitrant to conventional water treatment. In this study, biological sand filtration was assessed in laboratory column experiments for its ability to remove two microcystin analogues, microcystin-LR and microcystin-LA. A lag period of 3 days was evident prior to the commencement of degradation. Contact times were varied during the experiment; however, no microcystin was detected in the effluent after 4 days, even under conditions similar to those of a rapid sand filter. Removals of microcystin through the sand filters were shown to be primarily through biological degradation processes. Using polymerase chain reaction (PCR), biofilm, extracted from one of the sand filters that had effectively removed the microcystins, was shown to contain bacteria with the mlrA gene. Detection of this gene provided additional evidence that biological degradation of microcystin was the primary removal mechanism.

Bacterial Toxins↗

PubMed2006

[The characteristic IR spectra of microcystin-LR].

The IR spectra of mincrocystin-LR (mLR) were studied by Fourier transform infrared spectroscopy in the scanning range of 4,000-600 cm(-1). The characteristic IR spectra from main function groups such as monosubstituted benzene, guanidine residues and gamma-carboxylic groups etc have been identified.

Bacterial Toxins↗

PubMed2005

Effect of NOM, turbidity and floc size on the PAC adsorption of MIB during alum coagulation.

The effect of natural organic material (NOM) and turbidity on the powdered activated carbon (PAC) adsorption of the odour compound 2-methylisoborneol (MIB) was evaluated during alum coagulation. The character of the flocs, in terms of their size and fractal dimensions (Df), was used to interpret the observed adsorption behaviour of MIB during the coagulation process. As the alum dose was increased, the adsorption of MIB decreased. This was determined to be due to the size of the flocs, with larger flocs incorporating PAC into their structure, reducing the efficiency of mixing, and the bulk diffusion kinetics for the MIB molecule. The presence of turbidity also reduced MIB adsorption due to the formation of larger flocs. The character of NOM was found to have a greater influence on the adsorption of MIB than the floc structure.

Adsorption↗

PubMed2004

Characterization of natural organic matter fractions separated by ultrafiltration using flow field-flow fractionation.

Natural organic matter (NOM) from two sites in South Australia were separated by Amicon YM and YC ultrafiltration (UF) membranes into five nominal fractions (<0.5, 0.5-3, 3-10, 10-30 and >30 kDa). These nominal fractions were then characterized for size and molecular weight (MW) distributions using flow field-flow fractionation. The results show that separation by UF did not produce fractions with the expected MW and size. Electrophoretic mobility measurements of the NOM fractions adsorbed to colloidal goethite showed no significant difference between the fractions. However solid-state (13)C NMR of the NOM fractions showed that the separation was influenced by molecular structure as well as molecular size. The results suggest that great caution needs to be exercised when interpreting molecular size and speciation results for humic substances obtained by membrane UF.

Adsorption↗

PubMed2002

Influence of the character of NOM on the ozonation of MIB and geosmin.

Tastes and odours (T&Os) are a major concern in drinking water as they are not efficiently removed by conventional water treatment. Ozonation has been effective for their destruction in some studies. However, the natural organic matter (NOM) in waters can affect the ozonation process and subsequently affect the destruction of T&Os. Five NOM fractions were isolated and ozonated in synthetic waters. The fraction containing the more highly coloured, higher molecular weight compounds exhibited the highest ozone (O3) demand, whereas the low aromatic fraction exhibited the lowest O3 demand. The character of the NOM fractions influenced the ozonation of MIB and geosmin. The destruction of MIB and geosmin was significantly higher in the fraction with the highest colour and UV/visible absorbance at all O3 doses. The destruction of the compounds in the other fractions showed the same trends, increasing MIB and geosmin destruction with increasing UV/visible absorbing character of the NOM. MIB was also ozonated in two real waters. with results showing a competing effect between NOM concentration and NOM character. The O3 reaction time was shown to be important for the destruction of both compounds.

Camphanes↗