The use of aerobic spore-forming organisms as surrogate indicators for the presence of cysts of Giardia lambla and Cryptosporidium oocysts in surface water systems was investigated in a series of ...laboratory experiments with Bacillus subtilis inocula at various temperatures, in addition to other non-specific isolates from 2 different water treatment plants. The rates of inactivation of these spores in chlorinated waters were compared with CT values for Giardia prescribed in the Surface Water Treatment Rule. The resistance of the spores used in this study was greater than that of Giardia spores and increased with a rise in temperature. The inactivation of the experimental spores by chlorine could be represented using either the Chick-Watson or the Hom theoretical models. For disinfecting waters or high disinfectant demand, or the use of disinfectants such as ozone with rapid decay rates and for other types of micro-organism such as E. coli , the modified Hom model appeared to be a particularly good choice for predicting inactivation. Spores derived from aerobic bacteria were valuable in predicting disinfection efficiency. There are 31 references.
A rapid epifluorescence staining method using the LIVE/DEAD super( registered ) Bacterial Viability Kit (BacLight super(TM)) was applied to estimate both viable and total counts of bacteria in ...drinking water. BacLight is composed of two nucleic acid-binding stains: SYTO 9 super(TM) and propidium iodide. SYTO 9 super(TM) penetrates all bacterial membranes and stains the cells green, while propidium iodide only penetrates cells with damaged membranes, and the combination of the two stains produces red fluorescing cells. Optimal incubation conditions were found to be 15 to 20 min, at room temperature in the dark. Total (red+green) and viable (green) cells can hence be counted simultaneously. Factors affecting the staining procedure were tested (addition of glutaraldehyde, staining time, chlorine impact). In the absence of stress, BacLight viable counts were equivalent to m-T7 medium plate counts and to 5-cyano-2,3-ditolyl tetrazolium (CTC) counts. BacLight total counts were comparable to acridine orange counts (differing by <0.1 log/ml). However, the increase in environmental stresses (chlorine, growth rate or temperature) induced a decrease in viability that was more pronounced for CTC and plate counts than for BacLight viable counts.
Backwashing first-stage sand-BAC filters Niquette, P; Prevost, M; Maclean, R G ...
Journal of the American Water Resources Association,
01/1998, Letnik:
90, Številka:
1
Journal Article
The effect of filter backwash on the efficiency of first-stage sand-biological activated carbon (BAC) filters was evaluated by comparing concentrations of ammonia, biodegradable dissolved organic ...carbon, aldehydes and oxalate. Filter position was also studied to understand how flocs and particle accumulation influenced the efficiency of the first-stage sand-BAC filter. Filter backwash improved the efficiency of sand-BAC filters, especially in cold water sources. First-stage sand-anthracite filters did not adequately remove biodegradable organic matter and ammonia.
The influence of sodium thiosulphate on the batch-culture suspended-inoculum biodegradable dissolved organic carbon (BDOC) assay was investigated. The addition of thiosulphate to samples containing ...oxidant residuals was required to quench reactions between the oxidant residual and organic matter and to ensure that the sample was free from bactericidal agents. Thiosulphate was usually added in excess, leaving a residual concentration which interfered with the BDOC measurement. Interference increased with the amount added, and above 20 mg per litre a substantial underestimation of BDOC resulted. The natural bacterial inoculum used also contained bacteria capable of metabolizing thiosulphate.
In consideration of the future of software engineering as an interdisciplinary activity, this paper explores the existing coverage of interdisciplinary software engineering areas in established or ...emerging software engineering frameworks. In particular we investigate the Software Engineering Body of Knowledge (SWEBOK), the Capability Maturity Model (CMM) and related Capability Maturity Model Integration (CMMI), and the Rational Unified Process (RUP). Following the investigation of the interdisciplinary elements of these frameworks we explore potential areas of advancement and opportunities, that is, where and how future body of knowledge, process, and framework revisions might benefit from the interdisciplinary approach.
