Browsing by Author "Wright, R. C."

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    A comparison of the levels of faecal indicator bacteria in water and human faeces in a rural area of a tropical developing country (Sierra Leone)
    (Cambridge University Press, 1982-08-01) Wright, R. C.
    The levels of faecal coliforms (FC), indole-positive FC (presumptive Escherichia coli), faecal streptococci (FS), Streptococcus faecalis and Clostridium perfringens in the natural water sources used by 29 rural settlements in Sierra Leone were investigated. Levels of the same indicators in human faeces were also investigated. The incidence of Salmonella spp. in both habitats and the temperature, pH and conductivity of water sources were also recorded. All water sources were contaminated with the indicator bacteria, mean numbers of which occurred in the relationship FC greater than presumptive E. coli congruent to FS congruent to C. perfringens greater than S. faecalis. FC were also predominant in human faeces, the relationship of means being FC congruent to presumptive E. coli greater than FS greater S. faecalis greater than C. perfringens. The need for confirmation of FC counts obtained from water sources was indicated by the large number of positive tubes produced in the FC multiple-tube dilution test from some samples which could not be confirmed as presumptive E. coli. Salmonella spp. Were isolated from 13 water sources and 6% of faecal samples. Mean water temperature was high (26.2 degrees C), pH low (5.04) and conductivity low (34 microS cm-1). Presumptive E. coli was considered the most appropriate indicator of faecal pollution of the types of water investigated.
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    A medium for the rapid enumeration of Escherichia coli in the presence of other faecal coliforms in tropical waters
    (Cambridge University Press, 1982-04-01) Wright, R. C.
    A selective membrane filtration medium is described for use in the rapid assessment of water quality in tropical countries where the incidence of faecal coliforms other than E. coli presents problems in the interpretation of results. The medium gives comparable results to MPN values obtained in the multiple tube dilution test using modified Gray's glutamate medium, and to membrane filtration counts obtained using M-FC broth and membrane-enriched Teepol broth, whilst differentiation of E. coli is enhanced.
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    A MODIFIED FIELD VERSION OF THE WINKLER DETERMINATION OF DISSOLVED OXYGEN FOR TESTING REMOTE SOURCES OF WATER
    (Wiley, 1983-09-01) Wright, R. C.
    Summary A modification of a simple field method (Drew and Robertson, 1974) for the Winkler determination of dissolved oxygen is described. The modification, involving the addition of sulphuric acid and sodium azide as preserving agents rather than the precipitation of manganese hydroxides in the field, gives more accurate results when samples have to be stored before completion of the determination.
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    A new selective and differential agar medium for Escherichia coli and coliform organisms
    (Wiley, 1984-06-01) Wright, R. C.
    W right , R.C. 1984. A new selective and differential agar medium for Escherichia coli and coliform organisms. Journal of Applied Bacteriology 56 , 381–388. An enriched lauryl sulphate‐aniline blue agar medium which is selective for Escherichia coli and coliform organisms is described. From faecal samples, the medium gave higher counts of colonies producing acid from lactose than media containing bile salts. From contaminated water and food samples, the medium gave comparable or higher counts of colonies identified as E. coli than standard media. Colonies of E. coli were more readily differentiated from those of other coliform organisms.
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    A simplified 1,10‐phenanthroline technique suitable for the determination of dissolved iron in remote sources of water
    (Wiley, 1983-06-01) Wright, R. C.
    A simple technique is described for the determination of dissolved iron in water. It is useful for investigating remote sources and avoids errors due to post‐sampling precipitation of hydrated ferric oxides. A small sample is added to a mixed 1.10‐phenanthroline‐i‐acetate buffer solution in the field and this‘developed sample” can then be stored for up to 4 weeks before the absorbancc value is read.
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    INTERPRETATION OF FAECAL INDICATOR COUNTS FROM TROPICAL WATERS
    (Elsevier BV, 1983-03-01) Wright, R. C.