The influence of the microbial quality of wastewater, lettuce cultivars and enumeration technique when estimating the microbial contamination of wastewater irrigated lettuce.

P Makkaew, M Miller, N J Cromar, H J Fallowfield

    Research output: Contribution to journalArticle

    1 Citation (Scopus)

    Abstract

    This study investigated the volume of wastewater retained on the surface of three different varieties of lettuce, Iceberg, Cos, and Oak leaf, following submersion in wastewater of different microbial qualities (10, 102, 103, and 104 E. coli MPN/100 mL) as a surrogate method for estimation of contamination of spray-irrigated lettuce. Uniquely, Escherichia coli was enumerated, after submersion, on both the outer and inner leaves and in a composite sample of lettuce. E. coli were enumerated using two techniques. Firstly, from samples of leaves - the direct method. Secondly, using an indirect method, where the E. coli concentrations were estimated from the volume of wastewater retained by the lettuce and the E. coli concentration of the wastewater. The results showed that different varieties of lettuce retained significantly different volumes of wastewater (p < 0.01). No statistical differences (p > 0.01) were detected between E. coli counts obtained from different parts of lettuce, nor between the direct and indirect enumeration methods. Statistically significant linear relationships were derived relating the E. coli concentration of the wastewater in which the lettuces were submerged to the subsequent E. coli count on each variety the lettuce.

    Original languageEnglish
    Pages (from-to)228 – 238
    Number of pages11
    JournalJournal of Water and Health
    Volume15
    Issue number2
    DOIs
    Publication statusPublished - 1 Apr 2017

    Keywords

    • health risk
    • leaf morphology
    • lettuce
    • microbial risk
    • wastewater irrigation

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