Household slow sand filters in continuous and intermittent flows and their efficiency in microorganism’s removal from river water

Natália de Melo Nasser Fava, Ulisses Costa Terin, Bárbara Luíza Souza Freitas, Lyda Patricia Sabogal-Paz, Pilar Fernandez-Ibañez, John Anthony Byrne

    Research output: Contribution to journalArticlepeer-review

    Abstract

    This study aimed to evaluate the efficiency of four household slow sand filter (HSSF) models for the removal of microorganisms from river water throughout the development of their biological layers (schmutzdecke). Two models were designed to be operated continuously (HSSF-CC and HSSF-CT) and two intermittently (HSSF-ID and HSSF-IF). Filters were fed daily with 48 L pre-treated river water (24 h sedimentation followed by filtration through a non-woven synthetic blanket). Water samples were quantified by coliform group bacteria and analysed by bright field microscopy to visualize the microorganisms. Total coliform reduction was between 1.42 ± 0.59 log and 2.96 ± 0.58 log, with continuous models showing a better performance (p-values < 0.004). Escherichia coli reduction varied from 1.49 ± 0.58 log to 2.09 ± 0.66 log and HSSF-IF, HSSF-CC and HSSF-CT presented a similar performance (p-values > 0.06), slightly better than the one presented by HSSF-ID (p-value=0.04). Microorganisms, such as algae, protozoa and helminths were detected by microscopy in raw water and pre-treated water. Algae were the most significant group in these samples, although they were not visualized by bright field microscopy in the filtered water. Results showed the potential of HSSF in microbiological risk reduction from river water, which increases the range of point-of-use water treatments in rural communities. However, additional studies of the HSSF biological layer must be performed.

    Original languageEnglish
    Pages (from-to)1-10
    Number of pages10
    JournalEnvironmental Technology (United Kingdom)
    Early online date11 Nov 2020
    DOIs
    Publication statusE-pub ahead of print - 11 Nov 2020

    Keywords

    • biosand filter
    • decentralized treatment
    • drinking water
    • microscopy
    • schmutzdecke

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