Influence of slow sand filter cleaning process type on filter media biomass: backwashing versus scraping.

Autor: de Souza FH; Departamento de Engenharia Sanitária e Ambiental (ENS), Centro Tecnológico (CTC), Universidade Federal de Santa Catarina (UFSC), Campus Reitor João David Ferreira Lima, Florianópolis, Santa Catarina, Brazil, 88040-900; Department of Civil, Geomatic and Environmental Engineering (CEGE), University College London (UCL), Chadwick Building, Room GM11, Gower St, London WC1E 6BT, United Kingdom., Roecker PB; Departamento de Engenharia Sanitária e Ambiental (ENS), Centro Tecnológico (CTC), Universidade Federal de Santa Catarina (UFSC), Campus Reitor João David Ferreira Lima, Florianópolis, Santa Catarina, Brazil, 88040-900., Silveira DD; Departamento de Engenharia Sanitária e Ambiental (ENS), Centro Tecnológico (CTC), Universidade Federal de Santa Catarina (UFSC), Campus Reitor João David Ferreira Lima, Florianópolis, Santa Catarina, Brazil, 88040-900., Sens ML; Departamento de Engenharia Sanitária e Ambiental (ENS), Centro Tecnológico (CTC), Universidade Federal de Santa Catarina (UFSC), Campus Reitor João David Ferreira Lima, Florianópolis, Santa Catarina, Brazil, 88040-900., Campos LC; Department of Civil, Geomatic and Environmental Engineering (CEGE), University College London (UCL), Chadwick Building, Room GM11, Gower St, London WC1E 6BT, United Kingdom. Electronic address: l.campos@ucl.ac.uk.
Jazyk: angličtina
Zdroj: Water research [Water Res] 2021 Feb 01; Vol. 189, pp. 116581. Date of Electronic Publication: 2020 Oct 30.
DOI: 10.1016/j.watres.2020.116581
Abstrakt: Biomass was assessed as a new approach for evaluating backwashed slow sand filters (BSF). Slow sand filtration (SSF) is a simple technology for water treatment, where biological mechanisms play a key role in filtration efficiency. Backwashed slow sand filters were previously recommended for small-scale filters (~1 m² of filtration area) as an alternative to conventional filters that are usually cleaned by scraping (ScSF). Biomass was never evaluated in BSF, which is a gap in the knowledge of this technology, considering the importance of its biological mechanisms. Therefore, for the first time, two filters operating under the same conditions were used to compare the influence of backwashing on biomass; one filter was cleaned by backwashing and the other by scraping. Biomass along the filter media depth (40 cm) was assessed by different techniques and compared in terms of cellular biomass (by chloroform fumigation), volatile solids, bacterial community (by 16S rRNA gene sequencing), and observations by scanning electron and fluorescence microscopy. Filters were also monitored and compared regarding filtered water quality and headloss; their differences were related to the different cleaning processes. Overall, filtered water quality was acceptable for slow sand filter standards (turbidity < 1 NTU and total coliform removal > 1 log). However, headloss developed faster on scraped filters, and biomass was different between the two filters. Backwashing did not significantly disturb biomass while scraping changed its surface sand layers. Cell biomass was more abundant and spread across the filtration depth, related to lower headloss, turbidity, and cyanobacterial breakthrough. These results agreed with the water quality and microscopy observations. The bacterial community was also less stratified in the backwashed filter media. These results expand the knowledge of backwashing use in slow sand filters, demonstrating that this process preserves more biomass than scraping. In addition, biomass preservation can lead to bacterial selectivity and faster filter ripening. Considering the importance of biomass preservation on slow sand filtration and its biological filtration mechanisms, the results presented in this paper are promising. The novel insight that BSF can preserve biomass after backwashing may contribute to increasing its application in small communities.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2020 Elsevier Ltd. All rights reserved.)
Databáze: MEDLINE
Externí odkaz: