Study of slow sand filtration with backwash and the influence of the filter media on the filter recovery and cleaning

Abstract

Slow sand filters are considered as a great alternative for supplying drinking water in rural and/or isolated areas where raw water that is treatable with this technique is available. Some studies used backwashing as an alternative for cleaning the slow sand filter with the goal of applying the technology in small communities, since filters that supply water to a small number of people do not require much space. In this study the influence of the effective diameter on water quality in the filters and cleaning system was evaluated. A pilot system with six filters was built: three filters were conventionally cleaned by scraping and the other three were cleaned by backwashing, each with a different effective diameter of filter medium. Most filters had an average turbidity of less than 1.0 NTU, the turbidity required at the output of the filters by the Brazilian Ministry of Health Ordinance. In the study, the filters cleaned by scraping with smaller-diameter filter beds effectively filtered water better but had worse effective production. The opposite occurs in the case of backwashed filters.

Pre‐filtration followed by slow double‐layered filtration: Media clogging effects on hydraulic aspects and water quality

“…Following AWWA guidelines (AWWA, 2011), the body structure of the filtration columns had a diameter of 100 mm, in polyvinyl chloride (PVC). According to recommendations (Bellamy et al, 1985; de Souza et al, 2015; FUNASA, 2019; B. Pizzolatti et al, 2014), 40 cm of filtration layer thickness was adopted. A 5‐cm‐thick support layer of crushed stone, divided into sublayers with d 10 between 1.2 and 19.0 mm, was adopted in all columns.…”

“…The clogging forms are related to the size and shape distribution of the grains in the filter media and the characteristics of the suspended solids, chemical and biological compounds in raw water. It is determinative whether clogging occurs internally (in‐depth) or externally (on the bed surface) (de Souza et al, 2015; M. Soares & Pizzolatti, 2019). The clogging processes increase the fluid's hydraulic resistance through the porous media, causing the hydraulic head progressive increase in the system and above the surface of the filter media (A. di Bernardo, 2004).…”

Diagnóstico e discussão sobre uso da Filtração Lenta para abastecimento público em Santa Catarina, Brasil

“…Novos modelos de filtros foram desenvolvidos, alterando a operação ou características dos filtros, como o emprego de retrolavagem para a limpeza (MICHELAN et al, 2011;PIZZOLATTI et al, 2014;SOARES et al, 2010;SOUZA et al, 2016), uso de mantas sintéticas e o uso de carvão ativado granular para o emprego da adsorção (BAUER et al, 1996;CARNEIRO et al, 2016;DI BERNAR-DO;BRANDÃO;HELLER, 1999;LOGSDON;KOH-NE;ABEL, 2002). Diversos estudos foram desenvolvidos nos últimos anos a respeito do potencial de remoção de compostos dos quais ainda não se havia conhecimento, os chamados contaminantes emergentes.…”

FILTRAÇÃO EM MÚLTIPLAS ETAPAS (FiME) MODIFICADA POR MATERIAIS NÃO CONVENCIONAIS

“…),Souza et al (2016) eTerin (2017), para remoção de cor de 50%, 75% e 98%, respectivamente em filtros lentos, observa-se que os pré-filtros PFRC1 e PFRC2 apresentaram bom desempenho.Em conformidade ao exposto, Jayalath et al (2016) Rajapakse e Fenner (2011) também obtiveram resultados positivos com uso de materiais cerâmicos em detrimento ao uso dos tradicionais seixos nos pré-filtros.Desempenho do sistema piloto para a TurbidezA Tabela 10 traz dados acerca das estatísticas descritivas de turbidez para a água afluente e efluente a cada filtro, considerando os Estágios 1 e 2, respectivamente. Paralelamente, as Figuras 10 e 11 ilustram o comportamento temporal das etapas de filtração em relação à água bruta para os Estágios 1 e 2, respectivamente.Tabela 10: Nível de significância, IAPP e IDQA dos dados de turbidez (uT) -Estágio 1 existe diferença significativa; Nnão existe diferença significativa.Fonte: Autores (2021).…”