Household slow sand filters with and without water level control: continuous and intermittent flow efficiencies. 2020

Paulo Marcos Faria Maciel, and Lyda Patricia Sabogal-Paz
Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, São Carlos, São Paulo, Brazil.

Four household slow sand filters were made out of PVC and operated in continuous and intermittent flows, with and without using a float to control the maximum level of water inside the units. The efficiency was evaluated as a function of Escherichia coli reduction and turbidity in water from the study prepared with kaolinite and E. coli suspension. The correlation of the efficiencies with the following operational parameters was evaluated: operating time, time after maintenance, filtration rate and head loss divided by bed thickness. The filters were classified as intermittent with float (IFF), intermittent without float (IF), continuous with float (CFF) and continuous without float (CF). IFF, CFF and CF had a non-woven blanket installed on top of the media. The results indicated that no significant statistical differences were found in E. coli reduction and turbidity between IFF and IF, however the former had filter runs over 80 days and the latter almost a quarter of this value. CFF matured faster and had less turbidity remaining in relation to CF. When comparing IFF with CFF, the former presented lower turbidity remaining (0.89 ± 0.44 NTU versus 1.24 ± 0.91NTU), but a lower reduction of E. coli (1.40 ± 0.61 log versus 2.29 ± 0.74 log). The time after maintenance was the most important operational parameter when evaluating the efficiencies. The float helped to mature the filter more quickly in a continuous flow and, together with a non-woven blanket, extended the filter runs in the intermittent flow.

UI MeSH Term Description Entries
D004926 Escherichia coli A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc. Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli
D005374 Filtration A process of separating particulate matter from a fluid, such as air or a liquid, by passing the fluid carrier through a medium that will not pass the particulates. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Filtrations
D000080463 Sand A hard granular material that is a component of soil. It is composed of very small pieces (between 0.06 and 2.0 millimeters in diameter) of disintegrating rock. Sands
D014867 Water A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Hydrogen Oxide
D014871 Water Microbiology The presence of bacteria, viruses, and fungi in water. This term is not restricted to pathogenic organisms. Microbiology, Water
D018508 Water Purification Any of several processes in which undesirable impurities in water are removed or neutralized; for example, chlorination, filtration, primary treatment, ion exchange, and distillation. It includes treatment of WASTEWATER to provide potable and hygienic water in a controlled or closed environment as well as provision of public drinking water supplies. Waste Water Purification,Waste Water Treatment,Wastewater Purification,Wastewater Treatment,Water Treatment,Purification, Waste Water,Purification, Wastewater,Purification, Water,Treatment, Waste Water,Treatment, Wastewater,Treatment, Water,Waste Water Purifications,Waste Water Treatments,Water Purification, Waste

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