Biological Layer in Household Slow Sand Filters: Characterization and Evaluation of the Impact on Systems Efficiency

Helen Lubarsky, Natália de Melo Nasser Fava, Bárbara Luíza Souza Freitas, Ulisses Costa Terin, Milina Oliveira, Atônio Wagner Lamon, Natalia Pichel, John Anthony Byrne, Lyda Patricia Sabogal-Paz, Pilar Fernandez-Ibañez

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Abstract

Schmutzdecke, the biofilm formed on the top of the sand bed in household slow sand filters (HSSF) is a key factor for the filters’ high efficiency in removing particles and microorganisms from water. This paper aims to investigate the extracellular polymeric substances composition (carbohydrates and proteins), biomass, dissolved oxygen, and microbial community in two types of HSSFs and identify a correlation between them and their efficiency. A continuous- and an intermittent-HSSF (C-HSSF and I-HSSF) were studied to treat river water for 48 days. Their efficiencies for bacteria (E. coli and total coliforms), turbidity, and apparent color removals were analyzed. Results clearly showed an increase of carbohydrates (from 21.4/22.5 to 101.2/93.9 mg·g −1 for C-/IHSSF) and proteins (from 34.9 to 217/307.8 mg g-1 for C-/I-HSSF), total solids (from 0.03/<0.03 to 0.11/0.19 g L−1 for C-/I-HSSF), dissolved oxygen depletion inside the filter (6.00 and 5.15 mg L −1 for C- and I-HSSF) and diversity of microorganisms over time, pointing out the schmutzdecke development. A clear improvement on the HSSFs’ efficiency was observed during operation, i.e., E. coli removal of 3.23 log and 2.98 log for total coliforms, turbidity from 60 to 95%, and apparent color from 50 to 90%. 
Original languageEnglish
Article number1078
Pages (from-to)1-17
Number of pages17
JournalWater
Volume14
Issue number7
DOIs
Publication statusPublished - 29 Mar 2022

Bibliographical note

We acknowledge the Global Challenges Research Fund (GCRF) UK Research and Innovation for funding SAFEWATER; EPSRC Grant Reference EP/P032427/1 and the Royal Society for funding the project reference ICA/R1/201373 under the International Collaboration Awards 2020. The authors would also like to thank Coordination for the Improvement of Higher Education Personnel (CAPES-PROEX—Brazil, Financial code 001) for the MSc and PhD scholarships awarded and to Amanco-Mexichem (São Paulo, Brazil) for donating the materials to make the filters.

Keywords

  • drinking water
  • schmutzdecke
  • extracellular polymeric substances (EPS)

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