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Household slow sand filter efficiency with schmutzdecke evaluation by microsensors
Antonio Wagner Lamon1, Paulo Marcos Faria Maciel1, José Roberto Campos1
1Department of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, São Paulo, Brazil.
Environmental Technology
|June 7, 2021
Summary
Continuous and intermittent slow sand filtration show similar physical-chemical removal, but continuous flow better reduces E. coli. Biofilm growth, monitored by dissolved oxygen, correlates with filter efficiency.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Microbiology
Background:
- Slow sand filtration (SSF) is a widely adopted technology for providing safe drinking water in rural areas globally.
- Household SSF (HSSF) systems are crucial for decentralized water purification, particularly in low-resource settings.
- Understanding the impact of operational modes on HSSF efficiency is vital for optimizing water quality.
Purpose of the Study:
- To compare the performance of continuous (C-HSSF) and intermittent (I-HSSF) flow household slow sand filters.
- To evaluate the role of biofilm development, assessed via dissolved oxygen (DO) microprofiles, in HSSF efficiency.
- To determine the effectiveness of a non-woven blanket in facilitating HSSF maintenance and performance.
Main Methods:
- Two HSSF units (C-HSSF and I-HSSF) were operated for eight months, with maintenance every 30 days.
- Physico-chemical parameters (turbidity, color) and microbial indicators (total coliform, E. coli) were measured.
- Dissolved oxygen (DO) microprofiles in the biofilm were analyzed weekly using a Clark-type amperometric microsensor.
Main Results:
- No significant differences were observed between C-HSSF and I-HSSF for physico-chemical reduction and total coliform removal.
- Continuous flow HSSF demonstrated significantly better reduction of E. coli compared to intermittent flow (p=0.02).
- DO microprofiles indicated variations in biofilm growth, correlating with increased HSSF efficiency, with no significant difference in maximum DO depletion between flow modes (p=0.98).
Conclusions:
- Continuous flow HSSF offers superior E. coli removal, crucial for public health in rural settings.
- Real-time DO microsensor measurements provide valuable insights into biofilm dynamics and HSSF performance.
- The non-woven blanket aids in monitoring biofilm growth and understanding its contribution to water purification efficiency.
