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The sand selection and preparation are critical to ensure flow rate and effective treatment. The treatment efficiencies provided in the above table require an established biolayer; it takes up to 30 days to establish the biolayer depending on inlet water quality and usage. Removal efficiency and the subsequent effectiveness of the filter increase throughout this period. Although the filter does remove more than 98% of bacteria, below the infectious dose, disinfection is recommended as a final step for households with infants or the elderly. The filter should be used every day to maintain the biological layer.
The best performance requires a consistent water source; switching sources may decrease treatment efficiency. The swirl and dump maintenance will reduce efficiency until the disturbed biolayer re-establishes itself.