Slow Sand Filter and its estimation
Introduction
Slow sand filters, as shown, employ
a layered system for water purification. Sand (90-110 cm) acts as the main filter,
supported by gravel layers (30-75 cm) with increasing particle size. Unlike
other filters, they rely on a naturally forming biological film (bacteria,
fungi, etc.) on the sand for purification. Water flow rate is slow (100-200
liters/m²/hr) but effectively removes suspended particles, nearly all bacteria
(98-99%), and improves water aesthetics (color, odor, taste). The slow rate
necessitates large filters for high demand, and the growing biological film
requires periodic cleaning to maintain flow.
Estimation of a Slow Sand Filter
- Estimation of a Slow Sand Filter
- Review drawings to understand filter layout. Measure dimensions of components like filter bed, underdrain system, and supports.
- Calculate sand quantity for filter bed by multiplying area by depth.
- Estimate gravel volume for layers and calculate length of perforated pipes needed.
- Calculate concrete volume for walls, base, and supports. Include reinforcement materials if specified.
- Determine quantities of inlet/outlet pipes, valves, and fittings. Measure pipe lengths and specify valve types.
- Compile a comprehensive list of all required materials for procurement, including quantities of sand, gravel, concrete, steel, pipes, and fittings.
Fig: Slow sand Filter