DIY Biological Slow Sand Filter (Schmutzdecke)¶

BioSand & Media Filters • Est. CapEx: Low-cost / Locally fabricated

Technical Overview¶

A gravity-fed water purification system that uses a living biological biofilm—known as the schmutzdecke—atop a fine sand bed to remove bacteria, parasites, turbidity, and organic matter without chemicals, electricity, or proprietary cartridges. It is ideal for off-grid households, small farms, and emergency water security where supply chains are unreliable.

Key Specifications & Engineering Parameters¶

Parameter	Specification
Category	BioSand & Media Filters
Capital Cost	Low-cost / Locally fabricated
Primary Mechanism	Raw water percolates slowly downward (0.1–0.4 m/h) through a 1–2 meter bed of fine sand. A naturally forming gelatinous biological layer on the surface consumes and predates pathogens, while underlying sand performs physical straining, depth filtration, and adsorption onto grain surfaces. The system functions entirely by gravity and matures biologically over an initial ripening period.
Target Scale	Household / Village Cluster
Standard Lifespan	10 - 20 Years

Engineering Trade-Offs¶

✅ Advantages⚠️ Limitations

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Cross-Reference & Interactive Tools¶

Need to evaluate this technology for your specific field site? Run the WhatWater.info Selector Engine to compare it against 100+ alternative solutions.