Dynamic Sand Filters

Colloide‘s Dynamic Sand Filter offers an excellent treatment system for the removal of solids and other contaminants from a water/wastewater stream. This filter is always on line, continually filtering the incoming water while continually backwashing a small portion of the sand bed.

Summary of the Dynamic Sand Filter process:

  • The feed water is fed into the filter at the base of the active sand bed through the distribution ring.
  • It then flows upward through the downward moving sand bed where the solids are filtered out.
  • The clean filtrate exits the filter through the overflow weir. The continuous reject flow of washing water is discharged through a separate outlet.
  • The dirty sand is continuously removed from the active sand bed thanks to the action of the air-lift pump. This pump draws the contaminated sand from the bottom of the filter body.
  • A mixture of sand, dirty particles and water is transported upward through the air-lift pipe into the washing chamber at the top of the filter.

These filters can also be designed as Ammonia Removal filters, denitrifying filters and/or phosphorous filters.

All wetted parts are in stainless steel AISI 304L. Special construction materials available upon request.

Solutions for installation in a concrete basin of several basic filter inserts is available, as is that for single concrete filters of various sizes.

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Features & Benefits

  • Absence of any mechanical moving parts.
  • Unique continuous back-wash system using counter current variable velocity washing.
  • Simple plant with no backwash water storage and backwash pumps.
  • Higher suspended solids content in feed, high efficiency in removing fine solids.
  • Colloidal particles efficiently removed through simple in-line dosage of coagulants.
  • Coagulation, flocculation and filtration in one step thanks to the deep active bed.
  • Very low pressure drop across the filter, gravity feed is possible in many instances Easy maintenance thanks to the internal sand air-lift system.


Applications include:

  • Polishing of process waters for recycling oil, phosphorus and amonia removal from waste water.
  • Tertiary filtration for wastewater.
  • Denitrification for wastewater.
  • Cooling tower water filtration.
  • Drinking water filtration.
  • Algae removal from drinking water.
  • Pre-membrane filtration.