Colloide‘s dynamic sand filters are always on line, continually filtering the incoming water while continually backwashing a small portion of the sand bed.

Dynamic sand filters have a high efficiency in removing fine solids. Maintenance is easy with an internal sand air-lift system.

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 are available, as is that for single concrete filters of various sizes.

Features

  • Absence of any mechanical moving parts.

  • Higher suspended solids content in feed, high efficiency in removing fine solids.

  • Very low pressure drop across the filter, gravity feed is possible in many instances.

  • Easy maintenance thanks to the internal sand air-lift system.

  • Unique continuous back-wash system using counter-current variable velocity washing.

  • Colloidal particles efficiently removed through simple in-line dosage of coagulants.

  • Simple plant with no backwash water storage and backwash pumps.

  • Coagulation, flocculation and filtration in one step thanks to the deep active bed.

Applications

Wastewater

  • Polishing of process waters for recycling oil, phosphorus and ammonia removal

  • Tertiary filtration

  • Denitrification

Potable water

  • Cooling tower water filtration

  • Drinking water filtration

  • Algae removal

  • Pre-membrane filtration