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[ Contisand, Unidro Continuous Sand Filter ]

CONTISAND is a continuously operating sand filter with no need to stop the operation for backwashing or cleaning.

The principle of operation

Incoming water is distributed at the bottom of the filter and, flowing upward through the sand, reaches the filtered water outlet at the filter top side. Simultaneously with the filtration process, the sand is moving downwards, lifted by an airlift to the filter top where fouled sand is cleaned in a sand washer and the suspended solids are discharged with the wash water. Cleaned sand is then falling onto the filtering sand layer.

The advantages

CONTISAND does not require the usual backwash facilities (as pumps, sequencing ON/OFF valves, water hold-up tanks) nor PLC/DCS inputs as their operation is continuous and self-adjusting. They only need pressurized air or gas, either PA provided by utility system or generated by a dedicated small compressor.

  • No need for the filters to be put off service during backwash. Filtration and backwash occur simultaneously
  • The quality of filtrate is constant during the cycle
  • No need for storage of backwash water
  • No need for backwash pumps and blowers
  • No need of automatic sequencing valves and PLC to handle operation and backwash cycles


  • Municipal and industrials tertiary treatments
  • Final effluent treatment for phosphorus reduction
  • Industrial water recovery
  • Side stream filtration of cooling water circuits
  • Surface water treatment
  • Rain water treatment
  • Produced water filtration

The production of Unidro CONTISAND is standardized. Modular diameters are available and, for each diameter, different layer depth may be selected. Several materials for wetted parts are available (such as CS, SS, FRP and others). Fresh water, seawater, produced water, even saturated brine may be treated without any corrosion problem.

Waste water treatment and reuse
With a wide experience in the treatment of industrial wastewater and the knowledge to treat difficult process streams, we can match the most demanding regulations worldwide and handle the critical problem of water reuse.
Produced water treatment
With experience in water treatment, a wide separation equipment portfolio and a specific know-how on wellhead processes Unidro is a highly qualified partner for PWT.
Pure water treatment
With the company experience of four decades in the water treatment and the high specialization of our engineering staff, Unidro can propose for every project an optimized combination of process steps to make the water available at site suitable as Cooling Water, boiler feed water and process water in the industries.
Process Filters
Unidro process filters cover a wide range of application for gas and hydrocarbon filters, including solid removal from gas and liquid, liquid/gas and liquid/liquid separation.