Sand trap in wastewater technology

A sand trap is a special basin for mechanical wastewater treatment. It serves for the separation of larger particles in the area of ​​pre-cleaning.

Sand trap in the mechanical pre-cleaning

A sand trap is used in conjunction with a specially designed sedimentation basin. There larger particles can be separated.

On the other hand, scree catches find practically no application in sewage treatment. They are almost exclusively used for the purification of waters.

Sand traps today are often found to be unnecessary in the field of small wastewater treatment plants - a common settling tank is usually sufficient for household wastewater. With coarser dirt and sand or stones is generally not expected.

Feces can also be separated sufficiently in the classical sedimentation tank from the water, in which simple sedimentation is used.

Types of sand traps

  • unvented sand trap
  • ventilated sand trap
  • Long sand trap
  • Rolling sand trap
  • Circular Grit Trap

Ventilated and non-ventilated sand trap

Both types of sand traps have their own advantages and disadvantages. In many compact systems, they are used in combination. This often replaces the classic long sand trap.

The dimensioning of both types of sand traps is done according to the DWA rules in different ways:

Unvented sand traps are dimensioned via the surface feed. Ventilated sand traps, however, are dimensioned over the residence time of the waste water in the chamber.

Sand trap and sedimentation basin

Within a settling tank, sand trapping can be used to separate coarser impurities with larger particle sizes, in particular. These are, for example, sand or stones.

Depending on the design of the settling basin and the sand trap, different sedimentations are achieved in both basins.

In the settling tank the water must not flow. In the sand trap on the other hand, low flow velocities are sought in order to achieve settling of the heavier substances.

The flow rate in the sand trap is usually around 0.3 meters per second. For combined sand traps, the flow rates must be carefully adjusted.

Tips & Tricks

On a mechanical pre-cleaning can even be completely dispensed with, for example, composting toilets are installed. As a result, the space required for a small sewage treatment plant already significantly reduced.

Video Board: Tsurumi Sand Trap Pump KRS