Wastewater flowing into the sand trap are transferred to the integrated sprue chamber where they get loosened. Then the fluid flows to the filtering block, where solid parts are separated. Screenings are held on following parts, depending on the device model:
SB: Rotary slotted sieve drum with worm conveyor.
SP: Fixed, cleaned perforated sieve with worm conveyor and sweeping brushes.
KP: Slotted grid with sweeping combs.
Sieve/drum/grid automatic cleaning system is enclosed depending on wastewater level increase outside the device. The screenings are additionally cleaned, and in SB and SP devices are also drained in their compressing-draining segments. The preliminarily treated wastewater is transferred to the sand trap chamber, where it is aerated, which supports light solid matter and fat floatation. In sand trap the sand and other mineral elements sedimentation occurs. Sand collected in the bottom is transported to the sand wash bath where it is cleaned with water and compressed air. Clean sand is removed outside the device with the worm conveyor. In the upper part of sand trap the flotate sweeper (mixer) is assembled, which transports fat to the chamber, from where it is pumped or transported gravitationally.