Floating water source installations – radial settlers 

The initial stage of technological processes for the production of sugar and starch carried out in sugar factories and potato processing plants is the cleaning of the supplied raw materials (beets and potatoes). For this, water is used, which on the one hand is a washing agent, and on the other hand is a factor transporting raw materials during unloading and further transport to the washing station. The water used during these operations circulates in a closed circuit. Closing the float cycle is the main factor limiting the consumption of fresh water for this purpose in the plant, and thus the amount of produced float wastewater.

Float waters operating in a closed system require continuous treatment. The source of contamination in float water are impurities in the raw material, including: soil, debris, petioles, leaves, weeds and straw.

Floating water purification involves the mechanical removal of solids and suspensions. Leaves, weeds and straw are separated on special rake catchers, and stones and gravel on rock catchers: drum, pocket and bucket hoist. Sand and fine gravel are separated in sandpits with periodic (hydraulic installation) or continuous sand removal (scraper scraper).

Tails and fragments are retained on sieves with a rotary scraper (Maya chip catcher), arc sieves with a 5mm opening, vibrating sieves with 2 – 4 mm openings and rotating drum sieves. Curved screens with slots up to 2mm are used to retain the pulp. Heavy soil suspension is retained in various types of settling tanks, the operating principle of which is based on the physical and chemical processes of sedimentation, i.e. settling of suspension particles under the influence of gravity and supported by the use of appropriate flocculants. The most commonly used types of settling tanks:

• ground, horizontal
• concrete, horizontal with radial water flow, with continuous mechanical removal of float mud

Horizontal radial settling tanks are the best way to retain heavy soil suspension.

This type of settling tank is a reinforced concrete tank with a bottom inclined inwards and a cylindrical column in the middle. Inside the settling tank there is a circumferential rectangular trough equipped with adjustable sawtooth weirs with a deflector of floating parts. The trough is used to receive clarified supernatant water. The basic equipment of the settling tank is a movable platform with a bottom sludge scraper, floating parts scraper and a pumping installation for foam compaction.

Under the bottom of the settling tank there are pipelines: supplying dirty float water and draining float mud.

The overlying water from the settling tank will be pumped through the retention tank for reuse, hydrotransport and washing of the raw material. Float mud from the settling tank can be continuously pumped to:

• option I: storage in earth ponds, where it will be thickened by sedimentation, with periodic export
• variant II: dewatering on chamber filter presses in a continuous manner in an independent installation, with current export