Although particularly suitable for heavy sludges arising from sewage purification and industrial effluent treatment the echelon settling tank may also be used for secondary sludges. The circular tank is normally constructed with a floor slope of 7.5° to the horizontal although greater slopes can be accommodated.
A peripherally driven rotating half bridge is employed in conjunction with a robust scraper mechanism, the blades of which are arranged in an echelon formation to convey the sludge over the floor into a central well. A sludge draw-off pipe extends from the central well under the tank to an external chamber and a sluice valve controls the flow that is under hydrostatic head. For final settling tank applications an adjustable bellmouth is incorporated to enable the operator to regulate the rate of sludge removal.
Designed as a general purpose desludging mechanism for tanks with sloping floors up to 20° to the horizontal the radial settling tank is suitable for primary, activated and humus sludges as well as a variety of settlement applications associated with process liquors and trade effluents.
A peripherally driven rotating half bridge is employed in conjunction with a robust scraper mechanism, the blades of which are arranged in a radial formation to convey the sludge over the floor into a central well. A sludge draw-off pipe extends from the central well under the tank to an external chamber and a sluice valve controls the flow that is under hydrostatic head. For final settling tank applications an adjustable bellmouth is incorporated to enable the operator to regulate the rate of sludge removal.
Designed for the settlement and removal of light sludges in the shortest possible time, the suction lift setting tank is particularly suited to the needs of the activated sludge process, the efficiency of which depends upon the rapid return of sludge in a fresh and healthy condition. The equipment is equally suitable for humus tanks from which the sludge should be withdrawn before denitrification can occur. The circular tank has a flat floor that means that construction is simple and economical.
A peripherally driven rotating half bridge is employed in conjunction with a robust scraper mechanism, with blades arranged in a vee-shaped formation and supplied with uptake tubes, to lift the sludge under hydrostatic head to a sight box and transfer by siphon to a sludge outlet drum for return into the system. Plug valves are incorporated in the uptake tubes to enable the operator to regulate the rate of sludge removal.
A full range of ancillary equipment is available to complement the Lektratek range of settling tanks/clarifiers.
Central circular deflector drums (stilling wells) to create an even radial flow into the body of the tank.
Side scrapers for removal of light sludges from the tank wall.
Scum baffles with adjustable brackets.
Scum skimming and collection into a flooded hopper for discharge activated by passage of the bridge.
Adjustable peripheral weirs, plain or vee-notched, for even discharge of settled effluent.
Self adjusting brushes to clean weir plates and outlet launder sides and floor.
Thickening refers to the process of condensing biosolids to a concentrated solids product and a relatively solids-free supernatant.
Lektratek Water Technology has the ability and experience to provide either gravity thickeners, DAF and/or mechanical belt thickener systems to remove excessive sludge from effluents to reduce capital costs relating to the provision of sludge handling equipment and the operational costs of the handling and treatment of the sludge sludge.
We can supply centre drive or peripheral drive thickeners to suit any civil structure and manufactured in any material of construction.
Example of a centre drive unit
DISSOLVED AIR FLOTATION
Effluent, which may have already undergone chemical flocculation, is injected into a mixing chamber where it is placed in contact with air-saturated water resulting in the formation of small bubbles attached to the solids particles. Floated solids, being of a lower specific gravity, collect on the surface and are deposited into a trough by a surface skimmer. Separated liquid flows under a scum baffle prior to discharge.
Circular and rectangular units are available from Lektratek to suit the various applications and on larger sizes the flotation unit is equipped with a bottom scraper to facilitate the removal of any solids that may have settled on the tank floor.
The Lektratek linear screen has been developed to remove solid material from the effluent entering the treatment works. Various belt apertures are available to suit differing conditions and screenings loadings.
DAF thickener installed at Potsdam WWTW
LWT gravity linear thickener
MATERIALS OF CONSTRUCTION The full range of settling tank equipment, designed, manufactured and installed by Lektratek Water Technology, can be supplied in a variety of materials to suit all operating and environmental conditions.