Sigma specializes in designing several clarification systems. All systems are custom designed to suit the application, solids loading, and understanding the settleability of the composite water/wastewater. Clarification systems vary based on application, with gravity clarification being the most popular. High rate clarification results in lower surface area and foot print requirement. Dissolved Air Flotation, Inclined plate clarifier and tube settler are examples of high rate clarifiers. Some typical processes are described below.



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In the event of high suspended solids and oil & grease, a Sigma dissolved air flotation (DAF) clarifier is proposed for separation and solids clarification. Dissolved air flotation is an effective means for separating solids from liquid streams and has been used as an effective alternative to sedimentation for several decades. The Sigma DAF system works based on the principle of cavitation suction of atmospheric air through a high pressure patented multistage pump causing saturation of air with water under high pressure released to the atmospheric pressure causing milky white micro bubbles which aid in the flotation of fats, oils and greases. These micro bubbles attach to flocculated particles to form a air/solids aggregate which have a low apparent density to that of water.

Destabilization of colloidal charges is important for efficient separation. This is dependant on several physical parameters such as pH, water quality and the addition of coagulants. The air/solid aggregate rises to the surface where it forms a stable layer of sludge and continuously thickens. The scum is constantly removed by a surface skimmer. A geared motor is used as a driving mechanism for the scraper. Treated water from the DAF overflows the weir to downstream processes.

Sigma has reduced chemical consumption by less than half that is normally required using other forms of primary clarification. Reduction in the chemical consumption results in a lower sludge volume, hence reducing the associated costs with sludge disposal.


Sigma offers tube settlers for primary clarification applications including storm water and rain water treatment systems. Upon completion of coagulation and flocculation processes, the wastewater enters the tube settler clarifier at the bottom, where the solids higher in density settled and periodically purged from the system. Tube settlers use multiple tubular channels sloped at an angle of 60° and adjacent to each other, which combine to form an increased effective settling area. This provides for a particle settling depth that is significantly less than the settling depth of a conventional clarifier, reducing settling times. Tube settlers capture the settleable fine floc that escapes the clarification zone beneath the tube settlers and allows the larger floc to travel to the tank bottom in a more settleable form. The tube settler’s channel collects solids into a compact mass which promotes the solids to slide down the tube channel.