Clarifier is a device or tank in which clarification process is carried out, raw water is held to allow the settling of suspended matter by gravity. Clarifiers are circular or rectangular in shape with sludge collecting and removing mechanism at the bottom of tank.

Napier Reid has over a number of years designed and manufactured a wide range of clarifiers. All the clarifiers are working efficiently, meeting or exceeding the process requirements, and are testimony in itself of our design and manufacturing capabilities. Napier Reid range of clarifiers include the following:

1) CLARIFIER WITH TUBE SETTLERS: N-R Clarifiers with tube settler are available in circular as well as rectangular shape.

The chemically treated and flocculated feed water enters the stilling well of the clarifier. The water exits from the bottom of the stilling well and flows upward towards the weir located at the surface. The flow passes through specially designed tube-settlers.

Tube settlers consist of multiple tubular channels of various shapes, sloped at an angle, generally at 60o. They combine to form an increased effective settling area. This results in reduced settling depth and hence settling time is also significantly reduced. The tube settlers increase allowable flow capacity as it increases effective settling area and solids removal rate in settling tank. Hence, clarifiers with tube settlers are more efficient and compact than conventional clarifiers.

The settled floc or sludge slide down to the tank bottom for subsequent removal from tank. A scraper mechanism is generally provided in circular tanks to collect the settled solids and flocs for removal.

2) SOLID CONTACT CLARIFIER:These clarifiers are used to achieve suspended solids removal in less space than conventional clarifier. The general concept is that recycling of large quantities of flocs in the tank increases the chances of collisions of flocs. The small flocs collide and agglomerate with large flocs. As large flocs have faster settling velocity, higher flow rate per unit size of clarifier is possible compared to conventional clarifier.

The solid contact clarifier can be grouped into three categories: Upflow Clarifier, Reactor Clarifier and Sludge Blanket Clarifier.

• Upflow Clarifier: It is basically a sedimentation tank in which inflow enters the tank bottom or stilling well, and flows upward towards the weir located at the surface. Clarifier is designed to minimize short-circuiting of the flow, uniform withdrawal of clarified water and proper sludge removal without disturbing the settling process.
  
  Upflow clarifiers are best suited for clarification of water with heavy, non-colloidal solids.
  
  
• Reactor Clarifier: It is sometimes also known as Clari-flocculator. In reactor clarifier, coagulation, flocculation, and sedimentation processes are combined.
  
  A typical reactor clarifier consists of circular basin design. The feed raw water enters a conical or cylindrical shaped compartment that acts as a stilling zone as well as flocculation zone. Chemicals (coagulant and flocculant) are added in this compartment. Coagulation takes place in the primary mixing zone while flocculation takes place in secondary mixing zone. The flocculation process produces a large number of particle collisions resulting in smaller particles agglomerate to form larger flocs. Water flows out from bottom of mixing zone into the settling zone. The flocs and solids settle to the bottom and clarified water is collected over the weir at surface. The sludge settled at bottom is continuously or occasionally discarded.
  
  
• Sludge Blanket Clarifier: A sludge-blanket clarifier is similar to reactor clarifier, except that the water flowing from the bottom of mixing zone flows through a blanket of sludge that acts as a filter. As the flocculated water passes through the suspended sludge blanket, the particles are absorbed onto the larger flocs. This increases the size and weight of the flocs and it gradually settles to the bottom and is re-circulated. When the sludge in the clarifier reaches beyond a certain level, some sludge is wasted.

All Napier-Reid Clarifier come with superior features that make Napier Reid products a trusted and reliable name in water treatment industry. Standard features of N-R Clarifier are:

• Efficient design leading to higher hydraulic loading rate and smaller foot-print
  
  
• Heavy duty construction
  
  
• Well designed clarified water collection system and sludge scraper mechanism
  
  
• Efficient flocculator design to provide necessary re-circulation with minimum shear and break-up of flocs (for sludge-blanket clarifier)
  
  
• Variable speed drive to optimize the flocculation process (for sludge-blanket clarifier)
  
  
• High quality workmanship and aesthetic finish
  
  
• Full support of Napier Reid's core team of professionals in process and engineering field
  
  

Rectangular Clarifier with tube settlers

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