CLARIFIERS/TUBE Settlers

Technology and Process Description

Clarifiers are used as pre-treatment units for treating turbid waters having higher suspended and colloidal particles (surface water sources like rivers, streams and sea) and down / up stream of biological processes in waste water treatment. The clarifiers help settlement of colloidal particles by providing a larger surface area.

Conventional clarifiers as well as compact and space efficient tube settlers with smaller footprints are used for this purpose. Accessories like flash mixers, flocculators and chemical feeding systems are offered as part of the system.

A clarifier consists of a series of inclined plates which are arranged to form a separate sedimentation chamber between adjacent plates. The raw water first flows to the stilling chamber to break the turbulence and is then fed into a flash mixer. Chemicals like alum, lime, polyelectrolyte and similar coagulants / flocculation agents are dosed in the water prior to flash mixer for proper mixing of chemicals which enhances the efficiency of sedimentation / floc formation. Water from the flash mixer enters into the flocculator. The paddle type agitator provided in the structure facilitates gentle mixing.

The flocculated water enters the clarifier from the bottom section of the plates and flows upward between them. As the water moves upwards, solids settle downward onto the surface area provided by the plates. Solids continue to slide down the plate surfaces to the collection hopper. Near the top of each plate, water leaves through circular openings in the adjustable weir plate located along both the sides of the clarifier. The weir plate is set horizontally to provide proper distribution of liquid through each circular opening. Settled sludge is periodically drained by opening the drain valve at the hopper bottom. The collected sludge from the plant is finally pumped out.

MORF INDIA designs a wide range of clarifiers / tube settlers which are compact, involves low civil cost and adopts a modular design that minimizes field erection activities. High Rate Solids Contact Clarifiers (HRSCC) are used in raw water which has volatile physical characteristics. HRSCC ensures a highly clarified water quality and greater tolerance to variations in inlet conditions. With no major moving parts, it is highly maintenance-friendly and is designed to work totally on gravity.


General Features and Technical Information

Lamella settler technology is a versatile clarification-cum-separation arrangement in which solids, oil and grease can be removed from the feed water. The design of lamella plate settlers utilize a series of parallel plates which maintain a laminar, stable flow in between the plates to achieve excellent effluent quality. The plates are provided with a mirror finish to attract and settle the flocculated particles. The particles accumulate on the surface and slide down due to gravity. The sludge accumulates at the bottom cone. The collected sludge is removed from the bottom at regular intervals. Lamella clarifiers are compact and ideal for high suspended solids and chemical based sludge. Lamella separators use a variety of media like fiberglass plates, corrugated sheets, steel and concrete structures for effecting efficient separation. This type of clarifier occupies only 1/5th of space required by conventional clarifiers.

Lamella clarifiers can be operated continuously for any length of time. Lamella does not build up deposits and there is no specific / stipulated frequency of cleaning which results in minimal maintenance

Since there are no moving components, the maintenance problems are minimal. Sludge thickener zone having four slopped hopper bottoms completely replaces the extra thickness. Maximum effective settling area of the place increases due to better hydraulic distribution and collection arrangement. Lamella plates can be easily removed for cleaning without following the routine maintenance procedures like shutting down the unit, draining the tank contents and dismantling the tank internals. The plates can be easily slid up for inspection and maintenance as required. A single person can handle these operations.

Tube settlers utilize slanted tubular media to achieve a laminar flow in the media within a short distance and thereby assuring better separation. The media traps the floc particles. The particles accumulate on the surface and slide down due to gravity. The sliding particles accumulate at the bottom cone. The collected physical contaminants are removed from the bottom at regular intervals.

Lamella plate settlers and Tube settlers are used as Pre-Fit to Filtration units in raw water treatment and as secondary clarifiers in the sewage treatment plants.