POLLUTION ENGINEERINGS (M)
SDN BHD

MALAYSIA

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	Dissolve Air Floatation
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	Area Of Application Pre-treatment or post treatment; processes to remove or reduce suspended solids,  biochemical oxygen demand, chemical oxygen demand, oil & grease and heavy metals. Features Alternative to sedimentation process More compact than normal sedimentation tank/clarifier High removal rate for suspended solids and oil and grease Economical pre-treatment and post treatment processes Easy availability of spares 100% Malaysian made The PESB-DAF system is very efficient in the removal or reduction of the level of the following parameters from any wastewater: Oil and grease Suspended solid (SS) Dissolved solids Biochemical oxygen demand (BOD) & chemical oxygen demand (COD). Some flocculated metallic sludge. Most of the PESB-DAF systems are applied in the pre-treatment processes to reduce or remove the above parameters. It is quite common to note that the reduction efficiency achievable for oil / grease and SS is more than 99%, and more than 60% for BOD &COD. To improve the quality of discharge from an existing treatment plant, sometimes the DAF is installed after the secondary clarifier / sedimentation tank. This will help to reduce the BOD and COD of the treated effluent. The PESB-DAF system basically consists of two components, namely : the white water generator the flotation tank   The white water generator is an equipment that produces dissolved air in water. It consists of an air compressor, an air / water mixer, a compression tank and a high pressure pump together with controls.  An automatic air purging system is provided to avoid excessive accumulation of air in the compression tank.   The water will be mixed with air at a certain ratio and then subject to high pressure. The air will dissolve in the water completely. When released into the flotation tank, the dissolved air will escape in the form of very fine bubble, which makes the water look whitish. The fine bubble has sticky property, which will help them attach to the sludge or oil to increase their buoyancy.   PESB-DAF-System The flotation tank can either be circular or rectangular. The tank can either be constructed using reinforced concrete or fiber reinforced plastics. A special mechanical skimmer or scrapper will be provided to remove the floating sludge or oil from the surface of the flotation tank to a skid tank.   To ensure that the clean treated effluent only overflows in the designed pattern that will avoid the floating sludge from carrying over to the discharge pipe, an inclined baffle plate will be installed in the case of rectangular tank. For the circular tank, a specially designed cylinder and overflow weir will be installed at the center of the tank. Scourge pipes will be provided to draw off the sludge from the bottom of the tank.     Process Description The wastewater will first be mixed with chemicals in a mixing tank where flocculation process will be carried out. The wastewater with flocculated sludge or also called flocs will then flow by gravity through a static mixer. In the static mixer, dissolved air (in the form of very fine bubbles) will be injected into the wastewater. This fine air bubbles will attach to the flocs and increase flocs’ buoyancy. The uniformly mixed wastewater saturated with dissolved air will then allowed to be released into the flotation tank via a header pipe which is installed at the front of the flotation tank. The header pipe will spread the floating sludge or oil across the entire surface of the tank. The floating sludge or oil will be removed either by a skimmer or scrapper to a skid tank. The clean treated effluent will then be allowed to overflow to the next stage of treatment.