Industrial Wastewater Treatment Plants
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Dissolved Air Flotation (DAF)
A DAF system can help achieve compliance for sewer discharge and reduce costs associated with trade effluent charges.
DAF is a physical separation process used for removing contaminates from water. The process saturates effluent with air under pressure. On release into the atmosphere, micro-bubbles are formed, attaching to the contaminant as they rise to the surface.
The primary objective of a DAF system is to reduce Chemical Oxygen Demand (COD) loading by the removal of high COD contaminants including fats, oils and greases, colour, organic matter and colloidal material. A reduction of up to 90% of COD and suspended solids can be achieved. The system can be used with or without the addition of chemicals; depending on the waste type, chemicals can further enhance performance.
WPL DAF plants are small, compact and robust systems. Highly efficient, they can cope with variations in influent wastewater quality and flow. Balancing tanks can be used to even out very large variations.
Why choose WPL DAF?
- Main structural components are manufactured in 304 stainless steel for added corrosion resistance
- Higher specification can be supplied if required
- Reinforced plastic components reduce wear and corrosion, reducing maintenance time and cost
- White water system utilises a pressure vessel to negate the need for diffusers within the flotation tank, reducing maintenance requirements
- PVC coil pipe flocculator eliminates corrosion and comes with numerous sampling and injection points to improve efficiency
- System comes complete with safety guards, grids, ladders and handrails to provide safe working access
How it works
The WPL DAF is a purely physical process which operates on a simple design philosophy. Incoming effluent may require pre-treatment as necessary; for example the addition of chemical coagulant(s) and/or flocculant(s) may be required with associated mixing and coagulation/flocculation stages. Adjustment of pH may also be necessary to ensure optimum operating conditions.
The incoming effluent enters the flotation vessel where it comes into contact with recycled, treated effluent (sometimes termed ‘white water’). The percentage of the total effluent flow into which air is dissolved under pressure and subsequently recycled will be determined by several factors.Increasing the pressure within the vessel where the air is being dissolved ensures that a higher concentration of air dissolves into the liquid phase than is possible at atmospheric pressure.
Once this saturated effluent enters the flotation tank, the pressure is released back to atmospheric pressure. This immediately results in the recycled flow becoming supersaturated, generating micro bubbles as the dissolved air comes back out of solution.
These bubbles attach to, and form within, the solids orc hemical flocculants entering the vessel, causing them to float to the surface where they are retained and subsequently removed by a mechanical skimmer. Within the rectangular flotation tank, the skimmer mechanism consists of a series of paddles or ‘flights’ which run on a plastic corrosion-resistant chain, and skim just below the surface of the tank removing the ‘float’ into a trough for recovery of the sludge. To eliminate the risk of sludge build-up on the flotation tank floor, the design may also incorporate a floor scraper.
Technical details and dimensions
The DAF system is used in many industrial applications, including:
- Dairy waste
- Process waters
- Food processing waste
- Waste waters
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