Flotation for Industrial Wastewater Treatment

DAF Unit

Categories: Flotation

The best solution for cleaning wastewater from suspended solids including fats, oil products, and phosphates while reducing COD and BOD in wastewater.

Esmil DAF-unit is the best solution for cleaning wastewater from suspended solids including fats, oil products, and phosphates while reducing COD and BOD in wastewater.

Scope of application of DAF-Units:

Esmil Dissolved air flotation systems (DAF) are used for the treatment of wastewater in various industrial facilities:

food industry (meat, dairy, fish, canning, etc.),
textile and leather,
oil and fat plants,
iron and steel industry,
sludge thickening

Operational principle of Esmil DAF-Units

The initial wastewater is pumped to the mixer inlet, i.e. to the DAF-unit, where the effluents are treated with reagents and then enter the mixing chamber with the simultaneous supply of a water-air mixture. Air and suspended solids float to the surface in the form of coagulated particles. Larger flotation complexes reach the surface at the mixing chamber stage. The rest goes with the wastewater to the flotation chamber. The resulting foam is removed from the surface of the water by the scraper mechanism and discharged into the collection tray. Heavy contaminants settle on the bottom of the unit and are removed. The clarified wastewater is discharged from the installation. Part of the purified water is taken by the pump to saturate it with air. After this, the air-water mixture enters with the mainstream into the mixing chamber of the flotator. The water level in the flotator is controlled by changing the overflow height.

Esmil daf-unit

Advantages of Esmil DAF-Unit

The dissolved air flotation system (DAF) is designed for each specific case and the equipment can adapt to any environmental setting.
The type, size and shape of the containment as well as the internal construction of the DAF-unit are selected for each specific case and designed using (CAD) computer-aided design.
The cone shape bottom provides high-quality of sediments removal.
The synchronized patented scraper mechanism minimizes, the destruction of floating sludge during its movement on the surface of the water.
Lamellas specialized form of corrugated plates and individual sizing of the desired distance between the shelves makes using a thin-layer module as efficient as possible in each particular case.
Specially designed, patented mixers efficiently mix reagent solutions with effluents.
The complex system is controlled from the (HMI) human machine interface screen or other devices through remote access. The control cabinet is constructed using Siemens PLC and Schneider Electric components.

Benefits of using Esmil DAF-Unit

Effective separation of oil products, suspended solids, and fats help to increase performance and treatment quality.
Preparation of the wastewater facilities for discharge into the city networks.
Eliminating the risk of additional costs for exceeding the permissible wastewater indicators.
Elimination of problems concerning pipeline clogging and wear of other related equipment.
The unique design of the scraper mechanism allows changing the rotational speed of the drive, and the number of scrapers in cases where a large amount of floating sludge and foam is formed.

Efficiency of Esmil DAF-Unit (quality of treatment)

Industry	COD	Suspended solids	Oil products and fats	Phosphates	Sulphides	Metals
Slaughter and meat processing	55-80%	Up to 98%	Up to 95%	Up to 90%	Up to 99%	Up to 95%
Dairy industry	35-60%	Up to 98%	Up to 95%	Up to 90%	Up to 99%	Up to 95%
Oil refining	45-55%	Up to 95%		Up to 90%	Up to 99%	Up to 95%
Other industries	35-80%	85-95%	85-95%	Up to 90%	Up to 99%	Up to 95%

Durability of Esmil DAF-Units

The self-cleansing system of the thin-layer modules extends the period of routine cleaning of equipment.
The elements of the scrapers are made of polyurethane, which guarantees a long service life. The use of special elastomeric materials guarantee resistance to specific effluents.
The tank is made of AISI 304 stainless steel, optionally AISI316 or fibre-reinforced polymer (FRP).

Optional outfitting of Esmil DAF-Units

ventilation duct;
explosion-proof construction;
antifoaming devices in a collection tank;
saturation system;
design to transfer the DAF-unit data to the upper-level control system using standard communication protocols;
design of automatic integration with mechanical cleaning units, tanks, conveyors as well as dewatering systems.

Technical characteristics of Esmil DAF-Unit

Productivity, m³/h	2 - 280
Recirculation coefficient, %	20 - 200
Recycle pressure, bar	5 - 6,5
Flotation surface, m²	0,5 - 21,6
Lamella block volume, m³	0,5 - 16
Reduced lamella block flotation area, m²	5 - 94

How does flotation work?

The operation of the DAF-unit is based on the principle of physical and chemical wastewater treatment, i.e. pressure flotation, designed to remove oil products, fats, surfactants, oils and other insoluble impurities from wastewater using air bubbles. Flotation is based on the ability of particles present in wastewater to create flotation complexes (suspended solids sticking to air bubbles) which then rise to the surface passing into the foam layer.

Is there a need to use coagulants?

Air bubbles remove particles that are not wetted by water from the effluent. Coagulants and flocculants are often used in the DAF-unit for the process of cleaning to reduce the wettability of the contaminants and increase the cleaning efficiency.

What kind of wastewater treatment should be provided before DAF-Unit?

To ensure the reliable operation of the DAF-Unit, it is necessary to provide mechanical wastewater treatment - screens with perforation of 2-3 mm or slotted cloth of 0.5-1 mm.

What moisture will the flotation sludge have at the outlet and does it need to be additionally dewatered?

Typically, the moisture content of flotation sludge, depending on the industry, is 90-95%, while it is quite liquid. Our company can select and supply equipment for dewatering flotation sludge, which will simplify waste disposal and reduce its amount. Also, both complexes can be automated.