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HYDRIG DISSOLVED AIR FLOTATION UNIT - DAF UNIT

FL series DAF units are used for oil, grease, metal, suspended solids, SAS removing as well as for mixed liquid separation after biological treatment.The whole unit is made of stainless steel. To achieve maximum treatment degree chemical agents can be added: alkali, acid, coagulant, flocculant. HYDRIG flotation units are characterized by a recirculation process, allowing the treatment of highly concentrated effluent stream.

Напорный флотатор HYDRIG

Wastewater is fed to the DAF unit through the flocculation pipe and clear aired saturated water is fed through the saturator vessel. The flocculation pipe serves to supply wastewater which is processed by chemicals (coagulant, flocculant, acid and alkali). The saturator vessel is used for proportional dissolving of air in water. Its volume is calculated for necessary aeration duration (usually 1-3 min) at maximum pressure of 0.6 MPa. Air dissolved in the saturator has to account for 3-5% of processed wastewater volume. Air saturated water is fed to the flotation chamber, where the air is being released in the form of tiny bubbles. The bubbles adhere to the suspended matter, causing the suspended matter to float to the surface and form a froth layer which is continuously removed by a skimmer. The amount of water in the sludge depends on the speed of the scraper mechanism. A part of treated water is recycled; the other part is supplied to the treated water tank. Water stays in the flotation unit for 20-30 min.

Wastewater treatment by dissolved air flotation can be used at different stages (pretreatment, treatment or tertiary treatment). Equipment and process selection depends on the treated water qualities requirements.

Pretreatment

Properly selected pretreatment process allows the reduction of installation and maintenance costs. Flotation without chemical agents is used for the wastewater with a huge amount of suspended solids, grease and oil products. Less concentrated wastewater can be treated with a biological method.

Treatment

Meat-processing plant wastewater treated with a pressure flotation unit with chemical agents may be suitable to discharge into the municipal sewer system. COD and BOD as well as the amount of suspended solids meet the requirements of urban water services companies.

Table 1

Contaminants

Initial contaminant concentrations, mg/l

Treatment efficiency, %

COD

<5000

60-80

BOD

<2500

60-80

Suspended solids

<1000

90-95

Grease

<500

90-95

Oil products

<500

98-99


Tertiary treatment

Tertiary treatment of wastewater containing oil products can be performed in the ponds or DAF units of FL series. Efficiency is achieved through increasing the speed of oill particles floatation which adhear to air bubbles. By themselves 1.5 µm oil particles float up with the speed 1 µm/sec, while by flotation average speed is about 0.9 mm/sec. Consequently, floatation speed increases 900 times. The sludge is removed from the flotator surface and treated water can be fed into sewer system or used for the technical needs of the enterprise.

Dissolved air flotation is a good alternative to gravity sedimentation. It is suggested to use a DAF unit instead of a secondary settling tank in biological WWTP. It takes flaotation thickening 10 minutes to reach the same sludge thickness as gravity thickening reaches in 2 hours. Surplus activated sludge can be fed into the DAF unit after complete or incomplete biological treatment. As flotation process is accompanied by wastewater aeration, the process of activated sludge separation from water is simultaneous to bacteria, microorganisms and easily oxidable substances concentration reduction.

Table 2*

Model

Capacity, m3/hour

Overall dimensions, mm

Weight, kg

FL-1.5

0.9-1.2**

2000х1150х2100

360

FL-4

2.8-3.2**

3300х1700х2100 + detached saturator 2000х500х800

900

FL-7

5-5.6**

3600х2000х2000 + detached saturator 2400х600х1000

1300

FL-11

7.7-8.8**

3800х2300х2200 + detached saturator 2700х600х1200

1800

FL-15

10.5-12**

4000х2600х2500 + detached saturator 3000х600х1200

2200

*Flotation units of higher capacity are tailored individually
**Capacity depends on the wastewater type and pollution degree

High cleaning performance, minimal processing time, ease of maintenance and versatility of pressure flotation enable widespread use of this wastewater treatment method in almost any industrial sector.

Application:

  • food industry: wastewater treatment from oil and organic pollutants;
  • storm sewers treatment from oil products and suspended solids;
  • municipal water treatment from excess activated sludge;
  • galvanic wastewater treatment from heavy-metal ions.

Безымянный-2-02-01.jpg


Contaminants

Initial contaminant concentrations, mg/l

Treatment efficiency, %

COD

<5000

60-80

BOD

<2500

60-80

Suspended solids

<1000

90-95

Grease

<500

90-95

Oil products

<500

98-99


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