AS-FLOT 5-100

Photo: AS-FLOT  5-100

The technology (flotation unit) marketed under the AS-FLOT (flotation) trade name can be used to treat wastewater from the food-processing industry.

In particular, the AS-FLOT technology can be used in various branches, namely:

  • Meat processing industry
  • Breweries
  • Cattle slaughtering
  • Fish processing
  • Dairies
  • Production of potato chips, etc.
  • Cheese plants

The principle of the AS-FLOT technology is based on a separation process that is employed to separate dispersed particles from a liquid. During flotation, pollution particles accumulate with air micro-bubbles producing flotation foam, which is lighter than water. The foam rises to the flotator level, from where it is withdrawn to a storage tank.
Wastewater contains specific dissolved organic pollution that is manifested in high concentrations of the BOD5, COD, extractable substance, and solid substance indicators. The temperature also shows high fluctuations, mainly in water from meat production.
Depending on the requirements for output parameters, we are able to design, deliver, and ensure the assembly and operation of not only mechanical pre-treatment, but also biological after-treatment. Biological after-treatment is applied in cases when water should be released into a recipient.
Sewage is not subject to mechanical pre-treatment - flotation. After separate mechanical pre-treatment, it is directly routed to the activation part of the WWTP.

Table: Limits of monitored indicators

Average pollution of wastewater from the food-processing industry Assumed requirements for water released into the public sewerage system (prescribed by the Sewerage Rules)
Indicator mg/l Average [mg/l] Maximum [mg/l] Requirement for effectiveness[%]
BOD5 2500 750 1000 70
COD 4000 2000 2400 50
Solids 2500 500 800 80
Extractable substances 1000 50 100 90

Technological process of wastewater pre-treatment

In general, it consists of the following stages:

  • Rough filtration
  • Fine filtration
  • Chemical pre-treatment of wastewater
  • Pressurized-air flotation.

Rough filtration

Before wastewater enters the flotation stage, mechanical particles (undissolved substances) must be removed. With regard to the outlet of the inflow pipeline, the following devices can be designed:

  • Inflow basket at the entry of the pumping sump (deep sewerage inlet)
  • Self-cleaning racks with automatic wiping (in the supply sewerage)

Fine filtration

We use a rotary sieve with 0.5 mm filtration pores. The sieve is adapted to hot water flushing. The sieve is installed at such a height that captured solid substances can be accumulated in the waste container.

Accumulation sump

After the rough and fine filtration, wastewater flows into an underground accumulation sump. The tank is intensively stirred with a propeller stirrer that is installed on the activation device. The stirring can be done continuously or intermittently.

Wastewater pre-treatment

The purpose of chemical pre-treatment is the precipitation of pollution from wastewater to form larger particles that are subsequently separated from wastewater using the flotation process. The pre-treatment consists of two stages: coagulation and flocculation.

AS-FLOT flotation

The flotation unit is based on the principle of pressurized-air flotation. Recirculation and saturation with air is ensured in a "perlator" (aerator). A pump generates the pressure of the re-circulated water, while a compressor or the pressurized air system of the building generates the air pressure. Pollution particles accumulate on the surface where a continuous layer is formed, which is periodically removed with a scraping device and extracted to a collection trough.

Flotation foam flows to a container or underground sump. The foam consists of extractable impurities, which are mainly greases. As in the meat processing industry, grease contributes to the pollution of wastewater to a considerable extent: a high-percentage reduction of its content by capturing significantly reduces the pollution parameters, both as regards the grease itself and other indicators, such as undissolved substances, and indicators of dissolved organic pollution referred to as BOD5 and COD.

The drain of the flotation stage is located in the top part of the flotation tank. The drained water is the result of the pre-treatment process and it flows to the internal drainage system, and then via the external drainage system to the biological after-treatment stage. On the tank bottom, sediments accumulate that must be drained in a controlled manner. The system may be operated in a completely automatic mode or with some of its functions operated manually. This is mainly the case with scraping sludge from the surface and sludge removal from the flotation tank into the pumping sump, as well as the operation of the compressor. The control panel of the flotation unit is part of the main switchboard.

Selected references

Investor Location Capacity Q (m3/day) 
Kostelecké uzeniny,a.s Kostelec u Jihlavy, CZ  900
Masná výroba Josef Filák Horní Lideč, CZ   120
MAKOVEC a.s. Držovice, CZ 90
MASO V + W, s.r.o   Krnov, CZ  20
MVDr. Jaromír Steinhauser  Brno, CZ  76
ABOLIV  Mihai Viteazu, RO   80
Drůbeží polotovary    NANJUK Kolarovo, BG 40
SVAMAN, s.r.o.  Myjava, SK    210
Řeznictví  František Šutera Olešnice, CZ   45
Gordon Prod   Bisericani, RO    90
Drůbež CZ, s.r.o. Kunštát na Moravě, CZ 55
Masna Příbram, spol. s r.o.  Příbram, CZ   800
Mlékárna Hlinsko Hlinsko, CZ 700
Jatka Poběžovice  Poběžovice, CZ  75