Bio Mass Impianti dal 1973
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Dissolved Air Flotation “DAF”


Bio Mass Impianti designes Dissolved Air Flotation systems with Know-How matured in more than 35 years activity

Developments in technology

With the continuous development of DAF (Dissolved Air Flotation) technology, a new generation of machines allows the best efficiency performance as well as minimizing the footprint necessary for the treatment process.

The flotation process BMC-HR is the result of direct field experience and a high level of engineering applied to a process in which the solid/liquid separation is achieved with minimal surface area.

The solid / liquid separation occurs in turbulent flow conditions through two distinct and sequential stages, where the flocculated wastewater passes through a cloud of microbubbles, and where a high separation efficiency is obtained for optimization of aggregation kinetics in the reaction chamber and the subsequent filtration process that occurs through two fluidized beds under different dynamic motion.

The selection of the process also includes choosing the size of air bubbles during use. At large bubbles correspond local agitation speeds that develop phenomena’s of surface tension, small bubbles have an opportunity to join on the surface of flocks particles in large numbers, encouraging, therefore, very high final speed lifts. Furthermore, in turbulent flow conditions, a larger number of  microbubbles are counted against the flocks by adsorption in a very short time.

Therefore, the high-speed induced to the DAF process allows a much larger number of microbubbles to join flocks for turbulent diffusion rather than by simple tapping, as happens in conventional and well known processe’s.

Advantages & benefits of the process

The compact design of prefabricated systems enables rapid process activation of sewage treatment with considerable savings of occupied space.

Dissolved air flotation, compared to conventional systems, can in most cases, result in the following advantages:

  • Immediate setup of the entire process line, with automatic start/stop function according to the effluent to be treated;
  • High-speed separation with minimum retention time required, thus reducing the footprint occupied by the installation;
  • Quality and homogeneity of the treated effluent, also allowing water reuse in processing;
  • Increased level of sludge thickening, therefore economy of storage and/or subsequent treatment of dehydration;
  • Best performance in anaerobic digestion, due to the high concentration of sludge, preventing further thickening estimates.

Modern DAF systems with up to date technology also have the following advantages:

  • Reduced footprint of the machines with the same hydraulic flow, or significant increase in the hydraulic load applied to the process for the same yield and performance;
    • footprint of a high rate DAF is 30 times less than a conventional settler or clarifier;
  • Process divided into two sequential stages that enable acceleration and optimization of yield:
    • the first in turbulent flow, which allows optimization of flocculation, where possibility of contact between particles (chemical and/or biological flocks) and microbubbles  is largely increased;
    • the second in laminar flow with counter current filtration for a high quality of separation;
  • Limited and simplified maintenance since the whole tank is inspectable and has no partitions or devices that may be subject to clogging and difficult to inspect for cleaning;
  • With optimization of flocculation in the DAF tank, the use of special flocculation equipment upfront the DAF can be limited;
  • The high liquid level used in the DAF tank can allow a high thickness of the sludge surface blanket  with consequent benefit of a higher concentration of dry sludge removed from the surface;
  • The removal of surface sludge is carried out only by surface skimming over 360 degrees, therefore without moving the superficial stratification that, in some processes, may prove burdensome against unstable or weakly aggregations of flocks and microbubbles;
  • The different hydraulic segments that form the DAF tank are separated only by communicating vessels and not through mechanical seals and/or simple seals, which in time are subject to wear and ongoing maintenance.

Our range of machines and equipment

High rate dissolved air flotation units BMC.HR, are innovative high rate machines, developed as a result of long experience and experimentation, where the flotation process fulfils each of the third generation technologies, as defined in the acts of the most recent international conferences (Helsinki 2000 and Seoul 2007).


Modern concept for circular and rectangular section flotation units

BMI High Rate dissolved air flotation units, are innovative high rate machines, developed as a result of long experience and experimentation, where the flotation process fulfils each of the third generation technologies, as defined in the acts of the most recent international conferences (Helsinki 2000 and Seoul 2007).

Features and functionality

  • Flocculation under turbulence followed by distribution into a microbubble cloud, obtained in a particular reaction chamber, built into the flotation tank, where aggregation kinetics are optimised;
  • Optimized inlet to the DAF separation with uniform flow distribution that optimises microbubbles adsorption;
  • High dewatering percentage of the surface sludge removed, obtained by means of a spillway surface with variable speed exhaust operating at 360° with discharge into an annular collecting chamber;
  • High slope bottoms for collecting and manual or automatic removal of any regimented material;
  • Clarified effluent discharge through a telescopic valve with manual or automatic control to suit the needs of variable flow operation;
  • Saturation of the recycled effluent obtained with different systems depending on specific requests and/or applications;
  • There is no possibility of obstruction in the tank, therefore minimized maintenance and management;
  • Separation of the different sectors that form the DAF tank without means of any kind of mechanical seals, which in time are subject to wear and/or continuous maintenance;
  • Built entirely from stainless materials. Stainless Steel 304 (316 optional) and polypropylene;
  • Footprint reduced by 50 ÷ 70% compared to conventional DAF systems.

This type of machines are suitable for treatment of surface   water, as well as separation device after any coagulation/flocculation process of industrial effluents or as upstream treatment for biological systems, to reduce the organic loading and removal of fat or tertiary treatment downstream of inefficient or inadequate settlers or clarifiers.

Most of the machines designed by BMI are entirely prefabricated and ready for hydraulic connection on site. The main service equipment, such as saturation group, recycle pump/s and general control cabinet are usually assembled skid mounted in order to be  positioned in place close to the flotation unit. All machines require no special assembly or assemblies to be carried out on site, or neither special structures or support but only a suitable support Platform and the hydraulic connections for supply and discharge as well as interconnection with the recirculation and saturation skid.

To meet the requirements of small foot print, as well as minimizing the necessary facilities and installation work, in many situations all utilities for the process, such as equipment for the chemical pre-treatment, automation, etc., are housed in fully air-conditioned prefabricated containers, fully assembled with plumbing and electrical connections already made ready for commissioning.

Primary fields of application

  • Flottatori Circolari Monoblocco BIO MASS IMPIANTI
  • Primary treatment of  surface water
  • Tertiary treatment of municipal and industrial WW
  • Slaughter and meat processing plants
  • Fish Processing Industries
  • Dairy and/or production of butter and margarine
  • Food in general
  • Petrochemical Industry
  • Textiles
  • Industrial Laundries
  • Cosmetic Industry
  • Enhancement of biological systems with the possibility of pre-treatment or tertiary treatment
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