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Biological Aerated Flooded Filter - BAFF - Wastewater Treatment

BIOBEAD^® is the leading Biological Aerated Flooded Filter (BAFF) technology with close to 50 plants in operation or under construction with UK water utility companies. F.L.I. Brightwater's Biobead^® incorporates the latest process and engineering advances to provide small footprint plant with low capital and operating costs.

An innovative and flexible design approach allows construction of plant serving populations of 500 to 300,000+ and for varying consent levels. High effluent quality is a hallmark of the process that is used for a variety of secondary and tertiary treatment applications.

Benefits of BIOBEAD^® BAFF
Small footprint;
Resistance to shock loads;
Tolerance of saline conditions;
Low capital and operating costs;
No odours or fly nuisance;
Ease of upgrade;
Applicable for BOD reduction / ammonia reduction / combined BOD + Ammonia reduction / Denitrification; Reduces BOD to less than 5mg/l if required;
Reduces ammoniacal nitrogen to less than 0.5 mg/l;
Denitrification for total nitrogen removal.

BIOBEAD^® BAFF General Description

Biological Aerated Flooded Filters (BAFFs) provide high rate, compact and robust sewage treatment plants that are capable of producing high quality sewage effluents.

 

Various proprietary designs are available, but the F.L.I. Brightwater BIOBEAD^® system has been developed to include a number of process and engineering advances that make for simple and reliable plants that are economical to operate.

 

All BAFF plants work on the principle of partially treated aerated sewage flowing through a submerged medium upon which the biomass growth attaches to form the stable concentrations needed to treat sewage at loading rates of between four and ten times that of conventional treatment systems.

The BIOBEAD^® process uses a specially developed buoyant plastic granular media and it is this that is the major advantage of the process.
 

Partially treated sewage flows upwards through the media bed, which is retained by an overlying perforated stainless steel mesh. The media has a roughened surface to assist biomass attachment. Air is introduced into a sparge pipe system, which is located in the media bed, and rises concurrently through the media with the sewage to be treated. This air supplies the oxygen needed to sustain the biological reaction and also mixes the incoming sewage across the media bed.

Periodically excessive accumulations of biomass and filtered solids have to be removed. It is here that some of the main advantages of the BIOBEAD^® system become evident.

Each reactor has a retention volume above the media in which treated effluent is stored. Desludging is carried out under gravity by opening a backwash (desludge) valve and using the stored volume of treated effluent from a number of reactors to displace the sludge from the base of the reactor being cleaned.

No other sewage effluent is used in the cleaning cycle, and hence there is no need for clean backwash water holding tanks or pumps, and the pipework, valves and controls are much simpler. The volume of sludge produced is also kept to an absolute minimum.

A second interesting feature of the cleaning process involves the increase of air rate by approximately 6 times from the normal air rate, which has the effect of decreasing the density of the air / liquid mixture such that the media is no longer buoyant but instead becomes fluidised. This regime removes the excess biomass from the media, and after a few minutes the air rate is returned to normal allowing the media to repack under the grid and leaving the sludge produced in the fixed volume below.

This feature is particularly useful for removing screenings which may otherwise become trapped in the cell. Also, this more thorough cleaning procedure avoids mud balling, which can impair performance of some other granular media BAFF systems.

The control of biomass inventory is instrumental in giving the high oxygen transfer efficiencies found in the BIOBEAD^® system. Notably, in the event of a total failure of inlet screens, the system can be readily cleansed of screenings. This feature also allows BIOBEAD^® to operate with rather coarse 6mm inlet works screens and ensures removal of finely divided neutral buoyancy materials which are a problem with other systems.

During the cleaning cycle the flow that would otherwise have been treated in the unit being cleaned is equally divided between the other units. For a period of time after the cleaning cycle the effluent from the cleaned unit is directed to the sludge return, in order to prevent any loose solids being discharged into the final effluent.

Download the BIOBEAD^® product literature

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