BrightwaterTM BAFF® - Biological Aerated Flooded Filter

BrightwaterTM BAFF® is the UK's leading Biological Aerated Flooded Filter (BAFF) technology. BrightwaterTM BAFF® 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 from 500 to 350,000+ 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.

The BrightwaterTM BAFF® System offers:-

  • Robust reliable Biological Aerated Flooded Filter (BAFF) process for high quality final effluents - 5/10/0.5 mg/l (BOD/SS/NH3-N) or better.
  • Applicable for Carbonaceous, Nitrification and Nutrient Removal duties (C, N, C+N and De-Nit).
  • Resistant to shock loading including solids overload.
  • Operates under saline conditions
  • Requires only 6mm upstream screening

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 BrightwaterTM BAFF® 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 BrightwaterTM BAFF® process uses a specially developed buoyant plastic granular media called BIOBEAD® 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.

The Design & Performance

BIOBEAD® plant designs can accommodate carbonaceous removal (C), ammonia removal (N), combined C and N removal and de-nitrification. Therefore, flexible designs that allow plant extension to meet higher effluent standards are readily achievable.

BIOBEAD® plants produce consistent, high quality effluent to a level of 5 mg/l BOD, 10 mg/l SS, 0.5 mg/l NH3-N or better.

A single stage BIOBEAD® plant provides highly effective carbonaceous treatment for BOD removal which can ope rate under saline conditions. Typical loading rates are 2.5 - 5.0 kgBOD/m3day.

A separate stage with process conditions optimised for nitrifying bacteria can be added for ammonia removal and allows final effluent quality better than 10 mg/l BOD, 10 mg/l SS and ammonia concentrations less than 3 mg/l at loading rates of 0.6 kgNH3-N/m3day.

Alternatively, these processes can be combined and denitrification can also be included within a single stage to achieve high rates of carbon and nitrogen removal.

BIOBEAD® technology is applied across a wide range of scheme sizes and Brightwater have an extensive reference list from 500 to 350,000 PE.

Plants can be supplied in steel tanks or constructed within concrete tanks dependant on site specific requirements. Plant are designed and built in full consultation with the customer and incorporating the customer's design standards as well as our own. There is no limit to the capacity that BIOBEAD® can handle producing high quality final effluents for the most demanding applications. Full service and maintenance agreements are all part of our offering if required.