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Tertiary Filtration

for F.L.I. Brightwater's new Tertiary Solids Filtration mobile units, using the BMax^® floating media, please go to: www.hsaf.co.uk/filtration

Conceived following the achievements of the highly successful F.L.I. Brightwater BIOBEAD^® BAFF, FILTABEAD^® is a derivative of the BAFF filter which, unaerated, is effective as an upflow tertiary / effluent polishing filter, producing high quality effluent.

Benefits of FILTABEAD^®

- Small footprint
- High solids loading
- High rate
- High effluent quality (10 / 10 mg/l 95% or better)
- Simplicity of design, installation and operation
- Cost effective for populations between 500 – 300,000+
- Low capital and operating costs
- Low sludge production
- Easy and efficient cleaning of media
- Upgradeable to biological duty.

FILTABEAD^® Tertiary Filtration General Description

Tertiary filters provide high rate, simple, compact and robust solutions to improving / polishing the final effluent quality from an existing works.

Filtabead^® has two unique features: firstly, it is an upflow filter; secondly, and in this way is unique in the tertiary filtration field, it uses a buoyant plastic granular filter media rather than sand.
This media is similar to that developed by F.L.I. Brightwater for the BIOBEAD^® BAFF process. However it has simpler surface engineering to improve the cleaning and discourage biomass attachment. Secondary treated sewage flows upwards through the media bed, which is retained by an overlying perforated stainless steel mesh. In this way solely acting as a solids separation filter - allowing for cost effective compliance with stringent quality consents.

Periodically excessive accumulations of filtered solids have to be removed. It is here that some of the main advantages of the FILTABEAD^® system becomes evident.

Filters are cleaned one at a time by a vigorous air scour. The air rate employed in the scour has the effect of decreasing the density of the air / liquid mixture such that the media is no longer buoyant but instead becomes fluidised and agitated.
This regime removes the excess biomass from the media, and after a few minutes the air is stopped, allowing the media to repack under the grid and leaving the sludge produced in the fixed volume below.  

When the air scouring procedure and subsequent draining out of “sludge” from the base of the reactor has taken place there are two options (available to be made in the plants design phase) for the next stage in cleaning of the filter. The filters can be designed either with or without a treated effluent retention volume above the media – the latter case potentially leading to a slightly smaller filter and using influent to the filter to flush the remaining solids from the bed in the normal filtration upflow direction, the former using tertiary filtered effluent for a gravity (contra-flow) flush.

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. 

As can be seen from the photograph above, FILTABEAD^® can be readily supplied and retrofitted in coated carbon steel tanks onto a cast concrete slab. The plant, as seen above, was installed and commissioned approximately 12 years ago.

Flexible design allows FILTABEAD^® to be adapted easily for denitrification. The plant can also be upgraded to biological duty by addition of a process aeration grid. FILTABEAD^® is designed for high upflow rates, which can be up to 12 m/h depending on the application.

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