It was in the late 19th century when some cities began to utilise sedimentation systems to treat sewage. This remained the only means of treatment until the discovery of the activated sludge process in 1912.
Sedimentation systems, more commonly referred to as primary sedimentation tanks or clarifiers, are still used today. They are still incorporated into the design concepts and planning for future sewage treatment plants as they allow an initial Biochemical Oxygen Demand (BOD) reduction of approximately 40 per cent, increasing the efficiency of the downstream secondary stage of treatment.
Now there is new technology available that can replace clarifiers and operate with more efficiency.
The HUBER LIQUID Drum was developed as part of a research project on alternative technologies contributing towards energy utilisation. The LIQUID technology is an extension of the popular ROTAMAT Screening Process, which is proven in over 4000 references.
It is now distributed throughout Australia by Hydroflux Epco as an innovative alternative to primary clarifiers. It reduces the amount of space required for a clarifying tank by up to 90 per cent while reducing energy use and the high investment costs.
The system uses a fine mesh with 0.1 to 0.2mm holes in a star pattern to increase the effective surface area of the drum. This allows similar suspended solids removal rates when compared to conventional primary clarifiers.
The benefits of the HUBER LIQUID Drum include:
- freeing up space and land with a 90 per cent reduction in the space required compared to a clarifier
- its performance is as good as, or better than, sedimentation
- major savings in capital costs for installation
- the use of gravity to capture sludge in a wash press for thickening by four to six per cent without using polymer
- the ability to repurpose existing clarifying tanks; for example, they could be reconfigured into aeration basins
How it works
The HUBER LIQUID Drum is an in-channel fine screen that uses a drum with a mesh profile to separate fine solids from the sewage flow. It is typically installed in a concrete channel downstream of the inlet works. It is provided with a main frame, channel seal plate, covers, spray system and main drive.
As the fine solids accumulate on the screen face, the headloss gradually increases due to the blinding of the drum. At a preset headloss, the drum rotates through a wash recycle and the solids wash into a trough, before being sluiced out of the machine for further processing.
The mesh geometry provides low headloss values, and the drum sizing and water levels are configured to reduce headloss values across the total screen. Spray water is used for washing the drum in a low and high pressure system. Reclaimed effluent can be used for this purpose.
The discharge of the screened sewage gravitates to the next process step. The solids washed from the drum are sluiced from an internal trough. Typically, these solids are pumped for digestion or can be thickened using a HUBER WAP LIQUID Press.