Water Treatment Systems
Drives for Circular Trickling Filter Bed
Secondary treatment is optimized by the application of a motorised drive to the distributor. This ensures uniform distributor motion under all conditions. Rotational speed is easily altered to adjust the flushing intensify to meet changing conditions that can affect the treatment process.
This maximises treatment by regulating the loading on a filter unit and can therefore:
- Reduce excessive biomass.
- Improve oxygen transfer resulting in lower BOD and increase in ammonia oxidation capability.
- Prevent solids build up.
- Control fly infestation and odours.
- Remove risk of ponding.
- Achieve substantial energy savings should re-circulation become redundant or reduced.
TRADITIONAL METHOD OF ROTATION
Sewage fed to the distributor arms, either by syphonic action or direct from the primary settlement tank produces tangential forces due to jet reaction thus creating a state of self propulsion.
Unfortunately this form of propulsion is sensitive to wind, flow, blockage of jets and friction, to the extent that the distributor may even stop, causing unequal dosing and ponding. This results in low quality treatment and can even lead to consent failure. It can also result in the unwelcome growth of moss on the media surface.
Ponding also occurs when the flow is being shut off or when the flow is resumed and there is insufficient flow to produce rotation. Conversely. in times of high flow, the rotation of the arms can be too rapid. This can cause damage to bearings and result in excessive wear. Too rapid a rotation at normal flows can also cause problems with fly nuisance.
THE DRIVE SYSTEM PACKAGE
The "self propulsion" lottery is replaced by a constant torque gear motor unit, fed from a variable frequency inverter for speed adjustment and driving a ring which is clamped to the distributor arms and located
in the centre well. A pneumatic system maintains belt tension which is fully adjustable to suit flow conditions. The pre-selected speed is maintained under all conditions. The supporting framework is secured to the well wall or to the centre column and forms a rigid structure with
minimum deflection. All parts can withstand the corrosive action of the effluent and other elements of the environment.
Provision is made for automatically reverting to jet reaction propulsion should the electricity supply fail, ensuring continuous treatment, albeit at the natural jet reaction speed. This is achieved by releasing the drive belt tension. When the supply is restored, the drive is re-engaged and the distributor runs at the previously set speed.
The drive is torque limited to prevent damage should the arms be obstructed or to prevent injury to personnel who may be the cause of the obstruction. This is achieved by setting the belt tension so that the belt slips at a pre-determined torque.
Reaction guide rollers are introduced to ensure no side thrust is imposed on the drive ring, and subsequently the distributor
The drive transmission can take up vertical movements of the arms caused by unequal loading due to flow.
- Driving the distributor at very low speed (1-2 revolutions per hour) for control of flies with means of reverting to a higher speed for selected periods for increased retention time.
- Constant loading of the bed by varying the distributor speed in proportion to flow.
- Rotational sensing to indicate if the distributor has stopped after a selected delay time.
- Alternative speed ranges.
- Extra control functions as specified.
- A positive and continuous drive removes the risk of stoppage. Treatment is not left to chance and CONSENT COMPLIANCE IS THEREFORE MAINTAINED.
- Control of flushing intensity. REDUCES SOLIDS BUILD UP "CLOGGING" THE MEDIA.
- Reduced biomass IMPROVES OXYGEN TRANSFER.
- High flushing intensity ensures FLIES ARE SUPPRESSED.
- A continuous drive REDUCES PONDING.
- A continuous drive prevents high rotational speeds. MINIMISES MAINTENANCE.
The drive is generously rated in all respects and is equally suitable for use on all sizes of percolating filter beds at present in use. The torque transmitted to the rotating arms is fully adjustable by means of regulation of the air pressure applied to the pneumatic tensioner.
|Speed of Rotation
||Adjustable from 3 to 15 revs. per hour. as standard.
Other speed ranges can be provided for specific requirements.
|Electrical Mains Supply
||230V single phase 50 Hz
||230V three phase 10-50Hz
|Typical Power Consumption
||Planetary type. grease lubricated for life.
||Rocking Piston type - 7 bar maximum pressure
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