- Distributors For Percolating Filter Bed

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The percolating filter bed is widely accepted as the most flexible and resilient method of biologically treating wastewater. Ovivo offers filter distributors suited to almost all filter bed applications ranging between 3 metres and 50 metres diameter, accommodating various flow rates. Copa distributors can be fitted onto their own duckfoot for new installations, or retro fitted to any suitable existing flange as replacement for any make of filter distributor.

Ovivo manufactures three types of distributor and these can be fitted with four types of distribution arms that are selected to suit the requirements of the filter bed.

In recent years the emphasis has been on the need to control the speed of rotation of distributors under all flow conditions, and this has been achieved by the use of either electro hydraulic or electric distributor drive units.

Distributors

Turbine Distributor
Turbine distributors are suited to small sewage treatment works serving populations of less than 50 persons. The overhead fed turbine rotates even at the lowest flows. Turbine distributors are suitable for filter beds up to 8 metres diameter and flows up to 1.14 litres per second.

Waterwheel Distributor
Waterwheel driven distributors were introduced into the Copa range of filter distributors to meet the demands of the Water Industry for a low maintenance distributor. They can be fitted to beds ranging between 5 metres and 45 metres diameter. These machines have the advantage of requiring very little attention and thus are well suited for rural sites, requiring infrequent visits.

Waterwheel driven distributors can improve the quality of the treatment works effluent, by dispensing with the dosing syphon and providing a continuous flow pattern through the filter media. The performance of the humus tank is also improved due to smooth flow pattern.

Syphonic Distributor
Syphonic seal distributors are available for filter beds having a diameter up to 50 metres or with a feed pipe diameter of up to 450mm diameter. They can be used for both high rate and low rate applications.

Distributor Arms
Open Trough Arms
These arms are fitted to turbine and waterwheel distributors up to 10 metres diameter. Open trough arms are fitted with v-notch weirs for even distribution, and are supported by stainless steel tie rods. As the arms are open, they require only minimal operator attention.

Weir Box Arms
These arms are fitted to waterwheel distributors up to 22 metres diameter and to smaller syphonic distributors, the tubular arms feed through large rectangular apertures into the Copa unique non clog distribution weir boxes. This type of distribution only requires a low level of operator attendance.

Reaction Drive Arms
For syphonic machines, arms are normally manufactured from galvanised steel tube. The distance between the jets is graduated along the length of each arm to ensure complete and even wetting of the media surface with each complete rotation of the distributor.

The CopaSac screen provides an excellent lost cost and simple solution to prevent jets becoming blocked by debris bypassing the inlet works or headworks screens. The CopaSac screen can reduce maintenance downtime when used in this type of distributor.

High Rate Arms
For the larger high rate machines, the arms can be in the form of open channels, fitted with both jets and v-notches, to accommodate a wide range of flow variations; this enables normal flows to rotate the distributor by reaction, and at higher levels to overflow the arms via the v-notches.

Distributor Drives
It has been demonstrated that the biological efficiency of a percolating filter can be improved by controlling the periodicity of dosing, which in turn controls and regulates the growth of the biological film. This control can be achieved by using a Copa distributor drive unit as a speed controller.
Electro hydraulic and Electric drive options are available. These drive units can also be retro fitted to any type of distributor.

Electro hydraulic drive
An electro hydraulic power pack, located outside the filter bed, is connected to a hydraulic motor drive unit positioned in the centre. The drive is transferred to the distributor using a hydraulic motor and ram assembly which clamps onto a galvanised drive ring fixed to the distributor arms.
This design has the advantages of being intrinsically safe. It can be fitted in the centre well or filter media and will automatically disengage to allow the distributor to rotate freely in the event of power failure. This drive has a variable speed of rotation. This drive can be easily retro fitted to existing distributors as deep trenches across the media are not required.

Electric drive
This is a close coupled motor and gearbox mounted in the centre well, driving onto a galvanised central drive ring fixed to the distributor arms. To produce a positive drive, the drive wheels are clamped onto the drive ring. Speed of rotation is predetermined and set prior to delivery. Variable speed drives can be supplied if required. This drive can be easily retro fitted to existing distributors as deep trenches across the media are not required.

Distributor Dosing Syphon
A Copa dosing syphon is available for feed pipe diameters ranging from 100mm to 300mm. The syphon dome is cast iron and the air compression pipe work is galvanised steel.

Where practicable, it is preferable that each distributor has its own syphon, as this provides the best means of ensuring that the flow is equally divided between the filter beds.

Turbine Distributor
The water turbine distributor is positively driven by the weight of water collected in the turbine and eliminates the use of syphon chambers and the difficulties associated with syphon domes. The equipment is therefore most suitable for small rural treatment works since frequent attendance and maintenance is not required.

Given that adequate hydraulic head is available the machine can be installed on conventional circular distributor beds.

The distributor comprises a central bearing housing fixed to a concrete or brick support structure. A turntable with a vertical shaft is retained within the housing; comprising bottom ball thrust bearing and a top ball journal bearing.

The distributor is mounted on the turntable with the arms true and level.
The central turbine shaft is supported within the basin by a large ball thrust bearing, having nylon housings. At the top a nylon spherical journal assembly locates the turbine in its tilted elevation and is fixed by means of a bracket and retaining rod supported from the overhead feed pipe.

The top inlet feed chamber rotates with the machine basin and the outlet from this chamber is maintained in the same relationship with the offset turbine thrust housing, always discharging water into an elevated turbine compartment.

The filling of these turbine compartments with water provide the out of balance loading onto the eccentric positioned bearing housing. This can best be described as a walking stick type drive to rotate the basin.

Two open trough arms are provided with v-notch overflow weirs, spaced along each arm, staggered to evenly distribute the liquor over the filter bed media. The arms are supported by solid rods that will maintain level arms at all times. The arms cannot be choked, as with conventional arms. The open trough arms obviate the need for cleaning on a frequent basis to maintain performance of the distributing machine.

Waterwheel Distributor
The waterwheel driven distributor has been developed to help limit the time consuming visits by operative staff to small rural works and to eliminate the difficulties often caused by syphonic controlled dosing chambers.

Given that adequate hydraulic head is available the machine can be installed on conventional circular distributor beds.

The distributor comprises a centre column, supported on a duckfoot or equivalent under bed pipework arrangement with a basin surrounding the column and suspended via four rods from a top fulcrum bearing.

The basin has a short central inner tube, which is sufficiently tall as to prevent any central leakage of effluent. The outer wall of the basin is much higher and surrounds the drive wheels.

From the upper rim of the basin is fixed G.R.P. quadrant covers to prevent snow or other substances from causing problems in the basin.

The two waterwheels are pivoted from a bracket fitted to the central column. On the end of the wheel is a knurled aluminium wheel and this rotates on the rubber drive support ring which is retained by an angle fixed to the inner wall of the basin.

Effluent is discharged onto each waterwheel by discharge arms bolted to the side of the central column.

On the underside of the basin are three wind pressure pads to centralise the basin and to steady the basin in rotation.

From the basin two open trough or tubular arms are fixed spanning the diameter of the filter bed to evenly distribute settled liquor over the surface of the filter bed media. The arm level is adjusted after installation to give practical equal distribution of flow over the bed. Galvanised vertical and horizontal wire ropes support the arms.

The design principles are:

  •  That flow can be fed to the distributor at the rate at which it enters the works under gravity conditions or pumped flow. The feed arms at the central column discharge water to the two waterwheels via a two or three-stage overflow weir configuration. The low flow weir and the intermediate weir drive the waterwheels. The third weir (not applicable to the 100 dia. machine), overflows directly into the basin and therefore provides a restricted maximum flow discharge to the waterwheel, hence providing a controlled maximum speed of rotation for the machine.
  •  The arms cannot be choked, as with conventional arms. The large weir box openings obviate the need for cleaning on a frequent basis to maintain performance of the distributing machine.
  •  To reduce as far as possible on site mechanical maintenance. Waterwheel units are designed as hand removable 'Pods' so that replacement and maintenance can be made easy or undertaken in workshop conditions.

Syphonic Distributor
The syphonic filter distributor is suitable for use on new and existing circular filter beds. Flow to the machine is via a feed pipe from under the filter bed, into the central support column. Transfer of the influent from the stationary to the moving part of the machinery is through syphons fitted to the centre column referred to as ‘pending arms' and as such, no water seals or glands are required.

This machine utilizes a number of wind pressure pads fitted to the basin, which act as a steady bearing. They can be adjusted and locked into position.

The central basin, into which flow has been transferred, is supported by rods from the oil-filled top fulcrum bearing, designed for a low resistance to rotation and capable of correctly aligning itself to the out-of balance loads which occur during operation.

From the central basin are connected four distributing arms in a cruciform layout, supported by steel ropes taken back to the upper part of the centre column and stabilised laterally with steel wires from the adjacent arm.

The flow within the arms is distributed onto the filter bed through plastic 'venturi' shaped nozzles which are spaced along the tube providing equal distribution per unit area of the filter bed. The discharge from the nozzles also provides the driving force on 'jet reaction' machines.

The weir plates set within the central distributing basin divide the arms into two groups; 'high-flow' and 'low-flow' thus, on low flows only two arms will be discharging. As and when the volume of flow increases, the high-flow arms will discharge. It has been demonstrated that this method provides better distribution under low-flow conditions and hence an improvement in treatment standards.

The main components of the machine are manufactured in cast iron with steel central basin. The design of the machine is simple in concept, producing a robust, well-engineered machine, manufactured and protected to give a long and functional life.

  • For use with percolating filter beds
  • For normal and high flow rates
  • Can replace filter distributors on existing flange

  • Allows flexible, resilient biological wastewater treatment
  • Suitable for new installations and retrofits, minimizing installation costs and capital expenditure
  • Adaptable for a variety of flow rates

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