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The Grit King® is an advanced hydrodynamic vortex separator that augments gravitational forces to separate grit from water. The Grit King® is an economical choice for new or existing municipal or industrial wastewater and water applications.
The Grit King® Process separates, cleans and dewaters grit from raw sewage or other liquids prior to delivering the grit to a skip ready for disposal. The Grit King® process comprises of a Grit King® hydrodynamic separator with backwashing system using air or water, a grit removal system (pump or gravity); a Grit-Cleanse™ or Grit Classifier and all connecting pipework. The Grit King® requires no external power source; as it uses the inherent energy of the influent with a headloss of typically less than 150 mm.
Under normal circumstances the Grit King® is situated at the inlet to a sewage treatment works downstream of inlet screens. Flow enters the Grit King® Separator where grit is separated from the main flow of sewage.
The Grit King® separator is of a hollow, cylindrical vessel with a sloping base and a flat cover. The geometry of the interior and the shape and placing of the entry nozzle are such that the flow must follow a prescribed path through the vessel.
Raw liquid is introduced tangentially into the side of the cylinder causing the contents to rotate slowly about the vertical axis. The flow spirals gradually down the perimeter allowing the grit and sand particles to settle out by gravity. This process is aided by the drag forces at the boundary layer on the wall and base of the vessel.
An inverted cone, attached to the centre shaft, is mounted at the bottom of the vessel so that its edge is clear of the sloping base. A grit pot for the separated grit is located under the cone.
The internal components direct the main flow away from the perimeter and back up the middle of the vessel as a broad spiralling column, rotating at a slower velocity than the outer downward flow. In addition, a dip plate is suspended from the underside of a component support frame. This dip plate locates the shear zone, the interface between the outer downward circulation and the inner upward circulation where a marked difference in velocity encourages further grit separation. By the time the flow reaches the top of the vessel, it is virtually free of grit and is discharged to the outlet channel.
The grit is collected within the grit pot of the separator and transferred either by pumping or by gravity to a Series 3 or Grit Cleanse™ (Series 4 Classifier). The grit settles within the classifier and is transferred up by an archimedean screw to a grit skip for disposal.
The design programme will calculate the headloss. We recommend that the inlet velocity is between 1.0 m/s and 1.5 m/s at peak design flow and it may be necessary to adjust the inlet pipe diameter to maintain this. The system headloss will vary accordingly and it will be in proportion to the square of the inlet velocity.
In most cases it is obvious which system is to be used. However it will be necessary to carry out detail hydraulic calculations to assess if a gravity system is appropriate. The headloss at the inlet to a Grit-Cleanse™ is 1.81m above the centreline of the inlet pipe at the design flow of 20 l/s and there is a free discharge at the inlet to a Series 3 Classifier.
Yes. We would request that the client provides a grading curve and a specific gravity for the material to be separated and this would provide the information for our Research and Development department to size the unit. If the material is colloidal or very fine then vortex separation may not be appropriate.
In the UK we ensure that the minimum diameter of the grit pot is 900mm so that a wet well submersible pump will fit. The diameter of the Grit King® separator with this grit pot size is 2.10m.
There are two reasons for raising the feed pipe above Top Water Level (TWL) in the separator. Firstly to control the flow and secondly to prevent siphoning. A detailed hydraulic calculation is required to calculate the hydraulics and size the pump.
In the UK Stainless Steel 304 or 316 is used although other materials could be utilised.
The unit will accept higher or lower hydraulic flows than the peak design flow however if the flow is higher than the design flow then the headloss will increase and the performance reduce. If flows are very low then organics will settle out with the grit.
If the ratio of Peak Design Flow to Dry Weather Flow (DWF) is greater than 3 to 1 we recommend the use of a Grit-Cleanse™ Classifier and not the Series 3 Classifier. This is to enable the grit entrained sewage to be put through a secondary separation stage prior to the classifier archimedean screw thus reducing faecal organics discharged in the grit.
Although there is a grit spray bar provided on the Series 3 Classifier it is not connected to a water supply as standard. We do connect the spray bar on the Grit-Cleanse™ to a potable or washwater main as standard.
There are no moving parts at the top of the separator and therefore access is not required at high level for routine maintenance.
We recommend that the Grit King® process is operated after screens as in our experience the influent at a sewage works can contain very large objects. Also, if we are operating with a pumped system, rag balling can create a problem. Depending on the specific circumstances, we would consider installing upstream of screens but this would not be our preferred option.
It is important that the recommended control philosophy is followed and under these circumstances blockage problems are unlikely. If the control system is switched off for a prolonged period with flow continuing to run through the separator, then grit will continue to be collected in the grit pot and could build up to a level where it would be difficult to mobilise again. It is therefore important to be able to isolate the separator when the process control is switched off. Hydro do offer a bolted hatch to the bottom grit pot at an additional cost.
Either. The decision will depend on the availability and cost of water on site. Some sites have remote inlet works without a close water supply and in this case the supply of an airset may be preferable to providing a new water supply.