Combined sewage screening at overflow structures with the ROTAMAT® Storm Screen RoK 2
HUBER expand their range of products for combined sewage treatment
Environmental protection, and therefore the necessity of advanced combined sewage treatment, concerns everyone. This has led to increasing efforts to substantially improve the protection of waters. In the course of such further development HUBER has expanded its product range for this field in order to better meet the challenge.
In the field of advanced combined sewage treatment HUBER has developed the ROTAMAT® Storm Screen RoK 1 for reliable removal of floating and suspended material from combined sewage flows. With more than 700 installations worldwide this well-proven machine is firmly established in the wastewater technology mark 2000 ets.
In the course of further research and development a new type of screen has been developed for combined sewage treatment – the ROTAMAT® Storm Screen RoK 2. The ROTAMAT® Storm Screen RoK 2, like the ROTAMAT® Storm Screen RoK 1, belongs to the group of fine screens and is designed for high flow rates. The screen is horizontally situated immediately in front of the overflow sill.
A helically wound screw is installed onto the semi circular screening face. The screenings are transported to the screw end where the discharge opening is situated. Simultaneously, the screening face is cleaned by the action of a wear-resistant brush fitted to the periphery the screw flights. The screw is supported by a series of bearings and ensures a constant optimal removal efficiency. The major difference from the ROTAMAT® Storm Screen RoK 1 is however, that wastewater screening takes place in front of the overflow weir and not behind, so that the screenings remain in the tank or WWTP inlet. Another innovation is the removable screening basket that provides access to the screw from the top for brush replacement. The individual screen basket lengths have been limited according to the screen size and weight to enable them to be removed without the need for any auxiliary means, such as a crane or davit. This allows for a reduction in maintenance costs.
Figure 2 shows the removable screen baskets that are equipped with handles to facilitate disassembly and maintenance. A further difference with the ROTAMAT® Storm Screen RoK 2 is that it is available as a push screen only and not as a pull screen as the RoK 1. The screenings are discharged at the end of the screen basket through a kidney-shaped opening in the outlet end plate and back into the tank. It is, therefore, unnecessary to pump the screenings over the weir and back into the tank or WWTP inlet. Due to its design the ROTAMAT® Storm Screen RoK 2 is mounted on the wet side of the overflow weir in such a way that the flow approaches the full screening face within a relatively short time frame whilst still able to achieve the maximum screening efficiency.
Huber ROTAMAT® Storm Screens RoK 2 can be used for the following discharges in the combined sewage sector:
- storm-water tanks with overflow
- sewer with storage capacity and overflow
- storm-water tank retaining the first flush of storm-water
- retention tanks
- storm-water tank with overflow for settled combined sewage
This design results in the following benefits:
- Screenings remain on the polluted water side
- Suitable for retrofitting into existing structures
- Possibility of completely submerging the screen (emergency running properties)
- Optimal solids retention by means of two-dimensional screening
- The perfect solution for discharges with limited upstream head restraints
Figure 3 shows a ROTAMAT® Storm Screen RoK 2 under final assembly The specific hydraulic conditions make it necessary to leave a part of the screen basket unperforated. The kidney-shaped opening in the end plate is visible on the right. This opening ensures screenings discharge into the tank or WWTP inlet.
The following data specifies the available unit sizes:
The maximum design length of size 300, 500 and 700 is 7500 mm, whereas the size 1000 unit has the longest design length with 5000 mm. With the ROTAMAT® Storm Screen RoK 2 HUBER offers an additional machine for combined sewage screening in order to be able to better meet customer requirements and specific constructional and hydraulic site conditions.