A significant part of the precipitation is derived from sewage networks in towns and communities. Depending on the load and the drainage concept (mixing or separation system), heavy rainfall causes the discharge into the waters (receiving water). In this case, rainwater with contaminated or mixed with wastewater passes unfiltered or untreated into our rivers and lakes. The solid and liquid substances contained therein are partly harmful and pollute the environment. The current situation in the media about plastic particles in the waters and oceans is partly based here.
The majority of operators, planners and regulators of sewer networks meanwhile ensure that, at least at the overflows into the waters, there is extensive support of floating and rigid materials. This often happens through the use of immersion walls or, meanwhile, by automatic, mechanical fine screens. These are arranged on or in front of the weir thresholds or overflows and, depending on the filter performance, retain more or less additional contaminants. However, in severe rainfall events, to be safe and reliable, i.e. without the risk of backwater and flooding damage to hydraulically relieve the sewer system, fine screens are continuously and event-controlled cleaned or “freely combed” for unimpeded flow.
The required technical solution requires, on the one hand, maximum retention effect to protect the water, on the other hand, continuous possibility of hydraulic relief of the sewer system to ward off back damage. Obviously an irresolvable conflict of objectives – or not?
Further observations and measurements on overflows with mechanical fine screens have shown that improved fabric retention results from the retention of screenings themselves. The first retained screenings form a filter and support structure for further and finer screenings. The more screenings, the better the filtering effect. For water protection, that is certainly the primary objective.
In order to be able to provide the full hydraulic drainage / flow rate for relief, it must be ensured that the screenings filter cake is more permeable or even completely cleared. More fabric retention, higher relief safety, improved overall efficiency, how is this possible?
With the use of IntelliScreen and HSR-Screen!
The IntelliScreen extension turns the HSR-Screen into a smart machine with intelligent control. The IntelliScreen system, consisting of sensors, actuators and software, provides for proactive, process-oriented and on the basis of actual operating conditions for maximum fabric retention and relief in separation structures. The machine receives continuous data on the unloading and filtering process. The controllable drive technology then enables control of the filter performance on the basis of this data.
With IntelliScreen, you can increase your peace of mind and more fabric retention while keeping operating costs to a minimum. That’s what we call process efficiency.
How does the IntelliScreen system compare?
The standard wheel automation for the HSR-Screen works like a conventional computer system with a water level-dependent switch-on time. If a predetermined water level before the rake is reached, the cleaning device of the rake goes into continuous operation. This operating state is then maintained until the water level in front of the rake again falls below a previously set limit. During operation, the cleaning device of the rake always works at a constant speed.
Load-oriented and efficient, the rake works with the addition of the IntelliScreen process and machine control. The intelligent controller does not operate with fixed on and off times but regulates the travel speed of the cleaning system according to the actual unloading requirement. By this is meant that the cleaning process of the rake is infinitely variable. The cleaning process is initially dependent on the currently measured water level before the rake. Furthermore, the tendency of the water level (rising / falling) and the filter performance is included in the control. Thereafter, the cleaning intensity and filter performance are adjusted continuously.
With this mode of operation, by building up a filter cake at a low cleaning intensity, the amount of relief water can be reduced and, at the same time, the substance retention level can be increased. Since the rake works with a lower cleaning intensity or switches off earlier with decreasing water levels, this results in further advantages:
- Lowering operating costs
- Reduction of maintenance costs
- Longer lifetime of the screens
The mode of operation is different in a rain occasion when the rated water quantity is exceeded and discharge is absolutely necessary. With IntelliScreen it is possible to increase the cleaning capacity above nominal load by about 20% reserve (see diagram). As a result, an additional backwater safety is guaranteed at discharge quantities above the rated water quantity.
Inclusion of precipitation data from the precipitation pilot NiRA.web in the control
To make the discharge occasion even more efficient and secure, IntelliScreen also offers the possibility of including precipitation data from the catchment area of the rake in the controller using IoT data from the precipitation portal NiRA.web. By analyzing and evaluating these data, the rake can respond to rain events, dry weather periods and future events that are not yet noticeable to the probes on the rake itself. So the water level before the rake can sink after a previous event, but in the catchment area of the rake a new, strong event is taking place. In this case, the rake can already provide in advance by fast driving of the cleaning device for a higher discharge amount. This preventive cleaning prevents overflow of the rake, which relieves the contaminated or mixed rainwater unfiltered or untreated into the receiving water and thus into our rivers and lakes.
Summary graphic of how IntelliScreen works