PRACTICAL TIPS: STANDARD- AND 4.0 EQUIPMENT FOR MODERNIZATION AND NEW CONSTRUCTION OF STORM WATER BASINS – PART 1 OF 2
Focus: BASIN CLEANING
INTRODUCTION OF BASIN CLEANING
For decades, municipal wastewater treatment could rely on almost constant operating conditions and sufficient experience in wastewater engineering operations. In recent years, however, the boundary conditions have been subject to ever greater fluctuations. The prolonged dry periods of drought in the last few years recent years have shown what a lack of water and hence an insufficient dry weather flow can mean for the removal of deposits in sewer systems and for the operation of sewer systems and the associated special structures.
On the other hand, more extreme periods of heavy rain require larger storage capacities and, as a result, new cleaning strategies.
Less than two decades ago, basins and reservoirs were still being cleaned manually by the operating personnel. This was not only physically tiring, but also very time-consuming and therefore very costly. Furthermore, depending on the geometry and location of the basin or reservoir, it was sometimes difficult to reach all points and thus to clean sufficiently.
Faced with these challenges and the increasingly extreme conditions, the development of mechanical and automated basin cleaning got underway…
“Basin and reservoir cleaning”
But why do rainwater basins and reservoirs become soiled?
Particularly after heavy rainfall and the resulting impounding of basins and other storage volumes, the dirt and sludge from the sewers and roads remain in the basin. It accumulates on the bottom of the basin, on the walls and, in the case of underground reservoirs, even under the ceiling.
SURGE FLUSHING OR JET CLEANERS –WHAT IS THE RIGHT SOLUTION?
(for e. g., reservoir channels, small basins)
The technically simplest but, at the same time, weakest variant for cleaning by means of flow generators and aerators are static, one-dimensional jet cleaners.
A pump conveys the accumulated water into the injector set via which air is simultaneously drawn in. The resulting air/water mixture leaves the injector set as a bundled cleaning jet in a preset direction and has a comparatively narrow spray width. This method of cleaning is therefore best suited for cleaning hose-shaped/narrow basins and reservoir channels.
(for e. g., rainwater reservoirs, sedimentation basins)
If you wished to clean a basin that has a larger surface, several static one-dimensional jet cleaners would have to be placed next to each other in order to reach the whole of the base of the basin with the cleaning jet. This would result in high purchasing and operating costs.
For this reason, two-dimensional “pivoting” jet cleaners were developed as flow generators and aerators. They have a swivel drive that enables the cleaning jet to be rotated horizontally about an axis and to thus cover a large area.
(for e. g., large pump stations, central rainwater reservoirs)
Two-dimensional basin cleaning offers significant technical benefits compared with manual and one-dimensional jet cleaners. 2D jet cleaners clean large areas of the basin bottom and the lower wall area. 3D jet cleaners can clean the whole wall area and the ceiling of the building.
Three-dimensional jet cleaners significantly expand the cleaning area. The multidimensional range of movement enables almost 100% of the surfaces in the structure to be cleaned. This flexibility allows even surfaces which are further away to be reached.
SYSTEM COMPARISON: 2D VS. 3D
Comparison of the range of movement and accessible cleaning area between AWS Swivel Jet Cleaner (2D) (Fig. 10) and AWS 3D Jet Cleaner (Fig. 11):
The additional dimension (height) allows the 3D Jet Cleaner to reach a significantly larger cleaning area and thus ensures even more extensive cleaning.
AWS JET CLEANERS – INTELLIGRID PROCESS AND MACHINE CONTROL AUTOMATION LEVELS
With the standard HST automation, the Jet Cleaners operate with filling level-dependent switching points. During the whole cleaning process, the pump and swivel drive are in operation intermittently or continuously, depending on the filling level. In addition, routine movements (e. g., daily, weekly, etc.) can be performed to ensure operability.
Level I: IntelliGrid
When degrees of soiling are entered by the operator at the display or are detected by camera, the Jet Cleaner operates independently, depending on the degree of soiling. The automatic adaptation of the cleaning intensity, depending on the swivel position, allows energy to be saved or optimum use to be made of the available cleaning time when emptying the basin.
Level II: IntelliGrid.IoT
The expansion of the IntelliGrid automation system to include precipitation data from data portals, such as NiRA.web® and information from the sewage network and the upline system network (IntelliNet) enables the software to learn from the data so that it can decide pro-actively whether and to what extent cleaning is necessary.
Without IntelliGrid, the Jet Cleaners are controlled by means of fixed parameters. Each basin has individual flow conditions. As a result, dirt zones build up that can become thicker and thicker. If action is not taken in good time, failure of the complete basin is possible.
With IntelliGrid, the system learns from operation. The experience and dirt zones are stored and more efficient cleaning is guaranteed at each cleaning event. Clean areas are cleaned only briefly. The formation of dirt accumulations is reduced at each impoundment.
A two-chamber rainwater basin has been built directly next to the Porsche painting line in Stuttgart. A high-gloss finished is not only being ensured for the luxury limousines, but also the rainwater basin that collects the surface water from the factory premises. As for its own production, the luxury car brand has chosen to rely on quality “Made in Germany”. A total of six AWS Swivel Jet Cleaners remove all the soiling from the smooth concrete floor after rainfall. The complete basin equipment – including SECURA floor gates and stainless steel stairs – was installed by HST.
MODERNISATION AND UPGRADE
During the modernisation measures for the above-ground canals of the Emscher Genossenschaft in Dortmund-Scharnhorst, not only the new buildings were equipped with technology from HST. In order to upgrade the rainwater basins on the sewage treatment plant site, eight AWS Swivel Jet Cleaners with surface-mounted swivel drives were installed. As the original cleaning performance of the old units was no longer sufficient due to the higher dirt load, the pump capacity was increased. In order to save as much energy as possible, energy-efficient single-channel impellers for mixed water applications were installed instead of free-flow impellers.
For years, cleaning of the deposits in the storage basins of the Aschaffenburg sewage plant inlet was part of the daily work. “Normal” jet cleaners could not handle this soiling. Particularly in this region, the increase in the number of moist cloths is quite significant. Pumps have clogged and moist cloths have built up in layers in the impeller until the machine failed. Through the use of appropriate pump technology and an optimised arrangement of the flow generators, the basins are now cleaned completely until empty without the need for subsequent cleaning.