Good operability.
Low maintenance.

Good operability – low operating costs

Improvement desired

In the course of the new construction of the sewage treatment plant Schlösschen, in the beautiful Ore Mountains, the sewage treatment plant was also to be equipped with a new, efficient screen.

Clear decision for nrw contec screen

For the Schlösschen sewage treatment plant, a nrw contec screen offers decisive advantages over other solutions:

• Low consumption of energy and washing water with long-term positive influence on operating costs
• High operational reliability with optimal cost / effort ratio
• Space-saving installation with good accessibility
• Good operability and
• low maintenance

The implemented solution

The treatment system is designed for municipal wastewater with a connected load of 450 PE. The decisive mixed water inflow to the sewage treatment system was determined to be 6 l/s according to ATV-DVWK-A 198, i.e. Qh,max= 6 l/s = 21.6 m³/h. A pumping system conveys the wastewater at this maximum flow rate to the mechanical pre-treatment system, from where it flows freely downhill through the treatment system.
A classic activated sludge plant with nitrogen elimination and aerobic simultaneous sludge stabilisation is responsible for the biological treatment of the wastewater produced.

Mechanical pre-cleaning with internal emergency overflow

A fine screen of the RBS4 series from nrw Anlagentechnik is used for mechanical pre-cleaning. This is installed above ground in a separate room of the technical building.
The screening machine is used for the separation of floating, sinking and suspended solids. It has an internal emergency overflow which, for example, comes into operation automatically in the event of a blockage.

High separation efficiency, reliable and energy-saving

The semicircular perforated screen plate with an opening of 3 mm is horizontally flowed against by the waste water. This change in flow direction ensures a high degree of separation. The brushes, which rotate at approx. 1.6 rpm, reliably and energy-efficiently screen the retained solids, the screenings, from the perforated screen plate and discharge them into the integrated screenings washing and press. The pre-cleaned waste water flows downwards through the screen.

Dewatering of the Screenings to 30%.

In the Screenings press type PU100 the Screenings are dewatered from approx. 15 % to 28 to 30 % TSS and discharged via the Screenings with bagging system into the 240 l screenings container. The washing zone of the Screenings press has a ½” water connection for short rinses.

Service water for screenings washing only

Due to the mechanical cleaning of the screen surface by means of rotating brushes, process water for cleaning and rinsing is only required for washing the screenings material. The service water can be provided and used with relatively low upstream pressure, i.e. approx. 1.5 to 2 m WS. On a costly and maintenance-intensive pressure boosting system with up to 4 to 6 bar, as necessary with other screening machines, can thus be dispensed.

Free refilling of the original container

In practice, a storage tank (flushing tank) with a capacity of approx. 15 l is provided at a corresponding height above the screening machine. If required or in preselectable time cycles, the rinsing water is discharged into the washing zone of the screenings press via a solenoid valve in free flow. At the same time, the storage tank is refilled via a float-controlled valve. Due to the low water demand, drinking water is used. With the free refilling of the storage tank, a safe separation of drinking water / service water is guaranteed at the same time.

High satisfaction

The system was commissioned in June 2019 and has since been operating to the complete satisfaction of the operator. Within the scope of a maintenance contract, the screening machine is expertly checked for proper functioning, serviced and, if necessary, readjusted at fixed intervals. If you have any queries regarding the Schlösschen sewage treatment plant, nrw Anlagentechnik will be happy to provide advice and assistance at any time.