The patented solution for effective removal of fats, oils, grease (FOG) and organic matter in a lift station


Ro.Pa.Tec introduces patented ROLAPAC Floating Layer Remover 

August 2021

For several years now, the Scheveningen sewage pumping station, surrounded by houses on the Haringkade in The Hague, has been responsible for the drainage of the waste water from the Scheveningen district. The installation, built in 2015, can pump out more than 28,000 liters of water per minute through two pump installations with suction nozzles at the bottom of the pump cellar. 2 pumps for the Scheveningen area with a max of 1180 m3 per hour and 2 pumps for the Belgian Park section with a max of 530 m3 per hour.

The Delfland Water Board, together with the Municipality of The Hague, has improved the collection and transport of waste water in the region through an extensive program. In recent years, a lot of new buildings have been built in the region and, in combination with the increase in heavy rainfall, an expansion of the sewer system was a precondition for being able to pump the water in the future.

The Scheveningen sewage pumping station is managed by Delfluent Services, a subsidiary of water company Evides. Delfluent Services is responsible for the operational activities in the northern part of the Delfland Water Board region. For a period of 30 years, it will be responsible for the management and maintenance of the wastewater treatment plants (WWTP) Houtrust in The Hague and Harnaschpolder in Den Hoorn, municipality of Midden-Delfland and the associated transport system with 19 pumping stations.¹

Soon after the Scheveningen sewage pumping station was put into operation, the management of the pump cellar proved to be a major challenge. The sewage pumping station regularly appears to get stuck due to things that do not belong in the sewer. Think, for example, of wet wipes, dish cloths, deep-frying fat, sanitary towels and condoms.² These oils, grease and fats and wipes cake together in such a way that a 'floating fat layer' is formed on the waste water that flows into the sewage pumping station. This pollution causes the pumps to become so polluted that the pumps can no longer pump the waste water. If this happens, the risk of overflow into surface water from sewage water is a major risk, which puts a burden on the surface water because the oxygen content in the water then drops, resulting in fish mortality. That is why a cleaning action is now regularly carried out, which is expensive and labour-intensive to remove this pollution from the cellar. This sewer cleaning is done by means of various diesel-driven cleaning with suction spray cars, which is harmful to the neighbourhood as sewage pumping stations are often located in the middle of a residential area. During a maintenance stop, the sewage pumping station is thoroughly professionally cleaned for several working days. This work can only be carried out in dry periods because the water has to be stored in the sewage systems and this capacity is limited. Rainfall during a planned maintenance shutdown regularly causes maintenance activities to be rescheduled, resulting in rescheduling, permit applications and alignment of various parties. Up to 17 tons of waste can be removed during a stop. This waste is then carried away by means of the suction trucks to waste incineration plants; all in all a C0² intensive job. It is therefore a time-consuming, non-sustainable and very expensive process that has to be repeated several times a year. The shutdown of the Scheveningen sewage pumping station increases to 5 times per calendar year. For a maintenance stop, permission will always have to be given by the municipality of The Hague, because they are ultimately responsible for the sewer system.

Ro.Pa.Tec Technical Cleaning has been active in the sewerage world for many years with various cleaning and maintenance jobs. Ro.Pa.Tec Technical Cleaning has also been working with Delfluent Services for a long time. Delfluent Services attaches great importance to sustainability and the environment. After analyzing the challenge in the Scheveningen sewage pumping station and after various test setups, the patented solution, the ROLAPAC Floating Layer Remover, was devised. By using this device, cleaning the basement to prevent clogged pumps is a thing of the past. With the ROLAPAC application, wastewater is no longer only pumped out at the bottom of the cellar via the existing suction nozzles, but also the oil, fat and grease layer at the top of the pump cellar. Delfluent Services was willing to contribute ideas, which resulted in a pilot in the Scheveningen sewage pumping station. In mid-July 2020, Ro.Pa.Tec Technical Cleaning took care of the installation of the installation within one working day under the watchful eye of the management of Delfluent Services.

Function of ROLAPAC Floating Layer Remover

In the old situation, the waste water from the Scheveningen district is sucked away through the suction nozzles towards the waste water treatment plant (WWTP) Houtrust. Because the suction nozzles are placed at the bottom of the pump cellar, the floating grease layer at the top remains present. Over time, this floating fat layer gets thicker, causing problems for the transport pumps (clogged pumps). This is the point at which a maintenance stop should be scheduled.

By installing the ROLAPAC Floating Layer Remover, wastewater is no longer only extracted via the low-lying suction nozzles, but also via an additional opening at the top of the cellar. The modular ROLAPAC consists of new DN500 suction nozzles with a connection to the central DN350 discharge pipe. A custom-made basket is placed on top of the central discharge pipe through which the waste water with floating layer dirt can be sucked away. The basket and central tube are split via a specially modified pneumatic valve. The valve is linked to the central control and signaling system of the sewage pumping station. The whole is made of high-quality stainless steel. The central pipe is equipped with a flushing water connection so that any grease left behind in the pipe is flushed through.

Backwashing of the dirt to the suction mouth of the pump also has the beneficial effect that the pump is no longer clogged because the pressure at the suction mouth is increased, which ensures a better flow. This is also an additional positive effect.

The ROLAPAC Floating Layer Remover greatly reduces the accumulation of 'the fat layer' and it is no longer necessary to schedule a maintenance stop with associated professional cleaning five times a year. One annual check may suffice.

In summary, in a successful pilot with Delfluent Services, the ROLAPAC Floating Layer Remover has led to five benefits for the Municipality of The Hague, the Delfland Water Board and Delfluent Services: significant savings are made on the management costs (mainly cleaning costs) of the sewage pumping station. The solution contributes to Delfluent Services' sustainability label; the removal of the oil, fat and grease can be done by fewer vehicle movements and therefore lower CO2 emissions. Because more fats are transported to a waste water treatment plant (WWTP) Houtrust, which is equipped with a biogas plant, the production of biogas is higher. There is also less nuisance for local residents due to fewer maintenance stops and people are less dependent on the weather conditions, which can throw a spanner in the works during a maintenance stop.

Old situation.  

New situation including the ROLAPAC.


The ROLAPAC Floating Layer Remover is a patented product of Rolapac - The Netherlands. 

 ¹ souirce:

 ² source: