Another advantage and special feature of the RoMem liquid screen is that the screenings are discharged either by gravity or by pump and delivered to further treatment facilities. Like with primary settlement tanks the separated solids can be used as a co-substrate for sludge digestion. Optionally, they can be further dewatered in a wash press and discharged into a container. If the screenings are passed on to the sludge treatment system, the fibrous material contained can be introduced as additional bulking material. Compared to sludge treatment without introducing fine screenings, increased solids contents can be achieved with reduced coagulant agent volumes.
As mentioned above, the screenings can be further dewatered in a WAP Wash Press and discharged into a container instead of introducing them into the sludge treatment system. The WAP Wash Press achieves dewatering results of about 35% dry residue. The removal of solids and their disposal as screenings reduces the hydraulic load on the sludge treatment system.
As fine screening can achieve the same removal rates on a smaller footprint and with lower investment costs, it is a highly interesting alternative to primary settlement tanks. Fine screening should especially be considered as an economical and efficient option for upgrading smaller sewage treatment plants without preliminary treatment. Due to the high removal rates that can be achieved with fine screening the load on downstream biological treatment systems can be reduced and their clarification capacity increased accordingly. The screenings can be used for sludge digestion to increase gas production. Alternatively, they can be dewatered in a wash press before disposal.