We had to meet several specific customer requirements with our machines to be installed for the protection of the hollow fibre membranes:
- Reliable separation of disturbing material
- Space-saving installation downstream of the primary settling tank
- Easy removal and transport of the separated fine screenings
- Downstream treatment of the fine screenings
Three HUBER Perforated Plate ROTAMAT® STAR liquid screens were finally selected, two for parallel operation and one as standby unit. The throughput capacity per unit is 608 l/s. The fine screenings from each machine flow through gravity lines into a central pipeline through which they are flushed to a pump sump. From this pump sump, the water-solids mix is pumped to two HUBER Micro Strainer ROTAMAT® Ro9 units. The micro strainers are installed approx. 6 m above the fine screen. Due to its unique and special design the HUBER Perforated Plate ROTAMAT® STAR liquid screen can be installed at a small inclination angle. This, in addition to the 30% larger screening surface of the screen basket provided by the innovative STAR design, makes it possible to achieve very high throughputs. Moreover, the separated screenings can be passed on to further treatment as a water-solids mix without the need for an additional discharge screw. A great advantage of this solution is that the screenings do not have to be treated in the machine but can be treated centrally even at a distant location. Extra screw conveyors that would need a lot of space are therefore not necessary.
This concept has already been implemented in many installations around the world and this project will be the first of this kind in the USA. It is a very interesting and economical system for projects where space-saving solutions combined with high throughputs and maximum freedom of planning are required for the treatment of screenings.