RWWA custom built a waste water treatment backend biological polishing unit designed in an ultrafiltration plant packaged treating class C effluent to that of a true class A in final release standard.
The system was complete with front end glass media filtration, before being filtered through the ultrafiltration membrane elements. The membranes of choice for the biological treatment were the RWWA UF-PVDF-1060 hollow fibre filter housings with an effective filtration area of 78 m2. The membranes are configured to an outside-inside with air sparge backwashing, forward flush, top and bottom backflush and an independent Enhanced backflush EBF cycle also coded within the PLC. The PVDF fibre allows for greater tensile strength when filters are exhausted and feed pressures rise, due to uncontrolled front end treatment. The ability to rejuvenate the fibre element is second to none with an aggressive alkali and acid cleaning process the filters will bounce back yielding their intended designed flux. Other membranes constructed of improved PVC and simple PVC cannot withstand such harsh environments and are susceptible to fibre breakage, resulting in cross contamination of raw and treated water streams.
The system was constructed on a purpose built, 316 stainless steel frame. All pumps utilised for filtration, backwash and chemical injection where Grundfos in design and brand with the feed pumps being controlled by VSD allowing for variable flow treatment through the day. Process control pneumatic valves used on this application were the air torque actuators with separate limit switches, Ritork branded cast wafer valves complete the valve package. Burkert instruments were chosen by the client for the project and control automation was completed through an Allan Bradly 800 Series PLC and Panel view plus 7 – 9 inch HMI screen with a Ewon modem for remote telemetry access.
The membranes have been installed with individual isolation valves on all 3 streams allowing for the disconnection and replacement of the individual membranes units without isolating the system. Clear tubing has additionally been added to allow the operator to view the turbid backwash reject water exiting the system. All in all RWST has encompassed the very best in equipment supply and design in bring an excellent long lasting and durable system to the market one which will see many years of trouble free filtering.
The equipment was installed and successfully commissioned by the RWWA electrical and programming division on site.