MBR stands for “Membrane BioReactor”, which indicates the water purification process with activated sludge (BioReactor) in which the liquid-solid separation phase is performed by membrane filtration instead of secondary clarifiers units, like in conventional sludge plants.
The ZeeWeed membrane is a hollow fiber supported PVDF membrane. The PVDF membrane, characterized by a high porosity, acts as an impenetrable physical barrier for the microorganisms the activated sludge is composed by, while being easily permeable by water molecules at the same time. ZeeWeed membranes devices are immersed in the mixture to be filtered and work in an OUT-IN configuration: i.e. the direction of filtration moves from the outside of the hollow fiber towards the inside, so that the suspended solids remain outside the membrane while only the permeate (clarified water) reaches the internal channel of the fiber (lumen) where it is then collected and conveyed to the final discharge.
To control and minimize the natural loss of permeability caused by the filtration process, these filtration devices are equipped with an air scouring system that prevents, by creating a great turbulence close to the fibers, the formation of areas with a higher concentration of solids suspended near the hollow fibers themselves.
One of the main characteristics of the ZeeWeed membrane is the possibility of inverting the filtration flow, creating the conditions to perform a real back-washing cycle goingfrom the internal part of the membrane (lumen) to the external one (wastewater side). In terms of application, performing a back-washing of the membranes at pressures similar to or higher than those applicable in filtration (up to 0.5 bar) favours the possibility of the formation of areas with a high concentration of solids suspended near the membranes, and subsequently the risk of dehydrated sludge areas forming between the membranes.