AiRO, The Use of Two Phase Flow in Controlling Fouling in Spiral Wound Membranes
A major problem of nanofiltration or reverse osmosis membrane plants is the fouling of feed spacers in spiral wound membrane elements due to biofouling and particulate fouling. As a result of this, the pressure drop over the membrane elements increases which disturbs the flow distribution in the feed spacer channels and leads to operational problems in the membrane installation. It is important to reduce and/or prevent this phenomenon as efficiently as possible. Air/water cleaning is effective in reducing problems with biofouling and particulate fouling.
To effectively apply air/water cleaning in practice, an alternative nanofiltration (NF) or reverse osmosis (RO) design is necessary using vertically positioned spiral wound membrane elements, completely different from conventional NF/RO design applied worldwide. The most efficient use of the AiRO technology depends furthermore on the optimal use of air/water cleaning of spiral wound membrane elements. Specific parameters of interest are (i) air/water ratio, (ii) air and water flows, (iii) air/water cleaning duration and (iv) air/water cleaning frequency.
Although initial research showed the effectiveness of the process, many fundamental questions still remain unanswered. Some of these questions involve (i) the mechanical/ physical understanding of air/water cleaning of spiral wound membrane elements, (ii) the effectiveness of the air/water cleaning process in relation to different feed components and (iii) the long term behaviour of air/water cleaning. The first two research questions will be investigated using CFD modelling parallel to laboratory tests, using membrane fouling simulators (MFS) and small-scale 2.5-inch spiral wound membrane elements. Long term air/water cleaning behaviour will be investigated in on-site pilot-scale research in a parallel research project (in an Innowator AiRO research project).