Pushing the Limits: Optimizing Membrane Plants Via Correlating Fouling With Critical Flux

The concept of establishing direct correlations between the operating flux, represented by the conversion, and fouling potential of membrane systems has always been of tremendous interest to membrane technology researchers, plant end-users and membrane manufacturers since the advent of membrane technology’s commercial applications worldwide some forty years ago. Several attempts were made to effectively control biological and colloidal fouling in particular, as a means of optimizing plant design, operation and performance, by limiting the operating system conversion or flux below “safe” or “critical” values. However, such attempts resulted in designing plants that are not economically feasible to operate. Moreover, the concept of critical recovery or flux did not in reality allow for the implementation and utilization of new, innovative technologies, processes and equipment that continually optimize the operating and performance efficiencies and competitiveness of membrane processes. On the other hand, cost benefits resulting from increasing the conversion and flux can be prove critical in end-users’ ultimate decision to adopt membrane processes as the technology of choice for meeting the demand for reliable and cost-effective desalinated water. A more realistic and practical approach to correlate the fouling potential with operating recoveries and fluxes was therefore critically needed in the industry to achieve that goal. This paper directly addresses this dilemma by utilizing a new technology, known as the Silent Alarm, that measures and monitors the onset of fouling development or potential in membrane desalination systems in real-time, not as a long-term trend. A quantitative and early-warning parameter known as the “Fouling Monitor (FM)” has been employed to correlate the fouling potential of representative membrane desalination plants around the world as a function of plant operating conversion and flux based on actual system design parameters, operating history and maintenance requirements. The results of this evaluation show conclusively how to maximize site-specific operating conversion and flux of desalination plants incorporating RO and NF membrane processes, to much more practical and cost-effective values not attainable before, via real-time monitoring of the FM. More realistic on-site optimization of such values are now possible with the new approach. Potential future applications extend even farther to UF and MF membrane processes, especially when used to replace conventional pre-treatment at RO and NF plants. The tide has just turned in the eternal quest to achieve, implement and maintain the most optimum plant design and operating conditions of membrane desalination plants, resulting in delivering superior performance, maximum operating efficiency, maximum conservation and lowest total cost of water.