Low pressure membranes (hollow fiber micro- and ultrafiltration) have been employed in the production of industrial and potable water for two decades. The use of low pressure membrane technology has increased exponentially in this period. Low pressure membranes have been found to be able to replace conventional treatment systems, such as media filtration. Benefits over media filtration are smaller footprint, lower chemical consumption and better water quality, especially with regards to suspended solids and micro biology. High pressure membranes (spiral wound nanofiltration and reverse osmosis) have been commercially used even longer. This paper describes past and current developments in membrane technology and its impact on future water treatment plants in addressing contaminants. New hybrid membranes are being designed and implemented to address the following issues: Large organics, such as color in surface water (humic acids) or in waste water (dyes). Removal of these organics in conventional treatment requires large quantities of chemicals (coagulant, ozone) and generates large quantities of sludge and disinfection byproducts. This paper describes a hybrid (hollow fiber nanofiltration) membrane specifically designed for removal of dissolved organics from water with low mineral contents. This membrane exhibits high rejection for dissolved organics and close to zero rejection for dissolved inorganics. The benefits of this hollow fiber membrane over existing spiral wound membranes are: Chlorine resistant and a wide pH range for cleaning; Backwashable, easier to clean; Open feed channels, no blocking of feed channel spacer; Capability for Direct Integrity Testing according to the membrane filtration manual; Repairable, confirmed 4+ LRV rating for bacteria and viruses. This hybrid membrane is piloted for the production of potable water from highly coloured surface water and compared to performance of an existing state of the art water treatment plant. The piloting results are very encouraging: the nanofiltration pilot plant performs equal or better than the conventional treatment plant. The pilot plant does not require chemicals such as coagulants and flocculants to condition the water. This offers the potential benefit of elimination of the waste water sludge handling facility. THM forming potential of the nanofiltration permeate is consistently lower than the THM forming potential of the conventionally treated water. This offers the benefit of future implementation of more strict limits for THM?s in the drinking water. Currently this membrane has been piloted in a number of places around the world: The Netherlands, Scandinavia, The United Kingdom, Canada and Australia. Two full scale plants are under construction. These full scale plants will enter production by the end of 2015. This paper will detail the considerations that favoured hybrid membrane filtration over alternatives and design of these plants.
This presentation is available to AMTA Members only.
- Frans Knops
- Pentair X-Flow
- AMTA/SEDA Technology Transfer Workshop, Knoxville, TN
- AMTA/SEDA Technology Transfer Workshop
- Hollow Fiber, Ultrafiltration, Nanofiltration