Reverse osmosis is for the desalination and purification of water has been growing rapidly in industrial, municipal and waste water reuse. The technology is widely used, especially in areas of water stress such as the American West. Now, this revolutionary approach can be simulated reliably and accurately...
The traditional reverse osmosis process is sometimes limited to recovery levels of 75 to 85 %, wherein 15 to 25 % of the feedwater is not purified and becomes waste. In contrast, Desalitech’s Closed Circuit Reverse Osmosis (CCRO) offers recovery rates of up to 98 % by incorporation of a recirculation pump that returns the brine to the membrane feed and provides a high crossflow velocity. Now, specialty chemicals company Lanxess has included CCRO-processes in its Lewaplus software suite of reverse osmosis (RO) and ion exchange (IX) system dimensioning capabilities. The new module enables the dimensioning of RO systems using the latest available water treatment technology, helping system designers bring their water treatment footprint closer to zero liquid discharge (ZLD) or minimum liquid discharge (MLD) goals.
The CCRO system operates in two alternating modes: Closed Circuit (CC) mode at 100 % recovery and Plug Flow (PF), or flushing mode, at 10 to 50 % recovery. During CC operation, permeate is produced at a rate equal to the flow rate from the high-pressure pump. When a desired recovery percentage is reached, the operating mode is switched to PF mode in which concentrated brine is purged from the system and displaced by feed water from the high-pressure pump in a single plug-flow sweep.
Putting an End to Excel-Engineering
The new software module was developed cooperatively by Lanxess Sybron Chemicals and Desalitech (Newton, MA, USA). Until now, the modeling of the CCRO process was based on experience values without energetic optimization, which generally limited CCRO projections for recovery rates and system capabilities. This new module replaces the prior calculation protocol using multiple Excel spreadsheets to approximate system performance.
It incorporates the existing graphical user interface, user-friendly layout and linear process logic that is the hallmark of the Lewaplus design software. In addition, the new module includes tabs for power consumption, post-treatment and cost analysis. These additional analyses are available “within a second,” Mir emphasizes.
Versatility Included for Water Treatment
The new CCRO software module follows the same stringent reverse osmosis membrane design guidelines as traditional reverse osmosis modules. The process uses conventional reverse osmosis elements, such as the industry-standard 8-inch diameter x 40 inch long spiral-wound, polyamide-type thin film composite elements as offered in Lanxess’s proven Lewabrane portfolio. Desalitech assembles these standardized parts to create a unique system configuration which autonomously adapts to feed water changes, unlike the linear, constant filtering process of traditional reverse osmosis.
Desalitech’s CCRO process reaches much higher recoveries by recycling water through a single-stage membrane array until no further recovery is possible, at which time it discharges the concentrated waste. Constant variations in flow and salinity inhibit fouling and scaling, extending membrane lifespans. Furthermore, the process automatically adapts to variations in feed water conditions in order to maintain set recovery goals.