Lanxess LewaPlus Design Software Features New Closed Circuit Reverse Osmosis Module

Specialty chemicals company Lanxess adds to its LewaPlus software suite of reverse osmosis (RO) and ion exchange (IX) system dimensioning capabilities. The new module provides system modeling with Desalitech’s Closed Circuit Reverse Osmosis (CCRO) technology and 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.

Reverse osmosis is used for the desalination and purification of water and has been growing rapidly in industrial, municipal and waste water reuse applications. The technology is widely used, especially in areas of water stress such as the American West. 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, the CCRO process now available for modeling in LewaPlus reportedly offers recovery rates of up to 98%. This high recovery is achieved by incorporation of a recirculation pump that returns the brine to the membrane feed and provides a high crossflow velocity through the membrane array.

The 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.

The new software module was developed cooperatively by Lanxess Sybron Chemicals and Desalitech, Inc. 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 Lewabrane portfolio. Desalitech assembles the standardized parts to create a system configuration that autonomously adapts to feed water changes, unlike the linear, constant filtering process of traditional reverse osmosis.

Desalitech’s CCRO process reportedly 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. The process automatically adapts to variations in feed water conditions in order to maintain set recovery goals.