Specialty chemicals company, LANXESS, has made a significant addition to its LewaPlus software suite of reverse osmosis (RO) and ion exchange (IX) system dimensioning capabilities. The new module provides system modelling 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 per cent, wherein 15 to 25 per cent of the feedwater is not purified and becomes waste.
In contrast, the CCRO process now available for modelling in LewaPlus 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 with 100 per cent recovery and Plug Flow (PF), or flushing mode, at 10 to 50 per cent 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. (Newton, MA, USA). Until now, the modelling of the CCRO process was based on experience values without energetic optimisation, which generally limited CCRO projections for recovery rates and system capabilities.
“The new CCRO module inside LewaPlus allows for rapid and accurate reverse osmosis system designs utilising the existing performance algorithms and computational techniques that support the good performance of the Lewabrane elements in the reverse osmosis process,” Firuza Mir, President of LANXESS Sybron Chemicals, said.
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 emphasised.
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 by 40-inch long spiral-wound, polyamide-type thin film composite elements as offered in LANXESS’s proven Lewabrane portfolio. Desalitech assembles these standardised 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.
“Desalitech is helping many Fortune 500 companies and some of the most sophisticated water users on the planet substantially reduce their water consumption and operating costs,” Nadav Efraty, CEO of Desalitech, explained. “We are very excited about working with LANXESS to provide an easy to use and intuitive design software that will enable many organisations to take control of their own water future and do it with a membrane company that is as committed to technical excellence and leadership as themselves.”
