Kristal UF membranes, designed and developed by Hyflux, have proven performance in treating industrial and municipal wastewater as well as seawater, even in aggressive environments
One of the key components of Hyflux’s advantage that enables it to be one of the leading water and environmental companies is its proprietary ultrafiltration (UF) membranes – Kristal which is used for pre-treatment before the reverse osmosis (RO) process in membrane-based seawater desalination, drinking water treatment, wastewater reclamation, water recycling, and raw water purification and a wide range of other process applications.
The advantages of using UF membranes for RO pre-treatment instead of ordinary sand filters include:
Lower life-cycle costs
Excellent and consistent permeate quality regardless of fluctuations in feed water quality
The main functions of UF membranes that underpin its advantages in RO pre-treatment are described as:
Effectively removes all the suspended solids (TSS) from the RO feed water due to sufficiently small pore size of the membranes
Effectively removes bacteria, silicates, colloids, organics, pathogens and viruses, all of which often cannot be effectively removed by conventional pre-treatment or even with microfiltration
Results in an SDI value of the RO feed water always being less than 3 and turbidity being always less than 1, which is also the standard requirement most reputable RO manufacturers will require for the RO feed
Lower SDI and turbidity translates into lower RO feed pressure, thus saving on electricity costs
Lower SDI also results in less frequent RO cleaning, which translates into chemical cost savings and a lengthened lifespan of the RO membrane.
In addition to the regular advantages that the UF membrane brings to the pre-treatment process, Hyflux Kristal membranes have several additional features that provide it with an edge over other UF membranes.
Kristal is a polymeric hollow fibre membrane made of specially formulated modified and hydrophilised polyethersulfone (PES). This feature reduces fouling when handling streams of very high suspended solid organic content, and an ultra thin skin built above Kristal’s porous substrate allows it to achieve both high water flux and mechanical strength. It also has a simple, modular and compact design that enables it to provide a larger membrane area per unit volume at a smaller footprint size for lower capital and installation costs.
In addition, its out-to-in and cross-flow configuration reduces the challenges posed by fouling on the UF membrane itself, which improves the performance and lengthens the life of the UF membranes.
The out-to-in configuration means that the feed stream flows on the outside of the membrane with the filtrate flowing through to the inside of the fibres. This means that unlike an in-to-out filtration, where feed water is introduced into the fibres each of which sometimes being as fine as a single strand of hair, there is no possibility of entire fibres being irrecoverably choked due to foulants present in the feed water. This out-to-in configuration is particularly advantageous for effluent/sewage recycling and river water treatment applications due to the high possibility of surges in the TOC and turbidity of effluent arising from batch processes in the former and spikes in river water turbidity during monsoon season and flash floods in the latter.
This can be seen in the third-party study by China Water Network below, which shows that the irrecoverable flux decay in out-to-in membranes occurs at a significantly slower rate than in-to-out membranes.
Unlike dead-end filtration where foulants are continually pressed against the walls of the membrane, the cross-flow configuration maintains a minimum cross – flow velocity by re-circulating the reject stream. This re-circulation creates cross-flow shear, which keeps the solids present in the feed water in suspension, and prevents the accumulation of solids on the surface of the membrane. It is also possible for the balance of the reject stream to be bled-off to prevent the build-up of solids in the re-circulation loop during periods of high turbidity. Such feed and bleed operation allows the UF to operate continuously before the need for backwash, thereby improving recovery and availability of the system even when filtering very challenging feed water.
Besides the technological advantages of the Kristal membranes, you can expect other logistical and technical advantages should you choose to go with Kristal.
Quick Turnaround TimeHyflux Shop, which distributes the Kristal® membranes in India, has a dedicated office in Chennai equipped with a full team of proposal and site engineers using the latest membranes software, 3D modelling tools, in-house developed database to offer speedy advice that is tailored to Indian requirements. Similarly, membranes are also stocked in Chennai for quick delivery.
Strong technical supportHyflux offers strong support to its OEM customers for plants less than 10MLD by supplying membranes to them. Due to the company’s expertise in the EPC and O&M of membrane plants all over the world, Hyflux is also able to offer first-hand technical advice including suggestive designs for the UF system, complete with duty points and P&ID based on its own actual site operating experience. This will enable the OEM customers to easily create UF systems with its membranes for a large variety of water applications that will work well for the end-user. The company is also plans to accumulate a database of suppliers of other equipment in the UF system (eg: pumps, valves) that its OEM customers can tap when creating their systems.
Growing presence in IndiaThe company has been increasing its penetration in Indian market at a faster pace. One of its most recent achievements was the supply of Kristal UF membranes for the Bharat Heavy Electrical Limited (BHEL) projects of 10MLD UF system in Chennai. The purpose of the system is to produce pure water for thermal power plant from bore water.
Another important project in which Kristal UF membranes have been used is the 5MLD UF membrane system for Rashtriya Chemicals and Fertilizers (RCF) Ltd in Mumbai. This UF system recycles waste water for industrial reuse. n
Author:Shahid Showkath Ali , AM – Operations & BD, Hyflux Engineering India Pvt Ltd (A Hyflux Group Company)