New Developments in the Low Pressure Membrane Market

It has been a while since I have given an update on what is happening in the low pressure membrane market and there have certainly been some interesting developments in the past year. The major topics of interest for me are as follows:

MBRs Replacing MF/UF Systems for Indirect Potable Reuse Applications

While the potable market has been slow for Microfiltration/Ultrafiltration (MF/UF) systems I recent years, water reuse has been a nice new market to fill that void. This market could now dry up with the prospect of Membrane Bioreactors (MBRs) finally getting accepted for cryptosporidium, and giardia log removal credits in water reuse applications. The California Department of Public Health (CDPH) has announced it will provide 2 log removal credits for crypto and giardia based on challenge test conditions from an Australian study which means a separate MF/UF treatment step prior to RO is not needed to obtain the required 10 log removals for pathogens for indirect potable reuse (IPR). My understanding from a few presentations and discussions with experts in this field at the WateReuse Symposium in Austin this week (Sept 9-12) is to receive the removal credits a very specific set of conditions need to be met based on the Australian study (Tier 1 – I will describe in another post when I get a copy of the proceedings). So, it is not a blanket approval for MBR pretreatment, but I also understand that a number of US studies are underway or planned to demonstrate log removals for a broader range of operating conditions.

While CADPH has not yet formally approved log removals for MBRs, I am aware of at least one project that has been awarded in California this year for a future IPR system with an MBR directly feeding RO treatment and others are in the design phase. This is great for the suppliers of MBR systems but not so great for the MF/UF system suppliers. There is still a market for MF/UF systems in the reuse market for potable reuse from existing conventional wastewater treatment plants where additional biological treatment is not required, but for new wastewater treatment plants looking at IPR, the use of MF/UF systems will be rare in the future. My understanding is that to get enough log removal credits for potable reuse with MBRs used in place of MF/UF treatment (which gets 4 credits), removal credits from groundwater injection are also required, so this treatment train could not be used for direct potable reuse – I will clarify that also when I get the proceedings as I am still coming to grips with this new development.

Nanostone doing a 'Scinor' and chasing retrofits
In an attempt to get some reference installations for its ceramic membrane, Nanostone has been seeking opportunities to retrofit its modules at existing MF/UF installations where the ceramic membranes offer some process benefits over the incumbent polymeric membranes. Unlike Scinor which offers polymeric membranes that are exact replicas of a number of MF/UF modules on the market allowing easy replacement, to install the Nanostone modules, modifications of the piping to and from the modules as well as the supporting frames is required. Therefore, there needs to be some significant performance benefits to justify the modification cost. Nanostone has been successful in finding some installations where cold water and/or highly fouling feed water has reduced capacity and increased chemical costs of existing polymeric membranes, where these factors are not a problem for ceramic membranes. An advantage for Nanostone over other ceramic membranes on the market is the cleaning and backwash regimes that have been developed are similar to the polymeric membranes, so existing infrastructure can be used with minimal modifications. While the membrane surface area is around one third of Toray and Dow modules (258 sqft versus 775 and 829 sqft respectively), the ability to have significantly higher flux rates allows similar productivity per module in some cases. For smaller modules such as Pall/Asahi’s (538 sqft) the Nanostone module can provide higher productivity under the right conditions.

Universal Acceptance of Open Platform Systems

The days of Open Platform/Universal MF/UF systems being considered a novel concept are well and truly over. With several years of good performance for a growing number of installations, Open Platform/Universal systems are entering the mainstream MF/UF market. Of the MF/UF system specs I see now, my guess is around 50% of these now request Open Platform/Universal systems. The larger engineering firms have embraced these systems the most where they are more excepting of references from across the country while smaller regional engineers want to see local references – therefore some states have been slower to catch on. I think some engineers have even taken the concept too far wanting systems to accommodate up to 6 different modules, including a wide range of module sizes, which starts to diminish the advantage of a Universal system when you have to size the MF/UF rack for the smallest module and lose the advantage of a more compact system provided by the larger modules on the market.

But I should not complain and be thankful there is wide recognition now that there are other proven, high-quality MF/UF modules and system integrators available other than the proprietary systems provided by the ‘Big Three’ (Pall, GE/Suez, Evoqua).