Upen Bharwada, Executive, Business General Manager, Filters and Membranes, GE Water & Process Technologies spoke to Anoop K Menon and shared his perspectives on the key trends in membrane desalination in the context of GE’s desalination products and solutions portfolio. Bharwada has two patents and has catalysed more than 20 new product and process innovations in a career spanning 25 plus years. He was accompanied by Ralph Erik Exton, Global Sales Executive, Channel Partners, GE Water & Power Technologies.
Where is RO desalination headed in terms of chorine tolerance, membrane pre-treatment?
Upen Bharwada
You can use chlorine dioxide either on an intermittent basis or a continued basis; you will not negatively degrade the polyamide thin film composite structure of RO. Chloramines as a disinfectant for preventing biological growth is a proven way of running an RO plant. Chlorine, in itself, will surely degrade the polyamide structure. The moot question is why are you using a disinfectant?
If it is to control bio-growth, you have process know-how available. Hence, I don’t think there is a need as such to develop chlorine-resistant or chlorine-tolerant thin film composite polyamide membrane. In fact, there is a give-and-take aspect here. When you develop a different kind of a membrane, which is chlorine-tolerant, you may have to sacrifice efficiencies, in terms of flow and resistance, which could increase the capital costs while lowering the recovery.
(Exton): If you understand membrane chemistry and if you understand other ways to achieve the same results, there are ways to combine chlorinated products with polyamide membrane chemistries without any negative impact whatsoever. It does take a certain knowledge and application knowhow. This is an area that we specialise in; we have got deep domain knowledge and people in the business. If that needs to be a part of the overall solution, we have an answer. Hence, we feel that you don’t need to go all the way to developing a chlorine-resistant polyamide membrane if you understand what you can do with existing technologies.
We feel that membrane-based pretreatment for desalination is one of the most exciting areas in the industry right now, because membrane-based technologies replacing conventional multi-media types of technologies, is now becoming not only accepted, but has also proven to be cost effective. It is almost like we have turned the corner. You can see that even on larger projects, membrane-based pre-treatment is becoming a major part of the industry’s thrust forward. At GE Water, we have spent a lot of time, energy and investment in making sure that we have an approach that is technically and economically feasible, and is beneficial to the end-users.
What are the savings that you can get from large-diameter membranes?
A few years, the Bureau of Reclamation in the US had funded a project developed by a consortium of membrane element suppliers to create a new element diameter standard. The objective was to arrive at the threshold points in the size of a given desalination plant or a water treatment plant where large-diameter elements begin to make business sense. If I remember right, the study showed the threshold point to be in the region of 25 million gallons per day (MGD). At 25 MGD permeate capacity, the capital cost reduction was about 12.5% between the standard eight inch x 40 inch system versus a 16 inch x 40 inch system. The project resulted in the recommendation of 16 inches as the large- diameter standard for the next generation of membranes.
But I wouldn’t say large-diameter membranes have become a trend. In large projects, the cost of capital and the ‘beta coefficient’, which is assigned by banks or project finance outfits, is quite high for 16- inch membranes, compared to an eight-inch membranes. So the borrowing costs go up, which in turn, drag down the competitive position of a bidder. To my knowledge, only one company among the pressure vessel manufacturers has publicly committed to an invested capital in mandrels, that are necessary tools to make a 16-inch-diameter pressure vessels. Our industry is used to competition and homogeneity, and till all of that is available in the 16-inch segment, it won’t take off soon. It is still in the early adoption stage, in that the early majority and the late majority are still not there.
On the membrane development front, what are the areas that GE Water is working on?
In addition to thin film composite polyamides, we have a broader portfolio of base polymers, such as Polyacrylonitrile, Polyethersulfone and Polyether Ether Ketone, which we use to develop desirable properties. On the element construction side, we look at ways to use the available surface area more efficiently. There is a difference between availability of surface area and use of the surface area. In a given pressure vessel, you will have six to eight elements in series; depending on what the designs are, the recovery of a given element is about 10%. By the time you go from the first to the eighth element, the flux can vary from a high of 20 GFD (gallons per square foot per day) to a low of three GFD. So we, at GE, would look at how to better balance the flow, which would allow for better balance of the fouling.
Of the two major markets for membranes – desalination and wastewater treatment/re-use/recycling – which one do you think will grow faster?
Based on membranes as a key integral part of the process, both markets are proven. Whether it is tertiary wastewater re-cycle/re-use with dual membrane process (Ultra-Filtration followed by RO) or Membrane Bio-Reactor (MBR) followed by RO or seawater desalination, that part of the P&ID or PFD is proven. What is going to take these technologies to the next level of growth in this region is the back end or the distribution. How are you going to distribute what you are purifying or making? For example, you have a municipality which has a need for a 100 MGD recycle/reuse of a certain quality. The technology can come from GE, but it is the municipality’s responsibility to distribute it or sell it, and until that happens, as in the case of Singapore, the growth of wastewater recycle/reuse sector will be proportional to or dependent or restricted by the backend.
When it comes to high capacity SWRO plants (like the ones in Australia), what are the unknowns?
SWRO is a modular technology; hence, going from 10MGD to 100MGD is not engineering or technology or even a design risk. If I have to build a 50 MGD plant, and I have built 5MGD per train before, I will simply build 10 trains. The risk is very low from just the core technology of sea water reverse osmosis. The issue is not scaling up from 50MGD to 200MGD. The issue is – can you truly scale up intake structures, outfall structures as well as deal with the environmental impact of outfalls. These are the only unknowns that may pose some risk while scaling up to the mega plants.
Does this mean that developments in intakes, outfalls and dealing with environmental impact of outfalls haven’t kept pace with the core technology?
(Exton): I think there has been a lot of investment in the core technology of membranes. I also believe that the membrane technology has kept up, in pace, with what is needed in the markets today. My opinion is that there needs to be more investment and a more technical approach to intake and outfall structures to get into the bigger market. GE is primarily involved in the core technology that purifies the water, like membrane-based technology. However, we are also strategically involved and making investments in recycle/reuse solutions, such as thermally based technologies that evaporate and/or crystallise brine solutions, which is a form of mitigation, when it comes to outfall structures. If you can mitigate it, the more you can recycle/re-use. I think there is a major amount of technology that needs to be thought about when you are scaling up.
Is there a service side to GE Water?
We have a business structure and P&L that focuses on delivering water and owning all the assets – the Build-Own-Operate (BOO) model. When we do that, we take responsibility for the entire facility including concentrate discharge and other components. When you are in the service business and you own the assets, it is important to have the lowest life cycle costs, have unit processes that are latest in technology – whether it is pre-treatment, desalination or the intake – and also have sustainability built-in. If you are in the solutions business space, you also own the unit processes that go into developing the solution. We make the membranes, the pre-treatment systems, and also integrate them; we also fabricate PLC controls. I would say we are horizontally integrated and vertically deep.
