Ian Lomax, Strategic Marketing Manager, Dow Water & Process Solutions spoke to Anoop K Menon on the trends and challenges in the desalination industry, ranging from acceptance of large diameter RO elements to Boron regulations and concerns about chemical and brine discharge.
At the IDA World Congress 2009 in Dubai, there was a lot of buzz around large diameter elements taking the centre stage with regard to membrane desalination. Where are we today with these elements?
Ian Lomax
Five to six years ago, the industry (membrane manufacturers, vessel manufacturers, consultant engineers, endusers) realised that systems were getting bigger, so sizes bigger than the standard 8-inch are needed. The industry consensus was 16-inch; may not be the optimum, but it was a good compromise across the technologies. The thing that really limits it was vessel technology. At that time, the numbers implied that there were savings to be made in capex, opex and other areas by going to the bigger sizes. But the benefits are potentially capex savings rather than opex because 16-inch is a new segment. Dow can supply 16-inch elements on a large commercial scale as of today.
All said and done, the going has been slow for 16-inch. Being inherently conservative, the water industry is slow on the uptake with regard to new technology or innovations. Moreover, prices are on the higher side since nobody is producing 16-inch elements, valves and vessels in bulk today. As a result, engineering companies don’t see significant savings over what they can make more easily, with higher area 8-inch elements.
Moreoever, using 16-inch requires a rethink about the way people engineer and design desalination systems. If they regard 16-inch elements as a mere replacement of four pressure vessels with one pressure vessel while keeping the same number of trains, pumps and valves, the savings will be hard to come by. There has to be a change in the mindset on the lines of – instead of having 20 trains, we will do it with 10. For On the record that to work, somebody needs to be able supply pumps of twice the capacity at not more than twice the price or be able to produce 16-inch pressure vessels at no more than four times the price. At the moment, everything is at a premium.
I am positive this segment will grow as we see some headway being made with companies trying to bid with bigger systems that incorporate 16-inch. Once the first big system goes out, I expect it to have a pull through effect.
At the session on finance in the IDA Conference, an issue that came up was how existing financing models discourage new innovations on the grounds of higher risks and costs. Isn’t that a barrier to the adoption of innovations like 16-inch elements?
This isn’t restricted to this region; I think it is an industry-wide problem. Getting in new technologies, getting parameters changed is very difficult because a lot of drive in this industry is coming through consultant engineers and water authorities with solid (but) traditional water treatment backgrounds. Consultant engineers, by nature, tend to be very conservative because they are advising their customers based on their best practices and knowledge, and what they have built in the past. They tend to fall back on these specs. So, to get in new technology, the manufacturer will have to find an entrepreneurial contractor or a customer who can see the benefits, and then get the plant running. In Australia for instance, there is a requirement on the lines of showing you had this large system running for a minimum of two years, which really means they need a product we had five years ago. But we are moving ahead much more quickly; therefore, as manufacturers, we are now trying to persuade our customers to change. We spend a lot of time and effort writing technical/scientific papers that explain what we are doing, the benefits and the costs. Equally, we are trying to find engineering companies who are progressive and can work with new technology.
When you said earlier that the water industry is conservative, does it include all the segments?
When I said this industry is conservative, I meant end-users. From the industry end, whether you look at membranes or energy recovery, we are advancing quickly. One problem may be that the product you see today looks exactly like the one you saw 10 or 20 years ago because the change is not so much external than internal. An analogy that sums it up best is the microprocessor. It still looks the same, even though its processing capacity is doubling or tripling every few years. The same analogy applies to RO elements too. When I started in this industry, an RO element could produce 4,000 gallons/day; the one we exhibited in our booth at IDA can produce 12,000 gallons/day. Salt passage was four per cent; now it is less than one per cent or less than half of it.
The membrane industry has made massive strides in reducing energy and improving quality, and helped bring down the cost of water down. However, product looks the same from the outside. That’s why suddenly the 16-inch is interesting because it is physically different too.
One of the discussions I attended at the IDA was about regulations that limit boron levels in drinking water. How is the membrane desalination industry affected by such regulations?
There are two key drivers for boron. One is the World Health Organisation (WHO) standard, which set a preliminary limit of 0.5 mg/L for drinking water. As the WHO standard has been adopted by most public health authorities, the industry has to comply with the same. Boron removal increases the cost of water significantly in exchange for a relatively small improvement. Some countries are questioning why they should pay this cost? Most of the desalinated water is used for washing, cooking, bathing, while people prefer to drink bottled water. So they are asking, what is the health threat from boron? We have been hearing reports that WHO is going to relax the Boron guideline. It is included in the plan of work of the rolling revision of the WHO Guidelines for Drinking-water Quality. At its meeting in November 2009, the Drinking-water Quality Committee recommended revising the Boron Guideline Value to 2.4 mg/L. If the recommendation is accepted, it is good news for membrane systems. A Boron value of 0.5 mg/l has been difficult to achieve in typical single SWRO processes. If we are working on a band between 1 and 2 mg/l, it is relatively easy to achieve in a single pass, which helps save both capital cost and energy.
The other driver is boron toxicity, especially in the case of citrus plantations because too much boron can be problematic for the citrus crop. So if the area in question has citrus plantations, then a boron value of 0.3 or 0.5 mg/l has to be maintained. But the Gulf region, to my knowledge, doesn’t have citrus plantations. I don’t think date palms are as susceptible. The Gulf countries point of view, it comes down to what is the acceptable international standard, and where do they want to be with that standard. Even if WHO relaxes the boron guidelines, my feeling is that the industry will try to stick to 1 mg/l. If you are trying to get 1 and 1.1 acceptable, it is a different situation than if it is a warranty case and you have to go and prove it. For the industry, boron is purely a cost issue. It has had a positive spin-off in that it has driven technology and improved rejection.
Coming to the age old concerns about the discharge of chemicals and brine from the desalination plants into the sea, has there much progress in addressing them?
You have more of these issues with thermal desalination than with SWRO. The only chemical you would introduce into the environment with SWRO would a small level of anti-scalants. Membranes cannot tolerate chlorine so that isn’t an issue either. Are we adding salt? I don’t think so because all we are doing is taking a volume of sea water from the ocean, extracting the water and returning the same mass of salt in half of the volume. So we are not adding anything. It is akin to a natural process like evaporation. Only in this case, we are taking the water through the membrane and leaving the salt back in the ocean. So at a macro level, it doesn’t make a big difference. But at a local level where you have got very high concentration or intensity of desalination plants, you might have a local impact.
It is possible is take steps to diffuse the brine. The main criticism against SWRO is that produces a plume of discharge brine that is more saline and may have an impact on fish life, plants and marine environment. What we try to do is diffuse the plume as quickly as possible, though it adds to the cost. In the case of the Perth desalination plant, where they discharge into an enclosed lagoon and an ecologically sensitive area to boot, the standards are stringent. You are diluting the brine plume to bulk concentration in a very short distance. (The brine from the Perth plant is discharged through a multi-port diffuser, designed to achieve rapid mixing of the brine with seawater to one practical salinity unit (PSU) above ambient salinity within 50 metres of the diffuser – H20 editorial).
Do you think the future of desalination is SWRO?
The balance of installed capacity today is tilted towards thermal desalination. In the future, we will see SWRO growing more strongly. The big Multi-stage Flash Distillation (MSF) plants will tend to be specific instead of being the default choice. Moreover, this region has seasonal fluctuation in power demand but continual demand for water, so you will see more hybrid situations where MSF and membranes are run side by side. You can use the membrane system to produce water and load the station because it needs electricity rather than have to produce waste heat very wastefully, by producing electricity you don’t need. We will see Multi Effect Desalination (MED) probably taking a step forward because using nano-filtration ahead of MED will improve the efficiency as you can run at higher temperatures and reduce the amount of scaling chemicals.
