As water scarcity bites and the drive to recycle water grows, the focus on recovering clean water and other resources from brine is sharpening. The challenge is particularly pertinent for industrial operators.
Whether it’s in response to regulations that set strict discharge limits, or stems from a desire to cut down on brine disposal costs, better brine management is on the agenda.
“Almost every industry has some type of water treatment issue. In most cases, they don’t want to dispose of wastewater, they’d like to clean it up as best they can, and hopefully reuse it,” says Mark Nicholson, Veolia business development director, oil and gas, HPD evaporation and crystallisation group.
Traditionally, the first stage of that treatment process is reverse osmosis (RO), recovering 75 to 80 per cent of the water, and the second stage is a thermal, evaporative step, which is often energy intensive. Now new technologies are evolving, within industry and in the water market, that are challenging this conventional paradigm.
“The gap between membrane-based desalination and the start of the
evaporative process is closing.” Mark Nicholson, Veolia business development director,
oil and gas, HPD evaporation and crystallisation group
A new oil extraction technology developed to take the oil out of oil sands is one such driver. “In one of our big markets, in Canada, they put steam into the ground to loosen up the oil so that it can flow. The steam goes down, turns into water, and condenses. What comes up is oil and water. They separate out the oil, which goes to the refineries, and the water they want to make back into steam, but it’s highly contaminated. So they have to clean up that water before they can reuse it. That’s a relatively new process, and it’s a chemistry we had never run into before,” says Nicholson. “Essentially a silica chemistry, because they’re putting water into a sand formation, and sand is essentially silica, so it comes up loaded in silica and it’s a very difficult treatment process. We developed a proprietary process to handle that.”
Water companies are similarly devising new technologies, aiming to push the conventional boundaries of brine management. “The gap between membrane-based desalination and the start of the evaporative process is closing. Membranes have gained ground, so there is a little less demand for traditional evaporators. That’s good because those membrane processes are more economical, and they cost less to operate,” says Nicholson.
Membrane-based brine concentration
Modern Water has developed and is now commercialising a new membrane-based brine concentration technology, the All-Membrane Brine Concentrator (AMBC), which extends the range of membranes into the territory where thermal evaporation traditionally begins.
The AMBC requires electricity for pumping, but uses no thermal energy; and as such, the operating costs are “a fraction” of those of a thermal brine concentrator or a crystalliser, says Modern Water technical director, Peter Nicholl.
“We looked at some of the challenges facing the zero liquid discharge (ZLD) or near-ZLD market, including the capital and operating costs of thermal brine concentrators and crystallisers. AMBC takes the concentrated brine from an RO process (the typical inlet condition is 70,000 mg/l NaCl equivalent), and then at least halves the brine volume,” says Nicholl. Any subsequent treatment steps are therefore cheaper, because the required thermal equipment is smaller, and energy usage lower.
“It’s based on forward osmosis (FO). We were looking for ways to generate very, very high osmotic pressure solutions and out of that work, we have something we can use for brine concentration, with or without FO,” adds Nicholl.
Modern Water has built a large scale AMBC pilot plant, which has a typical inlet throughput of 1,200 litres/h at 70,000 mg/l as NaCl, and will produce a concentrated brine stream in excess of 140,000 mg/l as NaCl, with a product of around 500mg/l. Housed in a 20 foot container, it can be coupled with different pre-treatments depending on the nature of the wastewater.
In February 2017, the company sold its first AMBC, to an Indian textile dyes customer as part of a new ZLD facility that is expected to be operational by mid-2017. In this application, the AMBC has an inlet wastewater flow of 8,900 litres/h and will produce a concentrated brine of 130,000 mg/l.
“The water industry is very, very conservative, in the municipal sector and even
the industrial sector, operators don’t want to make mistakes. It’s very hard for
emerging and breakthrough technologies to change that very long-standing status quo.”
Nadav Efraty, Desalitech chief executive
Design thinking
Another way to reduce the volume of concentrate is to redesign the core RO process. Desalitech has done this with its closed loop RO system, which arranges membranes in parallel arrays, rather than sequentially. “These sequential RO systems don’t work at very high water recovery rates, they waste water and generate a lot of brine, they’re not very energy efficient, and are not always reliable. We have reinvented RO, making it into a parallel, closed loop circulation process,” says Desalitech chief executive Nadav Efraty.
Desalitech estimates that 80 per cent of the total cost of ownership of an industrial RO system goes on buying water that is never used as process water, and then paying to dispose of it as concentrate.
“Our system operates at 95 per cent water efficiency, so instead of buying an extra 33 gallons and disposing of them, we typically need to buy an extra six gallons and dispose, and that has major implications,” says Efraty. ‘We flow all our water through a parallel set of membranes and then we take all the brine and circulate it back, while not losing a drop of water or a psi of pressure. We are circulating it all back to the front, where it is constantly being mixed with fresh feed that goes to the membrane.”
As well as reducing water usage, the system design helps to reduce scaling and fouling of the membranes. “Every cycle is like another stage of membranes. The membranes are not immersed in very high concentration for more than the induction time of the salts, and that enables us to get to much higher concentration levels without scaling our membranes. The concentration variations also disrupt fouling, because there are some bacteria that like low salt concentrations, and some bacteria that like high concentrations — but no bacteria likes the concentration to go from X to 20X over 30 minutes, and then back to X,” says Efraty.
The company started in Israel in 2008, and relocated to the US at the end of 2013, winning customers including Coca Cola, Hershey, L’Oreal, ADM, and Procter & Gamble.
In the municipal sector, it has completed a “hugely successful” pilot with Padre Dam, near San Diego in California, says Efraty. “We took filtered municipal wastewater, and they started our system at 95 per cent recovery. After a few months they increased the recovery to 96 per cent, and it still didn’t need cleaning and was very stable, so they increased the recovery to 97 per cent, and in the end to 97.5 per cent, which is completely unheard of — 97.5 per cent is twice the recovery of 95 per cent, because you have 2.5 per cent brine, instead of 5 per cent.”
As a result, it is running a new pilot with the city of Los Angeles, and another pilot system was acquired by Orange County.
Commercialisation challenge
Getting a new technology adopted, particularly in the municipal sector, is a big achievement. “The water industry is very, very conservative, in the municipal sector and even the industrial sector, operators don’t want to make mistakes. So it’s very hard for emerging and breakthrough technologies to change that very long-standing status quo,” says Efraty. “But the status quo is bound to change, because there are more people on this planet, and even today the existing water resources are not enough.”
Another Israeli company, Lesico CleanTech, part of Lesico Group, is working to commercialise brine disposal technology WAIV with industrial customers. “We find industry more ready to adopt new techniques, compared to the desalination market for drinking water or irrigation,” says Nissim Asaf, Lescio CleanTech chief executive. “Stringent regulation and effective enforcement all over the world, and particularly in developing economies such as India and China,” are the big driver in industry, adds Asaf.
“We hit upon a vertically mounted surface. You have many vertical surfaces,
and you keep pumping the brine over them.” Jack Gilron, associate professor
at Ben Gurion University, partnering with Lesico CleanTech
WAIV, Wind Aided Intensified Evaporation, developed out of a search for an environmentally friendly brine disposal method for inland industries. “People were using evaporation, but it took so much land. Some companies tried spraying, but environmentally it’s a disaster, because that spray can contaminate significant sections of land downwind,” says Jack Gilron, associate professor at Ben Gurion University, with which Lesico CleanTech has a technology transfer agreement.
“We started looking at other possibilities. We hit upon a vertically mounted surface. You have many vertical surfaces, and you keep pumping the brine over them. And because you can pack a very high surface area, as high as 40 m2 of wetted surface per m2 of footprint, you can get significant expansion of evaporative capacity based on the footprint that’s available,” says Gilron, who shares the credit with department engineer Ygal Bolkman.
The surfaces are made of specially developed hydrophilic plastic geotextiles that water spontaneously spreads across, and they can be oriented parallel to the dominant windspeed, allowing the wind to blow through, pick up the water vapour, and carry it away.
The company is currently finalising a pilot project with a landfill site company in Australia, and hopes to begin a full commercial operation later this year; and has also run a pilot with a gas and fossil fuel company.
In tests conducted during the original development work, WAIV handled brines up to 30 per cent total dissolved solids (TDS), with sodium chloride precipitating out. “It continued to evaporate because we had humidities in the air lower than the relatively humidity of the brine. It has been tested by Lesico CleanTech down at the Dead Sea, where you have brines that are very, very concentrated, they used it to reduce volumes of concentrate as a potential way of recovering minerals,” adds Gilron.
Recovering minerals
The rise of the circular economy is putting resource recovery at the forefront of the latest thinking about brine. “The greatest challenge in brine disposal is to find a salt recovery treatment technology that works with complex waters, to offset the cost of brine treatment. A greater understanding of salt markets is required to make this happen,” says Karla Kinser, senior water treatment project manager and desalination practice lead at HDR.
“If you’re a bit more creative upstream with the chemicals that you use,
you might get certain salts or crystallisation processes where
you get actual useful and valuable fertilisers out of it.”
David van Lennep, Lenntech managing director
Lenntech, a Netherlands-based water purification company, is delving into these new ideas. “Upstream of a mining process, for example, you might use caustic/ NaOH, and to precipitate certain chemicals. Now we are asking, ‘could you use a different caustic?’ For example, ammonium hydroxide, so that later downstream you would get a concentrate which you might be able to precipitate and use as fertiliser,” says David van Lennep, Lenntech managing director.
“If you’re a bit more creative upstream with the chemicals that you use, you might get certain salts or crystallisation processes where you get actual useful and valuable fertilisers out of it,” says van Lennep.
Lenntech is involved in research and development as part of a European research consortium, together with universities and other partners, to see where it may be possible selectively to extract certain salts.
“In the mining sector, we have a specific application where we are looking at trying to get fertiliser concentrate; that’s already something we’re actively involved in. The very selective minerals or salts — calcium hydroxide, magnesium hydroxide — that’s more in the research phase, we are planning to have, together with partners, our first demonstration pilot in the next two years.”
Lenntech is also receiving lots of requests to optimise water circularity in the case of cooling tower feed water and blowdown, particularly in the cloud computing sector.
“Many existing cooling tower systems that have been put into place in the past years, data centres which have been built, left, right and centre for all these cloud computer companies. They have a huge demand for cooling, and often they are placed in situations where there is not much water available. For several plants we are building systems to optimise the blowdown, which is a brine. So either concentrating that, reusing that, or looking at the minerals going into the cooling tower so that the brine will be much less.”
Van Lennep says that the water industry still has some way to go on resource recovery from brine, with a lot of work in either the lab or pilot phases, adding “the end user industry is waking up, because it has a water shortage and a disposal problem.”
Salt markets
Meanwhile Saltworks, based in Canada, is at pilot stage with its hybrid RO-electrodialysis reversal (EDR) system, Saltsplitter, which is moving towards the reuse of salt byproducts recovered from brine.
Firstly, it electrochemically pre-treats the RO feed to remove the scaling ions, and removes the need for soda ash softening. “Soda ash is a very expensive chemical that people use today to deal with calcium. Soda ash is off the table, and that can save approximately 10 to 15 per cent on operating costs,” says Ben Sparrow, Saltworks chief executive.
“We use highly selective ion exchange membranes to permanently change
the water chemistry that’s facing the RO. At the same time we’re able
to be somewhat picky about where various ions go.”
Ben Sparrow, Saltworks chief executive
Secondly, the membrane system is high recovery — it’s producing sodium sulphate and calcium chloride at extreme concentrations about 200,000 mg per litre — which maximises the low cost capacity, and minimises the size of any downstream evaporator.
And step three “is where it gets interesting,” says Sparrow. “With the Saltsplitter, we’re able to manufacture somewhat semi-custom chemistries on the back end. So you start to move closer to reuse of the saline byproducts. We are just starting on that, working with three large industrial players. So far, we think we can probably recycle about 40 per cent of the solid waste.”
He continues: “We use highly selective ion exchange membranes to permanently change the water chemistry that’s facing the RO; and at the same time we’re able to be somewhat picky about where various ions go. So rather than the conventional process of having a mixed brine salt product at the end, we start to have selective salt products. For example sodium sulphate, which is used in making glass or detergents. Calcium chloride, which is used to harden roads or harden concrete. Or Calcium sulphate, which is used for gypsum in dry wall or plaster of paris.”
The company has licenses to the patents of Thomas Davis PhD, professor of civil engineering at the College of Engineering, University of Texas, El Paso. “We developed the membrane that Dr Davis needed, and we innovated on top of his process. So we are standing on Dr Davis’s shoulders. The fundamentals of this process — and this is just one example — is we permanently change scaling calcium sulphate into a non-scaling sodium sulphate and calcium chloride.”
Sparrow cautions: “You still cannot destroy the atom. The hazardous constituents still have to go somewhere, it’s just that you can get a bit more picky about that.”
Full scale production of the membranes and the stacks are in place, and Saltworks is running a series of pilots in different applications, in particular mining and flue gas desulphurisation.
“We are piloting with the full scale components. This is a modular technology, just like RO; you can build a plant with one module and have a small RO plant, or you can build a plant with tens of thousands of modules. So we are proving out the complete process end-to-end. And then we will start building commercial demo plants, and then commercial full scale plants,” says Sparrow. “It’s really just the two most widely used industrial technologies that already exist, tweaked, and hybridised. There is a tremendous demand from large industry. Those who are lined up as the first adopters are going to need to have courage, and to seek innovation.”
The Long Read: Do we have the technology for potable water reuse?