What’s on tap for water?

This increasingly precious resource is attracting more attention

By Seán Ottewell, Editor at Large

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Dow expects to launch these larger elements at the Aquatech Amsterdam exhibition that starts at the end of September. “These are important because they cut the capital cost of a desalination system by 10–20%,” notes Martz.

Figure 1. This module forms the heart of new reverse osmosis elements.
Source: Dow.

Dow, on July 10, announced plans to build a $15-million Water Technology Development Center at its Tarragona facility by the Mediterranean Sea in Spain. Due to open next year and employ 25 researchers, it will have ready access to seawater and will be able to obtain brackish water, industrial wastewater and treated river water. The idea is that the center will help Dow understand how to achieve the best performance and lowest operating costs for treating different water types.

At the same time, the company has launched two new seawater RO elements (Figure 1).

The first boasts better rejection of boron, a trace contaminant that causes a variety of different problems, not least in Israel where its presence in desalinated water has made artichokes go brown. The World Health Organization also warns against raised levels of boron in potable water.

The second targets energy use, which is the biggest cost associated with desalination.

Energy savings realized depend on temperature, water salinity, design flux, fouling tendency, efficiency of pumps and motors, and use and efficiency of energy recovery devices. In a typical seawater system, the savings are roughly 0.3 kWh/m3 and energy consumption of the membrane stage could be brought down from roughly 2-2.5 kWh/m3 to 1.7 to 2.2 kWh/m3. In selected scenarios (low temperature, higher fouling tendency, inefficient pumps, no energy recovery), the saving is more in the range of 0.6 kWh/m3. With an energy cost of five to 10 U.S. cents/m3, this is a savings of one to four U.S. cents/m3. “The trade-off is slightly elevated permeate salinity. In many cases the salinity will still be within WHO expectations.”

And this highlights the desalination crux: “We are always trying to make the membrane more permeable in RO, but at the same time reject unwanted salts. So we are always looking for new chemistries. What industry wants is to meet the required specification, whether for potable water or ultrapure water. Once you can meet this, you then look at the cost of water production. So we work with companies such as Siemens, Veolia and many others to try and find solutions that optimize the cost of the water coming out of the system,” says Martz.

Targeting industry

Pall, East Hills, N.Y., also sees industrial water treatment as a growing business. “In the last year we have set up a dedicated engineering applications group within our industrial water section. So we’re definitely gearing up for it,” says Thomas H Wines, senior marketing manager.

Figure 2. Combining microfiltration and reverse osmosis, this system can cope with significant variations in feedwater. Source: Pall Corp.

In particular, Wines points to growing interest in the company’s Integrated Membrane System (IMS) technology (Figure 2). “The point here is that a technology originally developed for municipal drinking water has moved into the industrial water sector and is a growing business,” he explains.

Origin Energy, one of the leading energy providers in Australia, New Zealand and the Pacific, is an early IMS beneficiary. One of the company’s main products, coal seam methane (CSM), is expected to produce 90% of the total gas required in Queensland, Australia. To recover the gas, however, requires water to be pumped from the coal seams to reduce the pressure and allow large volumes of gas to flow. This water traditionally has been difficult to treat with membrane technologies because of its wide variety of contaminants. To add to the challenge, the company’s Spring Gully development near Roma in central Queensland is in a drought-affected region of Australia where water management is especially critical.

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