Water/Wastewater / Water/steam

Chemical Makers Transform their Water Sourcing

Minimizing potable water intake is becoming more important as are conservation efforts

By Seán Ottewell, Editor at Large

In their ongoing efforts to optimize water use, large chemical manufacturers including Dow, Solvay, DuPont and BP are adopting a variety of strategies. These range from establishing partnerships with local water treatment companies and municipal water suppliers to getting involved in European Union (EU) research projects to investing in emerging technologies.

Dow, as one of the world’s largest chemical companies as well as a leading provider of separation and purification technologies, takes a very broad view of the issues associated with water use, stresses Snehal Desai, global business director for Dow Water & Process Solutions, Edina, Minn.

As an example, he cites the Terneuzen site in the Netherlands (Figure 1), Dow’s biggest in Europe: “The nearby city and important surrounding agriculture sector also make big demands on supplies of fresh water there. At one point the city was bringing in all its fresh water from over 120 km away,” he says.

So, Dow and two local organizations — Evides water company and the Scheldestromen municipal water board — established a public/private partnership to develop an integrated water use strategy.

Following installation of Dow’s own reverse osmosis (RO), fouling-resistant membrane and ion exchange resin technology at Evides’ water treatment plant, the flow and quality of permeate now is said to be ideal for use at the chemical site. Currently about 30,000 m3/d of the city’s wastewater is purified and used for steam and various process streams. “So that amount of water is now available for other uses by the city or agricultural sector. On top of that, Dow reuses the water again in cooling towers,” notes Desai. [For more details on efforts at Terneuzen, see: http://goo.gl/g6lkU0.]

By 2020, the company hopes to eliminate entirely its reliance on remotely sourced fresh water at Terneuzen and to exclusively use water sourced from the regional water-recycling program.

A similar project is underway at the company’s Tarragona site in southern Spain. Here, the local wastewater treatment plant uses Dow’s fouling-resistant membranes in the first pass and its low energy membranes in the second pass to supply 40% of the water used by the site’s cooling towers.

“This project is important because Tarragona is a very water stressed region. By using reclaimed water for industrial purposes, more water becomes available for municipal uses and the Ebro River Basin, which is a natural area protected by the UNESCO [United Nations Educational, Scientific and Cultural Organization],” adds Desai.

The goal is to be able to use up to 90% of reclaimed water at the site in the coming years — a strategy that also will involve the Tarragona plant installing filtration, ultrafiltration and RO treatment technologies to reuse its own wastewater more efficiently.

Sustainability Metric

Water optimization plays an important part in Dow’s overall quest for improved sustainability of its processes and products. The company has developed a sustainable chemistry index that considers how well managed resources are; it uses that metric to set goals and measure its performance (see “Sustainability Metric Spurs Efforts.”) The company already has significantly exceeded its 2015 target.

For water, Dow uses a three-step approach. The first step, reduce, focuses on fairly routine activities such as optimizing plant pipework and wastewater treatment systems, and using high efficiency cooling towers. Second is reuse, which includes the Terneuzen and Tarragona projects. Desai sees further improvements coming in this step as techniques pioneered by the food and beverage and hydraulic fracturing sectors for reusing their plant outflows become more widely accepted in the chemical industry.

The third step is renew, which brings desalination of seawater and brackish aquifers into the equation. “However, our view is that you have to pursue the first two “Rs” very, very aggressively before you move on to the third one,” he notes.

Desai also believes that future success will lie in “courageous collaboration” with organizations that might not be obvious partners for chemical companies.

One example is the Value of Water Coalition, Washington, D.C. Established in March, this group aims to increase understanding of water challenges in the U.S. and the need for major investments in infrastructure to address them. It was formed originally by water utility companies in very large U.S. cities and engineering companies that work with them.

“The industrial water user was missing from this setup… and you have to remember that, in terms of water use, the industrial sector is second only to the agricultural sector. Remember, too, that the industrial users, particularly chemicals, rely on robust and reliable municipal wastewater-treatment systems,” Desai stresses.

Initiatives such as the Value of Water Coalition will bring broader attention to water challenges. However, successfully addressing these challenges will require improvements in technology, he believes, adding that filtration and RO are very much part of the mix. He sees several critical issues. One is scale. Another is development of technologies that can treat increasingly difficult waste streams while suffering less fouling, cutting energy use and offering longer lives. Then there is technology integration. “We’ll need more integration, experimentation and willingness to use new technologies — along with an increased incorporation of green infrastructure such as [at] Dow’s Seadrift operations in Texas,” he concludes.

Strategic Effort

Water optimization efforts at Solvay, Brussels, Belgium, are part and parcel of its Solvay Way sustainability strategy.

“There are two main aims of the strategy: first, to reduce by 10% by 2020 (from a 2012 baseline) the water drawn from groundwater or drinking water networks and, more importantly, to ensure that hydraulically stressed sites have sustainable water management in place by 2020,” notes Laurent Sapet, Solvay global environmental director, Lyon, France.

A detailed water balance carried out in 2014 found that 13 sites were at risk from water scarcity. Of these, four already are making strides in demonstrating sustainable water management.

One is the Banksmeadow plant in Sydney, Australia. Here, the company has replaced potable city water with non-potable water from the nearby Orica treatment plant that handles contaminated groundwater from the Botany aquifer. The Orica plant now provides half of Bankmeadow’s water needs. The use of treated groundwater has necessitated more sophisticated control of treatment chemicals within the cooling water circuits and changes to the operation of the demineralized water unit.

Similarly at the company’s site in Monterrey, Mexico, more than 90% — 115,000 m3/y — of its needs come from a water recycling project at the local municipal wastewater treatment plant.

At Panoli, India, the focus has been on reusing the company’s own wastewater, especially as cooling water makeup and boiler feedwater. The project has involved upgrading several items of plant equipment, including the biological treatment unit, RO units, a multiple effect evaporator and a water hardness abatement unit. Thanks to these investments, the plant reuses 80% of its wastewater multiple times, while 35% of water now comes from contaminated groundwater rather than good quality surface water.

Its Vernon, Texas, plant originally relied on water supplied by the city. The manufacturing process there relies on water-intensive product washing steps. Redefining washing conditions enabled minimizing water use while still meeting product specifications. This, in combination with a successful recycling project, has cut water consumption by 20%.

The next target is to implement sustainable water management at the remaining nine plants in water stressed areas.

Sapet emphasizes that not all water optimization projects require huge commitments of time and money: “At our Baotou plant in India, we just picked the low-hanging fruit, which meant using better detection technologies to identify leaks in underground water pipes. At Vernon, we simply implemented a multi-stage washing process for a raw material which originally underwent several single-stage washings. They were all common-sense solutions that were quick to implement and didn’t require great investment.”

Solvay is looking beyond what it can do on its own. The company is involved in the EU’s Economically and Ecologically Efficient Water Management in the European Chemical Industry (E4Water) project.

E4Water aims to achieve a reduction of 20–40% in water consumption, 30–70% in wastewater production and 15–40% in energy use at its industrial case study sites.

One such site is that of Solvay’s subsidiary Solvic in Antwerp, Belgium. There are three objectives here: evaluation and implementation of an innovation plan to decrease drinking water intake to 20% from 60%; a reduction of emission load in final effluent by replacing waste generating steps or applying advanced treatment options to concentrate streams; and the transition of the demonstration unit known as the “industrial experimental garden” into a larger-scale plant where chemical companies will be encouraged to work together to develop water reuse strategies.

“As soon as new cost-effective technologies emerge from this project, they will be combined with the other chemical engineering technologies in our design guide which is used to optimize water use during plant designs and revamps. The name of the game here is to recycle at low cost,” says Sapet.

Internal Collaboration

At DuPont, interactions between teams of energy champions and environmental experts appointed at each site are helping to identify ways in which to improve the company’s environmental footprint.

Once a month, the teams meet to collaboratively solve problems, share ideas and pinpoint ways to further reduce emissions.

At the company’s Dordrecht site in the Netherlands, this strategy has helped to cut water consumption by 28% and energy use by 14% in the last nine years — reducing operating costs by over $1 million/y.

“The local energy champions have an annual target set in dollars and an evergreen list of opportunities related to utility savings or utility cost reduction. The areas focused on have to maximize the internal rate of return because they don’t have their own budget and have to compete with all other business projects,” explains Erik van Kempen, energy champion at Dordrecht.

One of the main factors in the 28% reduction in water consumption is improved cooling tower management. “Our cooling towers were the biggest user of drinking water because we are not allowed to use water from the nearby river. Following discussions with the vendors who supply our cooling tower technology, we were able to change our water treatment routine on one tower and this reduced the amount of tap water we purged. Due to this success, we implemented the same treatment on the site’s other cooling tower.”

Groundwater has become another vital resource. Normally, the plant would not be allowed to extract groundwater for cooling purposes. However, due to long-standing soil pollution in the area, DuPont received a dispensation from the local authorities to extract contaminated groundwater. “This we now treat, use and then return to the local river — again reducing our dependence on tap water,” adds van Kempen.

Advanced Technology

BP’s water optimization efforts are focused on developing new technologies, both with other vendors and in-house. For example, in December, BP Ventures invested in Saltworks Technologies, Vancouver, B.C., a specialist water treatment company that offers a number of technologies to help address and manage global water scarcity issues, either by using saline water sources instead of freshwater ones or by recycling wastewater, including produced waters from oil and gas operations.

Specifically, Saltworks develops new desalination processes that lower the cost and energy of making freshwater from saline water sources.

The investment follows successful bench and pilot scale tests between BP and Saltworks, although a BP spokesperson declined to comment on these.

In another thrust, in July of this year, the company announced the startup of the phase-3 purified terephthalic acid (PTA) plant at Zhuhai Chemical in China (Figure 2). With a design capacity of 1.25 million mt/y, it is the world’s largest single-train PTA unit, says BP. It also is the first to use the most recent version of BP’s PTA technology, which the company says boasts 75% lower water discharge than conventional technologies. (The technology also produces 65% fewer greenhouse gas emissions and 95% less solid waste, while also offering higher product yields, thus cutting demand for raw materials, claims the firm.)

BP explains the new technology reduces both the volume of freshwater feed and the volume of water that must go for wastewater treatment. Water-based streams containing small amounts of impurities that were sent for treatment in earlier generations of the technology now are more efficiently reused and recycled, resulting in reduced wastewater flow.

Ottewell2Seán Ottewell is Chemical Processing's Editor at Large. You can email him at sottewell@putman.net.