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.
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.