Wastewater reuse in cooling towers brings success

4 min read
An external view of Dow reverse osmosis membranes modules.
An external view of Dow reverse osmosis membranes modules.

Dow Water & Process Solutions, a business unit of The Dow Chemical Company (DOW), is participating in one of ten European Commission-funded projects that aim to stimulate innovation and improve cohesion within the evolving European water reuse sector. The company is a major player in the Demoware project located at the Camp Tarragona petrochemical complex, which specifically looks to demonstrate how water stress in a European region can be mitigated by fostering industrial water reuse, with emphasis on cooling towers. The project, which will last for three years and is due to end in December 2016, was presented in November at the 5th International Symposium RE-WATER Braunschweig, Germany. It is focused on novel technologies for wastewater reuse and involves, among others, the treatment of wastewater from the Spanish cities of Salou, Tarragona and Vilaseca in the Camp de Tarragona Advanced Water Reclamation Plant (CTAWRP), operated by Veolia and AITASA (the government owned water supplier to the petrochemical complex).

Two engineers at the Global Water Technology Center in Tarragona (Spain).

Dow Water & Process Solutions’ FILMTEC reverse osmosis elements were selected to be installed in the reclamation plant following the pre-treatment scheme from Veolia, consisting of namely Actiflo. The treated water is then redirected to various plants in the complex for use in their industrial processes, instead of being discharged into the Mediterranean Sea as it had been previously. Alexander Lane, EMEA commercial director, Dow Water & Process Solutions, says: “With wastewater reuse at the forefront of EU members’ sustainable policies, this project constitutes an important milestone to improve the efficiency of the European industrial sector, while also improving municipal processes. We are proud to be part of a regional initiative and contribute to its success.”

Freeing up fresh water resources

As companies in the Camp Tarragona petrochemical complex need a constant supply of fresh, clean water, Dow Water & Process Solutions’ main goal with this project was to develop a system to treat wastewater to a high enough quality to be used in cooling towers. These companies previously used 100% fresh water from the Ebro River to feed their heat rejection devices, placing a strain on the Ebro River and the surrounding municipalities, one of the most water stressed areas in Spain. The project helps free up these fresh water resources and helps to bring an increase in water availability for other uses such as municipal, tourism growth projects or agriculture. As a result of the project, the make-up water used in the cooling towers at Dow Chemical’s petrochemical production complex (Ethylene Cracker) now consists of 40% reclaimed water, equivalent to a flow of 160 m3/h of reused wastewater from the reclamation plant. It is expected that by the end of 2016 this will reach a figure of 90%, blended with only 10% from the Ebro River. Prior to the use of treated wastewater, the Dow cracker cooling tower ran solely on Ebro river water at 4 cycles. Due to the higher quality of the recycled water the cooling tower can be operated at seven cycles of concentration in summer when ambient temperatures allow high evaporation rates. The increase in both the amount of reclaimed wastewater as make-up cooling tower feed and number of cycles of concentration, will allow the system to operate in an almost closed loop mode.

Dow reverse osmosis treatments

A combination of Dow Filmtec Brackish Water Extra Fouling Resistance (BWXFR) and Brackish Water Low Energy (LE) reverse osmosis elements were selected to be installed in the double pass plant of the CTAWRP. The Extra Fouling Resistance membrane elements were used in the first pass and have been designed to deliver the highest quality permeate water while offering an excellent robustness due to the widest cleaning pH range (1 – 13) and chemical tolerance. The design of the second pass with Low Energy membrane elements helped the plant to deliver higher salt rejection at 33% lower pressure, as well as excellent silica, boron, nitrate, isopropyl alcohol and ammonium rejection.

The XFR-LE combination offers plant an optimum balance between high fouling resistance, high salt rejection and low energy consumption. For these reasons, the Dow Filmtec reverse osmosis elements were able to help increase the efficiency of the system and help reduce the operational costs following sustainable methods.

Interior of Dow reverse osmosis membranes.

An additional goal of the project is to optimize the performance of the CTAWRP that is currently producing 2.3 hm3 of treated water a year. At its maximum capacity, and following increasing demand requirements and rights conceded by the Government, the plant will be able to generate 6 hm3 of reclaimed water per year to be used by the chemical companies at the complex. One of the key pieces in this project is the Dow Water & Process Solutions Global Water Technology Center in Tarragona, one of the most relevant R&D facilities dedicated to water technologies in the world. It develops the next generation of water purification and separation technologies, products and applications improving quality of desalinated water, minimizing costs and energy consumption, extending the useful life of membranes and increasing the materials’ efficiency.

An overhead view inside the Global Water Technology Center in Tarragona (Spain).

Designed to function as a laboratory but also as an operational plant, the Center allows high-class testing and optimization of water treatment and reuse applications in a ‘real environment’. In many cases, this has enabled a reduction of the time from idea to launch by half – further highlighting the reliability and sustainability of Dow Water & Process Solutions’ products. A strong reason for selecting Tarragona as the site for this unique facility was its location. This area has an abundant variety of natural water resources, including sea, river and sewage water, which provide researchers at the site with the ‘aquatic building blocks’ to provide important innovations in clean water.

Demoware Consortium

The project coordinated by Dow Water & Process Solutions has received funding from the European Union’s Seventh Framework Program for research, technological development and demonstration under grant agreement no 619040 and it is the only one dedicated to explore wastewater for industrial uses within Demoware. In total, 27 companies around Europe are involved in this initiative as part of the Horizon 2020 framework, developed by the European Commission to decrease water usage through the continent. 

FILMTEC™ is a trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow and ActiFlo™ is a trademark of Veolia.