Cooling Water Treatment Provides Sound Results

Teaming ultrasonics with corrosion inhibitors offers environmental and economic benefits.

By Olaf Pohlmann, Ashland Hercules Water Technologies

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Manufacturing sites should strive to obtain maximum benefit from water they use. Getting the most from this water usually requires a treatment system — which incurs costs and affects the facility's environmental impact.

A two-year collaboration between Ashland Hercules Water Technologies (AHWT) and BASF Nederland B.V. has shown that using a combination of ultrasonic microbiological control and corrosion inhibitors can dramatically reduce total cost of operations and enhance environmental performance.

BASF Nederland decided to assess cooling water treatment in 2007 at its resin production plant in Nijehaske. The 150-m³ half-open cooling water circuit there provides indirect cooling of chillers and direct process cooling.

The evaluation revealed the need for a new dosing and storage system for chemical treatment. Cost to fulfill all legal requirements for a new system of three 1,000-L. chemical storage containers, including frost protection and a heater as well as new dosing and measurement equipment, would have totaled around €25,000 ($33,225).

Realizing that the European Union's Integrated Pollution Prevention and Control (IPPC) directive soon would be adopted (codified January 15, 2008), the company wanted the best available technology (BAT).

Key Considerations
BASF used nine criteria to review available water-treatment programs.
  1. emission to surface water;
  2. prevention of substances' leaks from the production process;
  3. energy consumption;
  4. potential leakage of cooling water additives;
  5. storage of the additives;
  6. application of alternative (non-chemical) cooling-water treatment;
  7. selection of cooling water additives;
  8. optimization of additives' application; and
  9. reduction of water consumption
The overriding objective was to evaluate a program's environmental performance and its potential to improve the plant's environmental footprint.

BASF followed the guidelines in the IPPC document for reduction of emissions of chemical substances to water. In line with the BAT approach, the company decided to reduce emissions to the aquatic environment by:
  • replacing the present chemical storage and dosing installation;
  • upgrading the dosing and control equipment for cooling water treatment;
  • switching microbiological treatment of cooling water from bleach dosage to an ultrasonic system; and
  • changing the present corrosion inhibitor to an environmentally friendly one that doesn't need sulfuric acid for pH adjustment.

BASF, of course, also considered cost in evaluating an effective water-treatment program.

The company determined that Ashland's Sonoxide ultrasonic water-treatment system was an essential part of an optimal overall program. "We looked into the best available treatment technology for our cooling water system and the benefits of Ashland's program are clear and simple — it just works," says Eduard de Baat, senior process engineer, BASF.

Engineers from BASF and AHWT worked together to replace the dosing and storage systems for cooling water chemicals and install a Sonoxide B25 system together with an Ashland Onguard E controller in combination with a corrosion rack.

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