Cooling Tower at Semiconductor Manufacturing Facility
New alternative to organic biocides improves microbial control in ammonia containing cooling loop
Major Semiconductor Manufacturer
EQUIPMENT & CHEMISTRY
MIOX’s Mixed Oxidant Solution (MOS)
Sodium Hypochlorite + Bromine
A major semiconductor manufacturer wanted to increase facility safety and meet chemical storage compliance limitations by reducing hazardous chemicals stored on site for cooling water treatment.
The manufacturing facility utilizes ammonia laden waste water from the tooling operations as make up water to the cooling towers. The ammonia in the waste water is estimated at 2-4 ppm. Utilizing the waste water as cooling tower make up is beneficial for decreasing wastewater discharge and fresh water consumption, but it also presents a substantial challenge in tailoring an appropriate biocidal treatment regimen for microbiological control.
Ammonia, when present in cooling system waters, is often thought to interfere with the microbial inactivation efficacy of oxidizing biocides. Operators using ammonia-containing waters for cooling systems often employ a mixture of oxidizing and non-oxidizing biocides due to this preconception. MIOX’s MOS, however, can react with the ammonia present in the water, resulting in the production of a chloramine and peroxide that is highly effectively at controlling the microbial populations in cooling system waters.
The customer commissioned a MIOX Vault M60 for the 11-cell cooling towers at the semiconductor manufacturer facility. The MIOX MOS system replaced the previous biocidal treatment regime of continuously dosed sodium hypochlorite and bromine with slug dosed isothiazoline and glutaraldehyde.
Validation of the efficacy of MOS for the treatment of the water was accomplished by conducting an extensive study of the outcomes of the biocidal treatment during the initial weeks of the use of the system at the site. The study was conducted from January to July of 2014, with the first 11 weeks of the study using the previously existing biocidal treatment regimen and the following 18 weeks utilizing only MOS as the biocide.
- $240K+/YR COST SAVINGS
The prior treatment regime cost the plant $265K/yr. The MIOX operational cost is $25k/yr which includes power, salt and MIOX service. The customer was able to reduce operational cost by $240K per year.
- RETURN ON INVESTMENT IN LESS THAN 1 YEAR
The plant was easily able to achieve return on investment in less than one (1) year with the MIOX equipment.
- PLANT SAFETY IMPROVEMENT
As a result of the installation, two large 5,000 gallon chemical tanks were removed from the operations room; helping the customer meet its hazardous chemicals storage compliance. MIOX’s MOS solution has a concentration less than 0.5% and as a result does not require any PPE or reporting in case of spill.
- 60% REDUCTION IN HALOGEN DOSE
Even under the high pH environment and in the presence of ammonia, MOS was shown to be as effective as the prior chlorine/bromine-based biocide regimen even though no additional biocides were used. And, the effective dose rate of MOS is about 60% lower than the chlorine/ bromine biocide.
- MAINTAINED BACTERIAL CONTROL
Results show that MOS, even when applied at a substantially lower effective dosage, was able to control microbial populations in the water.
MIOX’S MOS ADVANTAGE
Mixed Oxidant Solution (MOS) generated on-site from sodium chloride (salt) provides an attractive solution to concentrated biocides. MOS is generated at the site by passing a 3% salt brine solution through an electrolytic cell where the brine solution is converted to a powerful oxidant consisting of sodium hypochlorite (bleach) and hydrogen peroxide. MOS is generated at a free available chlorine (FAC) concentration of 0.5 % and a pH of 9.0.