MIOX Corporation - Johnson Matthey`s Water Technologies

Biofilm control strategies in industrial processing waters


Bacterial biofilms cause a number of serious problems for industrial fluid processing operations. Mechanical blockages, impedance of heat transfer processes and microbially induced corrosion result in billions of dollars of losses each year. In engineered systems, such as cooling water systems, food processing, and other industrial applications possible risk to public health and product spoilage and souring are also consequences of biofilm‐mediated contamination. This brief article addresses aspects of biofilm control strategies for industrial processes and introduces a promising disinfectant via case studies.

Overview of Biofilms
Biofilms are aggregates of predominately bacterial cells attached to and growing on a surface.i These biofilms are found in aqueous environments and are often resistant to disinfection. A biofilm forms when bacteria begin to excrete a slimy, sticky substance that allows them to adhere to surfaces. An additional structural feature, called the extracellular polymeric substance (EPS), is what is thought to provide the biofilm with increased resistance to antimicrobial agents and biocides. The biofilm mass often varies with location within a given contaminated system, and is typically composed of many species of microorganisms, including bacteria, fungi, algae, and protozoa. Biofilm is difficult to remove once initial adhesion occurs.ii Even small numbers of surviving organisms can regrow, damaging products or putting a companyfs reputation at risk in the event of a product recall due to negative health outcomes. Biofilms can also shelter disease]causing microorganisms, such as Legionella, Listeria, and temperature resistant bacterial spores, which are normally inactivated readily in their planktonic, or single cell form.

A safe, user]friendly, and viable method for controlling biofilms would have a significant impact on any industry that must control bacterial populations. These include water and wastewater distribution systems, cooling towers, swimming pools and remote areas where access to operations is difficult. Improved biofilm control technologies could also minimize system sizing or the use of high temperature or high energy processing steps, both of which provide the added benefit of decreasing costs.

Biofilm Removal Strategies
There are many strategies and chemical regimens for controlling biofilms. For example, many processing facilities use flooded clean‐in‐place systems. Flooded systems involve completely filling all the pipes exposed to product with water, chlorine, biocide, caustic or other chemical for a prescribed amount of time according to application protocol.iii Other applications use continuous biocide injection procedures to prevent biofilm growth.

MIOX . A Novel Biofilm Control Solution
Many biocide treatment regimes exist, including a multitude of combinations of cleaning (hot water or hot caustic, such as sodium hydroxide) and disinfection (quats, chlorine, proprietary biocides) chemicals. An alternative to these variable regimes is MIOXfs Mixed Oxidant Solution (MOS), a cost]effective, simple cleaning and disinfection solution for industrial process water applications that has the potential to also provide enhancements to biofilm control strategies. MOS, a proprietary blend of hypochlorite and other oxidants, has been generated on]site by MIOX Corporation since 1994 through the use of salt, water, and an electrolytic cell. The chlorine]based product of electrolysis has clearly exhibited the ability to remove biofilm in several different applications, a behavior unlike traditional chlorination technologies. Evidence for the biofilm control attributes of MOS includes third party research, visual documentation from municipal and industrial operators, and a number of improvements in water quality that are understood to result from removal of biofilms.

Case Study: KOA Kampground Facilities
Biofilm removal by MOS was initially observed in New Mexico in 1995, and later reported by Montana State University during a field study conducted at a KOA Kampground in Great Falls, Montana.iv The campsite has a small potable water supply, as well as showers and a swimming pool. The site previously used powdered sodium hypochlorite and experienced frequent positive coliform hits, even with free chlorine slug dosage levels as high as 1,000 ppm. The positive counts in the presence of free chlorine were indicative of biofilm contamination, which was also evidenced by a black biofilm slime that formed in the showers. The distribution system contained accumulated biofouling that required flushing from the system whenever a power outage occurred. The existing cartridge filters also required cleaning every 2]3 days due to the heavy accumulation of biofilm.

As a potential solution to this problem, MIOX installed a MOS generator at this site to replace the hypochlorite that had been used previously. Since conversion to MOS, the KOA Kampground has not experienced a non]compliance coliform event. The black slime in the showers disappeared within a few weeks after the conversion. Initially, biofilm visibly sloughed from the pipelines. The water eventually ran clear, indicating that the system had reached a stabilization point. Camp operators reported that the filters are cleaned every 3]4 weeks after converting to MOS, rather than every few days. Whenever power outages occur now, no discoloration of the water occurs, indicating that the biofilm does not regrow, even when disinfection is temporarily interrupted. The MOS system was responsible for elimination of biofouling at the Great Falls KOA Kampground, ultimately resulting in safer drinking water with no bacterial contamination, ease of maintenance with no flushing required, and greatly extended filter runs.

Case Study: Hot Springs and Swimming Pool Facilities
Hot springs are very popular in several cultures. However, the warm aqueous environment provides an ideal breeding ground for bacteria, and a number of the sites suffer from positive coliform counts and biofouling. At one such facility in 2002, dosing at 1.5 mg/L of free available chlorine (FAC) with sodium hypochlorite barely maintained a 0.2 mg/L residual. Coliforms and Legionella were frequently detected. After establishing a baseline borescope camera image (see before picture), the interior of the pipes was subsequently videotaped at 6 and 22 days after treatment with MOS began. Upon conversion, sloughing was immediately apparent. In the feed water pipe, substantial removal was evident after 6 days (photo not shown), and after 22 days (see after image above), biofilm removal appears to be complete. Bacterial monitoring and residual chlorine measurement provides quantitative data to complement the compelling borescope images. After conversion to MOS and removal of biofilm, the chlorine dosage was reduced by 60% to only 0.6 mg/L, while the residual more than doubled to 0.4 mg/L. Coliforms and Legionella were not detected.

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