Biocide is a chemical solution which effectively halts the growth of microbial organisms. To eliminate any risks associated with microbial growth, such as heat loss, corrosion of the under deposit and health risks, it is important to establish the correct biocidal treatment program.

In our previous blog, we provided the most significant factors to consider when choosing a oxidizing biocides. This blog post is focused on identifying the most effective closed-circuit biocides.

There are many factors that can adversely impact the microbial levels in closed-circuit systems. They should be considered.

1. Cleaning prior to commissioning

It is crucial to ensure the purity of the new system and to ensure that the use of the appropriate biocide for pre-commissioning cleaning (as per BSRIA the BG29/2020) is performed.

2. Concentration

It is crucial to ensure that the closed circuit biocide or inhibitors are present in the proper concentration. This can be verified by conducting a pressure test. This is also done on an ongoing basis.

3. Nitrite-based formulation

A low-cost formula that is neutral and nitrite-based, which passesivates quickly and is suitable to multi-metal systems with aluminum such as Polyhib LC could be a good choice. There are other products available. Please contact our technical department to determine the most suitable product. A suitable biocide must be used if Polyhib-LC is used to hold an entire system while it is filled.

4. Closing system chemistry testing and monitoring of microbiological activity

Closed system chemistry testing is an integral part of any maintenance program. Microbiological monitoring of the system also plays crucial roles. In response to high levels of bacteria, shock dosing with an appropriate Biocide chemicals is to be carried out to manage them.

5. Biocide sensitivity analysis

Over time, it is possible that resistance may develop to a specific biocide, and a change of biocide dosage may be required. It could be necessary for certain systems to undergo a biocide sensitivity analysis to determine the most effective biocide. Our on-site laboratory can accept samples for analysis of the biocide's sensitivity. We will then conduct the analysis on behalf of our customers. Contact us for more information and prices for this test service.

6. Biodispersants

If there are high levels of bacteria and biofilm build-up is observed, the administration of an effective biocide with a biodispersant that is compatible, like BV167 or BV1455 may be needed. It is essential to take into consideration the place where the biofilm is expected to be disposed of after it has been removed from metal surfaces. Filters and strainers that are scattered throughout a system must be cleaned and checked regularly. If the system has small bore pipework and no strainers or filters, blockages may occur. Biodispersants are not suitable for all systems.

7. Temperature

A biocide is not usually required if the temperature in fully circulated LPHW (Low Pressure Hot Water) systems remains constant at or at or above 60°C. Biocides should be added to any system which is used to cool and heat. BSRIA BG 50 recommends a minimum of an hour of circulation for cooling and heating circuits, as well as for systems that are seasonal.

8. Glycol

To prevent bacteria growth in chiller systems that contain glycol, it is necessary to ensure that the glycol concentration is at least 25 percent. This level of glycol is biostatic, i.e. it blocks the growth and development of bacteria. At lower levels, glycol can act as a nutrient that bacteria require.

Important to remember that biocidal products must be handled with caution and that all workers must use the appropriate Personal Protective Equipment (PPE). Before making use of any biocide, it is essential to read the Safety Data Sheet (SDS).