A biocide is chemical treatment designed to control microbial growth. To minimize any risks that are associated with microbial growth, such as heat loss, corrosion under deposit, and health hazards it is essential to establish the correct biocidal treatment strategy.
In our previous blog, we discussed the top factors to be considered when choosing the right biocide. In this blog we focus on picking the appropriate closed circuit biocides.
There are many factors which can negatively affect levels of microbial activity in closed circuit systems. They should be considered.
1. Pre-commission cleaning
When a new system is installed, it is important to ensure that the system is in good condition and that the cleaning procedure (as as described in BSRIA BGR29/2020) contains a suitable biocide for use in a biocidal flushing procedure in the event that this is needed.
2. Concentration
It is vital to ensure that the closed-circuit biocide or inhibitor are in the system at the right concentration starting by conducting a pressure test. This is also carried out on a regular basis.
3. Nitrite-based formulation
A cost-effective non-toxic, neutral nitrite-based formula that passesivates quickly and is suitable for multi-metal systems that contain aluminum like Polyhib LC may be the best choice. But, other products are available, so please contact our technical department to get guidance on the most appropriate product to meet this need. The right biocide should be used if Polyhib-LC is used to keep an entire system while it is filled.
4. Testing of closed system chemistry, and monitoring of microbiological health
Testing the chemistry of closed systems is an integral component of any maintenance plan. Monitoring of microbiological activity in the system is also a vital role. If there are high levels of bacteria, shock doses with an appropriate biocide is required to be done in order to control them.
5. Testing for biocide sensitivity
As time passes, it is possible that resistance may develop to a specific biocide, and a modification of the biocide dosage regimen could be necessary. For certain systems that have issues it is possible to carry out an analysis of biocide sensitivity to determine which one will be most effective. Customers can submit an item for analysis of biocide sensitivity to our lab on-site and we will carry out the analysis on behalf of you. For more details and pricing we invite you to contact us.
6. Biodispersants
In the event of high levels of bacterial growth and a build-up of biofilm is evident, the use of an effective biocide with a biodispersant compatible such as BV167 or BV1455 may be needed. It is important to consider the location where this biofilm is likely to be disposed of after it has been removed from metal surfaces. The strainers and filters which are scattered across a system will need to be cleaned and inspected frequently. If the system is comprised of smaller bore pipework but filtering equipment there is a possibility of blockages. A biodispersant may not be appropriate for all systems.
7. Temperature
A biocide is not usually required if the temperature in the fully circulated LPHW (Low Pressure hot water) systems is maintained over 60°C. If such a system is in seasonal use, it is recommended that a biocide is added and allowed to circulate through the system prior to the time it is switched off. BSRIA BG 50 recommends a minimum time for circulation in heating and cooling circuits of 1 hour per day, even in seasonally utilized systems.
8. Glycol
To stop the growth of bacteria in chiller systems that contain glycol, it is essential to maintain a concentration of 25 percent. This level of glycol is biostatic i.e. It inhibits the development and growth of bacteria. In the lower range glycol acts as a nutrient to bacteria.
It is crucial to remember that all biocidal substances must be handled with care, and workers must wear proper personal protection equipment (PPE) always. The Safety Data Sheet (SDS) for each biocide needs to be consulted before use.
