Water from a mains supply can contain bacteria. Water companies must remove harmful bacteria before it reaches homes and businesses to ensure it’s safe to drink. However, low levels of bacteria can enter domestic systems. If these bacteria multiply, they can become a problem.
A general bacteria test measures the total number of microorganisms in the water that can grow, known as the total viable count (TVC).
What is TVC in Water Testing?
‘Total Viable Count’ (TVC) is a microbiological test to estimate the number of microorganisms, like bacteria, yeast, or mould, in a water sample. It can also be called aerobic colony count. TVC results provide an idea of the contamination level and water quality.
How is Total Viable Count (TVC) Calculated in Microbiology?
Test parameters differ based on the type of sample. Samples are incubated at specific temperatures according to the environment. For instance, drinking water samples are incubated at 22˚C or 37˚C for 24 hours following BS EN ISO 6222. At 22˚C, the Total Viable Count (TVC) shows the number of live bacteria per ml of water at ambient temperature, typically harmless. At 37˚C, the TVC indicates live bacteria per ml at body temperature, with bacteria more likely to harm humans.
Cooling tower samples are incubated at 30˚C as per ACoP L8, HSG 274 Part 1. These conditions help isolate organisms that may cause infections. TVC testing is non-selective due to the broad range of organisms. This differs from testing for specific bacteria like Legionella and Pseudomonas aeruginosa, which uses selective media.
What is an Acceptable TVC?
There is no strict rule for TVC levels in drinking water (however, there are basic parameters we reference against based on years of reviewing these types of results). The guideline suggests there should be “no significant increase” from the mains supply which It is crucial to spot any irregularities and upward trends. Performing essential water management tasks should ensure regular TVC testing is recommended to understand baseline contamination levels, and then notice any significant changes.
What Does a High TVC Count in Water Mean?
A high TVC count, like 10,000 cfu per ml of water, indicates a large number of microorganisms. This suggests that biofilm contamination might be affecting the system. Microbial growth in biofilms can lower water quality and cause unpleasant tastes and odours.
Why Do We Take TVC Samples?
Businesses must ensure their water systems are safe for users and TVC testing shows water quality. High TVC can mean poor drinking water with a stale or stagnant taste or odour. Regular testing of TVC is crucial in maintaining water hygiene and understanding normal contamination levels to spot changes effectively.
Changes may signal a need for further checks and potential system issues. TVC testing checks water treatment effectiveness. High results in water coolers suggest improper cleaning, changing of filters or a need for more frequent cleaning.
What Control Measures are there to Reduce TVC?
Control measures are essential to reduce Total Viable Count (TVC) in water systems. Regular cleaning and maintenance of pipes and tanks help prevent microbial growth along with chlorinations or sterilisations where appropriate. Properly maintaining water temperatures also plays a crucial role. Keeping water systems below 20˚C or above 65˚C limits the survival of harmful bacteria. Installing effective filtration systems will also help remove microorganisms.
Monitoring water quality frequently ensures any issues are spotted early. When isolating specific organisms during testing, the correct choice of growth media plays a crucial role in accurately assessing microbial presence. Training staff on safe water practices is vital for maintaining water safety. Proper procedures for handling and storing water can also help reduce contamination risks. For reliable water testing services, please contact Comfort Service Group to ensure the safety and quality of your water supply.
What’s the Difference Between TVC and TBC?
TVC estimates the number of live cells that can grow into distinct colonies. TBC (total bacteria count) covers all cells, both dead and alive.
FAQs
Who Should Measure TVC?
TVC testing is important for both potable water and non-potable water, such as water used in industries such as manufacturing, food and beverage, healthcare, pharmaceuticals and office facilities. Routine water testing is crucial in treating drinking and industrial water. It helps monitor contaminants, corrosion and scale, indicating when a new treatment approach is needed. Testing for TVC is essential as it provides a clear indication of water quality and contamination levels.
Are there any regulations governing TVC levels in water?
Yes, there are guidelines that govern total viable count (TVC) levels in water in the UK. The Drinking Water Inspectorate (DWI) oversees water quality regulations. While there is no specific legal limit for TVC in drinking water, guidelines recommend that levels should not significantly exceed those found in mains supplies.
Water suppliers must regularly test their systems to ensure they meet safety standards. Any notable increase in TVC should prompt further investigation to protect public health. Compliance with these regulations helps ensure safe drinking water for everyone.
What types of microorganisms are typically counted in TVC assessments?
Total viable count (TVC) estimates the number of microorganisms present in a water sample. These include bacterial, yeast, or mould species. TVC is also known as aerobic colony count.
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