The length of time the organism is exposed to light determines how effective it will be. Other things like the wavelength and the intensity also play an essential part in getting the results. The results can also be affected by the presence of some particles that can protect the microorganisms from the UV light. If you want to obtain more accurate results, you have to pass the water or air several times through the UV in order to detect as many microorganisms by the UV light as possible. Many times sterilization is quoted as being achievable. Most businesses know that it is not easy to achieve such results as sterilization and therefore opt to use the word disinfection. Other companies will use the term 99% efficient. It is possible to repair damaged DN by the use of UV light. The process is referred to as light and dark repair. In this case the effectiveness will depend on the line of sight exposure to the UV light. With soil surrounding the bulb the effectiveness will be significantly affected. That will mean that the bulbs have to be cleaned periodically if the results will be more accurate.
To ensure that the effectiveness is maintained, the bulbs will also have to be changed from time to time. The lifetime of any germicidal bulbs depends on the design. They also rely on the various materials that are used. With increased airflow the lamp is cooled, and when that continues it affects the output of the UV. Therefore it means that it is important to shield the lamps flow airflow so that cooling does not take effect because if it does it will lower the effectiveness of the UV. If you want to increase the performance of the UV, you can use reflection. The results can be highly enhanced by the use of aluminum which is highly reflective. For you be able to measure the effectiveness of the UV in water disinfection, you need to compute the UV dose.
If you have to get accurate results, care must be exercised to make sure there is no interference with the process otherwise that will alter the results entirely. It is dangerous to get results that are far from the truth because that will mean the decision that are made are not correct and they will not have the intended effect. The products thus produced may not be trusted because they are based on processes that are already interfered with. That is why regulatory bodies need to ensure everything goes in the right way.