How to determine the bactericidal efficacy of biocides in circulating water

It can be determined by analyzing the bacterial count before and after addition: handshake

I think it is possible to judge water quality changes by reducing pollutant discharge, but of course the most accurate method is microbial analysis.

If the circulating water system uses chlorine for continuous sterilization, it is also possible to determine this by comparing the amount of chlorine added before and after the addition of the sterilant :)

Thank you all. Who knows what methods can be used for microbial analysis? (A rough estimate will suffice.)

I don’t understand. If you’re not sure whether the bacteria levels are excessive, why add a bactericide? ! Bacteria in circulating water can be analyzed selectively, mainly for heterotrophic bacteria and nitrifying bacteria, as well as total bacteria ；

Hehe, what the people above mentioned – such as \"judging by observing changes in water quality by reducing the amount of waste discharged\" or \"if chlorine is used continuously for disinfection in that circulating water system, it’s possible to determine the effect by comparing the chlorine dosage before and after adding the disinfectant\" – none of these methods allow for an accurate assessment of the effect of the disinfectant once it has been added. Comparing the chlorine dosages before and after is merely a way of calculating the amount of chemical used; the correct approach is to test the number of heterotrophic bacteria in the circulating water after adding the disinfectant, and then compare this figure with that before addition, so as to determine the effectiveness of the disinfectant.

It would be best to conduct a bacterial analysis, but it’s also possible to make judgments by visually checking for nitrifying bacteria and nitrite-oxidizing bacteria!

The presence of bacteria causes acidic corrosion, which can be quantitatively observed by suspending a scraper in water； Algae can be qualitatively identified using a cold plate. Observe

1. Direct observation of water quality changes 2. By counting bacterial numbers 3. Measuring residual chlorine

It would be best to conduct an analysis. I think 3M has a type of membrane that is useful for analyzing bacteria; it’s quite convenient. Of course, you can also ask your water treatment company to carry out the analysis for you :)

If the circulating water system uses chlorine for continuous sterilization, it is also possible to make a preliminary assessment based on the amount of residual chlorine; of course, the most accurate method is microbial analysis

For the original poster’s reference: our company uses ordinary sodium hypochlorite for sterilizing circulating water. To test the bactericidal effect, theoretically and based on experimental analysis, it is possible to examine bacteria, but many companies’ laboratories are not capable of carrying out such tests. If a biocide containing chlorine is added, it is possible to determine whether the dosage of the biocide is appropriate by testing the residual chlorine level in the circulating water at the peak value after addition. Residual chlorine can generally be measured in the laboratory; a residual chlorine level of 0.2–0.5 ppm at the peak is sufficient, with a level exceeding 1 ppm generally not being allowed.   If the poster doesn’t want to carry out these specific experimental data. There is another visual method for assessment, though it is relatively rough; it involves observing the concrete pillars near the edge of the pool. If the disinfection effect of the circulating water is poor, green moss-like plants will cover the surface of these pillars, especially those located in areas where the water flow is slower. The worse the disinfection effect, the more extensive and thicker this green coverage will be. If there’s none at all, perhaps the dosage of the bactericide added can be reduced further.   In addition, alongside the addition of biocides, a stripping dispersant should also be added to the circulating water. The stripping action involves removing dead bacteria, algae, and other such substances from surfaces where they are attached (such as pipes and equipment surfaces), while the dispersant helps prevent these substances from re-depositing on those surfaces (this is just one of the functions of the dispersant). Eventually, a portion of these substances can be removed through wastewater discharge.

In closed-loop cooling water systems, microorganisms are generally referred to in the industry as bacteria and algae. Bacteria are classified into heterotrophs, sulfate-reducing bacteria, nitrifying bacteria, iron-oxidizing bacteria, fungi, etc., while algae are classified into cyanobacteria, green algae, diatoms, dinoflagellates, etc. Their respective properties and hazards will not be discussed here! When biocides and algaecides are added to circulating water, the evaluation of their effectiveness in killing microorganisms and algae is generally carried out through visual inspection and biological analysis. Intuitive method: The sterilization effect is evaluated using an intuitive approach, primarily by observing visually the changes in algae and sludge in the exposed parts of the circulating water system. The main hazard of fungi and algae is the production of secretions; these secretions, combined with sediment and other substances, can lead to the formation of sludge! Algae also tend to attach to the surfaces of cooling towers or heat exchangers along with sludge. Before adding a bactericide, it is necessary to observe the color of the algae and the thickness of the sludge. (Generally, the algae and sludge form layers; the color of the algae is green or blue-green, while the color of the sludge can vary depending on the treatment process and the source of the water. However, it is important to understand its physical properties before applying the bactericide.) After an effective bactericide is added, the color and thickness (number of layers) of the algae will change as the bactericide circulates in the water. Initially, in the circulation, the concentration of the chemical was low, and there were no noticeable changes in the color of the bacteria and algae. As the uniformity of the chemical increased and its concentration rose, its duration of presence in water lengthened, and obvious changes began to appear in the bacteria and algae. However, as the concentration of the chemical decreased again, its bactericidal effect also came to an end. The overall sterilization trend follows a parabolic pattern, but the timing of the peak and the resulting effect (color change) are determined by the type and concentration of the chemical used. After sterilization, the attached slime algae begin to detach from their attachments, and eventually, under external forces such as water flow, they end up in the recirculating water tank, causing the turbidity of the recirculating water to increase gradually. Methods of identification: 1. The peeling effect of the clay – whether it peels off and enters the circulating water – depends on individual judgment. 2. The color of the fungi and algae changes from green or blue-green to yellow, then to brown, and finally to black; it eventually peels off along with the sludge. 3. Turbidity of the circulating water: During the sterilization process, turbidity can be monitored based on specific conditions. Generally, at the start of sterilization, the turbidity is low; as the sterilization time increases and the concentration of the chemical used rises, the turbidity begins to increase. When the trend in turbidity changes becomes less noticeable, it indicates that the effectiveness of the chemical has reached its peak. Although the turbidity may continue to rise, the peak has already been passed, and after operating for a further period of time, it is possible to discharge the water and replenish it with fresh water. 4. Determination of the amount of clay! Biological testing: Biological methods are used to detect other bacteria in water. The main method is the plate counting method! ((Due to time constraints, the specific testing methods will be provided later)) Technical exchange QQ number: 155338549 This post was last edited by ayan80120 on 2008-3-11 13:15]

I disagree! This post was last edited by dsj2008 on 2008-4-16 20:40.]

Could the friend on the 15th floor please analyze it? That way we can also learn*learn*!

Technical exchange QQ: 155338549

  I don’t know what level you’re at elsewhere, but just by hearing you say that, I can tell you have no basic sense of character! I know 2 of the people mentioned above; the others are all experts in circulating water treatment, with extensive experience in this field and plenty of on-site experience. I don’t know what kind of projects you’ve worked on or what on-site experience you have; feel free to share it so everyone can take a look!

It’s definitely necessary to test for bacteria, but it’s not essential to do tests on all of them; it’s sufficient to test only heterotrophic bacteria. This can be done using biochemical culture methods, and as long as the necessary equipment is available, the experiment is relatively simple.

Generally, after adding the fungicide, the water becomes turbid, which indicates that it is effective. The testing method involves using a microscope to clearly count the number of bacteria. After adding the chemical, the water is drained, and then more water is added.

Fungicides are divided into oxidizing and non-oxidizing types. Oxidizing fungicides are added on a regular basis, and their effectiveness can be determined by the residual chlorine level. Non-oxidizing fungicides are added in pulses, and their effectiveness is assessed based on the amount of sludge, the color of bacteria and algae on the walls of the tanks, as well as the turbidity of the water.