Regarding online biotoxicity meters, the broad biological indicators also include the biotoxicity of water, specifically using a certain organism as an experimental method to test its response to a specific water body to measure the comprehensive toxicity of water. Due to the wide variety and large quantity of toxic substances in water, it is almost impossible to analyze and exhaust these substances through physical or chemical means; Moreover, even if the content and toxicity of these substances in water are known, they will still affect the toxicity of water due to various interaction modes such as synergy, antagonism, addition, and independence, making it impossible to determine the final toxicity of water through physical and chemical methods. At this point, it is necessary to use organisms to directly evaluate the comprehensive toxicity of water.
The main organisms used for toxicity testing include luminescent bacteria, fish, fleas, algae, nitrifying bacteria, etc. The application of microbial fuel cells (MFCs) in toxicity testing has also been reported. At present, online toxicity analysis instruments using the above-mentioned organisms have mature products and market applications.
Among them, the luminescent bacteria method for measuring biological toxicity analysis is a very mature method, and there are laboratory measurement standard methods in both the International Organization for Standardization (ISO) and China. The standard codes and names are: ISO11348-3：2007 《Water quality — Determination of the inhibitory effect of water samples on the light emission of Vibrio fischeri (Luminescent bacteria test) — Part 3: Method using freeze-dried bacteria》; And GB/T15441-1995 "Test for Acute Toxicity of Water Quality - Luminescent Bacteria Method", the specific method is:; By utilizing certain self luminescent bacteria, such as Vibrio cholerae, Vibrio cholerae, and Vibrio fischeri, when encountering toxic substances, the bacteria will die, resulting in a decrease in luminescence intensity. The relative luminescence of these bacteria is significantly negatively correlated with the concentration of toxic components in the water sample (P ≤ 0.05). Therefore, by using a certain amount of luminescent bacteria as test reagents to measure their relative luminescence in specific water bodies, the toxicity level of the water sample can be characterized.
The existing luminescent bacteria method online biotoxicity analyzer automatically controls the entire process from water sample collection, transportation, reagent addition to result calculation through the above laboratory analysis methods and steps, thereby achieving real-time online monitoring of the comprehensive biotoxicity of the tested water sample. At present, there are two main injection methods for online biotoxicity analyzers using luminescent bacteria. One is the batch injection method commonly used in laboratory analyzers, which involves one injection and completing one analysis process before introducing the next water sample. As this instrument analyzes discontinuous water samples, it may lose some of the true data of the water sample when there is a sudden change in the water body. Another method is continuous injection, where water samples are continuously mixed with luminescent bacterial reagents in the reactor, and the instrument continuously detects changes in luminescence intensity. This injection method ensures that the online biotoxicity analyzer analyzes continuous water samples, which can more timely and continuously reflect changes in water toxicity compared to batch injection.
In addition, turbidity can also affect the disinfection effect of water: under the same water quality conditions, the lower the turbidity, the better the disinfection effect. More importantly, due to the complexity, large errors, and poor timeliness of microbial (especially "two worms") detection, it is difficult to timely and accurately characterize the removal effect of water purification processes on microorganisms. Using turbidity as a substitute indicator for microorganisms has the advantages of simple, fast, and accurate detection methods, which can facilitate the monitoring of the removal effect of microorganisms in water purification processes, evaluate the operation status of processes, and optimize and adjust process operating parameters in a timely manner.
