Improper setting or disposal of over-standard retained samples leads to over-standard data that cannot be verified.
When the water quality analysis measurement data exceeds the standard, is it a problem with the discharge or the monitoring equipment? Often, it is necessary for the water automatic sampler to collect relevant water samples after the monitoring data exceeds the standard. Verifying the water samples is an important method to determine the problem.
In practical applications, the water sampler is not associated with the measurement data of the analyzer, and there are many problems where it is impossible to retain samples that exceed the standard. At the same time, the unreasonable setting of sampling and sample supply methods can easily lead to the situation where the retained samples are not actual samples. For example, the water sampler does not have active sample supply, and the water quality analyzer draws samples from the sampling bucket and has a long pipeline, resulting in the lag of monitoring data. Or when the water quality analyzer has a pretreatment unit and the sample in the pretreatment unit cannot be emptied, the water sample replacement is incomplete, resulting in sample deterioration or data lag, and the retained sample is not the actual sample.
To address the issue of inconsistency between the over-standard retained samples and the measured data, the water sampler should operate in a linkage control mode with the analyzer. That is, the flow rate triggers the sampler to take samples. After the sampling is completed, it triggers the water quality analyzer to measure. When the measured data exceeds the standard, the water sampler retains the sample process for sampling, avoiding the sampling control mode where the sampler and the water quality analyzer take up time for sampling. After the sampler is installed at the same time, the pretreatment system of the original analyzer is not recommended to be used again, especially if there is a large static device, it should be avoided. The water sample collection tube of the water quality analyzer should be as short as possible.
Improper setting of the sample volume in the over-standard retained samples, especially when the sample volume is too small (less than 500mL), and the retained samples cannot be taken out in time for testing, is also a common problem in application. This is mainly manifested in the fact that some regional environmental management departments do not allow pollutant discharge units and operation and maintenance units to operate on the retained samples, and the management departments cannot detect the retained samples and on-site sampling in time. If the pollutant-discharging entity and the operation and maintenance entity are unable to verify and handle the data that exceeds the standard in a timely manner, it is recommended that the volume of the sample retained after exceeding the standard be between 50% and 80% of the sample bottle. When taking samples, the pollutant-discharging entity or the operation and maintenance entity should retain relevant image materials to facilitate the verification and analysis of the data that exceeds the standard.