Improper setting of the sampling method of the water sampler may lead to the suspicion of evading monitoring or being illogical.
Due to the influence of production and living conditions as well as the process routes of treatment facilities, the discharge of water pollution sources can be either continuous or intermittent. In most cases of continuous discharge, sampling is conducted at equal intervals, which can basically meet the requirements of discharge sampling and monitoring. However, there are also issues such as long sampling intervals or overly large volumes of individual samples collected. This leads to the problem of insufficient representativeness of the collected samples; If it is set to collect one sample every 30 minutes or more and the sampling volume is large, or one sample is collected every 15 minutes, and the volume of each sample collected is more than 3 liters.
For continuous discharge, you can refer to the technical specification examples to collect one sample every 15 minutes or no more than 15 minutes, and collect four or more samples per hour for mixing. The collection volume of each sample can be set according to the volume of the water sampler's sampling bucket (for example, if the volume of the sampling bucket is 5L and 4 samples are collected per hour) The collection volume of a single sample can be set to 1-1.25L, ensuring that the sampling volume is over 80% of the sampling bucket volume and does not overflow.
For intermittent emissions, the sampling method should be comprehensively considered based on the emission characteristics. For single emissions lasting more than one hour and with stable discharge flow, sampling at time intervals such as flow trigger can be adopted. The sampling time interval should not exceed 15 minutes. If the flow reaches the sampling threshold, the sampler should start sampling 400-500 ml. After waiting for 15 minutes, if the sampling flow threshold is still reached, sample again. After successfully sampling 4 times, the water quality analyzer is triggered to measure and supply the sample.
For water sampling with a single discharge within one hour and unstable discharge flow, it is advisable to adopt a flow-triggered flow-proportional method. The sampling ratio should be set based on the average daily single discharge volume to the volume of the sampling bucket. For instance, if the discharge time is less than one hour and the single discharge volume is 100 cubic meters, The sampling bucket has a volume of 5 liters, meaning the sampling ratio can be set to 400-500mL for every 10 cubic meters discharged. When the cumulative discharge is 100 cubic meters, measurement will be conducted after sampling is completed.