As discussed before, there are three kinds of samples. First is a discrete sample. The second and third sample type will be explained as below:
- Arranged discrete samples (integrated sample)
When the body of water at the sampling point comprises several flow channels, an ordered sample intended to represent the whole body shall be created. The ordered sample shall contain “n” sample portions (one discrete sample of each flow channel) with each sample volume proportional to the discharge rate of each channel.
- Composite samples
This kind of samples is intended to represent evenly the changes in the parameters of the body of water under study, over a fairly long period, in detail, and with limited work. The composite sample is divided into two types:
– Composite sample time
A composite sample was taken from the same location but at some time intervals. Each sample should be taken in the same amount so that it eventually reaches the desired total volume.
– Composite sample space
A composite was taken from several different locations but at the same time. Samples should be taken in equal amounts at each specified sampling point so that it eventually reaches the desired total volume.
The use of composite samples is only usable if the liquid waste meets the following conditions:
– Fluctuating characteristics for a given time range or area are small during its range of time or range of location where the sampling is performed. For example, the sampling of raw wastewater in the initial pond, the sampling of liquid waste in a large aeration tank.
– Parameters – liquid waste characteristics are fairly stable. For example, sampling for TSS analysis, and more.
Analysis of composite samples will save a lot of costs because laboratory analysis can be done at once to obtain the average value of parameters and characteristics. Nevertheless, it must be used through careful consideration.