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Water Quality Measurement

Sampling for water quality measurement is a critical point at this stage of the measurement of water quality. Sampling is the first step that can determine the accuracy of water quality data that will be used. Before learning the sampling technique you should know the kinds of samples / examples of water beforehand. Samples of surface water comes from the river water, lake water, water reservoirs, springs, swamp water, and water cave.

Testing of surface water intended for:
a. Knowing the quality of surface water so that it can be determined as a designation, such as drinking water, recreational water, industrial water, water for fisheries, agricultural water, etc.
b. Proving and controlling pollution
c. Setting a surface water management policy

Purpose sampling water quality is collecting sample volumes of water quality that will be investigated by the number as small as possible, but still represents a (representative), which still has properties similar to the sample source water quality (eg water bodies / rivers, lakes / reservoirs , springs, wells etc.). Characteristics of the waters might not be much change for some time, but many ever-changing flow of water in a short time.

For example, the characteristics of the water in the upstream generally only changed because of the influence of rain so that changes can be even hours daily. To obtain a representative sample of the actual situation to choose three methods:
1. Examples moment (Grap Sample)
Examples moment represents the state of water at a time from somewhere. When a water source has characteristics that do not change much within a period or within a certain time limit, the distance of the instantaneous sample adequately represent the circumstances of time and place. Generally, this method can be used for natural water sources but does not represent the state of waste water, or water that is heavily influenced by the waste material.

When an unknown source or the waste water has the characteristics that changed the moment a few examples taken successively for a certain period and the examination is done individually, not united like the combination method. Water sampling time period ranging from 5 minutes to 1 hour or more, generally a period of sampling for 24 hours. Examination of certain parameters require instantaneous methods such as measurement of temperature, pH, dissolved gas levels, CO2, sulfides, sulfates, cyanide and chlorine.

2. Example Combined Time (Composite Sample)
Examples of combined time was a mixture of samples taken from the moment a same place at different times. The combined sample test results show uneven state of the place in a period. Generally, sampling is done continuously for 24 hours but within a few days intensively for Djangkan a shorter time.

To obtain a sample composite (composite) need to be taken to ensure that each sample is mixed having the same volume. When the final volume of a composite sample 1-5 Liter, then for 1 hour intervals over a period of 24 hours required sampling each sample volume as much as 200-220 mL.

3. Example Combined place (Integreted Sample)
A mixture momentary examples taken from different places at the same time. The combined sample test results show the uneven state of an area or spot checks. This method is useful when the required water quality of a river flow in the cross-section or width or parts of the cross-section has a different quality.

This method is generally not done for checking the water quality of the lake or water reservoir because in general show symptoms of different quality because the depth or breadth. In this case the method is always used separate checks.