How do I choose between the simple turbidity methods?
To choose between methods you will need to understand what kind of water are you trying to measure, what range of turbidity are you looking to measure and how can you get the sample.
How do you make a simple turbidity measurement?
There are a number of simple methods available. Firstly take a sample of water representative of the body of water you need to measure, try to ensure you don’t create significant quantities of bubbles. You can then measure turbidity by slowly filling a turbidity tube with the sample liquid, until you can no longer see the bottom. This optical inspection will give you an idea of how turbid your solution is and the methodology is very similar to that of using a Jackson candle turbidimeter.
A sechhi disk is a large black and white disk used to measure turbidity in large bodies of water, such as a lake or the sea. It functions similarly to a turbidity tube and uses optical inspection. Spinning the disk as it is lowered once you cannot see the colour changes then you note the depth of the rope through the notches.
How do I use a turbidity tube?
Using a turbidity tube is a simple procedure. The basic principle is that your sample liquid is added to a clear tube until the cross on the bottom of the tube is no longer visible. The depth of the sample is then measured to the closest centimetre and this reading can be approximately converted to NTU using the scale on the side of the turbidity tube.
How do I collect a water sample for measurement?
You need to make sure the sample is representative of the whole water body you are trying to measure. It should be collected in a clean sample vessel such as a 1L HDPE bottle. This collection should be safety done with a sampler other type of dipping device.