Turbidity is defined as the amount of cloudiness in a particular water sample; the cloudiness is caused by the sediment in the sample. Turbidity is related to the amount of light that can pass through the water. It is normally measured using a meter although there are other ways to ascertain the turbidity levels of a sample. The particles measured by a turbidity meter are those that are so small that they will not settle to the bottom if agitated. Subsequently the water can appear turbid.
The water tested in a turbidity meter can come from a variety of sources; rivers are often tested to find silt levels. The readings from the meter can give an indication of the effects of agriculture and construction further upstream by the levels of silt present in the river. As well as silt and mud however, a turbidity meter can detect traces of bacteria and germs as well as certain chemicals. As such the meter is a powerful tool in producing safe drinking water and understanding the effect we have on the environment.
The turbidity meter is extensively used in the testing of domestic water supplies as these have to be safe for human consumption. It is also used in the treatment process to access how hard filters will have to work to treat rainwater from rivers. For instance, if there were heavy rains that picked up a great deal of silt and mud, a turbidity meter would be used to assess how much sediment would reach the filters and hence, the lifespan of those filters. In addition, water with high turbidity will block pipes and resist chlorination. As certain machines and systems are designed to remove sediment and particles, a meter that measures the sediment levels is an important tool for technicians and operators at all stages of the water purification process.
Fundamentally there are two ways in which to measure turbidity; either an electric meter or a tube. Naturally both have pros and cons and variations that make them suitable for certain tasks. The units of measurement for sediment levels are nephelometric turbidity units or Jackson turbidity units (NTU and JTLJ respectively). Although they are slightly different the two units can be considered generally equal.
There are a variety of different electric meter varieties on the market today; here are details of their advantages and disadvantages. In terms of pros the main benefit is the accuracy of the meter when measuring minute turbidities in samples. However they cost a lot and will need a power supply. Although newer models are currently incorporating more hardy designs, the older models of meter struggle in terms of hardiness, especially considering that they work with water on a regular basis.
The other form of measuring the sediment in water is to use a tube; this can be considered a far more simplistic form of measurement in comparison with the meter but can still perform the task effectively. The process includes filling a clear tube with the sample, after looking through the tube it will be possible to ascertain how much light can pass through it and subsequently its turbidity. While these tubes are hardwearing, affordable and simply designed they do have the disadvantage of being less than one hundred percent accurate.
No matter what type of method is used to measure turbidity, whether it is a meter or a tube, the process is useful in determining the quality and state of water. Used widely in the water purification process an extensively by environmentalists assessing the affects of society in river systems, they provide a valuable service supplying us with clean water and more information about the environment we live in.
Environmental science expert Thomas Pretty looks into the different aplications for the turbidity meter and how it aids society more generally.