What Turbidity Level Is Good For Drinking Water?
The WHO (World Health Organization) states that turbidity (suspended solids) should not be above 5 nephelometric turbidity units (NTU) and ideally should be below 1 NTU.
Turbidity means clarity of water, low turbidity means the water is clean and free of suspended particles, high turbidity of water is the reverse.
In order words, turbidity is the resistance of water to the passage of light through it. It can be caused by certain impurities in the water, such as silt, clay, algae, microorganisms, colloidal matter, and organic matter.
Turbidity depends largely on the soil at the water source and the velocity of the water. If the water velocity is high, turbidity can be high.
Effects Of High Turbidity
High turbidity is usually caused by algae and suspended solids, but there may be other causes as well. Various inorganic chemicals can cause water turbidity, such as paints, dyes, solvents and more. Most inorganic chemicals are toxic, so this is definitely a human and animal health issue.
Cloudy water is also usually not good for the organisms that live in it. Because less light passes through the water, it’s not good for plants growing in the water.
Fine suspended solids can trap animals at the bottom of a stream and create problems for fish.
Toxin-producing algae can kill wildlife, are dangerous to people who eat fish in these areas, and can eventually kill almost everything in the water when they die and absorb all the oxygen in the water.
Suspended particles absorb heat from sunlight, causing the turbid water to become warmer, which reduces the concentration of oxygen in the water (oxygen dissolves better in colder water).
Suspended particles scatter light, thereby reducing the photosynthetic activity of plants and algae, which contributes to an even greater decrease in oxygen concentration.
As a result of the particles settling to the bottom, shallow lakes fill faster, fish eggs and insect larvae become covered and suffocated, gill structures become clogged or damaged.
Why Is High Turbidity An Indicator Of Poor Water Quality?
High turbidity is due to the presence of finely distributed solid matter. This creates problems with achieving adequate disinfection of drinking water.
If the solid particles are of biological origin (a frequent occurrence), they may react with the disinfectant agent (chlorine, ozone) and thus reduce the concentration available for killing microorganisms.It serves as a substrate for bacterial growth.
Bacteria living on or in the particles are physically protected from disinfectant agents.
In natural waters, solid material can settle to the bottom of the water as a blanket. This can result in smothering of any organisms living on the bottom.
How To Measure Turbidity
Turbidity is measured in Nephelometric Turbidity Units(NTU). The instrument commonly used to measure it is called a nephelometer or turbidimeter, which measures the intensity of light scattered at a 90-degree angle as a beam of light passes through a water sample,
Turbidity is measured in Nephelometric Turbidity Units(NTU). The instrument used to measure it is called a nephelometer or turbidimeter, which measures the intensity of light scattered at a 90-degree angle as a beam of light passes through a water sample, this method is extremely accurate and measures very low turbidity.
In ancient times, the JTU (Jackson Turbidity Units), measured with a Jackson candle turbidimeter, was used. This unit is no longer used in standard practice.
In lakes, turbidity is measured with a Secchi disk.This is a black and white disk that is lowered into the water attached to a rope.
The depth at which the disk reaches is recorded before it disappears from view.This allows you to estimate the level of turbidity in the lake.