In this article we will try to explain the importance of water conductivity in wastewater and river treatment and how it affects us.
What is electrical conductivity?
Electrical conductivity (EC) measures the ability of water to conduct an electric current. The higher the concentration of dissolved charged chemicals (also known as salts) in water, the greater the electrical current that can be conducted. Examples of naturally occurring charged ions in river water are calcium, potassium, chloride, sulphate and nitrate.
Why is electrical conductivity important in wastewater treatment plants?
Electrical conductivity is essential for wastewater systemsIt indicates how many dissolved substances (total dissolved solids: TDS), chemicals and minerals the water contains. The more impurities the water contains, the higher the conductivity. It is essential to mention that even small amounts of pollutants are sufficient to change the electrical conductivity of wastewater.
In wastewater treatment facilities, changes in electrical conductivity indicate the presence of contaminants in the water. Although the EC measurement cannot tell us what type of contaminant is in the water, it will identify that there is a problem.
The measurement of electrical conductivity in wastewater can also indicate a leak in the sewer. For example, a defective sewerage system often raises the conductivity of water due to the presence of chloride, phosphate and nitrate.
Conductivity is a vital indicator in wastewater management, providing valuable information on the presence and concentration of pollutants, and helping to guide treatment processes to protect our water resources.
What affects conductivity in wastewater treatment?
Many different factors affect the conductivity of water. The most common factor is temperature; as the water temperature increases, the EC increases, and vice versa. For example, if the water temperature increases by 1℃, the EC will increase by 2-3%. It is therefore essential to measure the temperature as well as the EC of the water you are working with.
Other factors are divided into natural impacts and human impacts.
Natural impacts:
Evaporation
Rainfall
Human impacts:
Agricultural runoff
Industrial activity
Roadside salts
Landfill leachate
Electrical conductivity tests on waste water
Measuring the EC of water is a very easy and inexpensive way to identify how many ions are present in water. Conductivity measures the total concentration of ions in liquids, so using a conductivity meter is perfect for monitoring the build-up of dissolved ionic solids in wastewater.
Conductivity meters work by measuring the flow of electric current between electrons within a conductivity probe. The probe reads the electrical current and provides a conductance value.
Once the conductance value of the wastewater has been determined, the correct treatment method can be applied. If wastewater is not treated, it can cause significant damage to the environment and also a potential health risk to both humans and other animals that depend on water sources.
Damage to the ecosystem
Untreated wastewater can also cause chronic damage to the ecosystem through oxygen depletion due to high organic matter content and eutrophication due to increased numbers of nutrients in the water. Water containing excess nutrients poses a health risk from waterborne pathogens.
The simplest way to alter the EC of water is to increase or decrease its temperature. However, most industries reduce the conductivity of water by removing total dissolved solids (TDS) through an ion exchanger, flocculation, reverse osmosis (RO) or distillation.
Electrical conductivity refers to the ability of water to conduct an electrical current in solution over a certain distance, usually measured in Siemens (S) per distance (cm).
Gathering on conductivity in wastewater treatment
In wastewater treatment, electrical conductivity determines whether there are variations or changes in water quality. It can also be used to establish the number of chemicals that need to be added to the water during sterilisation and to control the conductivity of the activated sludge process.
If you have any questions about electrical conductivity or which conductivity probe best suits your testing needs, please do not hesitate to contact us.
Why should electrical conductivity also be measured in rivers?
Significantly elevated electrical conductivity may indicate that pollution has entered the river. A measurement of electrical conductivity cannot tell what the pollutant is, but it can help identify that there is a problem that may harm invertebrates and/or fish. Electrical conductivity can be high in a river with no visible effect on its water clarity, so it is necessary to measure it with a suitable sensor.
The higher the temperature of the water, the greater its ability to conduct electrical charge. For this reason, the electrical conductivity is always given at a reference temperature of 25 °C. The unit of measurement is micro Siemens per cm (S/cm). The electrical conductivity of a river can be very variable, but always within natural levels that do not cause any harm. Typical values for a chalk river range from 100 to 2000 S/cm.
What are the natural controls on electrical conductivity in rivers?
Geology and soil type are the main natural controls on the electrical conductivity of rivers. When it rains, water flows through and over the soil into our rivers, dissolving and picking up chemicals along the way. In regions with calcareous soil, rainwater penetrates the soil and flows into the calcareous soil. As the water moves through the chalk, it dissolves magnesium and calcium carbonate, which increases the electrical conductivity. It usually takes decades for the water to move through the chalk to the river, giving it enough time to dissolve the chalk. The residence time of water in rocks and soils is an important factor controlling electrical conductivity.
How can human activity modify electrical conductivity?
Any human activity that adds charged inorganic chemicals to a river will alter the electrical conductivity. For example, the electrical conductivity may be higher in a river downstream of a sewage treatment plant due to chemicals such as chloride and phosphate from household products.
Runoff from roads in winter, which contains salt, can have a very high electrical conductivity. If this runoff reaches rivers it can, depending on the amount of water, temporarily raise the electrical conductivity of the river.
