What do you mean by the strength of sewage?

Sewage is a mixture of saline materials in solution, nitrogenous and carbonaceous organic matter in solution and suspension, and a few other ingredients, in addition to some grit and mineral waste. But what do you mean by the strength of sewage?

Let’s understand the meaning of the strength of sewage!

The strength of sewage is defined as the amount of dissolved and suspended matter present in sewage, as determined by biochemical oxygen demand or suspended solids.

The amount of water consumed per person determines the strength of a typical household sewage system. The strength will typically rise if there are industrial wastes present. Of course, there are significant daily, seasonal, and storm water changes.

What are the two parameters to determine the strength of sewage?

Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) are the two primary indicators of sewage strength. The oxygen-demanding strength of the effluent is determined by both these characteristics.

What is COD or chemical oxygen demand?

Chemical oxygen demand is the quantity of oxygen needed for the chemical oxidation of organic and inorganic substances found in wastewater, using oxidizing agents like potassium permanganate, potassium dichromate, and others.

Without the use of any additional machinery, organic matter can be chemically oxidized quickly when COD is present. It is the sole approach for figuring out how much organic matter is present in sewage.

What does BOD or biological oxygen demand mean?

The amount of oxygen needed by sewage microbes for aerobic degradation of biodegradable materials is known as BOD. It is the most popular criteria for determining the strength of municipal or organic wastewater quality.

After five days of aerobic conditions at 20 degrees Celsius, the standard BOD test calculates the quantity of oxygen needed by microorganisms, to break down biodegradable materials in a wastewater sample. It is denoted in milligrams per liter.

Why do COD concentrations in wastewater treatment exceed BOD values?

As oxygen is utilized biologically and chemically to break down the organic matter, the higher the BOD/COD, the greater the capacity of the discharged effluent to rob oxygen when discharged into receiving waters, and the greater the risk of causing biological life harm in those waters.

Because, more organic compounds can be chemically oxidized than can be physiologically oxidized, COD is often higher than BOD. This contains substances that are harmful to biological life, which makes COD tests—which cannot be detected by BOD testing—very helpful when examining industrial waste.

Is COD test better suited then BOD test?

The BOD test requires at least 5 days, which makes it useless for monitoring treatment procedures.

The COD test is an alternative test that measures the amount of organic matter in both natural water and wastewater. In contrast to a BOD test that takes five days, COD can only be determined in three hours. In particular, the COD test is better suited to quantify organic matter found in industrial waste, which contains chemicals harmful to biological life.

However, because the test will oxidize substances like lipids and lignin’s, which are only slowly biodegradable, COD readings are typically greater than BOD values.

How can we help?

Netsol Water is one of India's largest water and wastewater management companies. We are focused on the design, production, and delivery of specialized wastewater treatment systems, commercial equipment’s, and opulent facilities for the water sector.

We manufacture top-of-the-line WWTPs, STPs, WTPs, and ETPs that are highly successful at removing pollutants, from commercial and industrial wastewater. For further information, contact us at +91 9650608473 or enquiry@netsolwater.com