Wastewater Biomass – How to Use the Autotrophic Index to Measure Water Quality


Microorganisms in wastewater and other organic matter increase the biomass of wastewater. This increase is inversely related to the quality of wastewater. In this article, I discuss in detail a formula used to determine the quality of wastewater.

Autotrophic Index (AI) in wastewater

To estimate the quality of wastewater, factors such as the biomass content of the wastewater and the chlorophyll present in the wastewater should be taken into account. In fact, to determine the quality of the wastewater, the value of the ratio between the (total) biomass of the wastewater and the chlorophyll in the wastewater is used. This value is called autotrophic index or AI for short.

When organic matter is elevated in wastewater or increases due to the additional influx of waste, the amount of heterotrophic microorganisms in the wastewater increases. These heterotropic organisms are mainly protozoa. But other examples of these organisms include fungi and bacteria. The increase in the quantity of these organisms leads to an increase in the value obtained by the aforementioned report. It is written as:

total biomass (weight of organic matter without ash) (mg / m ^ 3)

————————————————– ——————— = AI

chlorophyll a (mg / m ^ 3)

Note: When using this report, you must make sure that the sample is tested within half an hour. Some of the microorganisms may die due to changes in water temperature and the amount of oxygen and food in the wastewater.

Below are values ​​for some of the microorganisms grown and tested in the laboratory, likely to affect the overall IA of wastewater.

An algal culture showed an AI of 40 to 96;

A sample of marine phytoplankton culture showed AS of 76-200;

A pond water culture sample showed an AI of 44-221;

A marine seston culture showed an AI of 40-146;

A Seston Lake culture showed an AI of 457;

Knowing AI helps a lot of plant personnel to treat sewage.

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