Wastewater Operator Training: Lesson 13 - Microbiology and Biological Treatment

Vocabulary study set covering biological wastewater treatment environments, activated sludge mechanisms, nitrification pathways, and pathogen control principles from Lesson 13.

Microorganisms (in Wastewater Treatment)

Organisms—primarily bacteria, protozoa, and fungi—that consume biodegradable organic pollutants as food, converting unstable organic material into stable cellular mass, carbon dioxide, water, and other byproducts.

Aerobic Environment

A biological treatment environment where dissolved oxygen is present ($> 0$), used for carbonaceous removal.

Anoxic Environment

A treatment condition characterized by the absence of dissolved oxygen but the presence of chemically bound oxygen ($NO_3^-$), utilized for denitrification.

Anaerobic Environment

A treatment environment that is completely devoid of both dissolved oxygen and nitrates, typically used for sludge processing.

Activated-Sludge System

A suspended-growth biological treatment process where wastewater is mixed with a community of microorganisms (biomass) in an aeration tank.

Microbial Flocs

Clusters of microorganisms, bacteria, and organic particles that clump together, providing favorable settling characteristics that allow solids to separate effectively from treated water in secondary clarifiers.

Nitrification

A two-stage aerobic biological process where specialized bacteria convert ammonia ($NH_3$) into nitrite ($NO_2^-$) and subsequently into nitrate ($NO_3^-$), consuming dissolved oxygen and alkalinity.

Denitrification

A biological process occurring under anoxic conditions in which nitrate ($NO_3^-$) is reduced to nitrogen gas and released into the atmosphere.

Pathogens

Disease-causing microorganisms that are not guaranteed to be eliminated or inactivated by biological treatment alone, presenting a public health risk if not treated with downstream disinfection.

Disinfection Processes

Secondary or tertiary treatment methods (such as chlorination or ultraviolet irradiation) applied after biological treatment to destroy remaining disease-causing pathogens and safeguard public health.

Dissolved Oxygen Depletion

A significant drop in dissolved oxygen concentration within an aerobic tank that interferes with aerobic microorganisms and reduces the efficiency of biological processes such as nitrification.