Disinfection – A process used to destroy most pathogens in the effluent to a safe level. Disinfection does not destroy all microorganisms.

Biosolids – The nutrient-rich, organic byproduct of a municipal wastewater treatment plant that is utilized as fertilizer.

Process Control – The tools and methods used to optimize treatment plant operations.

Return Activated Sludge (RAS) – The settled activated sludge (biomass) that is collected in a secondary clarifier and returned to the secondary treatment process to mix with incoming wastewater. This returns a concentrated population of microorganisms back into the aeration basin.

Waste Activated Sludge (WAS) – The activated sludge (excess biomass or cell mass) removed from the secondary treatment process. For most treatment plants, this will be a portion of the Return Activated Sludge (RAS) flow stream.

Confined Space – A space that is large enough for an operator to enter and perform assigned work. It has limited or restricted means for entry or exit and is not designed for continuous occupancy.

Pathogens – Infectious microorganisms in wastewater that pose health risks.

Discharge Elimination System Permit – A permit is issued to wastewater facility owners, which contains facility effluent and biosolids/sludge limitations, conditions, and reporting requirements.