Basic General Wastewater Terminology

Flashcards covering key terminology related to wastewater management and treatment processes.

Biochemical Oxygen Demand (BOD)

A measurement of the organic strength of a sample by measuring the amount of oxygen consumed over a given time period.

Composite Sample

A sample prepared by combining a number of grab samples, typically over a 24-hour period.

Dissolved Oxygen (DO)

A measure of the amount of oxygen dissolved in water, expressed in mg/L.

Effluent

The treated wastewater discharged from a treatment plant to the environment.

Eutrophication

The excessive growth of plants and algae in receiving waters due to dissolved nutrients and their decomposition.

Flume

A restriction in an open channel used to measure flow.

Food to Microorganism Ratio (F/M or F:M)

The amount of BOD provided to the microorganisms in the treatment process.

Gallons per Day (gpd)

A common wastewater flow measurement expressed as the number of gallons flowing each day.

Gallons per Hour (gph)

A common wastewater flow measurement expressed as the number of gallons flowing each hour.

Gallons per Minute (gpm)

A common wastewater flow measurement expressed as the number of gallons flowing each minute.

Grab Sample

A single sample taken at a specific time and place that is representative of the current conditions.

Hydraulic Retention Time (HRT)

The period of time that wastewater remains in a tank, also known as detention time.

Influent

The raw (or untreated) wastewater entering a treatment process.

Milligrams per Liter (mg/L)

A concentration measurement of a substance in a liquid, equivalent to parts per million (ppm).

Million Gallons per Day (MGD)

A common wastewater flow measurement expressed in millions of gallons of wastewater flowing each day.

pH

A measure of the acidity or alkalinity of a sample on a scale of 0 to 14.

Septage

The high-strength waste pumped out of septic tanks.

Sludge Age

The theoretical length of time a particle of activated sludge stays in the treatment plant, measured in days.

Total Suspended Solids (TSS)

The measure of the total amount of solids suspended in a sample, expressed in mg/L.

Weir

A level control structure used to provide uniform flow.

Combined Sewer

A pipe conveyance that carries both wastewater and stormwater in a single pipe.

Inflow and Infiltration (I/I)

Any unwanted clearwater that leaks into a collection system, consisting of groundwater, rainwater, or snowmelt.

Lift Station

An underground chamber with pumps used to elevate wastewater to a higher grade.

Manhole

A structure providing access to a collection system, typically a round opening with an iron lid.

Sanitary Sewer Overflow (SSO)

A release of wastewater from a sewage collection system directly into a water body or onto land.

Storm Sewer

An underground pipe system that collects rainwater from streets and conveys it elsewhere.

Treatment Facility Overflow (TFO)

A release of wastewater from a facility into a water body or land surface other than through permitted outfalls.

Wet Well

A tank where wastewater is collected and then pumped out.

Aeration Basin

A tank where wastewater is aerated to achieve biological treatment.

Aerobic

A condition under which free and dissolved oxygen is available in an aqueous environment.

Anaerobic

A condition where free, dissolved, and combined oxygen is unavailable in an aqueous environment.

Anoxic

A condition where oxygen is only available in combined form such as nitrate, nitrite, or sulfate.

Biosolids

The nutrient-rich, organic byproduct of a municipal wastewater treatment plant used as fertilizer.

Clarifier

A tank used to remove floatable and settleable solids in wastewater.

Disinfection

A process used to destroy most pathogens to a safe level in the effluent.

Grit

Fine, abrasive particles removed from wastewater, such as sand and eggshells.

Headworks

The beginning of a treatment plant where influent flow is measured and where preliminary treatment occurs.

Microorganism

A living organism too small to be seen without a microscope, including bacteria, viruses, fungi, or protozoa.

Primary Treatment

A treatment process usually involving clarification by solid and liquid separation.

Process Control

Tools and methods used to optimize treatment plant operations.

Return Activated Sludge (RAS)

Settled activated sludge collected in a final clarifier and returned to mix with incoming wastewater.

Screenings

Materials in wastewater removed with screens at the headworks of treatment plants.

Secondary Treatment

A biological treatment process using bacteria to remove pollutants.

Selector

Part of the treatment system that selects for a specific type of microorganism by providing a favorable environment.

Sidestreams

Flows generated within the plant, usually from solids processing, recycled back through the plant.

Tertiary Treatment

A treatment process using physical, chemical, or biological methods to remove pollutants beyond secondary treatment.

Treatment Process

Physical, biological, or chemical action applied to wastewater to remove pollutants.

Treatment Unit

An individual structure or equipment within a wastewater treatment facility that is part of a treatment process.

Waste Activated Sludge (WAS)

Excess biomass or cell mass removed from the secondary treatment process.

Confined Space

A space large enough for an operator to enter and perform work, with limited means for entry or exit.

Pathogens

Infectious microorganisms in wastewater that pose health risks.

Wisconsin Pollutant Discharge Elimination System (WPDES) Permit

A permit issued to wastewater facility owners with limitations and requirements for effluent and biosolids.

Discuss where a wastewater treatment plant operator would find information on conducting wastewater tests.

The most authoritative source for conducting wastewater testing can be found in ‘Standard Methods for the Examination of Water and Wastewater’, prepared and published jointly by the American Public Health Association, American Water Works Association, and Water Environment Federation. It is commonly referred to simply as ‘Standard Methods’.