GRADE 1 WASTEWATER TREATMENT
OPERATOR CERTIFICATION GUIDE
QUESTIONS AND ANSWERS 2026
TSS (total suspended solids) - ANSWERSSolid material suspended in wastewater,
typically ranging from 100-350 mg/L in domestic wastewater.
BOD5 (biochemical oxygen demand) - ANSWERSAmount of oxygen required by
bacteria to decompose organic matter in wastewater over 5 days, typically ranging from
100-300 mg/L in domestic wastewater.
pH - ANSWERSMeasure of acidity or alkalinity on a scale of 0-14. Typical range for
domestic wastewater is 6.5-8.0.
NH3 (ammonia) - ANSWERSA compound of nitrogen and hydrogen, often found in
wastewater as a result of the decomposition of organic matter. Typical range in
domestic wastewater is 12-50 mg/L.
Inorganic waste - ANSWERSWaste material that does not contain carbon-hydrogen
bonds, including metals, minerals, and salts.
Organic waste - ANSWERSWaste material containing carbon-hydrogen bonds, derived
from living organisms, including fats, proteins, and carbohydrates.
Influent - ANSWERSUntreated wastewater flowing into a treatment plant or process
unit.
Effluent - ANSWERSTreated wastewater flowing out of a treatment plant or process
unit.
Constructed wetland - ANSWERSAn engineered system designed to treat wastewater
using natural processes involving wetland vegetation, soils, and microbial assemblages.
Septic conditions - ANSWERSAnaerobic (without oxygen) conditions in wastewater,
characterized by a rotten egg (hydrogen sulfide) odor and darker color, often black.
Infiltration - ANSWERSGroundwater entering sewer pipes through cracks, joints, or
connections.
Inflow - ANSWERSSurface water (like stormwater) entering sewer systems through
direct connections such as roof drains, manhole covers, or cross-connections.
,Eutrophication - ANSWERSExcessive richness of nutrients in a body of water, typically
caused by runoff from land or wastewater discharges, which causes dense growth of
plant life and potential death of animal life from lack of oxygen.
Domestic wastewater - ANSWERSWastewater originating from residential sources like
homes and apartments.
Commercial wastewater - ANSWERSWastewater originating from commercial
establishments like restaurants, hotels, and office buildings.
Industrial wastewater - ANSWERSWastewater originating from industrial processes and
manufacturing facilities, often containing specific contaminants related to the industry.
COD (Chemical Oxygen Demand) - ANSWERSA measure of the oxygen required to
chemically oxidize organic and inorganic compounds in water. Typically higher than
BOD as it measures more compounds.
TDS (Total Dissolved Solids) - ANSWERSThe combined content of all inorganic and
organic substances contained in a liquid that are present in a molecular, ionized, or
micro-granular suspended form.
Pathogen - ANSWERSDisease-causing microorganisms present in wastewater,
including bacteria, viruses, protozoa, and helminths (worms).
Receiving waters - ANSWERSThe natural water bodies (rivers, lakes, oceans) that
receive treated wastewater discharges.
Sanitary sewer - ANSWERSA sewer system designed to carry only domestic,
commercial, and industrial wastewater, not stormwater.
Combined sewer - ANSWERSA sewer system designed to collect both sanitary
wastewater and stormwater runoff in the same pipe.
CSO (Combined Sewer Overflow) - ANSWERSThe discharge of untreated wastewater
and stormwater from a combined sewer system directly to receiving waters during
heavy rainfall when system capacity is exceeded.
Wastewater collection system - ANSWERSThe network of pipes, pumps, and
appurtenances that collect and transport wastewater from its sources to the treatment
plant.
Headworks - ANSWERSThe initial structures and processes at a wastewater treatment
plant, typically including screening, grit removal, and flow measurement.
Bar screen - ANSWERSA device consisting of parallel bars or rods spaced to remove
large objects from wastewater.
, Fine screen - ANSWERSA screen with smaller openings than a bar screen, designed to
remove smaller particles from wastewater.
Comminutor - ANSWERSA device that cuts or grinds large solid materials in
wastewater into smaller pieces that can pass through downstream equipment.
Screenings - ANSWERSThe material removed by screens in wastewater treatment,
typically including rags, plastics, paper, and other debris.
Grit - ANSWERSHeavy, abrasive materials like sand, gravel, cinders, and eggshells
that can damage equipment and accumulate in tanks.
Grit chamber - ANSWERSA tank designed to remove grit from wastewater by slowing
the flow velocity to allow grit to settle while keeping organic solids in suspension.
Velocity (in grit chamber) - ANSWERSThe speed at which wastewater flows through the
grit chamber. It must be controlled carefully - fast enough to keep most organics in
suspension, but slow enough to allow heavy grit to settle.
Aerated Grit Chamber - ANSWERSA type of grit removal unit where air is introduced to
create a rolling action, helping to separate grit from organic matter and keeping the
lighter organics in suspension while grit settles.
Grit Washing - ANSWERSThe process of cleaning removed grit to separate out organic
material, reducing odor potential and volume before disposal.
Flow Measurement - ANSWERSThe process of quantifying the volume of wastewater
passing through a point in the treatment plant over a specific time period. Often done at
the headworks using devices like Parshall flumes or weirs.
Parshall flume - ANSWERSA specially shaped open channel flow measuring device
that creates a relationship between water level and flow rate.
Weir - ANSWERSA barrier over which water flows, used to measure flow rate based on
the height of water flowing over it.
Manually cleaned bar screen - ANSWERSA bar screen that requires periodic cleaning
by hand using a rake or similar tool.
Mechanically cleaned bar screen - ANSWERSA bar screen equipped with automatic
cleaning mechanisms like rakes, brushes, or chains that remove accumulated
screenings without manual intervention.
Vortex grit chamber - ANSWERSA grit removal system that uses a circular flow pattern
to separate grit by centrifugal force.
OPERATOR CERTIFICATION GUIDE
QUESTIONS AND ANSWERS 2026
TSS (total suspended solids) - ANSWERSSolid material suspended in wastewater,
typically ranging from 100-350 mg/L in domestic wastewater.
BOD5 (biochemical oxygen demand) - ANSWERSAmount of oxygen required by
bacteria to decompose organic matter in wastewater over 5 days, typically ranging from
100-300 mg/L in domestic wastewater.
pH - ANSWERSMeasure of acidity or alkalinity on a scale of 0-14. Typical range for
domestic wastewater is 6.5-8.0.
NH3 (ammonia) - ANSWERSA compound of nitrogen and hydrogen, often found in
wastewater as a result of the decomposition of organic matter. Typical range in
domestic wastewater is 12-50 mg/L.
Inorganic waste - ANSWERSWaste material that does not contain carbon-hydrogen
bonds, including metals, minerals, and salts.
Organic waste - ANSWERSWaste material containing carbon-hydrogen bonds, derived
from living organisms, including fats, proteins, and carbohydrates.
Influent - ANSWERSUntreated wastewater flowing into a treatment plant or process
unit.
Effluent - ANSWERSTreated wastewater flowing out of a treatment plant or process
unit.
Constructed wetland - ANSWERSAn engineered system designed to treat wastewater
using natural processes involving wetland vegetation, soils, and microbial assemblages.
Septic conditions - ANSWERSAnaerobic (without oxygen) conditions in wastewater,
characterized by a rotten egg (hydrogen sulfide) odor and darker color, often black.
Infiltration - ANSWERSGroundwater entering sewer pipes through cracks, joints, or
connections.
Inflow - ANSWERSSurface water (like stormwater) entering sewer systems through
direct connections such as roof drains, manhole covers, or cross-connections.
,Eutrophication - ANSWERSExcessive richness of nutrients in a body of water, typically
caused by runoff from land or wastewater discharges, which causes dense growth of
plant life and potential death of animal life from lack of oxygen.
Domestic wastewater - ANSWERSWastewater originating from residential sources like
homes and apartments.
Commercial wastewater - ANSWERSWastewater originating from commercial
establishments like restaurants, hotels, and office buildings.
Industrial wastewater - ANSWERSWastewater originating from industrial processes and
manufacturing facilities, often containing specific contaminants related to the industry.
COD (Chemical Oxygen Demand) - ANSWERSA measure of the oxygen required to
chemically oxidize organic and inorganic compounds in water. Typically higher than
BOD as it measures more compounds.
TDS (Total Dissolved Solids) - ANSWERSThe combined content of all inorganic and
organic substances contained in a liquid that are present in a molecular, ionized, or
micro-granular suspended form.
Pathogen - ANSWERSDisease-causing microorganisms present in wastewater,
including bacteria, viruses, protozoa, and helminths (worms).
Receiving waters - ANSWERSThe natural water bodies (rivers, lakes, oceans) that
receive treated wastewater discharges.
Sanitary sewer - ANSWERSA sewer system designed to carry only domestic,
commercial, and industrial wastewater, not stormwater.
Combined sewer - ANSWERSA sewer system designed to collect both sanitary
wastewater and stormwater runoff in the same pipe.
CSO (Combined Sewer Overflow) - ANSWERSThe discharge of untreated wastewater
and stormwater from a combined sewer system directly to receiving waters during
heavy rainfall when system capacity is exceeded.
Wastewater collection system - ANSWERSThe network of pipes, pumps, and
appurtenances that collect and transport wastewater from its sources to the treatment
plant.
Headworks - ANSWERSThe initial structures and processes at a wastewater treatment
plant, typically including screening, grit removal, and flow measurement.
Bar screen - ANSWERSA device consisting of parallel bars or rods spaced to remove
large objects from wastewater.
, Fine screen - ANSWERSA screen with smaller openings than a bar screen, designed to
remove smaller particles from wastewater.
Comminutor - ANSWERSA device that cuts or grinds large solid materials in
wastewater into smaller pieces that can pass through downstream equipment.
Screenings - ANSWERSThe material removed by screens in wastewater treatment,
typically including rags, plastics, paper, and other debris.
Grit - ANSWERSHeavy, abrasive materials like sand, gravel, cinders, and eggshells
that can damage equipment and accumulate in tanks.
Grit chamber - ANSWERSA tank designed to remove grit from wastewater by slowing
the flow velocity to allow grit to settle while keeping organic solids in suspension.
Velocity (in grit chamber) - ANSWERSThe speed at which wastewater flows through the
grit chamber. It must be controlled carefully - fast enough to keep most organics in
suspension, but slow enough to allow heavy grit to settle.
Aerated Grit Chamber - ANSWERSA type of grit removal unit where air is introduced to
create a rolling action, helping to separate grit from organic matter and keeping the
lighter organics in suspension while grit settles.
Grit Washing - ANSWERSThe process of cleaning removed grit to separate out organic
material, reducing odor potential and volume before disposal.
Flow Measurement - ANSWERSThe process of quantifying the volume of wastewater
passing through a point in the treatment plant over a specific time period. Often done at
the headworks using devices like Parshall flumes or weirs.
Parshall flume - ANSWERSA specially shaped open channel flow measuring device
that creates a relationship between water level and flow rate.
Weir - ANSWERSA barrier over which water flows, used to measure flow rate based on
the height of water flowing over it.
Manually cleaned bar screen - ANSWERSA bar screen that requires periodic cleaning
by hand using a rake or similar tool.
Mechanically cleaned bar screen - ANSWERSA bar screen equipped with automatic
cleaning mechanisms like rakes, brushes, or chains that remove accumulated
screenings without manual intervention.
Vortex grit chamber - ANSWERSA grit removal system that uses a circular flow pattern
to separate grit by centrifugal force.
