Grade 1 Wastewater Treatment Operator
Study Guide | Certification Practice
Questions & Exam Prep
2026/2027
,TSS (total suspended solids) Solid material suspended in wastewater, typically ranging from 100-350 mg/L in
domestic wastewater.
BOD5 (biochemical oxygen demand) Amount 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 Measure of acidity or alkalinity on a scale of 0-14. Typical range for domestic
wastewater is 6.5-8.0.
NH3 (ammonia) A 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 Waste material that does not contain carbon-hydrogen bonds, including metals,
minerals, and salts.
Organic waste Waste material containing carbon-hydrogen bonds, derived from living organisms,
including fats, proteins, and carbohydrates.
Influent Untreated wastewater flowing into a treatment plant or process unit.
Effluent Treated wastewater flowing out of a treatment plant or process unit.
Constructed wetland An engineered system designed to treat wastewater using natural processes
involving wetland vegetation, soils, and microbial assemblages.
Septic conditions Anaerobic (without oxygen) conditions in wastewater, characterized by a rotten egg
(hydrogen sulfide) odor and darker color, often black.
Infiltration Groundwater entering sewer pipes through cracks, joints, or connections.
Inflow Surface water (like stormwater) entering sewer systems through direct connections
such as roof drains, manhole covers, or cross-connections.
Eutrophication Excessive 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 Wastewater originating from residential sources like homes and apartments.
Commercial wastewater Wastewater originating from commercial establishments like restaurants, hotels,
and office buildings.
, Industrial wastewater Wastewater originating from industrial processes and manufacturing facilities, often
containing specific contaminants related to the industry.
COD (Chemical Oxygen Demand) A 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) The 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 Disease-causing microorganisms present in wastewater, including bacteria, viruses,
protozoa, and helminths (worms).
Receiving waters The natural water bodies (rivers, lakes, oceans) that receive treated wastewater
discharges.
Sanitary sewer A sewer system designed to carry only domestic, commercial, and industrial
wastewater, not stormwater.
Combined sewer A sewer system designed to collect both sanitary wastewater and stormwater runoff
in the same pipe.
CSO (Combined Sewer Overflow) The 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 The network of pipes, pumps, and appurtenances that collect and transport
wastewater from its sources to the treatment plant.
Headworks The initial structures and processes at a wastewater treatment plant, typically
including screening, grit removal, and flow measurement.
Bar screen A device consisting of parallel bars or rods spaced to remove large objects from
wastewater.
Fine screen A screen with smaller openings than a bar screen, designed to remove smaller
particles from wastewater.
Comminutor A device that cuts or grinds large solid materials in wastewater into smaller pieces
that can pass through downstream equipment.
Screenings The material removed by screens in wastewater treatment, typically including rags,
plastics, paper, and other debris.
Grit Heavy, abrasive materials like sand, gravel, cinders, and eggshells that can damage
equipment and accumulate in tanks.
Study Guide | Certification Practice
Questions & Exam Prep
2026/2027
,TSS (total suspended solids) Solid material suspended in wastewater, typically ranging from 100-350 mg/L in
domestic wastewater.
BOD5 (biochemical oxygen demand) Amount 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 Measure of acidity or alkalinity on a scale of 0-14. Typical range for domestic
wastewater is 6.5-8.0.
NH3 (ammonia) A 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 Waste material that does not contain carbon-hydrogen bonds, including metals,
minerals, and salts.
Organic waste Waste material containing carbon-hydrogen bonds, derived from living organisms,
including fats, proteins, and carbohydrates.
Influent Untreated wastewater flowing into a treatment plant or process unit.
Effluent Treated wastewater flowing out of a treatment plant or process unit.
Constructed wetland An engineered system designed to treat wastewater using natural processes
involving wetland vegetation, soils, and microbial assemblages.
Septic conditions Anaerobic (without oxygen) conditions in wastewater, characterized by a rotten egg
(hydrogen sulfide) odor and darker color, often black.
Infiltration Groundwater entering sewer pipes through cracks, joints, or connections.
Inflow Surface water (like stormwater) entering sewer systems through direct connections
such as roof drains, manhole covers, or cross-connections.
Eutrophication Excessive 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 Wastewater originating from residential sources like homes and apartments.
Commercial wastewater Wastewater originating from commercial establishments like restaurants, hotels,
and office buildings.
, Industrial wastewater Wastewater originating from industrial processes and manufacturing facilities, often
containing specific contaminants related to the industry.
COD (Chemical Oxygen Demand) A 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) The 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 Disease-causing microorganisms present in wastewater, including bacteria, viruses,
protozoa, and helminths (worms).
Receiving waters The natural water bodies (rivers, lakes, oceans) that receive treated wastewater
discharges.
Sanitary sewer A sewer system designed to carry only domestic, commercial, and industrial
wastewater, not stormwater.
Combined sewer A sewer system designed to collect both sanitary wastewater and stormwater runoff
in the same pipe.
CSO (Combined Sewer Overflow) The 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 The network of pipes, pumps, and appurtenances that collect and transport
wastewater from its sources to the treatment plant.
Headworks The initial structures and processes at a wastewater treatment plant, typically
including screening, grit removal, and flow measurement.
Bar screen A device consisting of parallel bars or rods spaced to remove large objects from
wastewater.
Fine screen A screen with smaller openings than a bar screen, designed to remove smaller
particles from wastewater.
Comminutor A device that cuts or grinds large solid materials in wastewater into smaller pieces
that can pass through downstream equipment.
Screenings The material removed by screens in wastewater treatment, typically including rags,
plastics, paper, and other debris.
Grit Heavy, abrasive materials like sand, gravel, cinders, and eggshells that can damage
equipment and accumulate in tanks.
