Wastewater Engineering 1

A comprehensive set of vocabulary flashcards summarizing essential terms and definitions from the lecture notes on wastewater engineering.

Influent

Raw wastewater flowing into a treatment plant.

Effluent

Treated water discharged from a wastewater treatment plant.

Domestic (Sanitary) Wastewater

Wastewater originating from households, commercial, institutional and similar sanitary conveniences.

Industrial Wastewater

Wastewater in which industrial wastes predominate, such as effluents from brewing or dyeing processes.

Storm Sewage

Liquid in sewers resulting from precipitation runoff during or after rainfall; conveyed by a separate storm system.

Combined Wastewater

Mixture of sanitary wastewater and storm water transported in one collection system.

Inflow

Water that enters sanitary sewers from surface connections such as roof leaders or manhole covers.

Infiltration

Groundwater entering sewers and laterals through defective joints, cracks, or manholes.

Direct Inflow

Stormwater that enters sanitary sewers through direct connections and causes an almost immediate rise in flow.

Total Inflow

Sum of direct inflow at a point plus any upstream overflow or bypass discharge.

Delayed Inflow

Stormwater that reaches the sewer system hours or days after rainfall, e.g., sump-pump discharges.

Gray Water

Wastewater from kitchens, bathrooms and laundry excluding toilet wastes.

Black Water

Wastewater from flush toilets containing feces and urine.

Yellow Water

Urine collected separately from toilets or urinals.

Brown Water

Black water without the urine fraction.

Total Solids (TS)

All matter remaining after a wastewater sample is evaporated at 105 °C.

Volatile Solids (VS)

Portion of total solids lost on ignition at 550 °C; represents organic material.

Fixed Solids

Inorganic residue (ash) remaining after ignition of a sample at 550 °C.

Suspended Solids

Solids retained on a standard filter; includes settleable and colloidal material.

Dissolved Solids

Solids that pass through a glass-fiber filter; also called non-filterable solids.

Total Suspended Solids (TSS)

Concentration of all suspended solids in wastewater, usually reported in mg/L.

Volatile Suspended Solids (VSS)

Organic fraction of TSS lost on ignition at 550 °C.

Fixed Suspended Solids (FSS)

Inorganic fraction of TSS remaining after ignition.

Total Dissolved Solids (TDS)

Sum of all dissolved solids present in a water or wastewater sample.

Chemical Oxygen Demand (COD)

Amount of oxygen equivalent required to chemically oxidize all organic and inorganic matter in a sample.

Biochemical Oxygen Demand (BOD₅)

Oxygen consumed by microorganisms to biodegrade organic matter in 5 days at 20 °C.

Dissolved Oxygen (DO)

Concentration of oxygen dissolved in water, essential for aquatic life and wastewater treatment.

Alkalinity

Capacity of wastewater to neutralize acids, expressed as bicarbonate, carbonate and hydroxide equivalents.

Acidity

Capacity of wastewater to neutralize bases; opposite of alkalinity.

pH

Scale expressing the acidity or basicity of a solution; typical wastewater ranges from 6.5 to 9.0.

Turbidity

Measure of water’s cloudiness due to suspended particles, affecting light transmission.

Apparent Color

Color of wastewater caused by suspended solids.

True Color

Color that remains after suspended solids are removed; due to dissolved substances.

Coliform Organisms

Rod-shaped bacteria from the intestinal tract used as indicators of potential pathogenic contamination.

Escherichia coli (E. coli)

Preferred indicator species within the coliform group for pathogen monitoring (non-pathogenic test strain).

Most Probable Number (MPN)

Statistical laboratory method to estimate the number of coliform bacteria in a water sample.

Membrane Filter Technique (MFT)

Laboratory method that filters a measured sample, incubates the filter, and counts bacterial colonies.

Rotifers

Aerobic, multicellular animals whose presence in effluent indicates a highly stabilized biological process.

Crustaceans (in wastewater)

Small aquatic organisms requiring high DO; their presence suggests well-treated, oxygen-rich effluent.

Total Kjeldahl Nitrogen (TKN)

Sum of organic nitrogen and ammonia nitrogen present in wastewater.

Organic Nitrogen

Nitrogen bound in organic compounds such as proteins or amino acids.

Ammonia Nitrogen

Nitrogen present as NH₃/NH₄⁺ produced from the breakdown of proteins and urea.

Phosphorus (in wastewater)

Essential nutrient for biological growth; typical concentration 6–20 mg/L in domestic sewage.

Fats, Oil and Grease (FOG)

Hydrophobic substances from animal or vegetable sources that can cause foaming and clogging in sewers.

Proteins

Principal constituents (≈40–60 %) of organic solids in wastewater; degrade to release ammonia.

Carbohydrates

Sugars, starches and cellulose contributing 30–50 % of organic matter in wastewater.

Nitrification

Biological conversion of ammonia to nitrite and then nitrate by autotrophic bacteria.

Oligotrophic

Describes water bodies with low nutrient levels and limited biological productivity.

Mesotrophic

Water bodies with moderate nutrient levels and intermediate productivity.

Eutrophic

Nutrient-rich water body prone to excessive algal growth (algal blooms).

Bacteria (in treatment)

Single-celled microorganisms; autotrophs use CO₂, heterotrophs use organic carbon; key agents of biodegradation.

Protozoa

Motile protists (e.g., Sarcodina, Mastigophora, Sporozoa, Ciliata) that graze on bacteria in biological treatment systems.