Wastewater Engineering 2

Traditional vocabulary flashcards covering key microorganisms, sampling, flow terminology, and preliminary treatment equipment presented in Wastewater Engineering Module 2.

Microbiology of Sewage

Study of microorganisms involved in converting raw sewage into stable sludge and harmless effluent.

Bacteria

Single-celled prokaryotic organisms that metabolize soluble food and reproduce by binary fission in wastewater.

Lag Phase

Acclimatization period where microorganisms adjust to a new environment before rapid growth begins.

Log Growth Phase

Exponential bacterial multiplication when food supply is abundant.

Declining Growth Phase

Stage where food becomes limiting, slowing the growth rate of bacteria.

Stationary Phase

Condition where food supply equals microbial mass; overall cell count remains constant.

Endogenous (Death) Phase

Period when microorganisms consume internal reserves, die, and release nutrients (lysis/cryptic growth).

Obligate Anaerobes

Bacteria that grow only in the absence of dissolved oxygen.

Aerotolerant Anaerobes

Bacteria that can survive in the presence or absence of oxygen.

Protozoa

Single-celled eukaryotes that prey on dispersed bacteria and indicate effluent quality.

Algae

Photosynthetic microorganisms that supply oxygen by day and assist in nutrient and coliform removal.

Fungi

Heterotrophic eukaryotes adept at producing extracellular enzymes, acids, and adapting to harsh wastewater conditions.

Virus

Smallest infectious particles; some survive 41 days in water and are resistant to standard disinfection.

Rotifers

Microscopic multicellular organisms found in well-operated plants; indicators of cleaner effluent.

Coliform Organisms

Rod-shaped, gram-negative bacteria fermenting lactose within 48 h; used as indicators of fecal contamination.

Total Coliform

All aerobic, facultative, and anaerobic non-spore-forming coliform bacteria in a sample.

Escherichia coli (E.coli)

Non-pathogenic fecal indicator present in high numbers, easy to detect, signalling potential enteric pathogens.

Most Probable Number (MPN)

Statistical method estimating coliform concentration from multiple fermentation tubes.

Membrane Filter Technique (MFT)

Rapid method giving direct coliform counts by filtering a known volume through a small-pore membrane.

Fecal Coliform / Fecal Streptococci Ratio

Indicator distinguishing human (>4.0) from animal (<1.0) fecal pollution sources.

Grab Sampling

Single sample taken at one time and place without regard to flow variations.

Composite Sampling

Mixture of grab samples collected over time, usually in proportion to flow, to measure average characteristics.

Continuous Sampling

Constant-rate withdrawal of a small fraction of flow for real-time analysis (e.g., pH, DO).

Average Daily Flowrate (ADF)

Mean wastewater flow over a specified period, used for chemical and sludge quantity estimates.

Peak Hourly Flowrate (PHF)

Highest flow measured in any hour of a 24-hour period; critical for hydraulic sizing.

Maximum Daily Flowrate (MDDF)

Greatest 24-hour flow expected during design period.

Turndown Ratio

Ratio of highest to lowest operating flow in a treatment facility or pump.

Screening

Preliminary operation removing large solids with coarse, fine, or micro screens.

Comminutor

Mechanical device that grinds coarse solids to a uniform size within wastewater.

Barminutor

Combination of bar screen and comminutor where rotating cutters shred rags collected on the bars.

Grit Chamber

Enlarged channel slowing flow to ~1 fps so heavy inorganic particles settle out.

Aerated Grit Chamber

Grit removal unit using diffused air to keep organics in suspension while grit settles.

Flow Equalization Basin

Tank that stores excess wastewater to dampen hydraulic and pollutant load fluctuations.

Adsorbent

Medium (e.g., activated carbon) whose surface attracts and holds contaminants.

Adsorbate

Contaminant species being collected on the surface of an adsorbent.

Unit Operation

Physical or chemical processing step (e.g., screening, sedimentation) in wastewater treatment.

Unit Process

Biological treatment step relying on microbial activity (e.g., activated sludge).

Cryptic Growth

Process during endogenous phase where living bacteria consume nutrients released from lysed cells.

Settling Velocity

Rate at which a particle falls through water; key parameter in grit chamber design.

Hydraulic Loading

Volume of wastewater applied per unit surface area or time, influencing treatment unit performance.

Presumptive Test (Coliform)

Initial lactose broth fermentation step indicating potential presence of coliform bacteria.

Confirmed Test (Coliform)

Follow-up culture on selective media to verify coliform presence after presumptive positives.