Wastewater Collection Operator Class III flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Permit-required confined space

A confined space that contains or may contain a hazard such as a hazardous atmosphere, engulfment, entrapment, or an internal configuration that could trap an entrant, requiring a permit before entry.

Atmospheric testing order

Test oxygen first, then combustible gas in percent LEL, then toxic gases such as hydrogen sulfide and carbon monoxide; test before entry and continuously while occupied.

Acceptable entry oxygen range

Oxygen between 19.5 and 23.5 percent by volume; below this is oxygen deficient and above it is oxygen enriched, both of which are hazardous.

Attendant role

The attendant stays outside the permit space, monitors entrants, maintains communication, keeps unauthorized persons out, and summons rescue without entering alone.

Hydrogen sulfide properties

A heavier-than-air, toxic, and flammable gas that deadens the sense of smell at higher concentrations, so odor cannot be relied on as a warning.

BOD5 definition

Five-day biochemical oxygen demand measured at 20 degrees Celsius; it estimates biodegradable organic matter consumed by microorganisms in a wastewater sample.

Infiltration versus inflow

Infiltration is groundwater entering through pipe and manhole defects, while inflow is direct stormwater entry through connections such as roof drains and sumps.

Diurnal flow pattern

Wastewater flow varies through the day, typically lowest in the early morning hours and highest in late morning or early evening, so design uses peak flow.

Peaking factor

The ratio of peak flow to average flow used to size collection and treatment facilities; peak hourly flow equals average daily flow times the peaking factor.

Self-cleaning velocity

A minimum flow velocity of about two feet per second at design flow that keeps solids moving and prevents deposition in gravity sewers.

Manning equation

Q equals 1.486 divided by n, times area, times hydraulic radius to the two-thirds power, times slope to the one-half power, for gravity flow.

Part-full gravity design

Gravity sewers are sized to flow partially full, commonly half to three-quarters of diameter, to allow ventilation and carry peak flows.

Manhole location requirements

Manholes are placed at changes in pipe size, slope, or alignment, at junctions, and at maximum spacing to allow access for cleaning and inspection.

PVC SDR rating

Dimension ratio for PVC pipe; a lower SDR means a thicker wall and higher pressure rating, with SDR 35 and SDR 26 common for gravity sewers.

Pipe bedding purpose

Bedding supports the pipe, distributes loads, and prevents deflection and joint separation; proper haunch compaction is essential for flexible pipe.

Deflection testing

A mandrel or go/no-go gauge is pulled through flexible pipe to confirm deflection does not exceed the specification limit, commonly five percent.

Ductile iron pipe

A strong pressure-rated pipe joined by push-on or mechanical joints, often cement-lined for corrosion protection and used for force mains and deep installations.

Hydrocleaning sewer

High-velocity water jetting removes grease, roots, and debris; nozzle type and pressure are matched to pipe size and material to avoid damage.

Cured-in-place pipe lining

A resin-impregnated liner is inserted and cured inside the existing pipe to seal defects and restore structural condition without excavation, slightly reducing capacity.

Sliplining

A smaller new pipe is pulled through the old pipe and the annular space is grouted; the method reduces capacity but rehabilitates without excavation.

Root control

Cutting removes roots at joints and defects, but the defect remains, so root cutting is combined with rehabilitation to prevent recurrence.

Pump operating point

The flow and head where the pump curve intersects the system curve; system head includes static lift plus friction and minor losses.

Force main septicity

Slow or stagnant flow in a pressurized main can turn septic and generate hydrogen sulfide, causing odor and corrosion; velocity and air release control it.

Wet well cycling volume

Adequate storage between pump start and stop levels limits starts per hour and prevents short cycling that damages motors and pumps.

Check valve function

A valve that allows flow in one direction only, preventing backflow when a pump stops; failure can cause reverse flow and overflow.

CCTV pipe inspection

A camera travels the sewer to record condition; defects are coded by type and severity so pipes can be ranked and prioritized for repair.

Smoke testing

Smoke is forced into the sewer to reveal inflow sources such as roof drains, sumps, illegal connections, and broken laterals that admit stormwater.

Dye testing

A tracer dye is released at a suspected source to confirm whether it connects to the sanitary sewer, verifying cross-connections and leaks.

NPDES permit

A Clean Water Act permit that sets effluent limits and monitoring and reporting requirements for discharges to waters of the United States.

Sanitary sewer overflow reporting

An SSO must be reported to the state regulatory agency within timelines set by state rules and the permit, with volume, location, and corrective actions documented.

Asset management

A program that tracks each asset's location, condition, maintenance history, and remaining life to plan repair or replacement and justify budgets.

Life-cycle cost

The total of capital, operation, maintenance, and replacement costs over an asset's life; the lowest first cost is not always the lowest life-cycle cost.