Wastewater Collection Operator Class I flashcards

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

Minimum self-cleansing velocity

Gravity sewers are designed to carry at least 2 feet per second (0.6 meters per second) at design flow, so solids stay suspended and the pipe scours itself clean.

Infiltration versus inflow

Infiltration is groundwater entering through defective pipe, joints, and manholes; inflow is stormwater entering directly through roof leaders, area drains, and manhole covers during rain.

Manning's equation

Gravity flow capacity is found from Q = (1.486/n) A R to the two-thirds power S to the one-half power in US units, where n is roughness, R hydraulic radius, S slope.

Crown corrosion by hydrogen sulfide

Sulfate-reducing bacteria in anaerobic slime on submerged pipe surfaces produce hydrogen sulfide gas, which oxidizes to sulfuric acid on the moist crown and destroys concrete pipe.

Smoke testing

Forcing smoke into a sewer section shows where it escapes at the surface, revealing illegal storm connections, broken laterals, and defective manhole covers.

Sanitary sewer overflow

A release of untreated wastewater from the collection system before treatment; it must be stopped, contained, cleaned up, and reported to the regulatory agency within the required time.

CCTV sewer inspection

A closed-circuit television camera travels through the pipe and records cracks, roots, offsets, grease, and debris, producing a permanent record used for repair planning.

Manhole spacing standard

Public gravity sewers normally have manholes every 400 to 500 feet and at every change in direction, grade, or pipe size, and at each junction.

Pump affinity laws

For a centrifugal pump at fixed impeller diameter, flow changes in proportion to speed, head with speed squared, and brake horsepower with speed cubed.

Cavitation cause

When available net positive suction head falls below the pump's required value, liquid boils and the bubbles collapse at the impeller, producing noise, vibration, and pitting damage.

Best efficiency point

The flow rate on a pump curve where efficiency peaks and shaft load and vibration are lowest; running far from it causes recirculation, heat, and early seal failure.

Check valve function

Installed on each pump discharge, it closes when the pump stops to prevent reverse flow, keep the force main from draining back, and stop the pump spinning backward.

Brake horsepower formula

Pump brake horsepower equals gallons per minute times total head in feet times specific gravity, divided by 3960 times the pump efficiency at that flow.

Explosion-proof motor location

Motors and electrical equipment installed in wet wells and other classified locations must be approved for flammable atmospheres, typically Class I Division 1 near the pumps.

Stuffing box drip rate

A properly adjusted packed stuffing box on a centrifugal pump leaks slowly, about 40 to 60 drops per minute, so the packing rings stay lubricated and cooled.

Megger insulation test

This test applies high voltage to motor windings and measures insulation resistance; low or falling readings indicate moisture, dirt, or deteriorated insulation before failure occurs.

Confined space oxygen limits

Entry is allowed only when oxygen is between 19.5 and 23.5 percent; below that is oxygen deficient, and above it flammable vapors ignite far more easily.

Ten percent LEL rule

A permit space is ventilated and retested until combustible gas reads below 10 percent of the lower explosive limit before entry and continuously while it is occupied.

Methane flammable range

Methane burns between 5 and 15 percent by volume in air and is lighter than air, so it rises and collects at the top of manholes and wet wells.

Hydrogen sulfide exposure limits

Hydrogen sulfide has a 20 ppm ceiling and is immediately dangerous at 100 ppm; it is heavier than air, collects in low areas, and deadens the sense of smell.

Confined space attendant duties

The attendant stays outside the permit space, keeps the entry log, maintains communication with entrants, monitors conditions, and summons rescue without ever entering the space.

Trench protective system

Sloping, shoring, or a trench box is required for excavations 5 feet deep or more, selected by a competent person based on the soil type present.

Two foot spoil setback

Excavated material, equipment, and supplies must be kept at least 2 feet back from the trench edge to reduce the load that can trigger wall collapse.

Lockout tagout sequence

Shut down the equipment, isolate every energy source, apply your own lock and tag, release stored energy, then try the controls to confirm de-energization.

NPDES permit

The Clean Water Act requires any point source discharging to waters of the United States to hold a permit setting effluent limits, monitoring, and reporting requirements.

SSO notification

Collection system overflows must be reported to the state regulatory agency, and often to the public, within the timeframe set in state rules, commonly 24 hours.

Discharge Monitoring Report

The self-reporting form that transmits permit monitoring results to the regulator, signed by a responsible official and kept with supporting records for the retention period.

CMOM program

EPA's Capacity, Management, Operations and Maintenance framework covers capacity assurance, asset management, training, and an emergency overflow response plan for collection systems.

Sewer use ordinance

The local law that sets who may connect to the publicly owned treatment works, which discharges are prohibited, and what permits, fees, and penalties apply.

Pretreatment program

Under 40 CFR 403, the treatment plant issues industrial user permits, sets local limits, samples and inspects significant industrial users, and enforces violations found.

Operator certification renewal

Certificates are issued by the state, matched to system classification, and renewed on a set cycle requiring continuing education contact hours and usually a renewal fee.

Hazard Communication Standard

OSHA requires labeled containers, accessible safety data sheets, and training for every worker exposed to hazardous chemicals such as chlorine, lime, or ferric chloride.