IN Water/WW Operator flashcards

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

CT value

Product of disinfectant residual concentration in mg/L and contact time in minutes, used to demonstrate inactivation credit; the required CT increases at higher pH and lower water temperature.

Jar test

Bench-scale test using multiple beakers with different coagulant doses and mixing speeds to find the chemical dose and pH that produce the clearest settled water.

Surface overflow rate

Clarifier design value equal to flow divided by surface area, in gpm/ft2 or m3/m2-h; particles settling slower than this rate leave with the effluent.

Filter backwash rate

Upward flow rate that expands and cleans granular filter media, typically 15 to 20 gpm/ft2 for rapid sand filters, often assisted by air scour.

Lime softening

Process that adds hydrated lime to raise pH so calcium carbonate precipitates, then adds more lime at higher pH to remove magnesium as magnesium hydroxide.

Pressure per foot of elevation

A column of water one foot high exerts 0.433 psi, so a tank surface 100 feet above a service connection provides about 43 psi static pressure.

Water hammer

Pressure surge caused by rapid flow velocity changes when valves close or pumps stop, controlled with slow-closing valves, surge tanks, and air release valves.

Hazen-Williams coefficient C

Roughness factor in the Hazen-Williams head loss equation; higher values mean smoother pipe, with about 130 to 140 for new cement-lined or plastic main.

Air gap

Physical separation between a potable water outlet and the flood level of the receiving vessel, giving the highest degree of backflow protection with no mechanical parts.

BOD5

Biochemical oxygen demand measured after five days of incubation at 20 degrees Celsius; it approximates biodegradable organic matter and is used to size aeration basins and set permit limits.

F/M ratio

Food-to-microorganism ratio in activated sludge, pounds of BOD applied per day divided by pounds of mixed liquor volatile solids under aeration, typically 0.2 to 0.5 per day.

Sludge volume index

Milliliters of sludge settled in 30 minutes per gram of mixed liquor suspended solids; about 80 to 150 indicates good settling and above 200 indicates bulking.

Nitrification alkalinity demand

Oxidizing one milligram of ammonia nitrogen to nitrate consumes about 7.14 milligrams of alkalinity as calcium carbonate, so nitrifying plants may need alkalinity supplementation.

Return activated sludge rate

Flow of settled sludge returned from the secondary clarifier to the aeration basin, commonly 50 to 100 percent of influent flow, to hold the target mixed liquor solids.

Self-cleansing velocity

Minimum velocity of about 2 feet per second in a gravity sewer that keeps grit and solids moving; velocities above 10 to 15 feet per second cause scour.

Manning equation

Open-channel flow formula in US units: velocity equals 1.486 divided by roughness n, times hydraulic radius to the two-thirds power, times slope to the one-half power.

Infiltration and inflow

Infiltration is groundwater seeping through defective pipe joints and walls; inflow is storm water entering manholes, roof drains, and illegal connections. Both add clear water to sanitary sewers.

Smoke testing

Blowing non-toxic smoke into a sewer section so it escapes at illegal storm connections, broken pipe, and defective manholes, revealing where clear water enters.

Confined space oxygen range

Acceptable entry atmosphere is 19.5 to 23.5 percent oxygen; below 19.5 percent is oxygen deficient and above 23.5 percent sharply increases fire risk.

Hydrogen sulfide IDLH

The immediately dangerous to life or health concentration for hydrogen sulfide is 100 ppm; the gas deadens the sense of smell, so odor is not a reliable warning.

Methane explosive range

Methane forms a flammable mixture in air between about 5 percent lower explosive limit and 15 percent upper explosive limit, levels that can occur in sewers and wet wells.

Trench protective system

Sloping, shoring, or shielding required for excavations 5 feet deep or more, with daily inspection by a competent person and spoil kept 2 feet from the edge.

Chlorine gas properties

Chlorine is about 2.5 times heavier than air, so leaks collect in low areas; the IDLH is 10 ppm and responders need SCBA with an escape pack.

Lead and copper action level

The 90th percentile tap sample must not exceed 0.015 mg/L lead or 1.3 mg/L copper; exceeding either triggers corrosion control treatment, public education, and source water evaluation.

Total trihalomethane maximum

The maximum contaminant level for total trihalomethanes is 80 micrograms per liter, calculated as a locational running annual average at each monitoring location.

Nitrate maximum contaminant level

The MCL for nitrate is 10 mg/L measured as nitrogen; higher levels cause methemoglobinemia in infants, so systems must notify the public quickly.

Tier 1 public notice

Required within 24 hours when a violation carries immediate health risk, such as an E. coli positive or nitrate exceedance, delivered by media, hand delivery, or posting.

Triple bottom line capacity

States evaluate water systems on technical, managerial, and financial capacity, which together show ability to reliably comply with rules and fund improvements.

Asset management plan

Inventory of assets with condition, criticality, and replacement cost, used to schedule preventive maintenance and capital renewal at the lowest life-cycle cost.

Chain of custody

Written record of each sample's handling from collection through laboratory analysis, including times, preservatives, and signatures, which makes results legally defensible.

Risk and Resilience Assessment

Under America's Water Infrastructure Act, community systems serving 3,300 or more people assess risks to critical assets and document emergency response, updating every five years.

Emergency response plan

Document assigning staff roles, mutual aid agreements, notification lists, and alternate water or power sources so service can be restored and the public warned during incidents.