LA Water Operator flashcards

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

CT value

The product of disinfectant residual concentration in mg/L and contact time in minutes. Regulators use CT to verify that a system achieves the required log inactivation of Giardia and viruses.

Chlorine demand

The difference between the chlorine dose applied and the free chlorine residual left after a defined contact period. It reflects chlorine consumed by ammonia, organics, and reducing agents.

Breakpoint chlorination

The chlorine dose at which ammonia and other demanding substances are fully oxidized so that any added chlorine persists as free residual, requiring roughly 7.6 mg Cl2 per mg ammonia-nitrogen.

Alum alkalinity consumption

Each mg/L of alum (Al2(SO4)3-14H2O) added consumes about 0.45 mg/L of alkalinity as CaCO3, which lowers pH and may require lime or caustic soda feed.

Uniformity coefficient

The ratio of the 60th-percentile grain size to the 10th-percentile grain size (d60/d10) of filter media. Values below about 1.5 indicate a well-graded bed that backwashes evenly.

HOCl versus OCl-

Free chlorine exists as hypochlorous acid and hypochlorite ion. HOCl is the far stronger disinfectant and dominates below pH 7, while OCl- dominates above pH 8.5.

Cryptosporidium inactivation

Chlorine and chloramines do not inactivate Cryptosporidium oocysts at practical doses. Systems must use UV, ozone, or chlorine dioxide, often with filtration, to earn inactivation credit.

Psi to feet of head

One psi equals 2.31 feet of water column, and one foot of water equals 0.433 psi. A 100-foot elevation difference therefore produces about 43 psi of static pressure.

Gallons per foot of pipe

Multiply the inside diameter in inches squared by 0.0408 to find the gallons held in one foot of pipe. This is used to size flush volumes and chlorine doses for mains.

Hazen-Williams C factor

A roughness coefficient in the head loss formula. New cement-lined pipe is about 130, while old tuberculated steel may fall to 80 or lower and greatly increases friction loss.

Thrust block

A concrete mass poured against fittings such as bends, tees, and hydrant branches to resist the unbalanced forces created by internal pressure and changes in flow direction.

Water hammer

A pressure surge caused by a sudden change in flow velocity, such as rapid valve closure or a pump trip. It can rupture pipe and blow joints apart.

Distribution chlorine residual

A detectable disinfectant residual must be maintained throughout the distribution system. Operators typically target at least 0.2 mg/L free chlorine at extremities to limit bacterial regrowth.

Dead-end main flushing

Routine or unidirectional flushing of dead ends and low-flow mains reduces water age, sediment, and biofilm that otherwise consume disinfectant residual and cause taste complaints.

Coliform repeat samples

After a routine total coliform-positive sample, the system must collect repeat samples within 24 hours: one at the original site plus one upstream and one downstream.

Bacteriological holding time

Samples for total coliform analysis must be chilled during transport and analyzed within 30 hours of collection. A sample exceeding that limit yields an invalid result.

DPD method

A colorimetric or amperometric procedure using the indicator DPD to measure free and total chlorine residual. Free chlorine should be tested on site because residual decays in transit.

Nephelometric turbidity

Turbidity measured by light scattered at 90 degrees from a sample and reported in NTU. It is the principal real-time indicator of filtration performance and microbial risk.

Hardness as CaCO3

Total hardness equals 2.497 times the calcium concentration plus 4.118 times the magnesium concentration, with both metals expressed in mg/L and the result reported as CaCO3.

pH buffer calibration

A pH meter is calibrated before use with fresh pH 4, 7, and 10 buffers. Slope and temperature compensation are checked so readings stay within about 0.1 unit.

Permit-required confined space

A space with limited entry, poor ventilation, and potential hazardous atmosphere. Entry requires a permit, atmospheric testing, an attendant outside, and retrieval equipment.

Oxygen entry range

Entry is allowed only when the atmosphere tests between 19.5 and 23.5 percent oxygen. Below that is oxygen deficient; above it is oxygen enriched and a serious fire hazard.

Chlorine gas density

Chlorine gas is about 2.5 times heavier than air, so leaking gas travels along the floor and collects in low-lying areas. Responders should work upwind and uphill.

Chlorine repair kits

Emergency repair kits are matched to container size. The A kit serves cylinders up to 150 pounds, the B kit serves ton containers, and the C kit serves rail tank cars.

Trench protective system

Cal/OSHA requires a protective system such as sloping, shoring, or a trench shield in excavations 5 feet deep or more, with a ladder within 25 feet of workers.

Hydrogen sulfide IDLH

Hydrogen sulfide has an immediately dangerous to life or health concentration of 100 ppm and a ceiling limit of 10 ppm. It deadens the sense of smell, so odor is not a warning.

TTHM MCL

Total trihalomethanes are limited to 80 micrograms per liter and five haloacetic acids to 60 micrograms per liter, each calculated as a locational running annual average.

Lead action level

The lead action level is 0.015 mg/L and the copper action level is 1.3 mg/L. Both are evaluated at the 90th percentile of tap samples from designated high-risk sites.

Consumer Confidence Report

Community water systems must deliver an annual report to customers by July 1 summarizing the prior calendar year's monitoring results, detected contaminants, and compliance status.

Nitrate MCL

The nitrate maximum contaminant level is 10 mg/L measured as nitrogen, and nitrite is 1 mg/L as nitrogen. Exceeding either is an acute violation requiring rapid public notice.

Acute violation reporting

Violations carrying immediate health risk, such as E. coli detection or a nitrate exceedance, must be reported to the state within 24 hours, with public notice also within 24 hours.

Backflow assembly testing

Cross-connection control programs require reduced-pressure and double-check assemblies to be tested annually by a certified tester, with test records kept for state review.