DE Water Operator flashcards

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

CT value

CT equals disinfectant residual concentration in mg/L multiplied by effective contact time in minutes, expressed as mg·min/L; it quantifies disinfection exposure for inactivation credit.

Chlorine demand

The difference between the chlorine dose applied and the residual remaining after a specified contact time. Demand comes from oxidizable matter such as organics, iron, manganese, and ammonia.

Hypochlorous acid fraction

HOCl is the stronger disinfectant form of free chlorine. Its fraction increases as pH decreases, dropping sharply above pH 7.5 where hypochlorite ion dominates.

Jar test purpose

A bench-scale test that determines the optimum coagulant dose and pH for turbidity and organic removal before full-scale treatment adjustments are made.

Filter uniformity coefficient

The sieve size at 60% passing divided by the sieve size at 10% passing of filter media. Values of 1.5 or less indicate well-graded media.

Combined filter effluent turbidity

Turbidity of all filtered water combined. Conventional systems must stay at or below 0.3 NTU in 95% of monthly samples and never exceed 1 NTU.

TTHM and HAA5

Total trihalomethanes and five haloacetic acids, disinfection byproducts formed when chlorine reacts with natural organic matter; both have enforceable running annual average limits.

Backwash purpose

Reverse flow through a filter at a rate that expands the media bed, releasing trapped particles and restoring head loss and run time.

Minimum distribution pressure

Twenty psi is the regulatory minimum at all points in the distribution system under all conditions, including fire flow and main break scenarios.

Feet of head to psi

One psi equals approximately 2.31 feet of water column. Convert head in feet to psi by dividing by 2.31.

Hazen-Williams head loss

Empirical pipe friction formula where head loss rises with flow to the 1.85 power and falls with pipe diameter to the 4.87 power and roughness coefficient C to the 1.85 power.

Air gap

A physical, non-mechanical separation between a potable water outlet and the flood-level rim of a receiving vessel; the only backflow protection immune to failure.

Reduced pressure zone assembly

A testable backflow preventer with two check valves and a relief valve, used where both backpressure and back-siphonage hazards exist.

Dead-end main risk

Mains with only one flow path stagnate, lose disinfectant residual, and grow biofilm; chloraminated systems may nitrify. Flushing or looping mitigates.

Main repair disinfection

After repair, the main is chlorinated, typically to 25 to 100 mg/L for at least 24 hours, flushed, then sampled for coliform and residual before service.

Storage tank turnover

The time needed to cycle tank volume. Long detention consumes residual and raises disinfection byproduct and stagnation risk, so operations target adequate turnover.

GWUDI definition

Groundwater under the direct influence of surface water, meaning it is hydraulically connected to surface water and may carry pathogens; it is regulated like surface water.

Turbidity as surrogate

Turbidity measured in NTU indicates particle levels and serves as a proxy for treatment performance and pathogen removal, not a direct pathogen measurement.

Hardness categories

Total hardness reported as mg/L calcium carbonate: soft below 60, moderately hard 60 to 120, hard 120 to 180, very hard above 180.

Iron and manganese limits

Secondary limits are about 0.3 mg/L iron and 0.05 mg/L manganese; above these, staining and taste complaints occur. Treatment is oxidation followed by filtration.

Nitrate MCL

The nitrate limit is 10 mg/L measured as nitrogen. Exceedance triggers public notice due to methemoglobinemia risk in infants under six months.

Langelier Saturation Index

An index comparing actual pH to calcium-carbonate saturation pH. Near zero is balanced, negative tends to be corrosive, positive tends to form scale.

Total coliform positive

A routine positive total coliform sample triggers repeat sampling at the site and nearby locations, plus testing for E. coli and fecal indicators.

Surface Water Treatment Rule log credits

The rule requires 3-log Giardia and 4-log virus removal or inactivation, achieved through filtration and disinfection credited by CT tables.

Stage 2 DBP LRAA

Disinfection byproducts are limited on a locational running annual average basis: TTHM 80 µg/L and HAA5 60 µg/L at each monitoring location.

Lead and copper action levels

Tap sample 90th percentile action levels are 0.015 mg/L lead and 1.3 mg/L copper. Exceedance triggers corrosion control treatment and public education.

Tier 1 public notice

Immediate notice, within 24 hours, for acute violations such as E. coli or nitrate MCL exceedance, using radio, TV, hand delivery, or other required methods.

Consumer Confidence Report

An annual report delivered to customers by July 1 that lists source water, detected contaminants, compliance status, and required health effects language.

Confined space atmosphere

Acceptable entry atmosphere is oxygen between 19.5 and 23.5 percent, flammable gas below 10 percent of LEL, and hydrogen sulfide below 10 ppm.

Chlorine gas behavior

Chlorine gas is about 2.5 times heavier than air and collects in low areas, so escape requires moving upwind and to higher ground with proper respiratory protection.

Lockout tagout steps

Identify all energy sources, notify affected workers, shut down and isolate, apply locks and tags, release stored energy, then verify zero energy before work.

Excavation protective system

Any trench 5 feet deep or deeper requires a protective system such as sloping, shoring, or a trench box; spoil and equipment stay at least 2 feet back.