IA Water Operator flashcards

33 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 (mg/L) and contact time (minutes). Used to determine log inactivation credit for pathogens; required CT varies with disinfectant, temperature, and pH.

Log inactivation

A 1-log reduction removes 90% of pathogens; 2-log removes 99%; 3-log removes 99.9%; 4-log removes 99.99%. Used to express treatment credit under the Surface Water Treatment Rule.

Jar test

Bench-scale simulation of coagulation, flocculation, and sedimentation. Used to determine optimal coagulant dose, pH, and mixing conditions before full-scale application.

Filter loading rate

Flow rate divided by filter surface area, typically expressed in gpm/ft². Rapid sand filters commonly operate at 2–5 gpm/ft²; exceeding design rate may cause turbidity breakthrough.

Chlorine demand

The difference between the chlorine dose applied and the free chlorine residual remaining after a specified contact time. Demand must be satisfied before a persistent residual can be measured.

Turbidity limit

Under conventional filtration, finished water turbidity must be ≤0.3 NTU in at least 95% of monthly measurements and must never exceed 1 NTU. Measured in NTU by nephelometry.

Distribution residual minimum

A detectable disinfectant residual must be maintained throughout the distribution system. Typical minimums are 0.2 mg/L free chlorine or 0.5 mg/L chloramine at all sampling points.

Water hammer

Pressure surge caused by sudden changes in flow velocity, such as rapid valve closure or pump trip. Prevented by slow valve operation, surge tanks, air valves, and proper pump sequencing.

Cross-connection control

Prevention of backflow between potable and non-potable systems. An air gap provides absolute protection; reduced-pressure zone and pressure vacuum breaker devices are testable mechanical alternatives.

Hazen-Williams formula

Head loss equation: hf = 4.52 × Q^1.852 × C^-1.852 × d^-4.87, where Q is flow in cfs, d is pipe diameter in ft, and C is the roughness coefficient. Used for distribution main design.

Storage tank turnover

The time required to cycle the volume of a distribution storage tank. Maintaining 3–5 day turnover prevents stagnation, disinfectant decay, and water quality degradation.

Specific capacity

Pumping rate divided by drawdown, expressed in gpm per foot. Indicates well efficiency; declining specific capacity may signal clogging, pump wear, or aquifer depletion.

GWUDI

Groundwater under the direct influence of surface water. Determined by hydrogeologic and water quality analysis; if designated, the source must receive surface water treatment including filtration and disinfection.

Cone of depression

The drawdown shape formed around a pumping well. Its radius and depth depend on pumping rate, aquifer transmissivity, and storativity; overlapping cones indicate well interference.

Saltwater intrusion

Movement of saline water into freshwater aquifers when pumping lowers the freshwater head below the seawater interface. Managed by reducing pumping, relocating wells, or artificial recharge.

TMDL

Total maximum daily load: the maximum amount of a pollutant a waterbody can receive and still meet water quality standards. Used in source water protection and watershed planning.

MCL vs MCLG

MCL is an enforceable maximum contaminant level set as close to the MCLG as feasible. MCLG is a non-enforceable health-based goal with no known or anticipated health risk.

Total coliform rule

Requires routine coliform monitoring. For systems collecting more than 40 samples per month, no more than 5% may be positive. Any E. coli positive is a violation.

Stage 2 DBPR limits

Sets MCLs for total trihalomethanes at 80 µg/L and five haloacetic acids at 60 µg/L, calculated as a locational running annual average at each monitoring site.

Lead and copper action levels

Action level for lead is 0.015 mg/L and for copper is 1.3 mg/L, based on the 90th percentile of samples. Exceeding triggers corrosion control treatment and public education.

Consumer Confidence Report

Annual water quality report delivered to customers by July 1. Must include source water information, detected contaminants, health effects, and educational statements required by regulation.

Public notification tiers

Tier 1 requires immediate notice within 24 hours for acute violations. Tier 2 requires notice within 30 days; Tier 3 requires annual notice for less urgent violations.

Confined space atmosphere

Before entry, test for oxygen (acceptable 19.5–23.5%), flammable gases (below 10% LEL), and toxic gases. A permit and attendant are required for permit-required confined spaces.

Chlorine gas IDLH

Immediately dangerous to life or health concentration for chlorine is 10 ppm. Response requires supplied-air respiratory protection and upwind evacuation; air-purifying respirators are inadequate.

Lockout/tagout

Hazardous energy control procedure: isolate energy sources, apply locks and tags, and verify zero energy before maintenance. Prevents unexpected startup or release of stored energy.

Trench protective systems

Excavations 5 ft or deeper require shoring, sloping, or shielding. Spoil piles must be at least 2 ft from the edge; access ladders within 25 ft of workers.

Eyewash and shower

Emergency eyewash and safety shower must be within 10 seconds travel distance of chemical hazards and flush for at least 15 minutes. Weekly activation verification is recommended.

GFCI protection

Ground-fault circuit interrupter protection is required for portable electrical tools used in wet or damp locations. It interrupts power when a ground fault is detected to prevent shock.

DPD free chlorine method

Colorimetric method using DPD indicator; free chlorine reacts to form a magenta color read at 515 nm. Monochloramine interference is addressed by differentiated procedures.

Turbidity measurement

Nephelometric method measures light scattered by suspended particles, reported in NTU. Calibrate with primary standards such as formazin and verify with secondary standards.

Heterotrophic plate count

Pour plate method incubating at 35°C for 48 hours; results reported as CFU/mL. Indicates general bacterial population and treatment effectiveness, not a regulatory MCL.

Chain of custody

Documentation tracking sample possession from collection through analysis. Includes sample ID, date/time, collector, preservation, and requested analyses; ensures legal defensibility of results.

Laboratory quality control

Each analytical batch includes a method blank, duplicate, and matrix spike. Duplicate relative percent difference typically must be ≤20% to accept results.