Water Treatment Plant Operator flashcards

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

Turbidity (NTU)

A measure of light scattering by suspended particles, reported in nephelometric turbidity units. Filtered water must be 0.3 NTU or less in at least 95 percent of monthly samples.

Hardness as CaCO3

The concentration of calcium and magnesium expressed as calcium carbonate equivalent. One grain per gallon equals 17.1 mg/L as CaCO3.

Groundwater under direct influence

Groundwater contaminated by surface water, judged by indicators such as turbidity or fecal coliform. It requires at least 4-log virus inactivation under the Ground Water Rule.

Total organic carbon

A measure of natural organic matter in source water. It is a precursor for disinfection byproducts and a driver of coagulant demand during enhanced coagulation.

Alum alkalinity consumption

Alum consumes about 0.45 mg/L of alkalinity as CaCO3 per mg/L of coagulant applied. Low-alkalinity waters can drop in pH sharply unless alkalinity is supplemented.

Jar test

A bench procedure using multiple beakers and paddle speeds to simulate rapid mix, flocculation, and settling, determining coagulant dose, pH, and polymer dose.

Velocity gradient (G)

A measure of mixing intensity in reciprocal seconds. Rapid mix is typically 300 to 1000 per second; flocculation is typically 10 to 75 per second.

Surface overflow rate

Clarifier flow divided by surface area, expressed as gallons per day per square foot. It represents the settling velocity that particles must exceed to be captured.

Stokes' law

Settling velocity of a discrete particle increases with the square of its diameter and its density difference from water, and decreases as water viscosity rises.

Dual-media filter

A bed of anthracite over sand over gravel. The coarse upper layer allows deeper solids penetration, producing longer filter runs and higher loading rates.

Filter backwash expansion

The percent increase in bed depth during backwash, typically 15 to 25 percent. Adequate expansion is needed to release captured solids without washing media to waste.

Filter-to-waste

Routing filtered water to waste during the ripening period after backwash and before returning it to the clearwell, reducing turbidity spikes and pathogen passage.

CT value

Disinfectant residual concentration in mg/L multiplied by contact time in minutes. Required CT increases as water temperature decreases and pH increases.

Breakpoint chlorination

The chlorine dose beyond which ammonia demand is satisfied and free chlorine residual begins to appear and increase with further dosing.

Hypochlorous acid

The dominant free chlorine species below about pH 7.5. It is a far more effective disinfectant than the hypochlorite ion that dominates at higher pH.

UV254 disinfection

Ultraviolet light at 254 nanometers inactivates Cryptosporidium without creating a residual. Effectiveness depends on turbidity and UV transmittance of the water.

Chemical feed rate formula

Feed rate equals flow multiplied by dose divided by solution strength. Feed pumps are verified by timed collection in a graduated cylinder.

Sodium hypochlorite storage

Hypochlorite degrades faster with heat, sunlight, and heavy metal contamination. Store it cool and shaded, rotate stock, and avoid long storage times.

Secondary containment

A curbed or lined area sized to hold the largest container plus precipitation. It prevents spills of acids, caustics, and coagulants from reaching drains or soil.

Affinity laws

For a centrifugal pump, flow varies with impeller speed, head with the square of speed, and power with the cube of speed.

Cavitation

Vapor bubble formation and collapse when available net positive suction head falls below required. It causes noise, vibration, and impeller damage.

Pump power equation

Brake horsepower equals flow in gpm times head in feet, divided by 3960 times pump efficiency. It sizes motors and estimates energy use.

System curve

A plot of head required versus flow, combining static lift and friction loss. Its intersection with the pump curve defines the operating point.

4 to 20 mA loop

An analog signal standard where 4 mA represents zero and 20 mA represents full scale. A current below 4 mA indicates a broken wire or fault.

pH meter calibration

A two-point adjustment using fresh pH 4 and 7 or 7 and 10 buffers with temperature compensation. Drifting readings indicate electrode fouling or aging.

Cross-connection

Any actual or potential link between a potable water supply and a source of contamination. Protection methods include air gaps and reduced pressure zone assemblies.

Air gap

The highest level of backflow protection: a physical separation of at least twice the pipe diameter and never less than one inch above the flood level rim.

Reduced pressure zone assembly

A testable backflow preventer with two check valves and a relief valve. It requires annual testing by a certified tester and visible relief discharge.

Water age

The average time water resides in the distribution system. High age from low demand or dead ends degrades residual and increases disinfection byproduct formation.

Lead and Copper Rule

A regulation using action levels rather than maximum contaminant levels. Exceeding the lead action level triggers corrosion control, monitoring, and public education requirements.

Public notification tiers

Tier 1 acute violations require notice within 24 hours, Tier 2 within 30 days, and Tier 3 within one year. Notices describe the violation and required actions.

Confined space entry

Entry into a space with limited access and poor ventilation requires atmospheric testing for oxygen, flammables, and hydrogen sulfide, plus a permit, attendant, and rescue plan.