AR Water 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 required pathogen inactivation credit.

Turbidity combined filter effluent

Surface water rule limit of 0.3 NTU in at least 95 percent of monthly measurements, with no single reading above 1 NTU.

Jar test purpose

Laboratory procedure that simulates coagulation and flocculation to determine optimum coagulant dose and pH for a given raw water.

Langelier Saturation Index

Difference between measured pH and saturation pH; negative values indicate corrosive tendency, positive values indicate scale-forming tendency.

Alum alkalinity demand

Alum consumes natural alkalinity during coagulation, so low-alkalinity source waters may require lime or caustic addition to maintain pH.

Cryptosporidium disinfection resistance

Oocysts are highly resistant to free chlorine; control typically relies on physical removal plus UV or ozone disinfection.

Minimum distribution pressure

Distribution systems must maintain positive pressure, commonly a minimum of 20 psi, to prevent backflow and contamination intrusion.

Water hammer cause

Sudden velocity change from rapid valve closure or pump trip creates pressure surges; mitigated by slow closure, surge tanks, and air valves.

Air gap backflow protection

Physical separation between a potable supply and a receiving vessel; the highest-level and most reliable form of cross-connection protection.

Unidirectional flushing

Flushing method sequencing valves to move water at high velocity in one direction, scouring sediment and biofilm from mains.

Hazen-Williams equation

Empirical formula relating head loss to flow, pipe diameter, length, and roughness coefficient C; widely used for distribution main design.

Storage tank turnover

Regular cycling of stored volume prevents stagnation, residual loss, and water quality degradation in distribution storage facilities.

Pipe flow velocity

Velocity equals flow divided by cross-sectional area; design values of roughly 2 to 5 ft/s limit head loss and pipe erosion.

Membrane filtration coliform method

Sample is filtered through a membrane, incubated on selective medium, and colonies counted and reported as CFU per 100 mL.

DPD chlorine method

Colorimetric test measuring free and total chlorine; combined chlorine is estimated as total minus free chlorine residual.

Turbidity units

Nephelometric turbidity is reported in NTU and instruments are calibrated with formazin or approved polymer primary standards.

Bacteriological holding time

Collected samples must be chilled and reach the laboratory within a short window, commonly six to eight hours, per state rule.

Grab versus composite sample

Grab samples represent one moment in time; composite samples combine flow- or time-proportioned aliquots for loading calculations.

Method detection limit

Statistically derived lowest concentration distinguishable from zero; differs from the reporting limit, which is the lowest routinely quantifiable value.

Chain of custody

Documentation tracking sample possession, collector, date and time, requested analyses, and each transfer between handlers.

TTHM MCL

Stage 2 rule locational running annual average limit of 80 micrograms per liter for total trihalomethanes in distribution systems.

HAA5 MCL

Stage 2 rule locational running annual average limit of 60 micrograms per liter for the five regulated haloacetic acids.

Lead action level

Ninetyth percentile lead concentration of 0.015 mg/L; exceedance triggers corrosion control treatment, monitoring, and public education.

Nitrate MCL

Maximum contaminant level of 10 mg/L expressed as nitrogen; nitrite is limited to 1 mg/L as nitrogen.

Consumer Confidence Report

Annual report delivered to customers by July 1 describing source water, detected contaminants, and compliance status of the system.

Tier 1 public notice

Immediate notification required within 24 hours for acute violations such as an E. coli MCL exceedance or nitrate exceedance.

Chlorine gas leak response

Chlorine is heavier than air; respond from upwind using self-contained breathing apparatus, never a cartridge respirator or dust mask.

Confined space oxygen range

Acceptable entry atmosphere is 19.5 to 23.5 percent oxygen; testing for flammables and toxics is also required before entry.

Hypochlorite and acid mixing

Combining sodium hypochlorite with acid releases chlorine gas; these chemicals must be stored and fed separately.

Trench protective system threshold

Excavations 5 feet or deeper require a protective system; spoils and heavy equipment stay at least 2 feet from the edge.

Water loss percentage

Calculated as system input volume minus authorized consumption, divided by system input volume, multiplied by 100.

Sanitary survey

Primacy agency inspection of source, treatment, distribution, and management; identified significant deficiencies require corrective action on a schedule.