NH Water/Wastewater Operator flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- CT concept
- Product of disinfectant residual concentration and contact time used to demonstrate pathogen inactivation; required CT increases with colder water and higher pH for free chlorine.
- Turbidity limit
- Combined filter effluent must be at or below 0.3 NTU in at least 95 percent of monthly measurements and never exceed 1 NTU for conventional filtration.
- Detention time formula
- Detention time equals tank volume divided by flow rate; keep units consistent, such as gallons divided by gallons per hour to yield hours.
- Overflow rate
- Surface overflow rate is flow divided by clarifier surface area, expressed in gallons per day per square foot; it governs particle settling performance.
- Minimum distribution pressure
- Twenty psi must be maintained throughout the distribution system under normal operating conditions; loss of pressure triggers notification and corrective action.
- Air gap backflow protection
- A physical separation between a potable supply and a receiving vessel; it is the highest level of backflow protection against backsiphonage and backpressure.
- Pump horsepower
- Water horsepower equals flow in gallons per minute times head in feet divided by 3,960; divide by pump efficiency for brake horsepower.
- Chloramine residual
- Formed by adding ammonia to chlorinated water; it is a weaker disinfectant than free chlorine but persists longer in distribution systems.
- BOD5 definition
- Biochemical oxygen demand measured over five days at 20 degrees Celsius; it estimates biodegradable organic matter in wastewater, typically 200 to 250 mg/L domestic.
- F/M ratio
- Food-to-microorganism ratio equals pounds of BOD entering per day divided by pounds of MLVSS in the aeration tank; it controls sludge bulking and nitrification.
- Sludge age (MCRT)
- Mean cell residence time equals solids mass in the aeration tank divided by solids leaving daily in waste sludge plus effluent; it controls biomass inventory.
- RAS purpose
- Return activated sludge recycles settled biomass from the clarifier to the aeration tank, maintaining mixed liquor suspended solids in the treatment range.
- Self-cleansing velocity
- About two feet per second in gravity sewers keeps solids suspended and prevents deposition; lower velocities allow grit and grease to accumulate.
- Infiltration and inflow
- Groundwater entering through defects is infiltration; stormwater entering through illicit connections is inflow. Both add clear water load to treatment.
- Fecal coliform limit
- Typical effluent limit of 200 colony-forming units per 100 milliliters as a monthly geometric mean, with chlorine residual maintained to ensure disinfection.
- Anaerobic digestion
- Bacteria break down volatile solids without oxygen, reducing sludge mass 40 to 60 percent and producing biogas containing roughly 60 to 65 percent methane.
- Turbidity measurement
- Nephelometry measures light scattered by suspended particles in NTU; instruments are calibrated with formazin primary standards and results below 1 NTU use two significant figures.
- Total coliform trigger
- A positive total coliform sample requires repeat sampling at the site; E. coli confirmation requires public notification within 24 hours.
- DPD chlorine test
- Colorimetric method where DPD reagent reacts with chlorine to form a colored compound; free and total chlorine are reported to 0.01 mg/L.
- pH calibration buffers
- A pH meter is calibrated with buffers at pH 4, 7, and 10 to bracket sample range; calibration is performed before each sampling day.
- Nitrate MCL
- Maximum contaminant level for nitrate is 10 mg/L as nitrogen; nitrite is 1 mg/L as nitrogen. Both are analyzed by ion chromatography or cadmium reduction.
- Lead action level
- The 90th percentile lead action level is 0.015 mg/L, based on first-draw one-liter samples collected after six hours without water use.
- Chain of custody
- Documentation recording sampler, date, time, location, preservation, and transfer signatures; it establishes sample integrity for regulatory and legal purposes.
- Sample holding time
- Maximum time a sample may be held before analysis; chlorine and pH are analyzed immediately, nitrate within 48 hours, and preserved metals within six months.
- Safe Drinking Water Act
- Federal law authorizing EPA to set maximum contaminant levels and treatment techniques; states with primacy enforce and report compliance.
- TTHM MCL
- Total trihalomethanes are limited to 80 micrograms per liter and HAA5 to 60 micrograms per liter, evaluated as locational running annual averages.
- Consumer Confidence Report
- Annual report delivered to customers by July 1, listing source water, detected contaminants, and required health effects language.
- NPDES permit
- Clean Water Act permit limiting effluent parameters and requiring monthly discharge monitoring reports for point source wastewater discharges.
- Confined space entry
- Entry requires atmospheric testing for oxygen, flammables, and hydrogen sulfide, plus a permit, attendant, and rescue plan before entry.
- Chlorine gas response
- Chlorine gas is heavier than air; responders use SCBA, evacuate upwind, and never use ammonia, which reacts to form dangerous compounds.
- Operator certification
- State-issued credential tied to system classification grade, requiring passing an exam and continuing education units for renewal.
- Hazard communication
- Requires accessible safety data sheets, labeled containers, and employee training on chemical hazards; lockout/tagout applies before equipment servicing.