AZ Water Operator cheat sheet

The hydrologic cycle: evaporation, transpiration, condensation, precipitation, runoff, infiltration, and groundwater recharge; about 97% of Earth's water is saline, and about 2% is frozen.

Surface water sources include rivers, lakes, and reservoirs; groundwater sources include wells and springs, typically with higher mineral content and lower turbidity than surface water.

A watershed (drainage basin) is the land area that drains to a common water body; source water protection focuses on preventing contamination within the watershed.

Safe yield of a water source is the maximum rate of withdrawal that can be sustained without depleting the source or causing undesirable effects.

Wellhead protection areas are delineated by time-of-travel (e.g., 1-year, 5-year, 10-year) or by fixed radius, and land uses within them are managed to prevent contamination.

Groundwater flows from higher hydraulic head to lower head; Darcy's law: Q = K·i·A, where Q = flow, K = hydraulic conductivity, i = hydraulic gradient, A = cross-sectional area.

Total maximum daily load (TMDL) is the maximum amount of a pollutant a water body can receive and still meet water quality standards; it includes point and nonpoint sources with a margin of safety.

Source water assessment includes delineation of the area, inventory of potential contaminant sources, susceptibility analysis, and public availability of results.

Coagulation destabilizes colloidal particles by neutralizing negative surface charges; common coagulants include alum, ferric chloride, ferric sulfate, and polyaluminum chloride.

Flocculation is gentle mixing (typically 30–60 minutes at 10–50 rpm) that promotes collisions and growth of floc particles after coagulation.

Sedimentation (clarification) removes settleable solids; typical overflow rates are 0.5–1.0 gpm/ft² for conventional clarifiers, and detention time is usually 2–4 hours.

Filtration removes residual particles and pathogens; rapid sand filters typically operate at 2–6 gpm/ft², with media such as anthracite over sand and gravel support.

Filter backwash is triggered by head loss (typically 6–10 ft) or turbidity breakthrough, and uses a flow rate of 15–20 gpm/ft² for 10–15 minutes.

Disinfection inactivates pathogens; CT (disinfectant concentration × contact time) is used to determine inactivation credit, with CT requirements increasing at higher pH and lower temperature for chlorine.

Chlorine residual must be maintained throughout the distribution system; free chlorine residual is typically 0.2–4.0 mg/L, and the maximum contaminant level (MCL) for total chlorine is 4.0 mg/L.

Turbidity is a key treatment performance indicator; conventional filtration must produce filtered water turbidity ≤0.3 NTU in at least 95% of monthly samples, and never exceed 1 NTU.

Chemical feed rate formula: feed rate (lb/day) = dose (mg/L) × flow (MGD) × 8.34 lb/gal.

For liquid chemicals, feed rate (gal/day) = (dose × flow × 8.34) / (solution strength × specific gravity × 8.34) simplifies to (dose × flow) / (solution strength × specific gravity).

Chlorine gas is stored in pressurized cylinders; 1 lb of chlorine gas produces about 1 lb of chlorine in water, and the gas is 2.5 times heavier than air.

Sodium hypochlorite (liquid bleach) degrades over time and with heat and sunlight; store in a cool, dark, ventilated area and use within recommended shelf life.

Chemical storage areas must have secondary containment (e.g., curbs, dikes) sized to hold at least 110% of the largest container's volume.

Acids and bases must be stored separately to prevent violent reactions; oxidizing agents (e.g., chlorine, permanganate) must be segregated from reducing agents and organics.

Chemical metering pumps (positive displacement) require calibration; stroke length and speed adjustments control feed rate, and calibration is verified by drawdown or weight checks.

Personal protective equipment (PPE) for chemical handling includes chemical-resistant gloves, goggles or face shield, apron, and respiratory protection as specified in the safety data sheet (SDS).

Centrifugal pumps are the most common in water systems; flow varies with head, and the pump operates at the intersection of the pump curve and system curve.

Cavitation occurs when the net positive suction head available (NPSHA) is less than the net positive suction head required (NPSHR); symptoms include noise, vibration, and reduced flow.

Pump affinity laws: flow varies directly with speed, head varies with the square of speed, and power varies with the cube of speed.

Motor power formula: brake horsepower (bhp) = (flow in gpm × head in ft × specific gravity) / (3960 × pump efficiency).

Valves: gate valves are for isolation (on/off), globe valves for throttling, butterfly valves for large-diameter isolation and some throttling, and check valves prevent backflow.

A pressure relief valve protects pumps and piping from overpressure; it should be set at or below the system's maximum allowable working pressure.

Preventive maintenance includes lubrication, vibration analysis, alignment checks, packing or mechanical seal inspection, and monitoring of bearing temperatures.

Electric motor current unbalance should be within 1–2%; higher unbalance causes overheating and reduced motor life.

Distribution system minimum pressure is typically 20 psi under normal conditions and 20 psi during fire flow; maximum pressure is usually 100–125 psi to prevent damage.

Water storage tanks provide equalization, emergency reserve, and fire flow; they must maintain a chlorine residual and be inspected and cleaned periodically.

Cross-connections are physical links between potable and nonpotable water; they are controlled by air gaps (the only absolute protection) or by backflow prevention assemblies (RPZ, DCVA, PVB).

An air gap must be at least twice the diameter of the supply pipe and never less than 1 inch above the flood-level rim of the receiving vessel.

Backflow can occur by backpressure (downstream pressure exceeds supply pressure) or by backsiphonage (negative pressure in the supply line).

Reduced pressure zone (RPZ) assemblies must be tested annually by a certified tester; test results must be reported to the water utility.

Water mains are typically flushed to remove sediment and biofilm; flushing velocities should be at least 2.5–3.0 ft/s to achieve scouring.

Disinfection of new water mains typically uses a chlorine concentration of 25–50 mg/L for 24 hours, followed by flushing and bacteriological sampling.

Sample collection must use clean, appropriate containers (e.g., sterile for bacteriological, amber glass for organics) and follow chain-of-custody procedures.

Bacteriological samples are collected in sterile bottles containing sodium thiosulfate to neutralize chlorine; sample volume is typically 100 mL.

Total coliform MCL: no more than 5% of monthly samples may be positive for systems collecting at least 40 samples per month; any positive sample requires repeat sampling and investigation.

E. coli is a fecal indicator; its presence in a distribution system requires public notification and corrective action.

Turbidity is measured in nephelometric turbidity units (NTU) using a nephelometer; it is a key indicator of filtration effectiveness.

pH is measured electrometrically with a pH meter calibrated with standard buffers (e.g., pH 4, 7, 10); it affects coagulation, disinfection, and corrosion control.

Chlorine residual is measured by DPD colorimetric or amperometric methods; the DPD method is common for field testing.

Quality control in the laboratory includes duplicates, blanks, spikes, and calibration verification to ensure accuracy and precision.

The Safe Drinking Water Act (SDWA) authorizes the EPA to set national drinking water standards; states may adopt primacy and enforce regulations.

National Primary Drinking Water Regulations (NPDWRs) are enforceable maximum contaminant levels (MCLs) and treatment techniques for health-related contaminants.

National Secondary Drinking Water Regulations (NSDWRs) are non-enforceable guidelines for aesthetic contaminants (e.g., chloride, color, odor, pH, TDS).

Consumer Confidence Report (CCR) must be delivered to customers annually by July 1 and include source water information, detected contaminants, and compliance status.

Public notification is required for violations; Tier 1 (immediate) for acute health risks within 24 hours, Tier 2 within 30 days, and Tier 3 within 90 days.

Lead and Copper Rule: action level for lead is 0.015 mg/L and for copper is 1.3 mg/L; compliance is based on 90th percentile of tap samples.

Disinfection byproducts (DBPs) regulated include total trihalomethanes (TTHM) and five haloacetic acids (HAA5), with MCLs of 0.080 mg/L and 0.060 mg/L, respectively.

Operator certification requirements vary by state; operators must meet education, experience, and examination requirements and complete continuing education for renewal.

Confined space entry requires a permit, atmospheric testing (oxygen 19.5–23.5%, LEL <10%, H2S <10 ppm, CO <35 ppm), ventilation, attendant, and rescue plan.

Lockout/tagout (LOTO) procedures isolate hazardous energy sources during maintenance; only authorized employees may apply locks and tags.

Hazard communication (HazCom) requires safety data sheets (SDS) for each hazardous chemical and labeling of containers.

Chlorine gas leak response: evacuate upwind, use self-contained breathing apparatus (SCBA), and never enter a chlorine atmosphere without proper PPE.

Emergency response plans should address power outages, main breaks, contamination events, and natural disasters, with mutual aid agreements and emergency contact lists.

Security measures include fencing, locked gates, intruder detection, cybersecurity for SCADA systems, and background checks for personnel.

Fire safety: use appropriate fire extinguishers (Class A for ordinary combustibles, Class B for flammable liquids, Class C for electrical, Class D for metals).

Bloodborne pathogens and personal hygiene: wash hands, use PPE, and properly dispose of sharps and contaminated materials.