Water Treatment Operator Class III cheat sheet

Surface water turbidity varies with runoff; groundwater turbidity is typically low but may contain dissolved iron and manganese.

Alkalinity is the acid-neutralizing capacity, measured as mg/L as CaCO3; it is not the same as pH.

Hardness = dissolved calcium and magnesium, expressed as mg/L as CaCO3; carbonate hardness is the portion removed by boiling.

Nephelometric turbidity is measured in NTU; regulatory limits for filtered surface water are typically ≤0.3 NTU in 95% of monthly samples and never >1 NTU.

Total organic carbon (TOC) in source water reacts with chlorine to form trihalomethanes and haloacetic acids.

Coliform bacteria are indicator organisms; their presence signals potential fecal contamination and treatment failure.

Nitrate in groundwater above 10 mg/L as N is a health concern, especially for infants (methemoglobinemia).

Temperature affects reaction rates, disinfection efficiency, and coagulation; colder water generally requires higher coagulant doses and longer flocculation times.

Coagulation destabilizes particles by neutralizing negative surface charge; typical alum dose is 10–50 mg/L.

Optimal coagulant dose is determined by jar testing; the dose producing the lowest filtered turbidity is selected.

Alum (Al2(SO4)3·14H2O) reacts with natural alkalinity: Al2(SO4)3 + 3Ca(HCO3)2 → 2Al(OH)3 + 3CaSO4 + 6CO2.

Each mg/L of alum consumes about 0.45–0.5 mg/L of alkalinity as CaCO3; insufficient alkalinity can drop pH below 6.0.

Flocculation provides gentle mixing (G value 10–75 s⁻¹) for 15–45 minutes to grow floc without shearing it.

Sedimentation basin overflow rate = flow ÷ surface area; typical design values are 0.5–1.0 gpm/ft² for conventional clarifiers.

Weir loading rate = flow ÷ weir length; high weir loading can cause short-circuiting and carryover of floc.

Sludge blanket depth in a clarifier is controlled by sludge withdrawal rate; rising blanket indicates solids overload.

Enhanced coagulation targets TOC removal; required removal percentages depend on source water alkalinity and TOC.

Rapid sand filters typically use 0.5–1.0 mm effective size media with a uniformity coefficient of 1.3–1.5.

Filtration rate = flow ÷ filter area; typical rapid sand filter design rates are 2–5 gpm/ft².

Filter run terminates when effluent turbidity exceeds 0.3 NTU, headloss reaches the design limit, or a preset run time is reached.

Backwash expands the filter bed 15–25%; required backwash rate depends on water temperature and media density.

Air scour followed by low-rate water backwash improves cleaning and reduces backwash water use.

Filter-to-waste or slow start after backwash prevents a turbidity spike from entering finished water.

Media loss during backwash occurs if the backwash rate is too high or troughs are improperly leveled.

Membrane filtration is rated by log removal value (LRV); LRV 4 = 99.99% removal.

CT = disinfectant concentration (mg/L) × contact time (minutes); required CT depends on disinfectant, pH, temperature, and target log inactivation.

Chlorine demand = applied dose − residual after contact time; demand must be satisfied before a free residual persists.

Free chlorine exists as HOCl and OCl⁻; HOCl is the stronger disinfectant, and its fraction decreases as pH rises above 7.5.

Combined chlorine (chloramines) forms when chlorine reacts with ammonia; it is a weaker disinfectant but produces fewer regulated DBPs.

Trihalomethanes (THMs) and haloacetic acids (HAAs) are regulated DBPs; their formation increases with TOC, chlorine dose, temperature, and contact time.

Ozone is a strong disinfectant but does not provide a persistent residual; a secondary disinfectant is needed in distribution.

UV disinfection inactivates Cryptosporidium at low doses but provides no residual and requires low-turbidity water.

Breakpoint chlorination is the dose at which free chlorine residual appears after all ammonia is oxidized.

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

Solution feed pump calibration: draw down a measured volume over a timed interval to verify mL/min output.

Sodium hypochlorite degrades over time; store in a cool, dark place and use within recommended shelf life.

Alum and other acidic chemicals lower pH; storage areas require secondary containment and corrosion-resistant materials.

Chlorine gas is heavier than air; gas detectors and emergency ventilation are required in chlorine rooms.

Ammonia and chlorine must be stored separately to prevent accidental formation of chloramines or violent reaction.

Fluoride feed systems require daily monitoring and recordkeeping; target levels are typically 0.7 mg/L.

Chemical metering pumps should be sized so normal dose falls in the 30–70% stroke range for accurate control.

Pump head (ft) = 2.31 × pressure (psi) for water at standard conditions.

Brake horsepower = (flow in gpm × head in ft) ÷ (3960 × pump efficiency).

Centrifugal pumps are primed before startup; running dry damages seals and impellers.

Pump cavitation produces noise and vibration when local pressure drops below vapor pressure; remedy by reducing suction lift or increasing suction pipe size.

A pump curve plots head versus flow; the operating point is where the pump curve intersects the system curve.

Gate valves are for isolation, not throttling; globe or butterfly valves are used for flow control.

Water hammer results from sudden valve closure or pump stop; surge tanks or slow-closing valves mitigate it.

Darcy–Weisbach or Hazen–Williams equations estimate head loss; Hazen–Williams C factors are higher for smoother pipe.

Jar tests simulate coagulation, flocculation, and sedimentation to select coagulant dose and pH.

Turbidimeter calibration uses formazin standards; verify with a secondary standard before each use.

pH meter calibration uses pH 4, 7, and 10 buffers; slope should be within 95–105% of theoretical.

Chlorine residual is measured by DPD colorimetric or amperometric methods; high turbidity or manganese can interfere.

Alkalinity is titrated to pH 4.5 endpoint; phenolphthalein alkalinity is titrated to pH 8.3.

Grab samples represent a single point in time; composite samples are flow-proportioned or time-proportioned.

Control charts (e.g., Shewhart) detect trends and shifts in process performance.

SCADA alarms should be set for turbidity, chlorine residual, and pH excursions outside target ranges.

Total coliform rule requires monitoring; any positive routine sample triggers repeat sampling and investigation.

Surface Water Treatment Rule requires 99.9% (3-log) removal/inactivation of Giardia and 99.99% (4-log) of viruses.

Stage 2 Disinfectants and Disinfection Byproducts Rule sets locational running annual averages for TTHM (80 µg/L) and HAA5 (60 µg/L).

Lead and Copper Rule action levels are 0.015 mg/L for lead and 1.3 mg/L for copper at the 90th percentile.

Consumer Confidence Report (CCR) must be delivered to customers by July 1 each year.

Public notification is required within 24 hours for acute violations (e.g., E. coli, nitrate exceedance) and within 30 days for non-acute violations.

Operator certification requires continuing education; Class III operators typically need 20–30 contact hours per renewal cycle.

Recordkeeping: monitoring records must be retained at least 3 years; some records (e.g., lead/copper) for 12 years.

Confined space entry requires atmospheric testing (O2 19.5–23.5%), ventilation, attendant, and rescue plan.

Chlorine gas exposure: evacuate upwind, use SCBA, and follow the emergency response plan; never attempt rescue without PPE.

Lockout/tagout (LOTO) isolates energy sources before maintenance on pumps, valves, or electrical equipment.

Hazard Communication (HazCom) requires SDS access and labeling of all chemical containers.

Emergency response plan includes contact lists, isolation procedures, and alternate water supply arrangements.

Security measures include fencing, locked hatches, intrusion alarms, and background checks for personnel.

Bloodborne pathogen and PPE requirements apply when handling sewage-contaminated water or sludge.

Fire safety: store oxidizers (e.g., chlorine, permanganate) away from combustibles and reducing agents.