Water Treatment Plant Operator cheat sheet

Total alkalinity and pH buffer source water against coagulant acid demand; low-alkalinity soft waters are prone to large pH swings after alum addition.

Turbidity is measured by nephelometry in NTU; regulatory treatment technique requires filtered water at or below 0.3 NTU in at least 95% of monthly samples, with a maximum of 1 NTU.

Hardness is expressed as mg/L CaCO3; 1 grain per gallon equals 17.1 mg/L as CaCO3.

Total organic carbon and UV254 indicate natural organic matter, a precursor for disinfection byproducts and a coagulant demand source.

Surface water under the direct influence of groundwater is treated as groundwater under the influence and requires at least 4-log virus inactivation.

Common source contaminants: nitrate from agriculture, arsenic from geology, radon from granite, iron and manganese from anoxic groundwater.

Temperature affects treatment: cold water raises coagulant demand, slows floc formation, and reduces disinfection kinetics.

Source water monitoring under the Ground Water Rule requires triggered sampling after a total coliform-positive distribution sample.

Common coagulants: alum (aluminum sulfate), ferric chloride, ferric sulfate, polyaluminum chloride; each consumes alkalinity, roughly 0.45 mg/L as CaCO3 per mg/L of alum.

Optimal coagulation pH is typically 5.5 to 6.5 for alum and 4.5 to 5.5 for ferric salts when targeting organic matter removal.

Jar tests establish coagulant dose, pH, mixing speed, and polymer dose; they simulate full-scale rapid mix, flocculation, and settling.

Rapid mix velocity gradient (G) is typically 300 to 1000 per second for 10 to 60 seconds; flocculation G is typically 10 to 75 per second.

The Camp number (G times detention time) for flocculation is generally 10,000 to 150,000, balancing collision frequency against floc shear.

Type I settling applies to discrete particles; Type II is flocculent settling; Type III is hindered (zone) settling; Type IV is compression.

Stokes' law settling velocity increases with the square of particle diameter and with the density difference between particle and water, and decreases with viscosity.

Surface overflow rate equals flow divided by clarifier surface area and is expressed in gallons per day per square foot; it sets the settling velocity a basin can capture.

Weir loading rate equals flow divided by total weir length; high weir loading can cause short-circuiting and solids carryover.

Conventional media: anthracite over sand over gravel; dual-media beds allow deeper solids penetration and longer runs than single-media sand.

Typical design loading rates are 2 to 6 gpm per square foot for rapid gravity filters; slow sand filters run at about 0.05 to 0.15 gpm per square foot.

Filter run terminates on turbidity breakthrough, headloss limit, or a preset run time; terminal headloss is typically 6 to 10 feet of water.

Backwash expands the bed 15 to 25 percent; air scour plus low-rate water wash improves cleaning of dual-media beds.

Filter-to-waste, slow starts, and media conditioning reduce ripening spike turbidity after backwash.

Membrane filtration is rated by log removal value and integrity testing; pressure decay or marker tests confirm fiber integrity.

Media loss, mudballs, and media boils indicate backwash problems; gravel support layers must be inspected after media loss.

Filter effluent turbidity spikes correlate with pathogen passage, so individual filter monitoring and continuous turbidimeters are used for compliance.

CT is disinfectant residual concentration in mg/L multiplied by contact time in minutes; required CT increases as temperature falls and pH rises.

Chlorine species shift with pH: hypochlorous acid (HOCl) dominates below pH 7.5 and is far more biocidal than hypochlorite ion (OCl-).

Free chlorine is a stronger, faster disinfectant than chloramine; chloramines are used for residual persistence and lower trihalomethane formation.

Chlorine demand is the difference between dose and residual after a contact period; breakpoint chlorination removes ammonia before free residual appears.

Ozone is a powerful oxidant that inactivates Cryptosporidium but provides no lasting residual and forms bromate from bromide.

UV254 disinfection inactivates Cryptosporidium at low doses but provides no residual and is affected by turbidity and UV transmittance.

Chlorine dioxide controls taste and odor and oxidizes iron and manganese but forms chlorite and chlorate as regulated byproducts.

Disinfection byproduct precursors are removed by enhanced coagulation; total trihalomethane and haloacetic acid limits are regulated by running annual averages.

Log inactivation is calculated from CT divided by the required CT value at the measured temperature and pH.

Chemical feed rate equals flow times dose divided by the solution strength; calibrate feed pumps with a graduated cylinder and stopwatch.

Saturated lime solution is about 0.17 percent at 25 degrees Celsius; lime slurry requires continuous mixing to prevent settling.

Chlorine gas weighs about 2.5 times air and accumulates in low areas; weigh-scale loss is the standard feed verification method.

Sodium hypochlorite degrades over time and is accelerated by heat, sunlight, and heavy metals; store cool and shaded and rotate stock.

Fluoride feed is limited by the maximum contaminant level of 4 mg/L and the secondary standard of 2 mg/L; feed accuracy requires daily verification.

Dry feeders must be calibrated by weight per unit time; volumetric feeders are verified by timed collection.

Chemical storage requires secondary containment sized for the largest container plus precipitation, and separation of incompatible chemicals.

Alum and ferric salts are corrosive and acidic; polymer spills create slip hazards and must be contained, not washed to drain.

Pump head is the sum of static lift, friction loss, and velocity head; friction loss rises approximately with the square of flow.

Centrifugal pump curves plot head versus capacity; the operating point is where the system curve intersects the pump curve.

Cavitation produces noise and vibration when net positive suction head available falls below required; it damages impellers.

Affinity laws: flow varies with speed, head with speed squared, and power with speed cubed.

Motor power in horsepower equals flow in gpm times head in feet divided by 3960 times pump efficiency.

Positive displacement pumps deliver nearly constant flow against varying pressure and require a relief valve on the discharge.

Valves: gate for isolation, globe for throttling, butterfly for large lines, check to prevent backflow, air release at high points.

Vibration, bearing temperature, and seal leakage are routine condition-monitoring indicators for rotating equipment.

Well pump setting depth, drawdown, and specific capacity (gpm per foot of drawdown) guide source pumping decisions.

Turbidimeters are calibrated with formazin or approved polymer standards; online units are verified against grab samples.

pH meters use two-point calibration with fresh buffer solutions at pH 4 and 7 or 7 and 10, and temperature compensation.

Residual chlorine analyzers require frequent zero and span checks; colorimetric grab tests verify online readings.

SCADA alarm setpoints and fail-safe states should be tested; loss of signal should drive equipment to a safe condition.

Flow meters: magnetic meters require conductive fluid, ultrasonic meters need adequate straight run, and orifice meters infer flow from differential pressure.

Level measurement uses ultrasonic, pressure transducer, or bubbler methods; each needs a reference point and calibration check.

4 to 20 mA current loops represent process variables; 4 mA is the zero value and 20 mA is full scale, allowing broken-wire detection.

Trending and data validation identify drifting instruments before compliance limits are exceeded.

Maintain a detectable disinfectant residual throughout the distribution system; free chlorine is typically maintained above 0.2 mg/L.

A cross-connection is any actual or potential link between a potable supply and a nonpotable source; backflow can be backsiphonage or backpressure.

Backflow prevention devices: air gap is the highest protection, followed by reduced pressure zone assemblies, double check valves, and vacuum breakers.

Air gaps must be at least twice the effective pipe diameter and never less than one inch above the flood level rim.

Reduced pressure zone assemblies must be tested annually by a certified tester and have their relief valve discharge visible.

Water age increases with low demand, long dead ends, and oversizing; it degrades residual and raises disinfection byproduct formation.

Flushing programs control sediment, stagnation, and biofilm; unidirectional flushing follows flow direction from clean to dirty areas.

Storage tank turnover and inspection prevent stagnation and contamination; tanks need vent screening and overflow protection.

Total coliform positives require repeat sampling; a fecal indicator positive triggers public notice and corrective action.

The Safe Drinking Water Act authorizes national primary drinking water regulations; the Lead and Copper Rule uses action levels rather than maximum contaminant levels.

Primary standards protect health; secondary standards address aesthetics such as color, odor, iron, and manganese.

Total coliform rule requires routine sampling based on population; a positive sample requires repeat samples within 24 hours.

Consumer Confidence Reports are delivered annually and summarize detected contaminants, sources, and compliance status.

Public notification: Tier 1 within 24 hours for acute violations, Tier 2 within 30 days, and Tier 3 within one year.

Disinfection byproduct compliance uses locational running annual averages for total trihalomethanes and haloacetic acids.

Surface water treatment rule requires combined filtration and disinfection achieving at least 3-log Giardia and 4-log virus removal and inactivation.

Operator certification requires state-issued credentials with continuing education; reporting to the state primacy agency is mandatory and timely.

Recordkeeping: monitoring records are retained for at least five years, and some records longer, per state requirements.

Confined space entry requires atmospheric testing for oxygen, flammables, and hydrogen sulfide, plus a permit, attendant, and rescue plan.

Hydrogen sulfide is lethal above about 100 ppm and deadens the sense of smell at high concentrations; never rely on odor.

Chlorine gas detection and escape respirators are required where chlorine is stored; self-contained breathing apparatus is used for entry.

Lockout/tagout isolates hazardous energy before maintenance; verify zero energy with a test after isolation.

Hazard communication requires safety data sheets, container labeling, and employee training for each hazardous chemical.

Emergency response planning covers power loss, chemical spills, main breaks, boil water notices, and source contamination.

Security measures include fencing, locked chemical and treatment areas, visitor logs, and vulnerability assessments.

Electrical safety: ground-fault protection, arc-flash boundaries, and qualified-person rules apply to pump and motor work.

Waterborne pathogen risk during emergencies is managed by boil water notices, increased disinfection, and public notification.

Turbidimeters are calibrated with formazin or approved polymer standards; online units are verified against grab samples.

pH meters use two-point calibration with fresh buffer solutions at pH 4 and 7 or 7 and 10, and temperature compensation.

Residual chlorine analyzers require frequent zero and span checks; colorimetric grab tests verify online readings.

SCADA alarm setpoints and fail-safe states should be tested; loss of signal should drive equipment to a safe condition.

Flow meters: magnetic meters require conductive fluid, ultrasonic meters need adequate straight run, and orifice meters infer flow from differential pressure.

Level measurement uses ultrasonic, pressure transducer, or bubbler methods; each needs a reference point and calibration check.

4 to 20 mA current loops represent process variables; 4 mA is the zero value and 20 mA is full scale, allowing broken-wire detection.

Trending and data validation identify drifting instruments before compliance limits are exceeded.

Maintain a detectable disinfectant residual throughout the distribution system; free chlorine is typically maintained above 0.2 mg/L.

A cross-connection is any actual or potential link between a potable supply and a nonpotable source; backflow can be backsiphonage or backpressure.

Backflow prevention devices: air gap is the highest protection, followed by reduced pressure zone assemblies, double check valves, and vacuum breakers.

Air gaps must be at least twice the effective pipe diameter and never less than one inch above the flood level rim.

Reduced pressure zone assemblies must be tested annually by a certified tester and have their relief valve discharge visible.

Water age increases with low demand, long dead ends, and oversizing; it degrades residual and raises disinfection byproduct formation.

Flushing programs control sediment, stagnation, and biofilm; unidirectional flushing follows flow direction from clean to dirty areas.

Storage tank turnover and inspection prevent stagnation and contamination; tanks need vent screening and overflow protection.

Total coliform positives require repeat sampling; a fecal indicator positive triggers public notice and corrective action.

The Safe Drinking Water Act authorizes national primary drinking water regulations; the Lead and Copper Rule uses action levels rather than maximum contaminant levels.

Primary standards protect health; secondary standards address aesthetics such as color, odor, iron, and manganese.

Total coliform rule requires routine sampling based on population; a positive sample requires repeat samples within 24 hours.

Consumer Confidence Reports are delivered annually and summarize detected contaminants, sources, and compliance status.

Public notification: Tier 1 within 24 hours for acute violations, Tier 2 within 30 days, and Tier 3 within one year.

Disinfection byproduct compliance uses locational running annual averages for total trihalomethanes and haloacetic acids.

Surface water treatment rule requires combined filtration and disinfection achieving at least 3-log Giardia and 4-log virus removal and inactivation.

Operator certification requires state-issued credentials with continuing education; reporting to the state primacy agency is mandatory and timely.

Recordkeeping: monitoring records are retained for at least five years, and some records longer, per state requirements.

Confined space entry requires atmospheric testing for oxygen, flammables, and hydrogen sulfide, plus a permit, attendant, and rescue plan.

Hydrogen sulfide is lethal above about 100 ppm and deadens the sense of smell at high concentrations; never rely on odor.

Chlorine gas detection and escape respirators are required where chlorine is stored; self-contained breathing apparatus is used for entry.

Lockout/tagout isolates hazardous energy before maintenance; verify zero energy with a test after isolation.

Hazard communication requires safety data sheets, container labeling, and employee training for each hazardous chemical.

Emergency response planning covers power loss, chemical spills, main breaks, boil water notices, and source contamination.

Security measures include fencing, locked chemical and treatment areas, visitor logs, and vulnerability assessments.

Electrical safety: ground-fault protection, arc-flash boundaries, and qualified-person rules apply to pump and motor work.

Waterborne pathogen risk during emergencies is managed by boil water notices, increased disinfection, and public notification.