GA Water/WW Operator cheat sheet

Detention time = basin volume ÷ flow. Conventional treatment typically uses 20–40 minutes of flocculation and 2–4 hours of sedimentation.

Surface overflow rate (gpm/ft²) = flow (gpm) ÷ clarifier surface area (ft²); a lower rate yields longer detention and better particle capture.

The jar test establishes coagulant dose and target pH; the optimum produces the lowest settled and filtered turbidity at the lowest chemical cost.

Alum coagulation works best near pH 5.5–7.5 and consumes roughly 0.45 mg/L of alkalinity as CaCO3 per mg/L of alum applied.

Rapid sand filters are designed at 2–4 gpm/ft² and are backwashed at terminal head loss (about 8–10 ft) or on turbidity breakthrough, with 20–30% bed expansion.

CT (mg/L·min) = disinfectant residual concentration × contact time; required CT increases as pH rises and decreases as water temperature rises.

Chlorine demand = applied dose − residual after the contact period; breakpoint chlorination must be passed before a free chlorine residual persists.

For conventional filtration, combined filter effluent turbidity must be ≤0.30 NTU in at least 95% of monthly samples and never exceed 1 NTU.

Aeration oxidizes soluble iron (Fe2+ to Fe3+) and strips H2S, CO2, and volatile organics; PAC handles seasonal taste and odor while GAC removes dissolved organics.

Maintain 20 psi minimum residual pressure at all points under normal demand and fire flow; lower pressures require assessment for contamination risk.

A detectable free chlorine residual must persist throughout the system; operators commonly target at least 0.2 mg/L leaving the plant and at dead ends.

Flushing scours mains at velocities of 2.5 ft/s or greater; unidirectional flushing moves from clean to dirty areas, valve to hydrant.

Hazen-Williams head loss: hf = 10.44 · L · Q^1.85 ÷ (C^1.85 · d^4.87) with Q in cfs and d in ft; C is about 130–140 for new cement-lined or plastic pipe.

AWWA C651: newly installed mains receive a 25 mg/L initial chlorine dose held 24 hours, leaving at least 10 mg/L residual, then are flushed and sampled for coliforms.

Backflow protection ranking: air gap is absolute protection, followed by reduced-pressure zone, double check, and vacuum breaker; RPZ devices are tested annually.

Water hammer surge is governed by closure time versus 2L/a; rapid closure produces the full Joukowsky surge Δp = ρ·a·ΔV and can rupture mains.

Storage tank turnover every 2–3 days limits nitrification and chlorine decay; low turnover plus warm water favors biofilm and nitrifying bacteria growth.

Leak detection uses acoustic correlation and minimum night flow analysis; a rising night flow with no customer demand indicates unreported leakage.

Primary clarifiers are designed at 600–800 gpd/ft² overflow rate with 1.5–2.5 hours detention and remove about 30% of BOD and 60% of suspended solids.

F/M = lb BOD applied per day ÷ lb MLVSS under aeration; conventional activated sludge runs 0.2–0.5 and extended aeration below 0.1.

MCRT = lb solids in the aeration system ÷ lb solids leaving daily; nitrification generally needs more than 10 days SRT at 20°C and longer in cold water.

Return activated sludge is typically 50–100% of influent flow; SVI of 80–150 mL/g indicates good settling and above 150 indicates bulking.

Nitrification consumes 7.14 mg alkalinity as CaCO3 and 4.57 mg O2 per mg NH3-N oxidized; denitrification recovers about 2.86 mg O2 per mg NO3-N.

Aeration basin dissolved oxygen is held at 1.5–2.5 mg/L; below 1 mg/L nitrification stalls and filamentous organisms gain a competitive advantage.

Anaerobic digestion runs mesophilic at 95–98°F with 20–30 day SRT and 40–50% volatile solids reduction; a volatile acid to alkalinity ratio above 0.3 signals souring.

Secondary clarifiers are sized at 400–800 gpd/ft² at average flow with solids loading kept below roughly 25 lb/day/ft².

Effluent disinfection is set by NPDES permit limits on fecal coliform; UV systems typically deliver about 30 mJ/cm² to secondary effluent.

Gravity sewers are designed for at least 2 ft/s at design flow so solids stay suspended, and no more than 10–15 ft/s to limit abrasion and hydrogen sulfide release.

Manning's equation: V = (1.486/n) · R^(2/3) · S^(1/2), with R the hydraulic radius in feet and n about 0.013 for new concrete or plastic sewer pipe.

A common minimum slope for an 8-inch sewer is about 0.4% (0.004 ft/ft); always confirm the slope by Manning's equation at design flow.

Infiltration is groundwater entering through defects; inflow is stormwater from direct connections such as roof drains and manhole covers - both add clear flow to treatment.

Lift station wet wells are sized for pump cycle times of at least 5–10 minutes to protect motors, with force mains sized at 2–4 ft/s to keep solids moving.

Hydrogen sulfide attacks concrete above the waterline; control with prechlorination, nitrate addition, or covers and scrubbers at force main discharge points.

Smoke testing locates inflow sources, dye testing confirms illegal connections, and CCTV inspection identifies cracks, roots, and offset joints.

Manholes and wet wells are permit-required confined spaces; test for oxygen, LEL, H2S, and CO before entry and ventilate continuously.

Acceptable confined space entry atmosphere: oxygen 19.5–23.5%, LEL below 10%, hydrogen sulfide below 10 ppm, and carbon monoxide below 35 ppm.

Chlorine gas has an IDLH of 10 ppm and requires SCBA; a leaking cylinder forms a yellow-green cloud that hugs low ground.

Hydrogen sulfide has an IDLH of 100 ppm, and because it deadens the sense of smell at high concentrations, odor is never a safe warning.

Methane's explosive range is 5% to 15% in air; combustible gas meters read % LEL and entry is stopped at 10% LEL.

OSHA requires a protective system for trenches 5 ft or deeper, a ladder within 25 ft of lateral travel, and spoil piles set back at least 2 ft from the edge.

Lockout/tagout sequence: notify affected workers, shut down, isolate all energy sources, apply locks and tags, release stored energy, then verify zero energy.

Emergency eyewash and shower must be reachable within 10 seconds of travel from corrosive chemical handling areas, and flushing continues for 15 minutes.

A confined space attendant remains outside the space at all times with a retrieval system or trained rescue team standing by.

Fall protection is required at 4 ft in general industry and 6 ft in construction; test the atmosphere before entry and continuously during occupancy.

Primary MCLs include nitrate 10 mg/L as N, nitrite 1 mg/L, and arsenic 0.010 mg/L; lead action level is 0.015 mg/L and copper 1.3 mg/L at the 90th percentile.

Stage 2 DBPR limits are computed as locational running annual averages: total trihalomethanes 80 µg/L and five haloacetic acids 60 µg/L.

Under the Total Coliform Rule and RTCR, E. coli is an MCL violation and any positive total coliform triggers repeat sampling and a system assessment.

The Surface Water Treatment Rule requires 99.9% (3-log) Giardia and 99.99% (4-log) virus inactivation, demonstrated with CT tables by disinfectant, pH, and temperature.

Public notification tiers: Tier 1 within 24 hours, Tier 2 within 30 days, Tier 3 within 90 days or in the annual consumer confidence report.

NPDES permits set effluent limits and monitoring; results are reported on monthly discharge monitoring reports that support compliance and enforcement decisions.

40 CFR Part 503 governs biosolids, requiring pathogen reduction, vector attraction reduction, and limits on land application of metals.

Operator certification is administered by the state under EPA primacy, with grade levels tied to system complexity and renewal through continuing education units.

Clean Water Act pretreatment programs apply categorical standards plus local limits to industrial users and require slug control and periodic inspection.

BOD5 is run at 20°C in the dark for 5 days with seeded dilution water; nitrification is inhibited, and depletion should be at least 2 mg/L with at least 1 mg/L residual remaining.

COD uses dichromate digestion for 2 hours at 150°C; COD exceeds BOD5 because it also oxidizes non-biodegradable and reduced inorganic matter.

TSS: filter through a glass fiber filter, dry at 103–105°C, and weigh; mg/L = (mg residue × 1000) ÷ mL of sample filtered.

pH meters are calibrated with two buffers bracketing the sample (commonly 4, 7, 10), with electrode slope accepted at 95–105% of theoretical.

Turbidity is measured nephelometrically against formazin primary standards and reported in NTU; samples are kept out of light and analyzed promptly.

Chlorine residual is measured by DPD colorimetry; amperometric titration is used when color, turbidity, or manganese interfere with the colorimetric reading.

Coliform analysis uses membrane filtration or enzyme substrate methods; drinking water samples are held at 4°C and analyzed within 8 hours of collection.

Typical holding times: BOD 48 hours, TSS 7 days, COD 28 days, nitrate 48 hours, and chlorine residual measured immediately in the field.

QA/QC for each batch includes a method blank, duplicate, matrix spike, and calibration verification, with recovery typically accepted within ±15%.