Water and Wastewater Operations

Tools in this group

• Pounds Formula - lb/day = MGD * mg/L * 8.34, with adjusted product feed at the chemical's purity.
• Filter Loading Rate and Backwash - Loading rate, backwash flow, and rapid-sand vs high-rate category.
• Detention Time - Detention time = volume / flow in min, hr, days; pass/fail vs target.
• Lab Dilution and Serial Dilution - C1V1 = C2V2 missing-side solve; serial dilution series with per-step concentrations.
• Pump Wire-to-Water Efficiency - Water HP, brake HP estimate, and wire-to-water % with good/ok/degraded category.
• SRT and F/M Ratio - Solids retention time and food-to-microorganism ratio with conventional-activated-sludge check.
• Coagulant Dose from Jar Test - Pure equivalent + product feed (lb/day, gal/day) for alum, ferric chloride, or PAC at the jar-test optimal dose.
• Sludge Volume Index (SVI) - SVI = SV30 * 1000 / MLSS in mL/g, with operator-typical operational bands (typical / pin floc / filamentous / bulking). Companion to the srt-fm-ratio tile.
• Disinfection CT (USEPA SWTR) - CT achieved (C * t10) compared to USEPA SWTR Guidance Manual required CT for 3-log Giardia inactivation by temperature and pH. Bundled <= 0.4 mg/L free-chlorine table; state primacy agency table governs final compliance.
• Pool Turnover Rate and Chlorine Demand - Required pump flow from pool volume and turnover target, plus the chlorine product to dose a free-chlorine target (cal-hypo / trichlor / liquid bleach). Per the NSPF CPO Handbook and ANSI/APSP/ICC 11.
• Well Drawdown and Specific Capacity - Drawdown, specific capacity (GPM per ft), and recommended pump-setting depth, with a marginal-well flag below 0.5 GPM/ft. Per AWWA A100 and USGS OFR 02-197.
• Cooling Water Makeup (Cycles of Concentration) - Evaporation, blowdown, drift, and total makeup flow from recirculation, range, and cycles of concentration, with scaling and drift flags. Per CTI and ASHRAE Systems and Equipment 2020 Ch. 40.
• Chlorine Residual Decay (First-Order) - First-order residual C(t) = C0 x exp(-k t), time to a target residual, and an optional booster distance. Per EPA 815-R-02-020 and AWWA M14; 40 CFR 141.74 governs the extremity residual.
• Backflow Assembly Test Pass Criteria - Pass/fail per assembly type with the governing field-test criterion: RP relief opens >= 2 psid below the #1 check and the #1 check >= 5 psid; DC each check >= 1 psid. Per the USC FCCCHR Manual and AWWA C511.
• Weir / Flume Open-Channel Flow - Open-channel flow over a 90-degree V-notch or rectangular (Francis) weir in cfs, GPM, and MGD from the head over the crest and an editable weir coefficient.
• Langelier Saturation Index - LSI and a corrosive/balanced/scaling interpretation from pH, temperature, calcium hardness, total alkalinity, and TDS.
• Chemical Metering-Pump Setting - Neat chemical (lb/day), solution feed (GPD and mL/min), and pump setting (% of max) from plant flow, target dose, solution strength, and specific gravity via the pounds formula.
• Clarifier Surface, Weir, and Solids Loading - Surface overflow rate = flow/area (gpd/ft^2), weir overflow = flow/weir (gpd/ft), solids loading = flow x MLSS x 8.34 / area. 1 MGD, 40 ft dia (1257 ft^2), MLSS 2500 -> SOR 796, weir 7,958, solids 16.6; double the flow and SOR passes the ~1000 limit (floc carryover). The state design criteria govern.
• BOD/TSS Mass Loading and Percent Removal - Load (lb/day) = MGD x mg/L x 8.34, removal% = (in - out)/in x 100. 1 MGD, 200 -> 20 mg/L -> 1,668 lb/day in, 1,501 removed, 90%; a 4 MGD plant carries 6,672 lb/day at the same 90% (load scales, efficiency does not). An effluent above influent flags an upset. The operator of record governs.
• Total Dissolved Solids from Conductivity - TDS (mg/L) = k x EC (uS/cm at 25 C), k commonly 0.55-0.75 (default 0.65). 1000 uS/cm -> 650 mg/L, with a 550-750 band from the k range so it is not read as exact. An estimate, not a gravimetric TDS; calibrate k to a lab result. The operator of record governs.
• Population Equivalent (Organic Load) - The population equivalent of a discharge, figured three ways -- from BOD (0.17 lb/capita/day), flow (100 gpd/capita), and suspended solids (0.20 lb/capita/day) -- with the GOVERNING value being the largest, not BOD alone. A 0.5 MGD cannery at 600 mg/L BOD is worth ~14,700 residents in oxygen demand though its gallons look like 5,000; billing on flow alone under-charges it.
• Return Activated Sludge (RAS) Flow Rate - The return-pump rate from the solids mass balance: Q_RAS = Q x MLSS / (RAS_SS - MLSS), plus the return ratio. The clarifier only thickens sludge 3-4x, so RAS_SS is capped -- cranking the pump to chase a higher MLSS floods the clarifier and washes solids over the weir. The mass balance, not the pump maximum, sets the rate.
• Settleability-Based RAS Rate (from SVI) - The RAS number straight from the settleometer, no RAS_SS lab result needed: the achievable return concentration is Xr = 1,000,000 / SVI, so the ratio for a target MLSS is R = MLSS / (Xr - MLSS) and Q_RAS = R x Q. Poor settling forces a much higher return - holding 2,500 mg/L on a good SVI of 100 needs a 33% return, but a bulking sludge at SVI 150 wanting 3,000 mg/L needs 82%, and if the pumps cannot deliver it the MLSS target is unreachable. The settleometer path to the same mass balance ras-flow-rate does from a measured RAS_SS. An operating aid, not a process design.
• WAS Rate to Hold Target SRT (Sludge Age) - The daily wasting decision: how much sludge to waste today to hold a target SRT. Q_WAS = (system_solids/SRT - effluent_solids) / (WAS x 8.34), in MGD and gpm. The inverse of a sludge-age readout; effluent solids over the weir count as wasted and cut the pump rate. SRT lags ~one SRT, so change gradually.
• Anaerobic Digester Volatile Solids Loading - The digester health metric: volatile-solids loading rate VSLR = VS_fed / volume x 1000 (lb VS/day per 1,000 ft^3), the VS fed, and the detention time. Overloading past ~400 sours the digester (acid-formers outrun the methane-formers, pH crashes). The loading rate, not a full tank, is the metric; a rich feed can overload at low flow.
• Digester Volatile-Acid to Alkalinity Ratio - The early-warning stability index the pH meter misses: ratio = volatile acids / alkalinity (common CaCO3 basis). Below ~0.1 stable, 0.1-0.25 acceptable, 0.25-0.4 begin corrective action (cut feed, add alkalinity), above ~0.4 souring. The bicarbonate buffer holds the pH steady until the alkalinity is consumed, so the ratio flags the upset days before the pH moves. A digester at VA 900 / alkalinity 3,000 (ratio 0.30) needs action now while its pH still reads normal. An operating aid, not a control setpoint.
• Digester Gas and Methane Production - The payoff side of anaerobic digestion, from the volatile solids destroyed: gas = VS_destroyed x yield (12-18 ft^3/lb, default 15), methane = gas x ~65%, energy = methane x 960 BTU/ft^3. A digester destroying 5,500 lb VS/day makes about 82,500 ft^3 of gas, 54,000 ft^3 of methane, and 51 MMBtu/day - enough to heat the digester and run a cogeneration engine. Turns digester-vs-loading's healthy feed rate into the gas-and-energy number the plant budgets around. A planning estimate, not a metered gas measurement.
• Activated-Sludge Oxygen and Blower Air Demand - The oxygen the aeration system must supply and the blower air to deliver it: O2 = factor x BOD_removed + 4.6 x NH3_nitrified, air_scfm = O2 / (0.075 x 0.232 x SOTE x 1440). Nitrification adds 4.6 lb O2 per lb ammonia-N (easy to forget); diffused-aeration SOTE is only ~10-35%, so the air demand dwarfs the oxygen pounds. The largest energy cost at a plant.
• Mixing Velocity Gradient (G / Gt) - The Camp-Stein velocity gradient G = sqrt(P / (mu x V)) and the Gt product that set floc formation: rapid mix wants G 500-1,000/s, flocculation G 20-70/s. G depends on water temperature through viscosity -- cold water is more viscous, so the same paddle delivers a lower G in winter and can drop below the 20/s floor. Too high a G shears the floc apart.
• Tapered Flocculation G Schedule - The mixing power each stage of a tapered floc train needs: P_stage = G_stage^2 x mu(T) x V, the same Camp-Stein relation flocculation-g-value validated, inverted across 2-3 stages of decreasing G. A 50/30/20 per-second taper in three 100 m^3 stages at 15 C needs 285 / 102 / 46 W - the last stage runs at a sixth of the first, the gentle finish that grows settleable floc without shearing it. Reports the composite Gt and flags a schedule that is not tapered or steps outside the 10-100/s band. A design aid, not a process design.
• Paddle Flocculator Power from Geometry - The power flocculation-g-value needs, computed from the paddle wheel: P = 0.5 x Cd x rho x A x v_rel^3, the Newtonian drag. Two subtleties - the power goes as the CUBE of the relative velocity, and the water slips (rotates with the paddles) so v_rel is only (1 - k) of the tip speed; ignoring the slip roughly doubles the power. A 6-ft wheel at 3 rpm with 40 ft^2 of blade delivers ~267 W. Cd (~1.8) and slip k (~0.25) are user inputs because references disagree; the drag is exact once chosen. A design aid, not a metered power.
• Gas Chlorine Cylinder Withdrawal Rate - Whether a gas chlorine container can physically deliver the feed rate: a 150-lb cylinder tops out near 40 lb/day and a 1-ton container near 400 lb/day at ~70 F, derated in a colder room. Pull gas faster and the container frosts over and the rate collapses -- a latent-heat ceiling no bigger regulator beats. Returns the containers to manifold and a frost warning.
• Pool Total Alkalinity Adjustment - Sodium bicarbonate to raise or muriatic acid to lower total alkalinity, by pool volume and the ppm change -- the buffer a tech sets before pH. A starting dose to add in portions and retest.
• Pool Cyanuric Acid Dose - Cyanuric acid to raise stabilizer, or -- since CYA leaves only by dilution -- the fraction and gallons of water to replace to lower it. A starting dose to add slowly and retest.
• Pool Salt Dose - Pool salt to add for a salt-chlorine generator, or the water to replace to lower an over-salted pool, by a straight mass balance. Reported in pounds and 40-lb bags.
• Pool Free-Chlorine Dose by Product - Free-chlorine dose = ppm x (gal/1e6) x 8.34 lb, divided by the product available-chlorine fraction, as dry oz or (liquid) fl oz. A 15,000 gal pool +2 ppm needs 6.2 oz of 65% cal-hypo, or 25.6 fl oz of 12.5% liquid. The product label governs.
• Pool Heater Sizing and Heat-Up Time - Heat-up energy Btu = gallons x 8.34 x rise, and time = energy/(output x efficiency). A 20,000 gal pool +10 F takes 5.2 h on a 400,000 Btu/h gas heater at 80%, but 11.1 h on a 150,000 Btu/h heat pump. Ignores cover/standby losses. The equipment ratings govern.
• Breakpoint Chlorination Dose - Combined chlorine (chloramines) = total - free, and the breakpoint shock dose = ratio x combined (commonly 10:1). Total 1.5, free 1.0 -> 0.5 ppm combined, a 5 ppm shock; shock past breakpoint (a partial dose worsens it). The label and testing govern.
• Chlorine Demand and Dose for a Target Residual - The chlorine consumed by the water (applied minus the measured residual) and the dose to hold a target residual (demand + target). A high or rising demand points to ammonia or organics - check the breakpoint curve. Standard Methods 4500-Cl / AWWA M14; the state primacy agency sets the compliance residual and method.
• UV Dose and Target Check - The delivered ultraviolet dose (intensity x exposure time, mW.s/cm^2 = mJ/cm^2) checked against a validated target (default 40 mJ/cm^2). A short dose points to an aged lamp, a fouled sleeve, or low UV transmittance. USEPA UV Disinfection Guidance; the validated reactor dose and the state primacy agency govern compliance.