Quick Reference Data
DO targets, pH ranges, loading rate benchmarks, unit conversions, and chemical data — organized for field use.
Process Parameters
[ Dissolved Oxygen ]
Operating Ranges by Process Zone
| Process Zone | Target DO (mg/L) | Notes |
|---|---|---|
| Aeration Basin (Nitrification) | 2.0 – 4.0 | Minimum 2.0 for full nitrification |
| Aeration Basin (General) | 1.5 – 3.0 | Below 1.0 risks filamentous growth |
| Anoxic Zone (Denitrification) | < 0.2 | DO inhibits denitrification |
| Anaerobic Zone (EBPR) | < 0.05 | Critical for phosphorus release |
| Secondary Clarifier Effluent | 4.0 – 8.0 | Higher DO indicates good aeration |
| Digester (Anaerobic) | 0 | Strict anaerobic conditions required |
[ pH Targets ]
Operating Ranges by Process
| Process | pH Range | Notes |
|---|---|---|
| Activated Sludge | 6.5 – 8.5 | Optimal range for biological activity |
| Nitrification | 7.2 – 8.0 | Below 6.8 significantly inhibits nitrifiers |
| Denitrification | 6.5 – 8.0 | Less sensitive to pH than nitrification |
| Anaerobic Digestion | 6.8 – 7.4 | Below 6.5 = acid phase; above 8.0 = inhibited |
| Chemical Phosphorus Removal | 5.5 – 7.0 | Alum optimal around 6.0–7.0 |
| Effluent Discharge (typical) | 6.0 – 9.0 | Varies by permit |
[ Loading Rate Benchmarks ]
Design & Operational Targets
| Parameter | Typical Range | Units |
|---|---|---|
| F/M Ratio (Conventional AS) | 0.2 – 0.4 | lbs BOD / lb MLVSS / day |
| F/M Ratio (Extended Aeration) | 0.04 – 0.1 | lbs BOD / lb MLVSS / day |
| MCRT (Nitrification) | 10 – 20 | days (varies with temp) |
| MCRT (Conventional) | 5 – 15 | days |
| SVI (Good Settling) | 80 – 150 | mL/g |
| SVI (Bulking) | > 200 | mL/g |
| Surface Loading Rate (Clarifier) | 400 – 800 | gpd/ft² |
| Solids Loading Rate (Clarifier) | 20 – 30 | lbs/day/ft² |
| VS Loading Rate (Digester) | 0.1 – 0.3 | lbs VS/day/ft³ |
| Digester Detention Time | 15 – 30 | days |
| VSR (Anaerobic Digestion) | 38 – 55 | % (Class B minimum 38%) |
[ Temperature Effects ]
Biological Process Performance by Temperature
| Temperature | DO Saturation | Nitrification | Notes / Guidance |
|---|---|---|---|
| < 5°C / < 41°F | ≥ 12.8 mg/L | Severely inhibited — < 30% of peak rate | SRT > 25 days; nitrification may fail; digestion near-zero |
| 5–10°C / 41–50°F | 11.3 – 12.4 mg/L | Significantly reduced — ~30–50% of peak rate | Increase SRT to 15–25 days; monitor effluent ammonia closely |
| 10–15°C / 50–59°F | 10.1 – 11.3 mg/L | Reduced — ~50–75% of peak rate | SRT 12–18 days; watch for seasonal compliance issues |
| 15–20°C / 59–68°F | 9.1 – 10.1 mg/L | Near-normal | Standard temperate operating range; standard SRT adequate |
| 20–25°C / 68–77°F | 8.2 – 9.1 mg/L | Optimal | Standard design condition; high biological activity |
| > 25°C / > 77°F | < 8.2 mg/L | Good, but O₂ demand rises | Monitor blower capacity; lower DO saturation tightens margins |
| 35–37°C / 95–99°F | 6.7 – 6.8 mg/L | N/A — digester range | Optimal mesophilic anaerobic digestion; target for heated digesters |
| 55°C / 131°F | ~5.5 mg/L | N/A — digester range | Optimal thermophilic digestion; PFRP / Class A treatment path |
[ Unit Conversions ]
Common Wastewater Conversions
| From | To | Factor |
|---|---|---|
| MGD | GPM | × 694.44 |
| MGD | CFS | × 1.5472 |
| MGD | L/s | × 43.813 |
| MGD × mg/L | lbs/day | × 8.34 |
| mg/L | lbs/MG | × 8.34 |
| ft³ | gallons | × 7.481 |
| acres | ft² | × 43,560 |
| °F | °C | (°F − 32) × 5/9 |
Chemistry & Dosing
[ Alkalinity ]
Targets & Nitrification Consumption
| Parameter / Process | Target Range | Notes |
|---|---|---|
| Aeration Basin Alkalinity | 80 – 120 mg/L as CaCO₃ | Below 80: pH drops, nitrification destabilizes |
| Effluent Alkalinity (minimum) | ≥ 50 mg/L as CaCO₃ | Residual alkalinity after nitrification; below this risks pH crash |
| Nitrification consumption | 7.14 mg alk / mg NH₄⁺-N | Theoretical; actual 6.0–7.0 in practice |
| Denitrification recovery | 3.57 mg alk / mg NO₃⁻-N | Denitrification returns ~50% of nitrification alkalinity draw |
| Sodium bicarbonate addition | 84 g/mol | 1 lb NaHCO₃ adds 0.595 lbs alkalinity as CaCO₃ |
| Hydrated lime addition | 74 g/mol Ca(OH)₂ | More reactive than NaHCO₃; raises pH quickly — dose carefully |
| pH below which to supplement | < 6.8 in basin | Supplement alkalinity; don't wait for effluent pH to drop |
[ Oxygen Demand ]
O₂ Requirements & Transfer Factors
| Parameter | Value | Notes |
|---|---|---|
| BOD removal O₂ demand (theoretical) | 1.0 lb O₂ / lb BOD₅ | Actual 0.8–1.2 depending on SRT and endogenous demand |
| Nitrification O₂ demand | 4.57 lb O₂ / lb NH₄⁺-N | Doubles total aeration load at high ammonia influent |
| Denitrification O₂ credit | 2.86 lb O₂ / lb NO₃⁻-N | Reduces net aeration demand; credit for anoxic zone |
| Endogenous respiration | 0.08 – 0.12 lb O₂ / lb VSS / day | Add to BOD demand for total basin O₂ requirement |
| Alpha factor (fine bubble, MLSS) | 0.65 – 0.85 | Reduces clean-water SOTR in mixed liquor; use 0.70–0.75 for design |
| Beta factor | 0.95 – 0.98 | TDS/salinity correction on DO saturation; near 1.0 for municipal WW |
| Fine bubble diffuser SOTE | 20 – 35% | Per meter submergence; decreases with diffuser fouling |
| Coarse bubble SOTE | 8 – 15% | Lower efficiency; simpler maintenance; used for mixing |
[ Chemical Feed ]
Typical Doses & Application Points
| Chemical | Typical Dose | Application / Notes |
|---|---|---|
| Alum (liquid, 48%) | 5 – 15 mg/L as Al | Phosphorus precipitation; optimal pH 6.0–7.0; reduces alkalinity |
| Ferric chloride (liquid, 37–42%) | 5 – 20 mg/L as Fe | Phosphorus precipitation; effective pH 4.5–8.0; more corrosive than alum |
| Sodium hypochlorite (12.5%) | 2 – 10 mg/L as Cl₂ | Disinfection; actual dose depends on CT requirement and effluent demand |
| Polymer (cationic, belt press) | 10 – 25 lbs/dry ton | Biosolids conditioning; jar-test to optimize; higher dose ≠ better cake |
| Polymer (cationic, GBT) | 5 – 15 lbs/dry ton | Lower dose than belt press; inject close to static mixer |
| Polymer (anionic, DAF) | 2 – 8 lbs/dry ton | DAF thickening; charge must match sludge — jar-test required |
| Sodium bisulfite (dechlorination) | 1 mg/L per 1 mg/L Cl₂ | Stoichiometric; slight overdose acceptable; monitor residual |
| Caustic soda (50% NaOH) | Varies — pH controlled | pH adjustment; extremely reactive — use automated dosing with pH feedback |
Solids & Biosolids
[ Solids Production ]
Typical % Solids by Sludge Type
| Sludge Type | Typical % TS | Notes |
|---|---|---|
| Raw primary sludge | 4 – 6% | Higher with longer primary HRT |
| Waste activated sludge (WAS) | 0.5 – 1.5% | Dilute; thickening required before digestion |
| Primary + WAS blend | 2 – 4% | Blend ratio determines concentration |
| Aerobically digested sludge | 1 – 3% | Often thinner than anaerobically digested |
| Anaerobically digested (liquid) | 2 – 4% | Reduced VSS; stabilized |
| GBT thickened WAS | 4 – 7% | With polymer conditioning |
| Belt press dewatered cake | 15 – 25% | Varies by feed solids and polymer dose |
| Centrifuge dewatered cake | 18 – 28% | More consistent than belt press |
| Heat dried biosolids | 90 – 95% | Pellet or granule form; Class A typical |
[ Biosolids Classification ]
Class A vs. Class B — Federal 503 Standards
| Criterion | Class A | Class B |
|---|---|---|
| Pathogen standard | Fecal coliform < 1,000 MPN/g TS or Salmonella < 3 MPN/4g TS | Fecal coliform < 2,000,000 MPN/g TS (geometric mean) |
| Vector attraction reduction (VAR) | One of Options 1–8 required | One of Options 1–10 required |
| VSR (anaerobic digestion) | ≥ 38% + time/temp requirement | ≥ 38% (Van Kleeck formula) |
| Common VAR method (anaerobic) | PFRP: thermophilic digestion (55°C / 15+ days) | PSRP: mesophilic digestion (35–55°C / 15+ days HRT) |
| Land application restrictions | No site access restrictions required | Site access restrictions: 30-day crop harvest hold, grazing restrictions |
| Public contact sites | Allowed without restrictions | 12-month site access restriction |
| Common treatment paths | Thermophilic digestion, heat drying, alkaline stabilization (≥ 70°C) | Mesophilic anaerobic digestion, aerobic digestion, composting |
| Testing frequency | More frequent — verify each pathogen batch | Less frequent once process reliability established |
Laboratory
[ Filamentous Organisms ]
Common Causes, Symptoms & Control Responses
| Organism | Associated Conditions | Symptoms | First Response |
|---|---|---|---|
| Nocardia spp. | Long SRT; high FOG loading; warm temps | Stable brown/tan foam; chocolate mousse appearance on basin surface | Reduce SRT; chlorinate foam; address upstream FOG sources |
| Microthrix parvicella | Long SRT; low temp (< 15°C); fat/oil loading | Brown stable foam; bulking; worsens in winter | Reduce SRT; foam wasting; control fat and oil loading |
| Type 021N | Sulfide in feed; low DO; low F/M | Tight non-settling floc; high SVI; pin floc possible | Increase DO; eliminate septic conditions; pre-aerate force main |
| Thiothrix spp. | Sulfide or reduced sulfur in influent; low DO | Bulking; rosette structures visible under microscope | Eliminate H₂S sources; increase DO; pre-aerate force main |
| Type 0041 / 0675 | Very low F/M; nutrient deficiency (N or P) | Viscous / zoogloeal bulking; stringy or gel-like floc | Increase F/M; verify N:P:BOD ratio; check influent nutrient loading |
| Type 1701 | Low DO; high soluble substrate | Diffuse floc growth; poor settling | Increase DO setpoint; check for anoxic zone bleed-over |
| Beggiatoa | High sulfide; anaerobic conditions in basin | White surface mat; settling interference | Improve aeration uniformity; address septicity in influent |
[ Lab Methods ]
Standard Methods Reference — Preservation & Hold Times
| Parameter | Standard Method | Preservation & Hold Time | Notes |
|---|---|---|---|
| BOD₅ | SM 5210B | Cool 4°C; no acid; 48-hour hold | Seed per method; dilute to keep depletion 2–8 mg/L DO |
| TSS | SM 2540D | Cool 4°C; 7-day hold | Glass fiber filter (GF/C); filter within 24h preferred |
| VSS | SM 2540E | Cool 4°C; 7-day hold | Sequential with TSS using same filter; pre-ignite filters |
| Total Alkalinity | SM 2320B | Cool 4°C; 14-day hold | Do not acidify; titrate within 15 min of collection when possible |
| pH | SM 4500-H⁺ B | Measure immediately; no hold | Calibrate with fresh buffers before each session; ATC required |
| Dissolved Oxygen | SM 4500-O G | Measure immediately; no hold | Membrane or optical sensor; calibrate at start of each shift |
| Ammonia-N | SM 4500-NH₃ | H₂SO₄ to pH < 2; cool 4°C; 28-day hold | Colorimetric or ISE; distill if matrix interference suspected |
| Nitrate-N | SM 4500-NO₃⁻ | Cool 4°C; 48-hour hold | Ion chromatography or cadmium reduction; check chloride interference |
| Total Phosphorus | SM 4500-P B/E | H₂SO₄ to pH < 2; cool 4°C; 28-day hold | Digest before colorimetric analysis |
| Total Kjeldahl Nitrogen | SM 4500-N | H₂SO₄ to pH < 2; cool 4°C; 28-day hold | Organic-N + ammonia-N combined; requires digestion step |
| Fecal Coliform | SM 9221E / 9222D | Na₂S₂O₃; cool 4°C; 6-hour hold | Quench chlorine at collection; strict hold time for permit samples |
| Chlorine Residual | SM 4500-Cl | Measure immediately; no hold | DPD colorimetric preferred; field measurement at discharge point |