 |  Wastewater Systems 48 Flashcards |  Start |
 | What is the typical range for BOD₅ in medium strength domestic wastewater? |  Card: 1 / 48 |
| 220 mg/L (range: 110-400 mg/L) | Card: 2 / 48 |
| True or False: The minimum velocity in gravity sewers should be 2.0 ft/s for self-cleansing. | Card: 3 / 48 |
| True. This prevents solids deposition and maintains pipe capacity. | Card: 4 / 48 |
| Calculate F/M ratio: Flow = 5 MGD, BOD₅ = 200 mg/L, Volume = 2 MG, MLVSS = 2500 mg/L | Card: 5 / 48 |
| F/M = (5 × 200)/(2 × 2500) = 0.2 day⁻¹ | Card: 6 / 48 |
| Which parameter measures biodegradable organic matter in wastewater over 5 days? | Card: 7 / 48 |
| C) BOD₅ | Card: 8 / 48 |
| What is Manning's roughness coefficient for PVC pipe in sewer design? | Card: 9 / 48 |
| 0.011 to 0.015 | Card: 10 / 48 |
| Fill in the blank: Primary clarifiers typically remove _____% of TSS. | Card: 11 / 48 |
| 50-65 | Card: 12 / 48 |
| Why do activated sludge systems require oxygen? | Card: 13 / 48 |
| Microorganisms need oxygen to metabolize organic matter and produce energy. | Card: 14 / 48 |
| What happens when SVI exceeds 200 mL/g in secondary clarifiers? | Card: 15 / 48 |
| Poor settling occurs, typically indicating filamentous bulking problems. | Card: 16 / 48 |
| True or False: Force mains should be designed for velocities between 2-8 ft/s. | Card: 17 / 48 |
| True. Minimum 2 ft/s prevents deposition, maximum 8 ft/s limits head loss. | Card: 18 / 48 |
| Which process converts ammonia to nitrate? | Card: 19 / 48 |
| B) Nitrification | Card: 20 / 48 |
| Calculate aeration basin volume: Flow = 8 MGD, HRT = 6 hours | Card: 21 / 48 |
| V = Q × HRT = 8 × (6/24) = 2.0 MG | Card: 22 / 48 |
| What is the typical detention time for primary sedimentation tanks? | Card: 23 / 48 |
| 1.5 to 2.5 hours at average flow | Card: 24 / 48 |
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| Fill in the blank: Trickling filters are _____-growth biological treatment systems. | Card: 25 / 48 |
| Attached | Card: 26 / 48 |
| A plant has high F/M ratio and poor settling. What operational change is needed? | Card: 27 / 48 |
| Reduce F/M ratio by increasing MLSS or reducing organic loading. | Card: 28 / 48 |
| True or False: Maximum depth in gravity sewers should be 75% of pipe diameter. | Card: 29 / 48 |
| True. This maintains adequate capacity and prevents pipe surcharge. | Card: 30 / 48 |
| Which equation is used for force main head loss calculations? | Card: 31 / 48 |
| C) Hazen-Williams | Card: 32 / 48 |
| What is the minimum pipe diameter for residential gravity sewers? | Card: 33 / 48 |
| 8 inches | Card: 34 / 48 |
| Calculate SRT: Basin volume = 2 MG, MLSS = 3000 mg/L, Waste rate = 0.2 MGD, Waste concentration = 8000 mg/L | Card: 35 / 48 |
| SRT = (2 × 3000)/(0.2 × 8000) = 3.75 days | Card: 36 / 48 |
| Why is alkalinity consumed during nitrification? | Card: 37 / 48 |
| Nitrification produces hydrogen ions (H⁺), which consume alkalinity for pH buffering. | Card: 38 / 48 |
| Fill in the blank: Secondary treatment must achieve _____% BOD₅ and TSS removal minimum. | Card: 39 / 48 |
| 85 | Card: 40 / 48 |
| What causes rising sludge in secondary clarifiers? | Card: 41 / 48 |
| Denitrification in sludge blanket produces nitrogen gas bubbles causing flotation. | Card: 42 / 48 |
| True or False: UV disinfection effectiveness depends on intensity × contact time. | Card: 43 / 48 |
| True. UV dose = intensity (mW/cm²) × time (seconds). | Card: 44 / 48 |
| Which process requires external carbon source for complete nutrient removal? | Card: 45 / 48 |
| B) Denitrification | Card: 46 / 48 |
| Calculate oxygen requirement: BOD removed = 1000 lb/day, sludge production = 400 lb VSS/day | Card: 47 / 48 |
| O₂ = 1000 - (1.42 × 400) = 432 lb/day | Card: 48 / 48 |
| Completed! Keep practicing to master all of them. |  Restart |
