RRR
50 KLD Sewage Treatment Plant – ASP Technology
Activated Sludge Process (ASP) — compact, proven and cost-effective. Designed for 20 hours/day operation.
Quick Summary
This page provides an indicative design for a 50 KLD (50,000 L/day) Sewage Treatment Plant using the Activated Sludge Process (ASP). Calculations are shown digit-by-digit (use as site-check template). Final design to be confirmed after site visit & jar test.
Design Calculations — step by step (digit-by-digit)
Given / Assumed:
Design daily flow (Qd) = 50,000 L/day (50 KLD).
Operating hours = 20 hours/day.
Influent BOD (assumed) = 300 mg/L (update after lab data).
BOD removal target = 80%.
Oxygen requirement = 1.5 kg O2 per kg BOD removed.
O2 in air ≈ 0.278 kg O2 per m³ air.
Design transfer efficiency (conservative) = 10%.
Design daily flow (Qd) = 50,000 L/day (50 KLD).
Operating hours = 20 hours/day.
Influent BOD (assumed) = 300 mg/L (update after lab data).
BOD removal target = 80%.
Oxygen requirement = 1.5 kg O2 per kg BOD removed.
O2 in air ≈ 0.278 kg O2 per m³ air.
Design transfer efficiency (conservative) = 10%.
Flow & Mass calculations
1) Design hourly flow (Qh)
Qh = Qd / operating hours = 50,000 L / 20 h = 2,500 L/h.
2) BOD mass/day
Influent BOD = 300 mg/L = 0.300 g/L.
BOD mass/day = 50,000 L × 300 mg/L = 50,000 × 300 mg = 15,000,000 mg = 15,000 g = 15.000 kg/day.
3) BOD removed (80%)
Removed BOD = 15.000 kg/day × 0.80 = 12.000 kg/day.
4) Oxygen demand (1.5 kg O2 / kg BOD removed)
O2 required = 12.000 kg/day × 1.5 = 18.000 kg O2/day.
5) Air required (using 0.278 kg O2/m³ air and 10% transfer)
Effective O2 per m³ (with 10% transfer) = 0.278 × 0.10 = 0.0278 kg O2/m³ air.
Air (m³/day) = 18.000 / 0.0278 = 18.000 ÷ 0.0278 ≈ 647.482 m³/day.
Air (m³/hour) = 647.482 / 20 = 32.374 m³/hr.
Recommendation: Provide blowers totalling ~ 35 – 50 m³/hr (2 blowers for duty + standby) for margin and distribution losses.
6) Power & equipment note (approx.)
Small plant motors & blowers: total installed motor power approx ~ 6 – 12 HP depending on blower selection, pumps and sludge equipment. Final selection after vendor datasheets.
Qh = Qd / operating hours = 50,000 L / 20 h = 2,500 L/h.
2) BOD mass/day
Influent BOD = 300 mg/L = 0.300 g/L.
BOD mass/day = 50,000 L × 300 mg/L = 50,000 × 300 mg = 15,000,000 mg = 15,000 g = 15.000 kg/day.
3) BOD removed (80%)
Removed BOD = 15.000 kg/day × 0.80 = 12.000 kg/day.
4) Oxygen demand (1.5 kg O2 / kg BOD removed)
O2 required = 12.000 kg/day × 1.5 = 18.000 kg O2/day.
5) Air required (using 0.278 kg O2/m³ air and 10% transfer)
Effective O2 per m³ (with 10% transfer) = 0.278 × 0.10 = 0.0278 kg O2/m³ air.
Air (m³/day) = 18.000 / 0.0278 = 18.000 ÷ 0.0278 ≈ 647.482 m³/day.
Air (m³/hour) = 647.482 / 20 = 32.374 m³/hr.
Recommendation: Provide blowers totalling ~ 35 – 50 m³/hr (2 blowers for duty + standby) for margin and distribution losses.
6) Power & equipment note (approx.)
Small plant motors & blowers: total installed motor power approx ~ 6 – 12 HP depending on blower selection, pumps and sludge equipment. Final selection after vendor datasheets.
Tank Sizing & Unit Volumes (20 h operation)
Design hourly flow = 2,500 L/h. HRTs are practical and conservative; volumes rounded to nearest constructible sizes.
| Unit | HRT / Note | Calculated Volume (L) | Rounded / Practical (m³) |
|---|---|---|---|
| Equalization / Collection Tank (with disc diffusers) | 6 hours | 2,500 × 6 = 15,000 L | 15 m³ |
| Bar screen & Grit / O&G chamber | 0.5–1 hour | ~2,500 L | 3 m³ (rounded) |
| Aeration Tank (ASP) | 6 hours (typical) | 2,500 × 6 = 15,000 L | 15 m³ |
| Secondary Clarifier (Settling) | 2 hours | 2,500 × 2 = 5,000 L | 5 m³ |
| Clarified Water / Buffer Tank (PSF feed) | Buffer | ~2,000 L | 2 m³ |
| Pressure Sand Filter / Activated Carbon Filter | Pressure vessels sized per flow | — | — |
| Final Treated Water Tank (Reuse buffer) | Buffer for reuse | ~5,000 L | 5 m³ |
| Sludge holding / Thickener | Intermediate storage | ~1,000 – 2,000 L | 1–2 m³ |
| Total (approx.) | ~41,000 L (excluding PSF/ACF vessels) | ~41 m³ |
Notes: Practical construction often rounds volumes (e.g., 15 m³ + 15 m³ aeration etc.). Prefab FRP/RCC options available. Final tank footprint depends on geometry and site constraints.
Process Flow (ASP) — Sequence
Toilets & Wastewater →
Bar Screen (coarse removal) →
Oil & Grit / O&G Trap →
Collection / Equalization Tank (disc diffusers) →
Raw Sewage Transfer Pump (cutter/grinding pump option) →
Aeration Tank (Activated Sludge — MLSS + fine bubble aeration) →
Secondary Settling Tank (Clarifier) — RAS pumped back to aeration; excess sludge → sludge holding & dewatering →
Clarified Water Tank → Filter Feed Pump → PSF → ACF → Hypochlorite Dosing → Final Treated Water Tank (Reuse).
For gardening and flushing: PSF + ACF + disinfection is adequate. For RO feed or critical reuse include UF/RO & lab verification.
Equipment, Materials & Controls
| Item | Recommended Specification / Note |
|---|---|
| Bar Screen | Manual or raked coarse screen at inlet |
| O&G Trap | Oil & grease separator with skimmer |
| Equalization Tank | Disc diffusers for mixing; RCC / MS epoxy lined / FRP options |
| Raw Sewage Transfer Pump | Sewage cutter pump — 2 nos (duty + standby) for reliability |
| Aeration System | Fine bubble diffusers + blower(s). Design air ≈ 647 m³/day (~32.4 m³/hr). Recommend blower capacity ~ 35–50 m³/hr. |
| Secondary Clarifier | Rectangular or circular clarifier with RAS pump & scum removal |
| Filters | PSF & ACF sized for 50 KLD flow |
| Dosing Pumps | Hypochlorite dosing; coagulant/polymer (if required) |
| Sludge Handling | Sludge holding tank, dewatering by drying bed or small filter press |
| Control Panel | Simple PLC/Auto control with level sensors, DO controller; remote monitoring optional |
| MOC (Tanks) | RCC / MS (epoxy lined) / FRP with rubber lining — choose per site & corrosivity |
Provide duty + standby for critical pumps. Use small footprint prefabricated options if site space limited.
Expected Performance & Reuse
| Parameter | Influent (Design) | Typical Treated (After PSF+ACF+Disinfection) |
|---|---|---|
| pH | 6.5 – 7.5 | 6.5 – 7.5 |
| BOD | ~300 mg/L | < 30 mg/L |
| COD | ~900 mg/L | < 200 mg/L (site dep.) |
| TSS | ~150 mg/L | < 30 mg/L |
| Oil & Grease | ~50 mg/L | < 5 mg/L |
Typical reuse: gardening, toilet flushing, car wash. For RO feed include UF/RO & validate by lab tests.
Operation & Maintenance (Key Points)
- Maintain DO in aeration: 2.0 – 3.5 mg/L (monitor frequently in small plants).
- Monitor MLSS & SVI weekly; typical MLSS for ASP: 2000–3500 mg/L.
- Clean diffusers, check blowers, and maintain dosing pumps regularly.
- Manage sludge wasting and dewatering schedule to prevent overload.
- Keep records for TNPCB/CPCB inspections and compliance.
Get Quick Quotation / Technical Proposal
Free site visit & jar test. Send site photos, sample report (if available) and project brief.
Contact
Sales / Technical: +91 97100 35249 • Service: +91 99623 95875 • Email: rrrenviro@gmail.com
Sales / Technical: +91 97100 35249 • Service: +91 99623 95875 • Email: rrrenviro@gmail.com