100 KLD Sewage Treatment Plant – ASP Technology
This page shows a practical design for a 100 KLD (100,000 L/day) Sewage Treatment Plant using Activated Sludge Process (ASP). All volumes and equipment indications are scaled for 20 hours/day operation and conservative design assumptions (influent BOD ~300 mg/L). Use this as a site-verification template — we will finalize after site visit & jar test.
Design Calculations — step by step
Design daily flow (Qd) = 100,000 L/day (100 KLD)
Operating hours = 20 hours/day
Influent BOD (assumed) = 300 mg/L (change after lab data)
Assumed BOD removal target = 80%
Oxygen requirement factor = 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 (digit-by-digit)
Qh = Qd / operating hours = 100,000 L / 20 h = 5,000 L/h.
2) BOD mass/day
Influent BOD = 300 mg/L = 0.300 g/L.
BOD mass/day = 100,000 L × 300 mg/L = 100,000 × 300 mg = 30,000,000 mg = 30,000 g = 30.000 kg/day.
3) BOD removed (80%)
Removed BOD = 30.000 kg/day × 0.80 = 24.000 kg/day.
4) Oxygen demand (1.5 kg O2 / kg BOD removed)
O2 required = 24.000 kg/day × 1.5 = 36.000 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 kg × 0.10 = 0.0278 kg O2/m³ air.
Air (m³/day) = 36.000 kg / 0.0278 = 36.000 / 0.0278 ≈ 1,294.964 m³/day.
Air (m³/hour) = 1,294.964 / 20 h = 64.748 m³/hr.
Recommendation: Provide blowers totalling ~ 70–90 m³/hr for margin (two blowers for redundancy; e.g. 2 × 40 m³/hr).
6) Power estimate (approximate)
Small plants have pumps, blowers and support systems. From 10 KLD example (3–4 HP), scaled ×10 → rough estimate: 30–40 HP total installed motor power (pumps + blowers + sludge systems). Exact selection after vendor spec; typical blower motor(s) combined ~ 7.5 – 15 HP depending on blower type and two-blower configuration.
Tank Sizing & Unit Volumes (20 h operation)
Design hourly flow = 5,000 L/h. HRTs are conservative and practical; volumes rounded to nearest practical tank sizes.
| Unit | HRT / Note | Calculated Volume (L) | Rounded / Practical (m³) |
|---|---|---|---|
| Equalization / Collection Tank (with disc diffusers) | 6 hours | 5,000 × 6 = 30,000 L | 30 m³ |
| Bar screen & Grit / O&G chamber | 0.5–1 hour | ~5,000 L | 5 m³ |
| Aeration Tank (ASP) | 6 hours (typical) | 5,000 × 6 = 30,000 L | 30 m³ |
| Secondary Clarifier (Settling) | 2 hours | 5,000 × 2 = 10,000 L | 10 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.) | ~83,000 L (excluding PSF/ACF vessels) | ~83 m³ |
Note: You can combine EQ + primary in one tank, or use prefabricated modular tanks (FRP/GRP) to save civil time. Civil footprint depends on tank geometry; rectangular tanks reduce footprint compared to circular clarifiers.
Process Flow (ASP) — Sequence
Use UF (ultrafiltration) if reclaimed water is required for sensitive reuse (e.g., cooling towers, RO feed). For gardening / toilet flushing / vehicle wash, PSF + ACF + disinfection usually suffice.
Equipment, Materials & Controls
| Item | Recommended Specification / Note |
|---|---|
| Bar Screen | Coarse screen with manual or raked option at inlet |
| O&G Trap | Skimmer & oil separation arrangement |
| Equalization Tank | Disc diffusers for mixing; MS/FRP/GRP or RCC with internal lining |
| Raw Sewage Transfer Pump | Sewage cutter pump (capable of handling rags) — 2 nos (duty + standby) |
| Aeration System | Fine bubble diffusers + blower(s). Air required ~ 1,295 m³/day → ~ 65 m³/hr (design). Recommend blower capacity 70–90 m³/hr (2 nos) for margin and redundancy. |
| Secondary Clarifier | Rectangular or circular clarifier with RAS pump & scum removal; hopper bottom for sludge collection |
| Filters | PSF (pressure sand filter) & ACF (activated carbon filter) sized for 100 KLD peak flow |
| Dosing Pumps | Coagulant / Polymer (if required), Hypo dosing pump (online) for disinfection |
| Sludge Handling | Sludge holding tank, dewatering (filter press or drying bed) + waste sludge pump |
| Control Panel | PLC based control, level sensors, DO controller, alarms; remote monitoring optional |
| MOC (Tanks) | RCC (buried/permanent) / MS (epoxy lined) / FRP with rubber lining — choose based on site & corrosivity |
Blower & air notes: Blower power depends on blower type and head losses. For design air ≈ 65 m³/hr, typical specification might be a 5–7.5 kW (7.5–10 HP) blower — select vendor & include 20–30% safety margin. Consider two blowers for duty + standby.
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 dependent) |
| TSS | ~150 mg/L | < 30 mg/L |
| Oil & Grease | ~50 mg/L | < 5 mg/L (after O&G removal & polishing) |
Uses: Gardening, toilet flushing, car/road washing. For sensitive reuse (RO feed, cooling tower), add UF/RO & booster pumps and perform full lab validation.
Operation & Maintenance (Key Points)
- Maintain DO in aeration: 2.0 – 3.5 mg/L (monitor online if possible).
- Monitor MLSS & SVI weekly; typical MLSS for ASP: 2000–3500 mg/L (adjust based on performance).
- Check and clean diffusers periodically; replace worn diffusers.
- Maintain sludge wasting schedule — expect higher sludge volumes for higher BOD loads; plan dewatering frequency.
- Maintain dosing chemical stocks (coagulant / polymer / hypochlorite).
- Keep detailed logbook for TNPCB/CPCB inspections.
Get Quick Quotation / Technical Proposal
Free site visit & jar test for final design & price. Send site photos, sample report (if available) and project brief.
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