30 KLD Sewage Treatment Plant — MBBR (Moving Bed Biofilm Reactor)
Quick Summary
Capacity: 30 KLD (30 m³/day). Technology: MBBR (moving bed biofilm reactor). Default design basis used here: 20 operating hours/day and media fill 50%. Final design will be confirmed after site survey and influent characterization (BOD, TSS, FOG, pH).
Process Flow (Text Diagram)
Sludge → Sludge sump → Thickening → Dewatering (drying bed or mechanical) → Disposal.
Design Basis & Digit-by-Digit Calculations
- Design flow Qday = 30.000 m³/day
- Operating hours assumed = 20 hours/day
- HRT in MBBR aeration tank taken = 4.0 hours (typical range 3–6 h)
- Media fill fraction = 50% of aeration tank volume (typical 40–60%)
- Specific surface area (SSA) for media (K1 / common MBBR) = 500 m²/m³ (vendor dependent)
- Assumed influent BOD₅ = 250 mg/L (typical domestic; final to use site analysis)
Step 1 — Hourly flow (digit by digit)
Step 2 — Aeration tank volume (HRT method)
Step 3 — Media volume & available biofilm surface area
This large surface area supports high biomass concentration while keeping suspended solids lower — main advantage of MBBR vs conventional suspended growth.
Step 4 — Suspended biomass (MLSS) estimate
Mass of suspended biomass = MLSS (kg/m³) × Vaer = 3.0 × 6.000 = 18.0 kg mixed liquor solids present in tank (in addition to attached biofilm on media).
Step 5 — BOD load & oxygen requirement
Oxygen demand (assume 1.4 kg O₂ per kg BOD removed) → O₂ required ≈ 7.5 × 1.4 = 10.5 kg O₂/day.
Blower sizing depends on oxygen transfer efficiency (site & diffuser type). For 30 KLD MBBR systems a practical blower recommendation is 2 – 4 kW (single duty) with duty + standby arrangement — final blower selection after OTR (oxygen transfer rate) calculations and site conditions.
Step 6 — Secondary clarifier sizing (SOR approach)
Circular clarifier diameter d = √(4A/π) = √(4×1 ÷ 3.1416) ≈ 1.13 m — choose practical diameter 1.5 – 2.0 m for good weir loading and maintenance.
Main Components & Scope of Supply
- Bar screen & grease / grit trap
- Equalization / collection tank with mixer and level control
- Raw sewage transfer pump (submersible / dry pit)
- MBBR aeration tank with carrier media (≈ 3.0 m³ media @ 50% fill)
- Fine bubble diffusers & blower(s) (2–4 kW range, duty + standby)
- Secondary clarifier with RAS (return activated sludge) pump
- Polishing filter (PSF / cartridge / UF optional) and disinfection (UV / hypo dosing)
- Sludge sump, thickening & dewatering (drying bed or mechanical as per site)
- PLC control panel, level sensors, DO sensor, flow meter, pressure gauges
- Piping, valves, supports, civil anchors, installation & commissioning
Expected Performance & Applications
| Parameter | Typical Influent | Expected Effluent (After MBBR + Polishing) |
|---|---|---|
| BOD₅ | 200 – 400 mg/L | < 30 mg/L (depends on design & O&M) |
| TSS | 150 – 350 mg/L | < 50 mg/L (with polishing) |
| COD | 600 – 1200 mg/L | < 200 – 300 mg/L |
| Turbidity | Varies | < 5 NTU (with PSF/UF) |
| pH | 6.5 – 8.5 | 6.5 – 8.5 |
For reuse for flushing/landscape/cooling, additional polishing (UF/RO) and disinfection may be required depending on end-use quality targets and regulatory limits.
Operation & Maintenance
- Daily: inspect inlet screens, pumps, blowers and DO levels (maintain DO typically 2–3 mg/L), check RAS and sludge blanket.
- Weekly: clean diffusers, check carrier movement, inspect clarifier weir & desludge as needed.
- Monthly: calibrate sensors, service blowers, check media condition (no excessive scouring), inspect valves and piping.
- Sludge handling: periodic dewatering (drying beds or mechanical) based on sludge generation — expect ~3–5 kg dry solids/day (site dependent).
- Provide operator training, spares list and AMC options for continuous performance.
FAQ — 30 KLD MBBR STP
Q1: What is the advantage of MBBR over conventional ASP?
MBBR offers higher biomass per unit volume using attached media (reduces footprint), better tolerance to shock loads and lower sludge production. It is compact and suitable where space is limited.
Q2: How often is media replacement needed?
Carrier media is durable (polyethylene); generally lasts many years (5–10+ years). Periodic checks recommended; replace only if damaged or lost voidage.
Q3: Do you provide startup and AMC?
Yes — we provide commissioning, startup support, operator training and AMC packages across India.
Q4: What sample reports do you need to confirm design?
Send raw influent: BOD, COD, TSS, TDS, Turbidity, FOG, pH, temperature and any industrial-specific parameters (e.g., phenols, heavy metals). We also perform jar tests and SDI/OTR tests on site if required.