Which option is better — ASP or MBBR for 900 KLD?

Both are viable. ASP needs trained operators and usually lower media cost. MBBR is compact, robust to shock loads and ideal for retrofit. We advise final selection after site & influent analysis.

What data is required for final design?

Raw influent lab report (BOD, COD, TSS, TDS, FOG, pH), site levels, power availability and reuse/discharge requirements.

Do you provide performance guarantees?

Yes — after site survey and agreed scope we provide performance guarantees and AMC packages.

900 KLD STP Price

Design Basis — Common Inputs

Plant capacity Q_day = 900 m³/day (900 KLD).
Operating hours = 20 hr/day.
Assumed influent BOD₅ = 250 mg/L (confirm with lab).
Oxygen requirement factor = 1.4 kg O₂ / kg BOD.
Clarifier SOR = 30 m³/m²·day.
Sludge yield = 0.5 kg DS / kg BOD.

General hydraulic calculations (digit-by-digit)

1) Hourly flow
Q_hr = Q_day ÷ operating_hours = 900 ÷ 20 = 45.0 m³/hr.
Q_hr in litres per hour = 45.0 × 1000 = 45,000 LPH.

Q_hr = 900 ÷ 20 = 45.0 m³/hr Q_hr_LPH = 45.0 × 1000 = 45,000 LPH

2) BOD load
BOD load/day = Q_day × Influent_BOD ÷ 1000 = 900 × 250 ÷ 1000 = 225.0 kg BOD/day.

BOD_load = 900 × 250 ÷ 1000 = 225.0 kg/day

3) Oxygen requirement
O₂ required/day = BOD_load × 1.4 = 225.0 × 1.4 = 315.0 kg O₂/day.

O2_req = 225.0 × 1.4 = 315.0 kg/day

Option A — 900 KLD STP — ASP (Activated Sludge Process)

ASP is a continuous suspended-growth biological system — proven for large, stable flows where trained operation is available.

ASP Design Calculations (digit-by-digit)

4) Aeration tank volume (HRT method)
Assume Aeration HRT = 6 hours.
Working volume V_aer = Q_hr × HRT = 45.0 × 6 = 270.0 m³ (working).
Add 15% freeboard → physical volume ≈ 270.0 × 1.15 = 310.50 m³.

V_aer = 45.0 × 6 = 270.0 m³ V_physical ≈ 270.0 × 1.15 = 310.50 m³

5) MLSS & biomass
MLSS = 3,000 mg/L = 3.0 kg/m³. Biomass mass = MLSS × V_working = 3.0 × 270.0 = 810.0 kg suspended solids.

Biomass = 3.0 × 270.0 = 810.0 kg

6) Clarifier sizing
SOR = 30 m³/m²·day → Area A = Q_day ÷ SOR = 900 ÷ 30 = 30.0 m².
Choose circular clarifier diameter d: d = √(4A/π) = √(120 ÷ π) ≈ √(38.197) = 6.18 m. Choose practical diameter ≈ 6.2 m (or provide multiple modules).

A = 900 ÷ 30 = 30.0 m² d ≈ sqrt(4×30 ÷ π) ≈ 6.18 m → choose 6.2 m

7) Sludge estimate
Sludge DS/day = BOD_load × yield = 225.0 × 0.5 = 112.5 kg DS/day.
At 3% cake solids → wet sludge ≈ 112.5 ÷ 0.03 = 3,750 L/day.

DS/day = 225.0 × 0.5 = 112.5 kg Wet_sludge ≈ 112.5 ÷ 0.03 = 3,750 L/day

8) Blower sizing (indicative)
O₂ req/day = 315.0 kg O₂/day. Using 1.2 kg O₂ per kW practical allowance → blower_kW ≈ 315.0 ÷ 1.2 = 262.5 kW. Recommend distributed blowers (for example: 6 × 50 kW or 4 × 75 kW with redundancy and VFD control) sized after detailed oxygen transfer and DO setpoints are confirmed.

Blower_kW ≈ 315.0 ÷ 1.2 = 262.5 kW (indicative)

ASP Process Flow (text)

Inlet → Bar Screen → Oil & Grease Trap → Grit Chamber → Collection/Equalization Tank (with mixer) → Raw Sewage Transfer Pumps → Aeration Tank (ASP) with diffusers → Secondary Clarifier → Polishing (PSF/ACF/UF if required) → Disinfection → Treated Water Tank → Reuse/Discharge. Sludge: Sludge sump → Thickening → Dewatering → Disposal.

ASP Main Equipment & Scope

Mechanical bar screens & grit removal
Collection / equalization tank with mixers
Aeration tank (270 m³ working / 310.5 m³ physical) with fine-bubble diffusers
Blowers: total indicative ~262.5 kW (split duty + standby), DO control, silencers & VFD
Secondary clarifier (Ø ~6.2 m) with hopper & RAS pumps
Polishing train: Pressure Sand Filter, Activated Carbon Filter, UF/Cartridge options
Hypochlorite dosing skid for disinfection
Sludge handling: sump, sludge pump, dewatering (belt press/drying beds)
PLC control panel, instrumentation (DO, level, flow)

ASP MOC & Notes

Tank MOC: RCC / MSEP / FRP with rubber lining (as per site & budget)
Piping: HDPE/UPVC for process; SS304 for critical wetted parts if required
Electrical: MCC, backup generator provision recommended for continuous operation

Option B — 900 KLD STP — MBBR (Moving Bed Biofilm Reactor)

MBBR uses floating carriers to develop biofilm — compact, robust to shock loads, lower suspended sludge yield and often smaller footprint.

MBBR Design Calculations (digit-by-digit)

1) Aeration/reactor volume (HRT method)
Assume MBBR HRT = 4 hours.
V_working = Q_hr × HRT = 45.0 × 4 = 180.0 m³ working.
Add 15% freeboard → physical volume ≈ 180.0 × 1.15 = 207.0 m³.

V_MBBR = 45.0 × 4 = 180.0 m³ V_physical ≈ 180.0 × 1.15 = 207.0 m³

2) Carrier media volume
Media fill fraction = 50% (typical) → media volume = 180.0 × 0.50 = 90.0 m³ of carriers (e.g., Kaldnes type).

V_media = 180.0 × 0.50 = 90.0 m³

3) Clarifier sizing
Use same clarifier SOR: A = 900 ÷ 30 = 30.0 m². Circular dia ≈ 6.2 m (same as ASP) or multiple smaller modules as preferred.
4) Sludge estimate
MBBR has lower sludge yield; choose conservative yield = 0.4 kg DS/kg BOD → DS/day = 225.0 × 0.4 = 90.0 kg DS/day.
At 3% cake solids → wet sludge ≈ 90.0 ÷ 0.03 = 3,000 L/day.

DS/day = 225.0 × 0.4 = 90.0 kg Wet_sludge ≈ 90.0 ÷ 0.03 = 3,000 L/day

5) Oxygen & blower sizing (indicative)
O₂ req/day = 315.0 kg O₂/day (same BOD load). Use oxygen transfer efficiency & mixing allowance; using 1.2 kg O₂/kW → blower_kW ≈ 315.0 ÷ 1.2 = 262.5 kW (indicative). MBBR may require slightly more mixing energy — design with vendor ATS and pilot tests.

Blower_kW ≈ 315.0 ÷ 1.2 = 262.5 kW (indicative)

MBBR Process Flow (text)

Inlet → Bar Screen → Oil & Grease Trap → Grit → Equalization Tank → Raw Sewage Transfer Pumps → MBBR Reactor (aeration + carriers) → Secondary Clarifier → Polishing (PSF/ACF/UF) → Disinfection → Treated Water Tank → Reuse/Discharge. Provide media retention screens at outlets and media handling plan.

MBBR Main Equipment & Scope

Equalization tank & transfer pumps
MBBR reactor (180 m³ working / 207 m³ physical) with ~90 m³ carriers
Fine bubble diffusers & blowers (~262.5 kW indicative) with VFD
Media retention screens, secondary clarifier (Ø ~6.2 m)
Polishing: PSF, ACF, UF options
Hypochlorite dosing & PLC controls

MBBR MOC & Notes

Reactors: RCC / MSEP / FRP with rubber lining
Carriers: HDPE proven vendor media; retention screens & sample ports mandatory
Retrofit-friendly: MBBR can be installed into existing tanks to save civil cost

ASP vs MBBR — Quick Comparison (900 KLD)

Feature	ASP	MBBR
Footprint	Moderate (aeration + clarifier)	Smaller (higher surface area with carriers)
Sludge yield	Higher (~112.5 kg DS/day)	Lower (~90.0 kg DS/day)
Operator skill	Requires trained operators	Less operator-intensive, more robust
Retrofit	Possible with modifications	Excellent for retrofit (drop-in carriers)
Capital cost	Lower equipment cost, more civil	Higher media cost, lower civil

Operation & Maintenance — Common

Daily: Check screens, pumps, blowers, DO (target 2–3 mg/L in aeration/reactor), sludge blanket, alarms
Weekly: Inspect diffusers, remove ragging, backwash polishing filters
Monthly: Calibrate DO & level sensors, inspect blower filters & motors
Periodic: Sludge dewatering, media inspection (MBBR), diffuser replacement, CIP if needed
We offer operator training, spare parts & AMC packages for large STPs

Common Issues & Troubleshooting

Low DO: Check blower runs, VFD settings, diffuser clogging.
Clarifier solids passing: Adjust RAS, check sludge return, inspect SRT/MLSS balance.
Foaming: Identify surfactant source; dose anti-foam and control SRT/MLSS.
Media loss (MBBR): Verify outlet screens and repair media retention pockets.

Item	Indicative
Aeration tank (ASP)	270.0 m³ working (310.5 m³ physical)
Aeration reactor (MBBR)	180.0 m³ working (207.0 m³ physical) + ~90 m³ carriers
Clarifier area	30.0 m² (Ø ≈ 6.2 m)
Sludge (wet)	ASP ≈ 3,750 L/day • MBBR ≈ 3,000 L/day
Blower (indicative)	~262.5 kW total (split units)

900 KLD Sewage Treatment Plant — ASP & MBBR Options

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