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AUTOMOBILE INDUSTRY CASE STUDY
How a 500 KLD Automobile ETP Restored Healthy MLSS & Eliminated MBR Foaming
Industry: Automobile Manufacturing (Fuel Vehicles & EVs, Painting & Assembly Operations)
Location: Halol, Gujarat, India | Capacity: 500 KLD
Core Tech: Primary Clarifiers (PHOS & ELPO streams) → 3 Aeration Tanks → MBR
Zero Foam
MBR & Aeration Foaming Eliminated
Grey → Brown
Biological Color Restored
97 mg/L
True Filtered Dissolved COD
This automobile wastewater treatment case study explains how a 500 KLD automobile manufacturing ETP restored healthy MLSS, eliminated heavy MBR foaming, and reduced turbidity using BactaServe De-Bulking. The integrated bio-debulking programme and controlled sludge wasting removed dead biomass, improved MLSS:MLVSS balance, stabilised biological treatment, and restored healthy brown biomass across the aeration system.
Background & Technical Challenge
Plant Overview
A leading automobile manufacturing plant in Halol, Gujarat, produces both internal combustion engine (ICE) and electric vehicles (EVs). The facility operates a 500 KLD combined Effluent Treatment Plant (ETP) that treats wastewater generated from vehicle painting and assembly operations.
The ETP receives two chemically distinct wastewater streams, Phosphating (PHOS) and Electrophoretic Deposition (ELPO). After separate primary treatment, both streams are combined and treated through three aeration tanks in series followed by a Membrane Bioreactor (MBR).
During operation, the biological treatment system experienced excessive dead biomass accumulation, resulting in grey sludge formation, heavy MBR foaming, high turbidity, unstable MLSS:MLVSS ratios, and inconsistent COD removal. To restore biological activity and stabilise treatment performance, the plant implemented BactaServe De-Bulking together with a controlled sludge wasting programme.
The Technical Challenge & Risk
Dead Biomass Accumulation: Excessive dead bio-sludge reduced biological activity, increased turbidity, and caused grey biomass throughout the aeration system.
Heavy MBR Foaming: Dead microbial cells generated persistent grey foam in the aeration tanks and MBR, indicating deteriorating biological health.
False High COD Readings: Dead biomass inflated unfiltered COD values, masking the actual biological treatment efficiency and complicating process control.
High Turbidity & Membrane Fouling Risk: Sludge carryover increased turbidity and elevated the risk of MBR fouling, reduced membrane performance, and higher maintenance costs.
Need for Stable Biomass: The plant required a specialised bio-debulking programme to restore healthy MLSS, stabilise the MLSS:MLVSS ratio, eliminate foaming, and improve overall biological treatment performance.
Treatment Process Flow Diagram
The 500 KLD combined Effluent Treatment Plant (ETP) receives wastewater from two independent process streams—Phosphating (PHOS) and Electrophoretic Deposition (ELPO). Each stream undergoes separate physicochemical treatment before being combined for biological treatment through a series of aeration tanks and final polishing in a Membrane Bioreactor (MBR).
Process units mapped based on the actual plant flow:
PHOS Stream → Flash Mixers (Lime & Alum Dosing) → Primary Clarifier 1 → PHOS FES Tank
ELPO Stream → Flash Mixers (Lime & Alum Dosing) → Primary Clarifier 2 → ELPO FES Tank
Combined Effluent → Aeration Tank 4 → Aeration Tank 3 → Aeration Tank 2 → Membrane Bioreactor (MBR) → Treated Water
Bio-Sludge Recirculation (RAS) → Aeration Tanks | Waste Activated Sludge (WAS) → Sludge Disposal
Process Overview
PHOS & ELPO Pre-Treatment: Independent physicochemical treatment removes suspended solids, paint residues, phosphates, heavy metals, and other chemical contaminants before biological treatment.
Combined Biological Treatment: Treated wastewater from both streams is combined and processed through three aeration tanks in series, where microorganisms degrade biodegradable organic matter and maintain healthy activated sludge.
Membrane Bioreactor (MBR): The MBR separates treated water from biological solids, producing a low-turbidity effluent while retaining biomass within the biological system.
RAS & WAS Management: Return Activated Sludge (RAS) maintains the required MLSS concentration, while controlled Waste Activated Sludge (WAS) removes excess and dead biomass to restore healthy biological activity and prevent MBR foaming.
WAS Protocol & Bio-Debulking
Why BactaServe™ De-Bulking Was Selected
The automobile ETP required a specialised biological solution to restore healthy activated sludge rather than relying solely on increased sludge wasting. BactaServe De-Bulking was selected to regenerate active biomass, improve biological treatment performance, and stabilise the MLSS:MLVSS ratio while reducing turbidity and MBR foaming. The treatment programme combined targeted bio-augmentation with a controlled Waste Activated Sludge (WAS) strategy to remove accumulated dead biomass from the system.
Key Benefits
Restored healthy MLSS and MLVSS
Reduced dead biomass accumulation
Eliminated grey MBR foaming
Improved biomass settling characteristics
Reduced turbidity across the biological system
Enhanced biological COD removal
Improved resilience to organic shock loads
Stabilised long-term ETP performance
Microbial Restoration Strategy
Amalgam Biotech implemented a 30-day bio-debulking programme using BactaServe De-Bulking across all three aeration tanks, combined with a controlled Waste Activated Sludge (WAS) protocol. As healthy microbial populations developed, dosing was gradually reduced while sludge wasting was progressively increased to remove inactive biomass without disrupting plant operations. This integrated approach restored biological stability, improved sludge quality, and enhanced overall ETP performance.
BactaServe De-Bulking (Aeration Tanks 2, 3 & 4)
Target: Dead biomass removal, MLSS recovery & healthy floc formation
Controlled Waste Activated Sludge (WAS)
Target: Excess dead sludge accumulated in the MBR
Biomass Regeneration
Target: MLVSS improvement & MLSS:MLVSS ratio stabilisation
Biological Process Recovery
Target: Turbidity reduction, foam elimination & improved COD removal
BactaServe De-Bulking 30-Day Dosing Schedule
Stage / Tank | Days 1 – 10 (kg/day) | Days 11 – 20 (kg/day) | Days 21 – 30 (kg/day) | Total Product Dosed |
Aeration Tank 4 | 2.0 kg/day | 1.0 kg/day | 0.5 kg/day | 35 kg |
Aeration Tank 3 | 3.0 kg/day | 2.0 kg/day | 1.0 kg/day | 60 kg |
Aeration Tank 2 | 2.0 kg/day | 1.0 kg/day | 0.5 kg/day | 35 kg |
Combined System Total | — | — | — | 130 kg over 30 Days |
*Dosing schedule is based on this plant case study and may vary depending on plant operating conditions and site-specific factors.
Performance Results & Analytics
Key Metrics Achieved
Healthy Biomass Restored: The colour of the activated sludge changed from grey to healthy brown, indicating successful regeneration of active biomass and recovery of biological treatment performance.
MBR Foaming Eliminated: Persistent grey foaming in the aeration tanks and MBR was significantly reduced following the bio-debulking programme and controlled sludge wasting, improving overall process stability.
Improved Turbidity: Progressive removal of dead biomass lowered turbidity throughout the biological treatment system, resulting in clearer mixed liquor and healthier sludge characteristics.
60.7% Filtered COD Reduction: Filtered COD in Aeration Tank 3 decreased from 247 mg/L to 97 mg/L, confirming improved biological degradation after restoring healthy biomass.
Stable MLSS & MLVSS Performance: The combined BactaServe De-Bulking and controlled WAS programme restored a healthier MLSS:MLVSS balance, improving sludge quality, biological stability, and resilience to organic shock loads.
Turbidity Reduction Across the Biological Treatment System
Date | Aeration Tank 4 | Aeration Tank 3 | Aeration Tank 2 | MBR Tank |
11-08-2023 | 270 | 252 | 218 | 244 |
12-08-2023 | 262 | 224 | 192 | 228 |
13-08-2023 | 249 | 213 | 206 | 231 |
14-08-2023 | 272 | 245 | 235 | 246 |
15-08-2023 | 262 | 218 | 200 | 240 |
16-08-2023 | 231 | 194 | 168 | 212 |
17-08-2023 | 244 | 215 | 154 | 230 |
COD Degradation
System Unit | Unfiltered Sample COD (mg/L) | Filtered Sample COD (mg/L) | Dead Biomass Contribution to COD (mg/L) |
Aeration Tank 4 | 760 | 247 | 513 |
Aeration Tank 3 | 619 | 97 | 522 |
Aeration Tank 2 | 628 | 168 | 460 |
MBR Tank | 792 | 176 | 616 |
Before & after turbidity comparison shows the removal of dead biomass, restoration of healthy activated sludge, and improved biological treatment following BactaServe™ De-Bulking.
Client Feedback: MLSS Restoration & MBR Foam Control
“Our 500 KLD painting ETP was experiencing thick grey foam and unhealthy biological sludge. Amalgam introduced controlled WAS wasting along with BactaServe De-Bulking. Within weeks, the grey surface foam disappeared, the biomass returned to a healthy brown colour and the MLSS balance was restored.”
Senior Plant Manager
Automobile Assembly Plant, Halol, Gujarat
⭐⭐⭐⭐⭐
Struggling with Dead Sludge or MBR Foaming in Your ETP?
Let our bio-engineers analyze your MLSS, MLVSS, and turbidity parameters to design a custom debulking and bio-augmentation schedule.
Step 1: Share your process details and treatment objectives.
Step 2: Our engineers assess your system and operating conditions.
Step 3: Receive a tailored solution and implementation plan.
Frequently Asked Questions
Q1: How did BactaServe De-Bulking eliminate heavy MBR foaming in a 500 KLD automobile ETP?
BactaServe De-Bulking restored healthy biological flocs by breaking down dead microbial cells and extracellular polymeric substances (EPS). Combined with a controlled Waste Activated Sludge (WAS) programme, it eliminated persistent grey foam, restored healthy brown biomass, and reduced mixed liquor turbidity within 30 days.
Performance Highlights:
Target Facility: 500 KLD automobile manufacturing ETP in Halol, Gujarat, treating Phosphating (PHOS) and ELPO paint shop wastewater.
Biomass Recovery: Restored biomass colour from unhealthy grey to healthy brown across all three aeration tanks.
Filtered COD Reduction: Reduced true dissolved COD in Aeration Tank 3 from 247 mg/L to 97 mg/L, achieving a 60.7% reduction.
Q2: Why does dead biomass cause false high COD readings and persistent foaming in MBR systems?
Dead microbial cells break down inside the aeration tank, releasing cell debris and organic matter that increase unfiltered COD readings. This can contribute more than 500 mg/L of false COD, create thick grey foam, and increase membrane fouling in Membrane Bioreactors (MBRs).
Analytical Insight:
Unfiltered vs Filtered COD: In Aeration Tank 4, the unfiltered COD was 760 mg/L, while the filtered sample showed the true dissolved COD was only 247 mg/L. The remaining 513 mg/L came from dead biomass.
Process Control Rule: Testing filtered samples helps measure the true dissolved organic load instead of suspended biological solids.
Q3: How does the combined Phosphating (PHOS) and Electrophoretic Deposition (ELPO) wastewater stream affect biological ETPs?
PHOS and ELPO wastewater contain heavy metals, phosphates, paint resins, and chemical coagulants. Each stream requires separate physicochemical treatment using flash mixers, lime, alum, and primary clarifiers to remove heavy metals and adjust pH before both streams are combined for biological treatment.
Process Sequence:
PHOS Stream: Lime and alum dosing → Primary Clarifier 1 → PHOS FES Tank
ELPO Stream: Lime and alum dosing → Primary Clarifier 2 → ELPO FES Tank
Combined Stage: The treated wastewater enters Aeration Tanks 4, 3, and 2 in series before final MBR treatment.
Q4: What was the 30-day BactaServe De-Bulking dosing schedule across the three aeration tanks?
The 30-day programme used a total of 130 kg of BactaServe De-Bulking across three aeration tanks. Aeration Tank 3 received 60 kg, while Aeration Tanks 2 and 4 each received 35 kg.
Dosing Progression:
Days 1 to 10 (Initial Regeneration): High dosing of 7 kg/day across all tanks to quickly restore healthy biomass.
Days 11 to 20 (Controlled Wasting Stage): Reduced dosing to 4 kg/day, combined with increased WAS discharge to remove dead biomass.
Days 21 to 30 (Stabilisation Stage): Maintenance dosing of 2 kg/day to maintain healthy MLSS:MLVSS ratios and low turbidity.
Q5: Why is managing the MLSS:MLVSS ratio critical for preventing bio-sludge bulking and MBR fouling?
The MLSS:MLVSS ratio shows the proportion of active microorganisms (MLVSS) compared with total suspended solids (MLSS). Too much dead biomass reduces the active MLVSS content, affecting oxygen transfer, causing sludge bulking, increasing turbidity, and leading to severe MBR membrane fouling.
Operational Benefits:
Improved SVI (Sludge Volume Index): A higher active biomass content improves sludge settling in clarifiers and MBR systems.
Better Shock Load Resistance: Healthy MLVSS levels help the biological system handle sudden organic load increases from paint shop operations.
Q6: What role does Waste Activated Sludge (WAS) management play alongside bio-augmentation in automobile ETPs?
While BactaServe De-Bulking promotes the growth of healthy bacterial flocs, controlled Waste Activated Sludge (WAS) discharge removes dead biomass from the system. Together, they prevent sludge build-up, maintain the correct sludge age (SRT), and support stable biological treatment without causing MBR foaming.
System Balance:
Return Activated Sludge (RAS): Recirculates active biomass to maintain the target MLSS.
Waste Activated Sludge (WAS): Removes dead biological sludge for dewatering using equipment such as an ANDRITZ Filter Press or Screw Press, helping maintain long-term biological performance.
Written by Ashutosh Vadanagekar
Technical Director, Amalgam Biotech
Ashutosh Vadanagekar has over 22 years of experience in water and wastewater treatment, with expertise in process design and bioculture technology. He develops and implements eco-friendly biological treatment solutions for ETPs and STPs across industries, addressing challenges such as high COD and BOD, ammonia, FOG, odour and biological process instability. He also contributes technical expertise and practical insights to Amalgam Biotech’s wastewater treatment case studies. Connect on LinkedIn