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Renewable Energy: Anaerobic Digestor Plant

Achieved a 2.2MW of daily electricity generation (~30,000 m³/day Biogas). 60% of treated effluent is used for on-site recycling, and the sludge after digestion is further processed by composting to produce fertiliser.

Challenge

To retrofit and upgrade the existing Anaerobic Digestor Plant for energy recovery from chicken manure and organic food waste.

Solution

We implemented a comprehensive “treatment train” to transform chicken manure waste into energy (biogas) while ensuring the remaining liquid is polished to meet strict environmental standards.

  • Step 1 – Pre-Screening
    Wastewater undergoes pre-screening for removal of large debris (e.g., rags, plastics, wood, and other solids) before it enters the treatment plant.
  • Stage 2 – Anaerobic Digestion
    The wastewater then undergoes Anaerobic Digestion, which involves the decomposition of organic matter and the reduction of inorganic matter in the absence of molecular oxygen to generate biogas.
  • Stage 3 – Solids Separation
    The digested sludge from Anaerobic Digestion undergoes solids separation by firstly being transferred to a series of screw presses for solid separation and dewatering. In the screw press, the sludge is chemically conditioned to promote particle aggregation for optimal floc formation before being pressurized during the dewatering process. This produces sludge cake and filtrate water which has been squeezed out from the sludge. The sludge cake is managed as per local authorities’ guideline while the filtrate water is transferred to the DAF for further treatment.
  • Step 4 – Dissolved Air Floatation (DAF)
    In the DAF system, the filtrate is chemically conditioned to form larger floc. Air bubbles attach to suspended matter, causing it to float to the surface for skimming and transfer to the Sludge Holding Tank, while the supernatant naturally flows to the next treatment process.
  • Step 5 – Ammonia Stripping
    The treated water from the DAF system is transferred to the Ammonia Stripping System, where pH is adjusted to convert ammonium into free ammonia. The water then enters the stripping tower, where high-rate counter-current airflow removes the free ammonia. The stripped ammonia is absorbed by sulfuric acid to produce ammonium sulfate, which can be recovered as fertilizer.
  • Step 6 – Anoxic/Aerobic/Membrane Bioreactor (MBR)
    After ammonia stripping, the wastewater undergoes an anoxic-aerobic biological treatment process for nutrient removal to meet effluent discharge standards and onsite recycling requirements. The submerged membranes then retain active bacteria, producing clear, high-quality effluent that supports up to 60% onsite water recycling.

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