How to Cultivate and Acclimate Biofilms?
The process of attaching metabolically active microbial sludge onto the filler media in a biological treatment system is called biofilm
formation (or "biofilm seeding"). This process involves both the cultivation and acclimation of biofilm-based sludge.
During the initial biofilm formation stage in a biological film treatment system, two key objectives must be achieved:
- Microbial Growth & Proliferation – Ensuring microorganisms colonize the filler surface until a sufficient biofilm layer develops to meet wastewater treatment requirements.
- Acclimation to Wastewater Quality – Gradually adapting microorganisms to the specific wastewater characteristics (e.g., organic load, toxicity).
Methods of Biofilm Formation
Two primary methods are used:
1.Direct Biofilm Seeding
- Applicable Systems: Bio-contact oxidation tanks & tower biofilters (due to aeration and high filler porosity).
- Process:
-Operate the system continuously under optimal conditions (DO, pH, BOD₅, C/N ratio, temperature).
-Suitable for domestic sewage, municipal wastewater, or industrial wastewater mixed with domestic sewage.
-Timeframe: Typically 7–10 days for complete biofilm formation.
2.Indirect (Stepwise) Biofilm Seeding
- Applicable Systems: Conventional biofilters & rotating biological contactors (RBCs), especially for hard-to-degrade industrial wastewater.
- Process:
-Pre-culture and acclimate activated sludge separately.
-Mix the sludge with industrial wastewater in a recirculation tank.
-Introduce the mixture into the biofilm system while recycling effluent and settled sludge.
-Gradually increase industrial wastewater concentration (start at 20%) until full strength is achieved.
Key Considerations for Biofilm Cultivation
- Nutrient Balance: Maintain adequate N & P (COD:N:P ≈ 100:5:1).
- Uniform Water & Air Distribution: Critical to prevent clogging and ensure even biofilm growth.
- Regular Maintenance:
-Clean clogged nozzles/pipes.
-Optimize reflux flow.
-Minimize sludge deposition.
Causes & Solutions for Severe Biofilm Detachment
During Cultivation Phase
- Normal: New biofilms are fragile, especially with industrial wastewater.
- Solution: Persist with acclimation; adjust loading gradually.
During Normal Operation
- Abnormal Causes:
-Sudden increase in toxic/inhibitory substances.
-pH shock or extreme temperature changes.
- Solutions:
-Improve influent quality.
-Strengthen pretreatment (e.g., grease/solid removal).
-Optimize aeration and hydraulic flow.