Upon completion of wastewater treatment system construction, bioreactor debugging is often necessary. This process begins with sludge inoculation. So, how is the sludge dosage calculated? Concurrently, the addition of specialized wastewater treatment bacteria is required for cultivation. How much bacterial culture should be added?
Bioreactors utilizing activated sludge cultivation typically employ dried sludge, activated sludge, or concentrated sludge. For bacterial cultures, products like Gando Composite Bacteria, Nitrifying Bacteria, and Denitrifying Bacteria are commonly used. Combining these two approaches can rapidly propagate biofilm or biological flocs.
Sludge Debugging Methods:
1. Dried Sludge Inoculation Method (Using Sludge from Filter Presses)
Dried sludge typically has a moisture content of about 75%-80%, meaning the solid content is approximately 20%.
The target Mixed Liquor Suspended Solids (MLSS) concentration in the bioreactor is typically around 3000 mg/L (or 3 kg/m³).
Therefore, the minimum dosage of dried sludge required per cubic meter of aeration tank volume is 3 kg/m³ / 20% = 15 kg/m³.
Example: For a 100 m³ bioreactor, the required dried sludge amount would be 15 kg/m³ × 100 m³ = 1500 kg.
Priority should be given to using dried sludge free of flocculants.
Advantages: Lower quantity required, convenient transportation.
Disadvantages: Often contains flocculants, which can inhibit microbial cultivation in the bioreactor.
2. Microbial Cultivation Using Existing Activated Sludge
Utilize a vacuum truck to transport the sludge-water mixture from an existing wastewater treatment plant's sludge holding tank.
Typically, the volume of the pumped sludge-water mixture should be about 60% of the debugged tank's volume.
Example: For a 100 m³ tank, approximately 60 m³ of mixture would be required. When the tank is filled to 100% capacity (with additional water/influent), the target sludge concentration should be around 3000 mg/L.
Advantages: No chemicals introduced into the bioreactor; faster acclimatization.
Disadvantages: Large volume required, high transportation costs, longer cultivation period.
3. Cultivation Using Concentrated Sludge
The dosage is typically 5-10% of the total bioreactor volume. A common starting point is adding 5% (v/v) concentrated sludge, resulting in an initial sludge concentration representing about 5% of the wastewater volume after filling. This refers to naturally settled, concentrated sludge with a moisture content close to 100%.
Example: For a 100 m³ bioreactor, the required volume of concentrated sludge is 100 m³ × 5% = 5 m³.
4. Dosage of Wastewater Treatment Bacterial Cultures
Microbial inoculants consist of pre-activated, viable bacteria.
The dosage generally ranges from 500 to 800 grams per cubic meter of the effective volume of the bioreactor (including aerobic and anaerobic zones).
The specific dosage can vary depending on the product used and should be adjusted based on actual conditions.
Advantages: Shorter cultivation period, cost-effective, rapid reproduction, and fast biofilm formation.