The following is A detailed description of the combined process of "grid + air flotation oil removal tank + coagulation sedimentation tank + hydrolysis acidification tank + anaerobic reactor + A/O+MBR" for the daily treatment of 300 tons of kitchen wastewater:
1.Grating
Function: Remove large suspended particles (such as food residues, plastic bags, etc.) from wastewater.
Principle: Through physical interception, the large impurities are retained by the gaps between the bars (typically 1-5mm).
2. Air flotation oil removal tank
Function: Separates oil and fine suspended particles
Principle: Dissolved air flotation. By pressurizing the dissolved air water, micro-bubbles are released. These bubbles adhere to oil droplets and suspended matter, causing them to float to the surface and form a scum.
Chemical assistance: A demulsifier may be added to disrupt the structure of emulsified oil.
3. Coagulation and Sedimentation Tank
Function: Further remove colloidal substances, fine suspended solids, and some soluble organic matter.
Coagulation: Add PAC (polyaluminum chloride) or PAM (polyacrylamide), neutralize the charges of colloids to form flocs.
Settlement: Flocs settle under the influence of gravity (for example, inclined tube sedimentation tanks can enhance efficiency).
4. Hydrolysis and Acidification Tank
Function: Decompose large organic molecules into smaller ones, thereby enhancing the biodegradability of wastewater.
Hydrolysis: Facultative bacteria secrete extracellular enzymes to break down proteins, fats, etc. into amino acids and fatty acids.
Acidification: Acidifying bacteria convert small molecules into volatile fatty acids (VFAs) and alcohols.
5. Anaerobic reactor
Function: Efficiently decomposes organic matter and generates biogas.
Principle: Hydrolysis acidification → Producing hydrogen and acetic acid → Producing methane
Sludge bed: Granular sludge provides a high biomass, and the upward flow promotes mass transfer.
6. A/O Process (Anoxic/Aerobic)
Function: Remove nitrogen and phosphorus and deeply degrade organic matter.
Oxygen-deficient zone: Denitrifying bacteria utilize the carbon source in the raw water to reduce NO₃⁻ to N₂.
Aerobic section: Nitrogen-fixing bacteria oxidize NH₄⁺ to NO₃⁻; Polyphosphate-accumulating organisms absorb excessive phosphorus.
7. MBR (Membrane Bioreactor)
Function: Replace the secondary sedimentation tank, enabling efficient separation of sludge and water and disinfection of the effluent.
Membrane filtration: The hollow fiber membrane traps sludge and microorganisms.
