? Characteristics of wastewater? Restaurant wastewater has complex components, low PH value, high SS, high turbidity and high organic matter content, mainly including food fiber, starch,
Fat, animal and vegetable fats, various seasonings, detergents and protein. According to the detection of catering wastewater in some areas, COD, SS, NH4+-N, BOD5, pH and TN in catering wastewater are 300-2633mg/L, 300-900mg/L, 5.8 1-6.55 and 3.4-400 mg/L respectively. However, the quality and quantity of catering wastewater are greatly influenced by people's living and eating habits. Sometimes the content of pollutants in catering wastewater in some places is dozens of times more than that in ordinary catering wastewater. Coupled with the limited space, it brings more severe difficulties to the treatment of this kind of wastewater. ?
What are the main treatment technologies for restaurant wastewater? Due to the particularity of its water quality, the treatment methods of restaurant sewage are generally divided into two stages: pretreatment and treatment.
In practical application, many technologies are often combined, and the main goal of treatment is to remove COD, suspended solids and animal and vegetable oils from catering wastewater. Pretreatment is the basis of treatment process, and treatment is the deepening of pretreatment process, both of which are indispensable. ?
The pretreatment technology of restaurant wastewater contains a lot of suspended solids and animal and vegetable oils, which can prevent dissolved oxygen from entering the water body. In the process of treatment, oil will wrap microorganisms, leading to their death from hypoxia, which will affect the therapeutic effect. A large number of suspended solids are mostly food crumbs, with large particles, which are difficult to be utilized by microorganisms, and it is easy to block treatment facilities during treatment, which brings difficulties to treatment. Therefore, the pretreatment of restaurant wastewater has become a very important link and means in the treatment process.
Pretreatment technologies mainly include coarsening, adsorption, air flotation and electrochemical methods.
? (1) coarse granulation method
Coarse granulation method is also called coalescence filtration method. Using lipophilic and hydrophobic materials, when oily wastewater passes through, tiny oil beads will be attached to its surface.
When the oil film reaches a certain thickness, it will leave the surface of the filter material under the buoyancy and shear force of the water flow, forming oil beads with larger particles to float to the water surface for oil-water separation.
? (2)SBR method
In view of the intermittent discharge of catering wastewater and the large fluctuation of water quality and quantity, Yu Jinlian and others adopted SBR process to pass indoors
In the simulation experiment, the relationship between sludge concentration and load, aeration time and treatment effect was investigated to determine the optimal operation cycle conditions. The effluent quality meets the secondary discharge standard of GB8978- 1996, and this process has strong pertinence for the treatment of restaurant wastewater. ?
? (3) Membrane bioreactor method
Membrane bioreactor is a new wastewater treatment system which combines membrane separation technology with biological treatment technology. Replace it with a membrane module.
The terminal secondary sedimentation tank of traditional biological treatment technology can maintain a high concentration of activated sludge in the bioreactor, increase the organic load, reduce the occupied area of sewage treatment facilities, and reduce the excess sludge by maintaining a low sludge load. Membrane separation equipment is mainly used to intercept activated sludge and macromolecular organic matter in water. After advanced oxidation pretreatment and advanced treatment, the COD of MBR effluent can be reduced from several thousand mg to several tens mg.
? (4) Electrochemical method Electrochemical method means that when the electrolyte solution undergoes electrochemical reaction under the action of current, the toxic and harmful substances in the solution undergo redox reaction at the anode and cathode, and are reduced to low molecular weight organic substances or directly oxidized to CO2 and H2O. Although this method has a good treatment effect, it consumes a lot of energy and cannot be widely used.
? (5) biological contact method
The essence of this method is to fill the tank with filler, and the oxygenated sewage will hang biofilm when it flows through the biofilm on the filler at a certain flow rate.
The uptake and utilization of microorganisms on the surface, thus removing pollutants in sewage and purifying sewage. It is a biological treatment technology between activated sludge process and biofilter, which has both advantages. In view of the characteristics of scattered pollution sources, serious pollution and poor treatment effect of catering wastewater, UASB+AF—- contact oxidation combined process was used to treat catering wastewater, and the treatment effect was better when the total hydraulic retention time was 8 h. The biological contact oxidation method has the advantages of strong impact load resistance, convenient operation, simple operation, easy maintenance and management, and no need for sludge backflow. However, the packing is easy to block, the water distribution and aeration are uneven, and some areas may not have dead ends.