Hotel catering wastewater is mainly a mixture of various kinds of wastewater generated in the business process, including swill and swill generated in the process of washing vegetables, washing rice, cooking and washing dishes and chopsticks. ? ? Characteristics of wastewater?
Restaurant wastewater has complex components, low PH, high SS, high turbidity and high organic content, mainly including food fiber, starch,
fat, animal and vegetable oils, various seasonings, detergents and protein. According to the detection of catering wastewater in some areas, it is shown that COD, SS, NH4+-N, BOD5, pH and TN in catering wastewater are 311-2,633 mg/L, 311-911mg/L, 3.4-45mg/L and 3.4-45 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 more than dozens of times that in ordinary catering wastewater. Coupled with the limitation of space, it brings more severe difficulties to the treatment of this kind of wastewater. ? What are the main treatment technologies of restaurant wastewater?
Because of the particularity of its water quality, the treatment methods of restaurant wastewater 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 restaurant wastewater. Pretreatment is the basis of treatment process, and treatment is the deepening of pretreatment process, and both are indispensable. ? Pretreatment technology of catering wastewater
Catering wastewater contains a large number of suspended substances and animal and vegetable oils, which will block dissolved oxygen in the atmosphere from entering the water body, and oil will be wrapped around microorganisms during the treatment process, causing them to die of hypoxia, which will affect the treatment effect. A large number of suspended substances are mostly food crumbs, with large particles, which are difficult to be utilized by microorganisms, and it is easy to block the treatment facilities during the treatment process, which brings difficulties to the treatment. Therefore, the pretreatment of restaurant wastewater has become a very important link and means in the treatment process.
The pretreatment technologies mainly include coarse granulation, adsorption, air flotation and electrochemical method.
? (1) coarse granulation method
coarse granulation method is also called coalescence filtration method. Using oleophilic and hydrophobic materials, when oily wastewater passes through, tiny oil droplets are attached to its surface < P > to form an oil film. When it reaches a certain thickness, it will leave the surface of the filter material under the action of buoyancy and water flow shear, and form large oil droplets 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 used SBR process, and through indoor
simulation experiments, the relationship between sludge concentration, load, aeration time and other factors and treatment effect was investigated, so as to determine its optimal operation cycle conditions. The effluent quality meets the secondary discharge standard of GB8978-1996, and this process has a strong pertinence for the treatment of catering wastewater. ?
? (3) Membrane bioreactor method
Membrane bioreactor is a new type of wastewater treatment system which organically combines membrane separation technology and biological treatment technology. The membrane module is used to replace the terminal secondary sedimentation tank of the traditional biological treatment technology, so as to maintain high activated sludge concentration in the bioreactor, increase the organic load, reduce the occupied area of sewage treatment facilities, and reduce the excess sludge by keeping the sludge load low. 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 thousands to tens of milligrams.
? (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 be absorbed and utilized by the microorganisms on the biofilm
when it flows through the biofilm on the filler at a certain flow rate, so as to remove the pollutants in the sewage and purify the 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 hours. The biological contact oxidation method has 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, and the water distribution and aeration are not uniform, so there may be no dead ends in some areas.