Overview: Catering wastewater refers to untreated wastewater discharged by the catering industry, which mainly comes from food preparation, tableware washing, food residue leachate and so on. The main pollutants in catering wastewater are food fiber, starch, fat, animal and vegetable oils, various condiments, detergents and protein, etc. At the same time, due to the complexity of diners, there is also the problem of pathogenic bacteria pollution. Most of these substances exist in colloidal state, and only a few of them exist in suspended matter, which is characterized by small quantity and many sources, complex components and great changes in water quality. The CODcr is generally 511-3511 mg/L. Because of the complex composition and high concentration of pollutants in catering wastewater, it pollutes the urban environment seriously, and the grease in sewage is easy to condense on the inner wall of the pipeline, forming a thick grease layer, which reduces the water capacity of the pipeline and even blocks it. It must be treated to meet the national discharge standards before it can be discharged into urban sewers or directly discharged into other water bodies, otherwise it will have serious adverse effects on the ecological environment and people's daily life.
Sewage treatment process
The process adopts a full biochemical process, and it is designed as air flotation+anaerobic hydrolysis+biological fluidized bed+filtration process. Acidification and hydrolysis are used for anoxia, and biological fluidized bed process is used for aerobic part. Mature and reliable process, simple operation and low investment and maintenance costs.
sludge treatment: excess sludge from grid well, anoxic tank and secondary sedimentation tank is discharged to sludge concentration tank for concentration and internal digestion before being transported out.
the supernatant of the sludge concentration tank flows back to the regulating tank.
Description of sewage treatment process flow
Sewage is collected into the grid well, and the grid in the grid well is used to intercept the larger floating objects and suspended substances in the water, and then it enters the regulating tank (pre-aeration is adopted in the regulating tank), where the water quality is homogenized, and then it is lifted by the water pump to enter the air-entraining flotation equipment, where oil and part of suspended substances in the sewage are removed by air flotation, and then it flows into the A-class acidification tank by itself, where the sewage is hydrolyzed and acidified, and the macromolecular organic substances that are difficult to biodegrade are decomposed into the micromolecule organic substances that are The effluent from the A-level acidification tank flows into the integrated biological fluidized bed reactor by itself. Because the sewage is hydrolyzed and acidified in front, the biodegradability of the sewage is greatly improved, and a large number of microorganisms are used to completely remove the organic matter in the sewage. At the same time, aerobic microorganisms are used to carry out nitrification reaction in it, and ammonia nitrogen (NH3-N) in sewage is converted into nitrite (NO2-) and nitrate (NO3-). The effluent from the integrated biological fluidized bed reactor enters the discharge tank through a multi-media gradient density filter. The backwashed sludge from the multi-media gradient density filter is lifted to the sludge concentration tank by the sludge pump for internal digestion and then transported out regularly. The supernatant of the sludge concentration tank is refluxed to the regulating tank.
Description of process products
Entrained air flotation is a new mechanical air flotation technology, which is a system specially designed for removing grease, colloid and solid suspended solids from industrial and urban domestic sewage, and is mainly used for sewage pretreatment. At present, dissolved air flotation (DAF) is mostly used in air flotation process in China. When using DAF to treat restaurant wastewater, the process of air dissolving into water is often limited by various factors, and the air compressor and circulating water pump used in DAF system not only consume a lot of electric energy, but also cause difficulties in equipment management and maintenance because the releaser is easily blocked.
(introduction of THK system: THK system is a new technology invented by HydroCal Environmental Protection Company of the United States in 1985, which can effectively solve the problems existing in dissolved air flotation (DAF). THK system simply introduces air into the system in the form of tiny bubbles (not dissolved in water) because of its unique technology, without air compressor, dissolved air tank and circulating water pump, and air naturally enters the air flotation system through suction pipe without releaser, so THK system has all-round advantages.
(1) The operation is simple, there is no complicated machinery and equipment, and the degree of automation is high, and there is basically no need for manual participation. Unlike DAF dissolved air flotation system, it includes many necessary equipment such as pressure vessel, air compressor and circulating pump.
(2) The operation flexibility is large, and it can adapt to a wide range of suspended solids concentration. Because the number of bubbles generated by THK system is four times that of DAF, THK system has no special requirements for the concentration of suspended solids in wastewater, and its application range is wide.
(3) Low operating cost. The energy consumption of THK system is low, only 1/8~1/11 of DAF, which can save 41~91% of the operating cost.
(4) It has good supporting integrity, small floor space and random installation location, and can be installed on the ground, underground or high.
(5) no noise.
integrated biological fluidized bed reactor
The biological fluidized bed technology is a new and efficient sewage treatment technology that has emerged since 1971s, and it is an important application in the sewage treatment field after the fluidized bed technology is widely used in the chemical field.
The biological fluidized bed reactor organically combines the advantages of ordinary activated sludge process and biofilm process, and improves the treatment efficiency of sewage treatment system by introducing fluidization technology. In the biological fluidized bed reaction system, the carrier is in a fluidized state, so that solid (biofilm), liquid (wastewater) and gas (air) are fully contacted, mass transferred and mixed, particles collide violently, and the surface of biofilm is constantly updated. This technology can maintain a high concentration of biomass in the bed, and the mass transfer efficiency is extremely high, so that the substrate degradation speed of wastewater is fast, the hydraulic retention time is short, the operating load is 11-21 times higher than that of the general activated sludge process, the impact load resistance is strong, the reactor occupies a small area, and the capital investment and cost are low.
(1) The small particle size carrier of the biological fluidized bed provides a huge surface area for microbial growth, which makes the biological concentration of the reactor high, reaching 4-5g/l, thus greatly increasing the volumetric load of the reactor, reaching 3-6kg/m3.d, even reaching 11 kg/m3.d;
(2) The mass transfer conditions in the reactor are good and the matrix transfer rate is high, so the biochemical reaction rate is fast, especially for the reaction system with good biodegradability and high organic concentration, the mixed mass transfer advantage of the biological fluidized bed is more obvious, and its biodegradation rate is fast;
(3) The high biomass and good mass transfer conditions make the biological fluidized bed reduce the volume of the reaction tank, save investment and floor space while maintaining its treatment efficiency;
(4) Compared with the activated sludge process, the biological fluidized bed has stronger impact load resistance, and there is no sludge bulking problem.
The integrated biological fluidized bed reactor is the latest product developed step by step on the basis of "three-phase biological fluidized bed". By optimizing the structure of the reactor, the technical integration is improved, which has the characteristics of high treatment efficiency, low energy consumption, small floor space and simple operation and maintenance, and can be widely used in the treatment of high concentration and good biodegradability sewage such as catering wastewater, food and brewing.
The integrated biological fluidized bed reactor has the following advantages:
(1) Under the condition of typical urban sewage influent quality, the reactor volume load can reach 7 ~ 13 kg COD/m3 d, and when the influent COD is 411 ~ 1111 mg/L, the COD removal rate is 81% ~ 91%;
(2) It occupies 41% ~ 51% of the traditional sewage treatment process, and greatly reduces the intensity of operation and management.
(3) The integrated biological fluidized bed reactor not only maintains the advantages of the traditional three-phase fluidized bed, such as good mixing performance, fast mass transfer rate, large biomass and high organic load, but also solves the problems of the traditional three-phase fluidized bed, such as excessive growth of biofilm thickness, uneven mixing and mass transfer, and difficult membrane removal.
(4) Small loss of carrier: Because the reactor adopts horizontal circulation and central sedimentation area for solid-liquid separation, the carrier is hardly lost in the whole reaction process by using the difference of sedimentation performance between carrier and biofilm.
(5) The carrier has good fluidization performance: in order to ensure the full fluidization of the carrier, the traditional three-phase biological fluidized bed must adopt a large height-diameter ratio without reflux. The integrated biological fluidized bed reactor adopts the form of water circulation, and realizes good carrier fluidization through the aeration and flow-pushing effects of jet aerator. At the same time, there is no upflow zone and downflow zone, so there is no carrier stratification in the traditional three-phase fluidized bed, and the carrier fluidization has good uniformity, which is very beneficial to the good growth of biofilm.
(6) High oxygen transfer efficiency: In the traditional three-phase biological fluidized bed, all the gas escapes from the top of the reactor, while in the BFBR biological aerobic fluidized bed, the liquid circulates in the reactor, which prolongs the gas-liquid contact time, so the oxygenation efficiency is high.
in the case process, the effective volume of the integrated biological fluidized bed reactor is 111m3, the hydraulic retention time is about 2 hours, the influent CODcr concentration is designed to be 711mg/L, the effluent CODcr concentration is 111mg/L, and the CODcr removal rate is over 81%.
ammonia nitrogen removal effect: the integrated biological fluidized bed reactor adopts a reactor with anoxic-aerobic denitrification function. When the influent is typical domestic sewage, the NH3-N concentration of the effluent can reach the first-class discharge standard of GB8978—1996.
removal effect of SS: the effluent containing biochemical sludge in the reactor has a high removal efficiency through the multi-media gradient density filter, which can control the effluent SS below 11mg/L ..
removal effect of TP: the removal of TP by the reactor is the result of microbial metabolism and sludge discharge. The average removal rate of TP is 51%, but a multi-media gradient density filter is added at the end of the reactor. If iron and aluminum salts are added for flocculation and chemical phosphorus removal, the average concentration of TP in the effluent is 1.88mg/L and the total removal rate is 85%.
Multi-media gradient density filter
In the water reuse system in sewage treatment, the filtration equipment is the key. By physical filtration, the solid particles in the water body are removed and the suspended solids in the effluent are reduced. At present, most of the water treatment and filtration systems for reclaimed water reuse in China use crude equipment such as sand filtration, and the sand tank is the main filtration equipment. The sand tank is a typical particle filtration method, which uses sand and gravel as the filtration medium to realize filtration through the adsorption of particle filter material and the interception of solid suspended matter in water by pores between sand particles. It has small specific surface area, small sewage interception, slow filtration speed and low filtration accuracy, and is not suitable for rapid filtration of suspended matter in reclaimed water reuse system.
The multi-media gradient density filter adopts asymmetric fiber bundle materials with different particle sizes and densities as the filter material, which has the advantages of both particle filter material and fiber filter material. Through the special structure, the porosity of the filter bed quickly forms a gradient density with large up and small down, which makes the filter have fast filtration speed, large sewage interception and easy backwashing, and is especially suitable for solid suspended matter filtration in reclaimed water reuse system.
Prevention and control of secondary pollution
1. Prevention and control of odor
a. All pools in the sewage station are sealed to prevent odor from escaping;
b, each pool body that may generate odor shall be provided with air pipes for aeration and aerobic digestion, so as to minimize odor generation.
2. Noise control
A. The system facilities are designed in the corner of the factory, which has little impact on the outside world;
b, the fan shall be of low noise type, and the noise of this machine shall be ≤81dB. The muffler shall be used at the inlet and outlet of the fan, the base shall be provided with isolation pads, and the flexible rubber flexible joints shall be used for the inlet and outlet air ducts.
c, ensure the ambient noise: ≤61dB during the day and ≤ 51dB at night.
3. Sludge treatment
a. Part of the sludge generated in the sludge treatment process is discharged into the sludge tank for gravity concentration and aerobic digestion and decomposition, thus reducing the sludge volume and improving the sludge stability;
b, the excess sludge in the sludge pool is pumped out by the cleaning management department regularly, thus effectively solving the problem of sludge outlet and avoiding secondary pollution.
Electrical control and production management
1. The automatic control system of the project scope is configured by the sewage treatment engineering process, and the automatic control major mainly involves the interlocking of water pump and liquid level, alarm, alternating action of fans, regular work of solenoid valves, etc. in the sewage treatment system.
2, control level, automatic and manual combination.
for reference only.