Dairy sewage treatment equipment process

Dairy processing wastewater mainly comes from washing water of various equipment, ground washing water and wastewater for producing various dairy products. Waste water contains a lot of fat, protein and lactose. In addition to lactose, it can be dissolved in water in the form of a true solution. Milk protein is a suspension of gum and milk fat is an emulsion. At present, the domestic AO process is mainly used to treat dairy products. At the same time, the air floatation and sedimentation unit are combined, the process is relatively mature, the effluent water quality is stable, and the operation and management are convenient, but the sludge is large in production, difficult to handle, and high in power consumption such as aeration.

1 Waste water quality and quantity

The sewage treatment station mainly treats wastewater from dairy processing plants and a small amount of domestic sewage, and the designed daily processing capacity is 1 200 m3. Dairy processing plant wastewater contains a large amount of organic matter, mainly containing milk solids (milk fat, casein and other milk proteins, lactose, inorganic salts), the content of which varies according to different varieties and different methods of dairy products, and is soluble in water. Or colloidal suspension.

2 Process and process characteristics

2.1 Process

The waste water from the dairy processing plant and a small amount of domestic sewage enter the regulating tank, and then the wastewater is directly transported to the inlet of the drip filter bed by the lifting pump. The effluent from the drip filter bed is further processed into the contact oxidation pond to ensure that the effluent reaches the discharge standard and the effluent enters the second sink. The pool is precipitated and discharged.

2.2 Process characteristics

Because the COD of dairy processing wastewater is about 1 000 mg/L, and its biochemical property is quite good, the conventional treatment adopts the processes of hydrolysis acidification + contact oxidation or A/O. During the operation, there are often more foams and more scum in the pool. The operation and management problems such as difficult pH control and easy sludge expansion in the biochemical pool, so choosing a suitable treatment technology has become a new exploration in the dairy industry.

2.2.1 Working principle of the drip filter bed

The filter material in the trickling filter bed is processed by volcanic rock, which has a relatively large specific surface area, which provides a good carrier for microbial growth. The biofilm layer formed on the surface of the filter material contains a large amount of aerobic, facultative bacteria and fungi. , algae and protozoa, etc. [4]. When organic pollutants carry oxygen from the atmosphere and diffuse through the liquid phase to the surface of the biofilm, they enter the biofilm and are decomposed and transformed by microorganisms. When the biofilm reaches a certain thickness, oxygen is completely consumed before passing through the membrane layer, and an internal anaerobic aerobic environment is formed on the surface of the filter material. In such an environment, when NH4+-N has also diffused into the surface of the biofilm, part of NH4+-N is used for the growth and reproduction of microorganisms, and some of the surface nitrifying bacteria are oxidized to nitrate nitrogen, and nitrate nitrogen enters the biofilm. In an anaerobic environment, denitrifying bacteria are used for denitrification to remove NH4+-N.

2.2.2 Advantages of the trickling bed

Compared with aerobic processes such as CASS and activated sludge process, the drip filter bed has the advantages of low energy consumption and low operating cost without mechanical aeration and natural gas supply. At the same time, the drip filter can be based on water quality. The water quantity can adjust the reflux ratio at any time, the fluctuation of the received water is small, and the impact load is strong; its strict biofilm operation, the mud production is very small, and the maintenance and operation are simple.

The dairy wastewater adopts the trickling filter process to solve the problems of the concentration water quality, the difficulty of deep anaerobic control, the low efficiency of hydrolysis removal, and the high power consumption of direct aerobic.

2.2.3 contact oxidation process

After the trickling filter treatment, COD has been degraded by about 50%, just as a low-cost primary treatment, and contact oxidation as an immersed biofilm, also has the advantages of impact load resistance, no sludge expansion, etc. Combined with the trickling filter bed, it can greatly reduce the pool capacity, and the operation management is extremely simple.

3 Main structures and equipment parameters

3.1 Adjustment pool

Due to the concentrated discharge time of production wastewater, the instantaneous flow rate is large, and the different sections and types of milk are different, resulting in large differences in wastewater quality. The design has a residence time of 8 h, an effective volume of 400 m3, a design size of 23 m × 8 m × 2.5 m, and a seat.

The design of integrated sewage treatment is mainly for the treatment of domestic sewage and similar industrial organic sewage. The main treatment method is to adopt the relatively mature biochemical treatment technology to contact oxidation method. The water quality design parameters are also designed according to the general domestic sewage water quality. Calculated, according to the level of BOD5200mg / l, effluent BOD5 according to 20mg / l, a total of six components: (1) primary sedimentation tank (2) contact oxidation tank (3) secondary sedimentation tank (4) disinfection tank, disinfection Device (5) sludge tank (6) fan room and fan. Here we introduce the integrated underground sewage equipment:

(1) Primary sedimentation tank: The primary sedimentation tank is a vertical flow sedimentation tank. The rising flow rate of the sewage in the sedimentation tank is 0.2-0.3 mm/sec, and the settled sludge is lifted to the sludge tank by air. (Note: WSZ0.5-5m3/h does not contain primary sink)

(2) Contact oxidation pond: the water after the initial sedimentation flows to the contact pool for biochemical treatment. The contact pool is divided into three stages, the total residence time is 4-6 hours, the filler is novel trapezoidal filler, easy to conjunctate, no blockage, filler ratio The surface area is 160m2/m3, and the gas-water ratio of the contact pool is about 12:1. (Note: WSZ0.5-5m3/h contact pool is level 2)

(3) Secondary sedimentation tank: the biochemical sewage flows to the secondary sedimentation tank, and the secondary sedimentation tank is operated in parallel with two vertical flow sedimentation tanks. The upward flow rate is 0.1-0.15 mm/sec, and the sludge is sent to the sludge tank by air. . (Note WSZ0.5-5m3/h sludge flows from the sludge tank)

(4) The disinfection tank and disinfection tank shall be in accordance with the specification: (TJ14-74) for 30 minutes. If it is hospital sewage, the disinfection tank may increase the residence time to 1-1.5 hours. Disinfection uses solid chlorine tablets in contact with dissolved disinfection method. The disinfection device can continuously change the dosage according to the amount of water, and achieve the purpose of adding more water and less medicine. Other disinfection devices are required and can be prepared separately. (Note: If used in industrial sewage, disinfection tanks and disinfection equipment may not be required)

(5) Sludge tank: all the sludge in the primary sedimentation tank and the secondary sedimentation tank are extracted into the sludge tank of WSZ by air for aerobic digestion. The supernatant of the sludge tank is returned to the contact oxidation tank for reprocessing and digestion. After the sludge is scarce, it is usually cleaned once every 1-2 years. The cleaning method can be carried out from the inspection hole of the sludge tank to the bottom of the sludge tank for suction and then transported. (Note: WSZ0.5-5m3/h sludge is anaerobic digestion)

(6) Fan room and fan: The fan room is located above the disinfection tank. The fan room entrance adopts double-layer sound insulation. The air inlet has muffler and fan filter, so there is basically no noise during operation.

One: integrated sewage treatment equipment product features

1. Buried below the surface of the earth, the surface above the equipment can be used as a greening or other land, without building, heating and heat preservation.

2. The secondary biological contact oxidation treatment process adopts push-flow biological contact oxidation, and its treatment effect is better than the complete mixed or two-stage series fully mixed biological contact oxidation tank. It is smaller than the activated sludge tank, has strong adaptability to water quality, good impact load resistance, stable effluent quality, and no sludge expansion. The new elastic three-dimensional filler is used in the pool, the specific surface area is large, the microorganisms are easy to hang the membrane, and the membrane is removed. Under the same organic matter load condition, the organic matter removal rate is high, and the solubility of oxygen in the air in water can be improved.

3. The biochemical pool adopts biological contact oxidation method, the volume load of the filler is relatively low, the microorganism is in its own oxidation step, and the amount of mud production is small. It takes only three months (90 days) to discharge the mud once (pumping with a drunk vehicle or Dehydrated into a mud cake for export).

4. The deodorization method of the buried domestic sewage treatment equipment is not only the conventional high-altitude exhaust, but also the soil deodorization measures.

5. The whole equipment processing system is equipped with a fully automatic electric control system and equipment fault alarm system. The operation is safe and reliable. Generally, no special person management is required, and the equipment needs to be maintained and maintained in a timely manner.