1. Debugging technology of printing and dyeing wastewater using A/O activated sludge method
The pollutants in textile printing and dyeing wastewater are mainly dirt on textile fibers such as cotton wool, salts, and oils. Classes and lipids, as well as various slurries, dyes, surfactants, additives, alkali, etc. added during processing. The main process used: "Grid? +? Adjustment pool? +? Anaerobic pool? +? Aerobic pool sedimentation pool? +? Disinfection pool." Using the method of simultaneous inoculation, culture, and acclimation for debugging, good activated sludge can be successfully cultivated within one month, and it can successfully meet the acceptance standards after three months. ?
⑴? Divide the entire debugging process into two stages: ? The first stage: The composition of printing and dyeing wastewater is very complex, and there are no two identical wastewaters. Although we inoculate activated pollutants from similar wastewater treatment stations, Mud, but the various enzyme systems in the inoculated microbial cells still need an adaptation process to the new wastewater. After the microorganisms go through the adaptation period, the cells begin to divide, the microorganisms begin to proliferate, and the microbial cells increase geometrically. After the bacterial proliferation is vigorous, the bacteria multiply and proliferate in large quantities, and the nutrients in the wastewater are consumed in large quantities, and the nutrients gradually become the basis for bacterial proliferation. Limiting factors. When the residual organic pollutants (BOD5) in the aeration tank are low and the ratio of organic matter to bacteria (F/M) is low, activated sludge can be well formed. Therefore, in the first stage of debugging, intermittent operation was used to inoculate 15% of the tank volume with activated sludge from the printing and dyeing wastewater plant. After one day of exposure, the water temperature in the regulating tank was controlled to be at 42°C and the pH was at 6?~10. Next, the water inlet and aeration run intermittently. The daily water inflow is 40% of the total design volume, and the aeration volume is 25% of the normal operation. The biodegradability of printing and dyeing wastewater is low, and the nutrients in the wastewater are not enough to maintain the reproduction and growth of activated sludge microorganisms. Add carbon sources to the anaerobic and aerobic pools every day (dosage: increase the BOD5 in the anaerobic and aerobic pools by 200mg/L). The dosage of nitrogen and phosphorus: the anaerobic tank should be added in the ratio of BOD5:N:P=300:5:1, and the aerobic tank should be added in the ratio of BOD5:N:P=100:5:1. During intermittent processing, the amount of sludge in the sedimentation tank is small and all returns to the aerobic tank. After 20 days of intermittent operation, activated sludge flocs with good sedimentation properties appeared in the aerobic tank. The sludge concentration reaches 1000mg/L?. ? Second stage: In the activated sludge treatment system, the essence of the removal process of organic pollutants from wastewater is the process in which organic pollutants are absorbed, metabolized and utilized as nutrients by activated sludge microorganisms. This is the so-called "activated sludge reaction" process. The result of this process is that the wastewater is purified, the microorganisms gain energy to synthesize new cells, and the activated sludge grows. After intermittent operation, the formation of activated sludge floc with good sedimentation performance and the increase of activated sludge microbial biomass have created conditions for the continuous operation of the biochemical system. At the beginning, 50% of the total daily treatment capacity was continuously fed with water. During operation, the growth of sludge is mainly affected by the sludge load (F/M). If F/M is too low, the activated sludge microorganisms will deflocculate and age due to lack of nutrients, which is not conducive to the growth of activated sludge. If the F/M is too high, the bacterial gel will deflocculate into free bacteria, which is also not conducive to the growth of activated sludge. Therefore, it is very important to control the F/M in the aerobic pool. We control the F/M in the aerobic pool at 400mg/LBOD5/mgMlss·d, and use a frequency converter to control the DO of the aerobic pool effluent to 3mg/L. The sludge in the anaerobic tank itself grows very slowly. In order to speed up the sludge concentration in the anaerobic tank, aerobic activated sludge accounting for 5% of the anaerobic tank volume is returned to the anaerobic tank every day. The BOD5 in the anaerobic tank is controlled at 300~ 400mg/L. Except for a small amount of activated sludge in the sedimentation tank, all the activated sludge in the sedimentation tank flows back to the anaerobic tank. The return flow rate is guided by Q1=Q·SV30/(1-SV30)? (Q1 is the sludge return Flow, Q is the water inlet volume), use it flexibly, and gradually increase the water inlet volume as the activated sludge concentration increases, under the condition that the sludge load (F/M) is met. After 3 months of continuous operation, the daily treated wastewater reached the design volume, the sludge concentration in the anaerobic tank was as high as 10?Kg/m3, the chroma removal rate was as high as 70%, the COD and BOD removal rates were over 30%, and the pH was at 6.8 ~7.5. The sludge concentration in the aerobic tank reaches 3.5?Kg/m3, SVI=200~300, and the COD and BOD removal rate reaches more than 85%.
The COD of the sedimentation tank effluent is <100mg/L, BOD<20mg/L, SS<30mg/L, PH: 7~8, and chroma: less than 40 times. ?
⑵? Problems encountered during the debugging process and their solutions
① Sludge expansion: Sludge expansion is generally reflected in two aspects: First, the sewage in the aerobic tank The mud load is relatively low, and the specific surface area of ??filamentous bacteria is larger than that of the micelle. When nutrients are restricted and controlled, the ability of filamentous bacteria with a large specific surface area to obtain substrates is stronger than that of micellar microorganisms. As a result, the growth of filamentous bacteria dominates the aeration tank, causing sludge expansion. Solution: Appropriately increase the water inflow, reduce the amount of sludge in the aerobic tank, and add more carbon, nitrogen, and phosphorus to the aerobic tank. Second, the sludge load in the aerobic tank is high, which can easily cause the aerobic tank to be hypoxic. Under anoxic conditions, it is conducive to the dominant growth of filamentous bacteria, leading to sludge expansion. Solution: Increase the sludge concentration and aeration volume of the aerobic tank, and appropriately reduce the water inflow. ?
②? Large pieces of sludge floated up in the sedimentation tank: Large pieces of sludge floated up in the sedimentation tank. The floating sludge was light rust-colored, not smelly, and had small bubbles attached. It was analyzed as sludge. denitrification. Solution: increase the return ratio, shorten the mud age, increase the sludge load, and discharge more mud.
2.