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China Coatings Online News Information
paint wastewater mainly comes from the cleaning of ingredient tanks, reactors and the preparation of different colors of paint process. The concentration of wastewater organic matter is high, and the color and suspension content are also high. In addition, it contains a large number of nanoscale inorganic materials, such as titanium dioxide, kaolin and a variety of colored pigments.
Scholars at home and abroad have done a lot of research on the treatment of paint wastewater, Wu Yongsheng used sedimentation method to treat fluorine paint wastewater, COD and other indicators significantly reduced, but will produce a large number of sludge, and sludge dry after incineration treatment, poor economy. Wang Jufang used extraction-break-coke adsorption method for pretreatment of high-concentration organic coating wastewater, and then mixed with low-concentration wastewater by gas floating-electrolytic-oxidation pond treatment, water COD<200mg/L. Zhao Xue and other processes using gas floating pool and two-stage aeration biofiltration pool to treat paint wastewater, but also achieved good results.1, engineering examples
1.1 wastewater quality, water quantity
Changzhou Environmental Protection Coatings Co., Ltd. mainly produces industrial coil coatings, water-based coatings, automotive coatings, anti-corrosion coatings, architectural coatings, special coatings, resin coatings and other seven series of products. The amount of wastewater is 200m3/d, of which 5% has a COD of about 25,000mg/L and the remaining 95% has a COD of about 500mg/L, sometimes reaching 1000mg/L. The two types of wastewater are mixed. The main components of wastewater: benzene, esters, ketones, as well as a small number of solids (pigments, fillers, mechanical impurities, etc.).
water quality and discharge standards for wastewater are set out in Table 1.
1.2 process
high concentration paint wastewater TSS content is high, gas float treatment is required to remove a small amount of SS and oily substances, gas float treatment water and low concentration wastewater mixed into the regulatory pool. Regulating the water out of the pool into the hydrolytic acidification pool, water into the integrated oxidation ditch, mainly to complete the removal of organic pollutants and synchronous nitrite de nitride denitrification, and then through the biological absorption tower and deep treatment process, to ensure that the discharge of water standards. The specific process is shown in Figure 1.2, the main structure and design parameters
2.1 pre-treatment
(1) adjustment pool
to adjust the water quality, water quantity, if necessary, the water heating, in order to improve the efficiency of the follow-up treatment process. The effective pool capacity is 240m3 and the steel mixing structure is.
(2) gas floating
design flow of 10m3/h, carbon steel anti-corrosion structure. Equipped with a scraper 1 with a width of 3m.
(3) accident pool
storage of waste water discharged during production accidents, the effective volume of 486m3, steel mixing structure.
(4) the initial rainwater
the collection plant and entered the aerobic system for treatment. The effective volume is 1269m3 and the steel mixing structure.
2.2 anaerobic
a small amount of activated carbon is added to the hydrolytic acidification pool to provide a growth carrier for anaerobic sludge. The effective pool capacity is 532m3, the dwell time is 48h, and the steel mixing structure. Equipped with 2 pushers, 400mm in diameter and 3kW in power.
2.3 one-in-one oxidation
using blowing aeration. The aerobic microorganisms in wastewater use oxygen to reproduce themselves, degrade most of the organic matter in the water, and remove nutrients such as N and P. In which activated carbon is also added to improve the removal effect.
the effective volume of the oxidation ditch is 1500m3, the steel mixing structure, the dwell time is 10d, and the volume load is 0. 45kgCOD/(m3·d)。 Main equipment: 4 thrusters, diameter of 1. 8m, power 0. 75kW; Two typhoons with a wind volume of 10m3/min and a wind pressure of 63. 7kPa, power 18. 5kW。
2.4 two sinking pool
the effective volume of the second sink is 275m3, the surface load is 0. 17m3/(m2.h), steel mixing structure.
2.5-set mud
sludge from the sedimentation pool passes through the pool and flows back into an all-in-one oxidation ditch. The effective volume is 75m3 and the steel mixing structure. Main equipment: sludge reflow pump, flow rate of 50m3/h, flue is 150kPa, power is 3. 0kW, 1 with 1 preparation.
2.6 Deep Treatment Pool
has a flocculation and activated carbon adsorption device in the deep treatment pool to further reduce the concentration of pollutants in the water discharged from the two sinks. The effective volume is 275m3 and the surface load is 0. 17m3/(m2.h), steel mixing structure.
2.7 clearing pool
(1) clear pool
is mainly used for storage depth treatment of water, partly used as a cooling tower recycling water, part of the outer discharge. The effective volume is 275m3, the dwell time is 2d, and the steel mixing structure.
(2) clear pool two
effective volume of 138m3, dwell time of 2d, steel mixed structure.
2.8 sludge tank
is mainly used to store the slag emitted by the gas floating pool and the residual sludge emitted in the sedimentation area of the one-in-one oxide ditch. The effective volume is 138m3 and the steel mixing structure.3, operation effect analysis
3.1 removal of organic matter
the project after 4 months of debugging into a stable operation phase. The removal of organic matter during stable operation is shown in Figure 2.
figure 2 shows that the stable operation phase due to the intermittent discharge of paint wastewater, water COD is still very volatile, the initial water COD as high as 2000mg/L or more, but the water COD basically maintained at 100mg/L The following, COD removal rate of >95%, which shows that after the pre-commissioning operation, the microorganisms in the hydrolytic acidification pool and oxidation ditch have basically adapted to the water quality of the wastewater and the sludge activity is high, can fully degrade the organic matter in the wastewater. After that, the in-water COD drops to about 1000mg/L, and the water-out COD drops below 50mg/L. But on the 42nd to 48th days, the COD concentration of the water was 118. 2~237. 6mg/L, exceeding emission standards. The final water COD is stable at 60 to 85 mg/L, and the average water COD concentration is 70 mg/L, which meets the standard of "Urban Sewage Recycling Industrial Water Quality" (GB/T19923-2005).
3.2 pairs of ammonia nitrogen
the removal of ammonia nitrogen by this project is shown in Figure 3.
from Figure 3, the concentration of ammonia nitrogen in the water was basically maintained at 10 to 40 mg/L, after treatment, ammonia nitrogen in the water dropped to 0. 01 to 4mg/L, the removal rate > 90%, which shows that the oxidation ditch has a good removal effect on ammonia nitrogen. In addition, when the concentration of ammonia nitrogen in the water rose sharply to about 100 mg/L, the ammonia nitrogen in the water remained at 0. 5mg/L or less, significantly lower than the emission standard of 10mg/L, which indicates that the microorganisms in the oxidation ditch are in good condition and have strong impact resistance to water quality.
3.3 to the total phosphorus removal
figure 4 is the total phosphorus removal situation.
figure 4 shows that the total phosphorus in the water is lower, basically below 5mg/L, after hydrolytic acidification pool-oxidation ditch treatment, the total phosphorus in the water drops to 0. 5mg/L or less, capable of meeting emissions. However, the operation also found that the 42nd to 46th day of total water phosphorus is basically more than 1mg/L, exceeding the emission standards, so in the depth treatment pool need to be added to the appropriate amount of potions, chemical phosphorus removal.4, operating costs estimated
4.1 chemical costs
(1) adjustment pool with lye
1 yuan/m3.
(2) gas floating PAC, PAM
gas floating pool into the water, need to add a certain amount of PAC, PAM, so that the suspension to generate flocs, easy to remove the gas float. PAC price is 2000 yuan / t, PAM (cation) is 30000 yuan / t, PAC drug delivery is 0. 02kg/m3, PAM dosing is 0. 005kg/m3, cost 0. 19 yuan/m3.
(3) deep processing of PACs, PAMs,
The PAC's dosing volume is 0. 04kg/m3, PAM dosing is 0. 008kg/m3, cost 0. 32 yuan/m3.
(4) sludge conditioning agent
system sludge yield of 150m3/d, water content of 99. 2%。 Sludge dehydration requires the addition of a certain amount of anion PAM, PAM cast plus 0. 005kg/kgDS, PAM (anion) price is 12,000 yuan /t, then the cost is 0. 3 yuan/m3.
(5) Chemical analysis
conventional COD, VFA and other analytical drug costs of about 0. 02 yuan/m3.
above totals 0. 93 yuan/m3.
4.2 electricity
total installed power is about 103. 5kW, of which 24h power is about 51. 05kW。 The price of electricity is 0. 57 yuan / (kW.h) calculation, electricity is 0. 145 yuan/m3.
4.3 labor costs
2 fixed staff, wages are calculated at 2000 yuan / (monthly person), then labor costs are 0. 67 yuan/m3.
operating expenses for the above costs total, a total of 1. 74 yuan/m3. 5, Conclusion
Using hydrolytic acidification/integrated oxidation ditch process to treat wastewater production paint, and in hydrolytic acidification ponds and oxidation ditches to add bioactive carbon, achieved better results, the treatment of water quality reached the "urban sewage recycling industrial water quality" (GB/T19923-2005) standard, can also be discharged directly into the urban sewage network.
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