Example analysis of environmental protection of leather base cloth wastewater by AB method
With the development of economy and the progress of science and technology, synthetic leather has been widely used in leather products. Due to the increase of leather products and the shortage of genuine leather, the technology of synthetic leather is constantly updated, and the development of synthetic leather technology also promotes the development of leather base fabric industry. By introducing advanced equipment at home and abroad, developing marketable high-grade synthetic leather base fabric products plays an important role in improving the economic benefits of enterprises.
A certain amount of waste water will be produced during desizing, bleaching, jigging and cleaning of PU leather-based fabrics, and there is also a certain amount of washing water on the workshop floor. At present, there is no introduction about the treatment methods of leather-based fabric wastewater in domestic literature. We know from practice that leather base cloth wastewater and printing and dyeing wastewater are similar, but they are different. According to the related literature [1-4], at present, the treatment methods of printing and dyeing wastewater mainly include chemical method (chemical coagulation method, chemical redox method, photocatalytic oxidation method and electrochemical method), physical and chemical method (adsorption (air flotation) method, membrane separation technology and ultrasonic air vibration technology) and biological method. We believe that the combination of chemical coagulation and biological treatment is effective for dyeing and finishing wastewater produced in the production of leather base fabric, and it is feasible technically and economically.
A, water treatment process scheme
The wastewater discharged by printing and dyeing enterprises has complex components, including dyes with large molecular weight, chemical pastes, chemical additives and other substances that are difficult to biodegrade, as well as starch and other substances that are easy to biodegrade. Wastewater has high chroma and pH value, which makes it difficult to treat. The wastewater discharged in the dyeing and finishing process of leather-based fabrics is different from the general dyeing and printing wastewater. Due to the production technology of leather base fabric and the large number and variety of dyes and auxiliaries used. Therefore, the concentration of pollutants in dyeing and finishing wastewater of leather base fabric is higher than that of general dyeing and finishing wastewater; Secondly, in the finishing and dyeing process of leather base fabric, a large number of tiny fluff fibers will fall off, and the suspended solids in wastewater are very high. In the process of wastewater treatment, it is necessary to go through multiple grids and multiple precipitations to achieve the ideal treatment effect. In addition, because the grey cloth of leather-based cloth is mostly treated with chemical pulp or starch pulp, most of the pulp will be transferred to the wastewater after cooking and desizing, which makes the sludge produced after the wastewater treatment of leather-based cloth large and sticky, and the dehydration and drying of sludge has also become a big problem. We use chemical coagulation combined with two-stage biochemical method, that is, the improved AB biochemical method with biosorption-facultative hydrolysis-aerobic biochemistry as the main body, to solve the problem of dyeing and finishing wastewater treatment caused by leather base fabric production technology, and achieved ideal results.
The main features of this process are:
A, multi-level biochemistry, diverse strains, complete degradation of pollutants. Two-stage facultative hydrolysis is set in the process flow, which gives full play to the facultative hydrolysis function, degrades macromolecules and macromolecular compounds that are difficult to be biochemical into low-molecular compounds that are easy to be biochemical, creates favorable conditions for subsequent aerobic biochemical treatment, and can give full play to the aerobic biochemical function. At the same time, because the facultative section operates under low dissolved oxygen and high pollution load, the energy consumption for removing unit COD load is low.
B, isolate each biochemical stage to prevent different strains from competing with each other and improve the pollutant removal rate. In the process, an inclined plate isolation tank is set up to isolate the facultative microorganisms in the facultative section from the aerobic microorganisms in the aerobic biological section, thus avoiding the disadvantage that two different microorganisms mix and compete to inhibit the aerobic biochemical function. Improve aerobic biochemical function.
C, make full use of biological coagulation to reduce the dosage of coagulant and sludge output. In the process flow, the sludge in the facultative and aerobic sections flows back, and a biological adsorption reaction section is set up, so that the pollutants in the returned sludge and sewage can be adsorbed and rolled. Compared with the sludge non-reflux process, the dosage of coagulant can be reduced by about 30%, and the sludge production is also reduced accordingly.
D, reasonable and compact layout, small floor space and convenient operation and management. The regulating tank is arranged underground, and the other treatment tanks are arranged on the ground. The same large pool is divided into different functional pools on the same horizontal plane, and the whole system runs continuously and produces water continuously.
E, aerobic combined treatment, nitrogen and phosphorus removal effect is good.
Second, the example application analysis
(1) Overview
The main product of a leather base fabric company is leather base fabric, with an annual production capacity of 25 million meters. The main raw materials are grey cloth, sulfur dyes, disperse dyes and additives. Main waste water sources: waste water from desizing, bleaching, jigging and cleaning, as well as washing water and domestic sewage from workshop floor. The design capacity of the company's wastewater treatment facilities is 800 tons/day, with three shifts, and the average hourly water treatment capacity is 34 tons. Water quality before design treatment: CODcr 1450mg/L, BOD5 500mg/L, SS 800mg/L, chroma 1000 times.
The company's wastewater treatment scale is 800 tons/day, and the process
The flow chart is as follows:
(2), the main unit process parameters
A. Grille ditch: 4m3 brick-concrete structure, built-in three-layer thick and thin grille to remove coarse impurities and fibers.
B. Regulating tank: 533m3, effective volume 426m3, HRT 13h.
C, inclined plate primary sedimentation tank 1: 19 1m3 concrete, effective volume 153m3, HRT4.5h
D, inclined plate primary sedimentation tank 2: 19 1m3 concrete, effective volume 153m3, HRT4.5h
E. facultative hydrolytic biosorption tank: 19 1m3 concrete, effective volume 153m3, HRT4.5h
F, inclined plate isolation tank: 19 1m3 concrete, effective volume 153m3, HRT4.5h
G. aerobic biological contact oxidation tank: the designed volume is 573m3, the effective volume is 458m3, and the hydraulic retention time is13.5h. ..
H. Inclined plate secondary sedimentation tank: design volume 19 1m3, effective volume 153m3, HRT4.5h
1. Sludge concentration tank: the designed volume is 173m3, and the sludge concentration time is 36h.
(3), the operation effect
In order to understand the treatment effect of wastewater treatment facilities, we measured the wastewater treatment facilities of this company.
1. Working conditions during monitoring.
During the monitoring period, the production load is 90%, which meets the requirements of Technical Specification for Monitoring the Completion Acceptance of Environmental Protection Facilities.
4. Monitoring points and analysis projects.
Before wastewater treatment, a monitoring point is set at the outlet of the primary sedimentation tank, the outlet of the biochemical tank and the discharge port of the treatment facility. The analysis items are pH, CODcr, BOD5, SS, sulfide and chromaticity.
13. Monitoring results and opinions
The average result of wastewater monitoring is shown in table 1, and the wastewater treatment effect of each section is shown in table 2.
Table 1 Summary unit of monitoring results: mg/L (except pH and chromaticity)
monitoring point
CODcr
BOD5
sage
chrominance
sulfuret
pH value
Import of treatment facilities
1 190
424
745.5
729
3 1. 18
7.45
Effluent from primary sedimentation tank
5 12
205
36
25
0. 17
8.08
Effluent from biochemical pool
67.5
24.4
13
25
0.02
7.80
Discharge port of treatment facility
43.4
17.2
six
20