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Hybrid micro electrolysis technology used in the treatment of printing and dyeing wastewater (1)

Introduction: the field test results of hybrid micro electrolysis process for the treatment of printing and dyeing wastewater show that this dynamic micro electrolysis overcomes the shortcomings of the traditional micro electrolysis process, not only improves the treatment effect of COD, but also reduces the demand for equipment

key words: printing and dyeing wastewater micro electrolysis mechanical agitation

Chinese figure classification number: x703

document identification code: c

article number: (2002)

the size, dyes, additives and dyes and fabric reactants contained in printing and dyeing wastewater are often difficult to biodegrade. These substances need to be separated and removed before biochemical treatment in the treatment of printing and dyeing wastewater. Conventional pretreatment is to add coagulants (such as FeSO4, AlCl3, etc.). The research of suyuping et al. [1] shows that conventional dosing requires a large amount of coagulants. Due to overload, there are a series of chain reactions (for example, the appropriate dosage of FeSO4 is 750 ~ 950mg/l), which will increase the treatment cost of waste water. In actual operation, a large amount of sludge will be produced, and the effluent will turn yellow (adding FeSO4). Recently, the mixed micro electrolysis process has achieved good results in the field test of wastewater treatment in a printing and dyeing factory in Guangdong

the main mechanism of micro electrolysis in removing pollutants from printing and dyeing wastewater is as follows:

① complexation and coagulation. Fe2+ released continuously by micro electrolysis reaction becomes complexing agent and high-efficiency coagulant

② reduction, the new ecological hydrogen produced by micro electrolysis decolorizes the chromogenic groups of some dyes

③ oxidation, micro electrolysis produces a certain amount of new ecological oxygen, which has strong oxidation. For example, decorative strips or other decorative components in the central console or instrument panel can oxidize some inorganic and organic substances.

1 field test

1.1 process flow

in the past micro electrolysis applications, most of the micro electrolysis processes were designed as a fixed bed (similar to quartz sand filtration), allowing wastewater to pass through the static micro electrolysis iron filings layer, and micro electrolysis reactions occurred in this process. However, in the actual operation, the following two problems were found in this design:

① the efficiency of the micro electrolysis process decreased after running for a period of time, This is because an inert layer appears on the surface of iron filings, which prevents the micro electrolysis reaction from continuing; ② due to the existence of fabric fibers in printing and dyeing wastewater, it is easy to be blocked by micro electrolytic iron filings. Aiming at the shortcomings of the traditional micro electrolysis reactor, the micro electrolysis reactor is designed as a mechanical stirring type, which can not only destroy the inert layer on the surface of iron filings, but also avoid fiber blockage. In addition, the strong agitation of each dustpan with a span of 1 mile (about 1.6 km) accelerates the reaction speed and can accelerate the production of fe2+. After the micro electrolysis reaction, part of the wastewater can be directly mixed with the raw water to obtain a good treatment effect. This process is called mixed micro electrolysis technology, and the volume ratio of the water from the micro electrolysis reaction when mixed with the raw water is called the mixing ratio

the process flow of mixed micro electrolysis is shown in Figure 1

the wastewater is divided into two parts after being lifted by the water pump from the sump. The first part enters the micro electrolysis reactor, and its flow can be controlled by the flowmeter; The second part enters the mixing tank, mixes with the micro electrolysis effluent and then settles, and its flow is also controlled by the flowmeter. The first part of the available information is very little. Before the wastewater enters the micro electrolysis reactor, add acid to adjust the pH value of the wastewater to about 3. When the effluent from the micro electrolysis reactor is mixed with the second part of wastewater, a small amount of lime should be added according to the pH value of the wastewater, and the pH value of the effluent should be adjusted to 8 ~ 9. The sedimentation condition in this pH value range is good. The supernatant after sedimentation is discharged from the upper part, and the sludge is settled at the bottom of the tank, and then discharged regularly through the sludge discharge pipe

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