The nictric acid is an organic acid, which is mainly used in food industry, medicine, chemical industry and so on. Generally, starch is the main source of nictric acid. The production of citric acid will produce a large amount of wastewater. This paper mainly introduces several methods of treating nictric acid wastewater, such as emulsion liquid membrane, comprehensive treatment and recycling neutralization wastewater technology. Among them, filtration membrane of the ceramic membrane
is used in emulsion liquid membrane process.
Emulsion liquid membrane method
Waste from nictric acid production
mainly comes from waste neutralizing liquid, concentrated sugar water, sugar washing water, tank washing water and cloth washing water produced in fermentation and extraction processes. Liquid membrane separation technology is widely used in separation of biological and heavy metals engineering, and this method is more efficient in wastewater treatment with higher concentration. The first step of liquid membrane treatment of waste water is to put the emulsion and waste water together and stir them so as to fully integrate them. During the mixing process, the citric acid in the waste water is concentrated in the membrane through the liquid membrane, and then the citric acid is decomposed. The emulsion liquid membrane separation process is relatively simple, and the separation efficiency is high. It is more practical for industrial application. The emulsion can be reused and the separation effect is unchanged.
Comprehensive treatment method
Anaerobic-Aerobic Biological Combination Method
The two biological methods mentioned above have their corresponding advantages, but the single treatment method is difficult to meet the national discharge requirements, so the wastewater is treated after the combination of the two methods. The nictric acid wastewater with concentration of 5000-50000mg/L is treated, mixed into low concentration wastewater, and then entered into biological contact oxidation tank. The wastewater treated by the above methods can meet the national discharge standard, which increases the utilization rate of water resources to a certain extent. The discharged water can be used for farmland irrigation, industrial water and so on. At present, the anaerobic-aerobic biological combination method has been applied to the treatment of nictric acid wastewater.
Anaerobic-facultative-aerobic biological combination method
In the process of combined anaerobic and aerobic biological treatment of wastewater, the operation effect of the anaerobic unit treating the effluent of the anaerobic unit is poor, which greatly reduces the efficiency of wastewater treatment. Based on the interaction between anaerobic unit and aerobic unit, a bioconverter is added between them. After the wastewater is anaerobically treated, the oxygen content in water is increased by the converter, and the anaerobic substances in water are removed, so as to prepare for the aerobic unit and improve the treatment efficiency of the aerobic unit.
Recycling and neutralizing wastewater technology
There are many kinds of wastewater discharged in the process of nictric acid
production, among which neutralization wastewater is the largest and the pollution is the most serious. Therefore, the treatment of neutralization wastewater is very important and directly related to the ecological environment. The technological process of neutralization wastewater technology is neutralization catalytic oxidation sand filtration adsorption. With this method, CODCr can be reduced from 16642 mg/L to 2308 mg/L with a removal rate of 86.1%. After treatment, the wastewater can be used for farmland irrigation, making full use of industrial wastewater and saving water resources.