Degradation Of Indigo By Different Co-metabolism Substrates In Wastewater

Nowadays, jeans become more and more popular because of its unique style. People usually define indigo dyed blue as the main color, and others as parti-colored. Since the application of indigo dyes in denim dyeing is very extensive, there are plenty of indigo was used in denim dyeing each year. Thus, there will produce a large number of waste water that containing indigo dye. Indigo dye is a kind of indigoid dyes characterized by reducibility, small dissolution rate and difficult degrading. So search for a kind of effective method of degradation of indigo is very important.Co-metabolism is a unique form of bio degradation. In the process of reaction, the microbe is induced to produce non-specific key enzymes. The key enzymes can make non-biodegradable organics easily to degradation. As a result the co-metabolism received widespread attention.The research designed a flask-Shaking experiments based on the uniqueness and high efficiency of co-metabolism in the treatment of refractory material. The study included the biodegradability of indigo and the affection of co-metabolism on indigo degradation while adding different co-metabolic substance, as well as the biodegradation kinetics and biodegradation pathway of indigo. The following conclusions were obtained:(1) Through a homemade reactor and by using simulation wastewater, a directional domestication was done to the activated sludge from a sewage treatment plant, so mature domesticated activated sludge was obtained. By using the mature domesticated activated sludge, experiments were carried out on the biodegradation of indigo. The study finds that adding co-metabolizing materials can contribute to the degradation of indigo.(2) In the process of biodegradation, COD removal efficiency in the water samples of different stages was compared with the density of indigo and the result showed that their removal ratios were different. The removal efficiency of indigo in the solution was higher than the degradation efficiency of COD in the solution, which indicates certain intermediate products will be formed in the process of indigo degradation and that the intermediate products will also produce certain COD value.(3) Adding different co-metabolizing materials has different promotion effects on the biodegradation of indigo. The order of promotion effects from high to low is sucrose, sodium acetate, glucose, starch and ethanol. Ascorbic acid has certain effects of inhibition.(4) Adding the same metabolizing material according to different mass dosing ratios has different effects on the degradation of indigo. Each co-metabolic substrate has its best mass dosing ratio. The best mass dosing ratio of indigo to sucrose, sodium acetate, glucose or starch is all1:1; the best mass dosing ratio of ethanol to indigo is1:2.(5) Indigo degradation kinetic equations were established based on Lawrence-Mc Carty model. Without co-metabolic substrate, the saturation constants was210.73mg/L and the maximum degradation rate was7.928mg/(L·h). Adding sucrose, starch, glucose, sodium acetate, ethanol, ascorbic acid as co-metabolic substrate, the saturated constants were152.03,181.98,180.31,163.98, and191.83mg/L respectively, the corresponding maximum degradation rates were10.124,8.748,9.408,9.612and8.252mg/(L·h) respectively.