The Study On The Effects Of Dyes And Auxiliaries On Alkaline Protease Hydrolysis

The textile printing and dyeing industry is the traditional pillar industry of China's national economy,but it is also one of the heavy polluting industries.Priting and dyeing sludge is one of the main pollutants produced after printing and dyeing wastewater treatment.The effective and environmentally friendly treatment and disposal for it is important.The material composition of dyeing sludge is very complex,containing dyes,printing and dyeing auxiliaries,and heavy metals that are not completely degraded in the treatment process of printing and dyeing wastewater.They are all very harmful to the environment and humans.At present,the treatment and disposal of dyeing sludge at home and abroad mainly use incineration and landfill.However,high energy consumption may cause secondary pollution to the environment,and is not consistent with the concept of sustainable development.Therefore,it is particularly important to seek a green and low-pollution printing and dyeing sludge treatment method.Enzymatic hydrolysis is a gentle,low-energy sludge treatment technology.Extensive research has been conducted on the enzymatic hydrolysis of excess sludge at home and abroad.There are also some studies on the effect of pollutants on enzymatic hydrolysis.But the studies on the application of enzymatic methods to the treatment of dyeing sludge,especially those on the effects of dyes and additives on enzymatic hydrolysis of sludge are few.The main research contents of this thesis are as follows: the first step is to optimize the reaction conditions for alkaline protease hydrolysis of sludge(optimal enzyme dosage,reaction pH,reaction temperature,and reaction time).The second step is using methyl orange(MO)and sodium hexametaphosphate(SHMP)as simulated dyes and auxiliaries to study on the effect of these two pollutants on the effect of alkaline protease hydrolysis of sludge.The last step is to optimize the reaction cconditions for hydrolysis of dyeing sludge(optimal enzyme dosage,reaction pH,reaction temperature,and reaction time)based on the hydrolysis of excess sludge by alkaline protease.By measuring the contents of soluble chemical oxygen demand(SCOD),protein and polysaccharide in the sludge hydrolyzate,analyze the hydrolysis effect of alkaline protease and compare alkaline protease hydrolysis printing sludge with excess sludge.The main conclusions obtained in this paper are as follows:(1)The study on the process of hydrolysis of excess sludge by alkaline protease shows that as the concentration of alkaline protease increases,the contents of SCOD,protein and polysaccharide in the hydrolysate are all gradually increased.It shows that with the increase of enzyme concentration,the rate of sludge hydrolysis is getting higher and higher.When the concentration of alkaline protease reaches 0.1g/gtss,the organic dissolution trend become flat.When the reaction pH is 11.0,the contents of SCOD,protein and polysaccharide in the sludge hydrolyzate are all maximum,and the organic matter is the most soluble.When the temperature is 55 ?,the contents of SCOD,protein and polysaccharide are all maximum,and the organic matter is the most soluble.In the first 2 h of the hydrolysis reaction,the contents of SCOD,protein and polysaccharide are increased more significantly,and organic matter is eluted faster.After reacting for 2-4 h,the increase of organic dissolution become less.After reacting for 4 h,the contents of SCOD,protein and polysaccharide are increased a little.The optimal conditions for the hydrolysis of sludge by alkaline protease are 0.1 g/gtss,pH=11.0,temperature of 55?,and reaction time of 4 h.Under this hydrolysis condition,the fluorescence intensity and fluorescence area of protein and humus in the three-dimensional fluorescence diagram of the hydrolyzate are greatly increased,indicating that the protein and humus elutedd in large amounts after sludge is hydrolyzed.The SEM images of sludge show that the floc structure become loose,the particle size become small and the surface become fuzzy,and it shows a loose network structure,indicating that the alkaline protease destroyes the structure of the sludge and can promote the dissolution of organic matter.(2)The study on the effects of six sodium phosphate and methyl orange on alkaline protease hydrolysis shows that with the increase of the concentration of sodium hexametaphosphate(SHMP),the content of SCOD,protein and polysaccharide in the sludge hydrolysate are all increased.Sodium hexametaphosphate(SHMP),as a dispersant,can make the sludge and the enzyme more uniform,accelerate the dissolution of protein and carbohydrate,destroy the EPS structure,and increase the contact between the enzyme and the substrate.After adding sodium hexametaphosphate,the content of SCOD,protein and polysaccharide in the hydrolysate are all increased.The fluorescence intensity and fluorescence area of the protein and humus in the three-dimensional fluorescence diagram are increased,the particle size of the sludge particles is decreased,and the network structure is more obvious.It indicates that SHMP can promote the hydrolysis of sludge by alkaline protease.With the increase of the concentration of methyl orange(MO),the content of SCOD in the sludge hydrolyzate is gradually decreased,the content of polysaccharide is decreased slightly,and the content of protein is slightly increased.The reason is that methyl orange(MO)is adsorbed on the surface of sludge particles,which prevents the dissolution of organic matter,and its toxicity stimulates the microorganisms in the sludge to secrete a little protein and forms a protective layer on the surface.After adding methyl orange(MO),the fluorescence intensity and area of the protein in the three-dimensional fluorescence image of the hydrolysate are increased a little,and the fluorescence intensity and fluorescence area of the humus are decreased significantly,indicating that the protein elution amount is increased slightly and the humus dissolved amount is decreased significantly.Compared with the SEM image of sludge without adding methyl orange,the particles become big and the surface become smooth.This shows that methyl orange can inhibite alkaline protease hydrolysis of sludge.(3)The study on Alkaline protease hydrolysis of dyeing sludge shows tha as the concentration of alkaline protease increases,the content of SCOD,protein and polysaccharide in the hydrolysate are all gradually increased.It shows that with the increase of concentration of enzyme,the effect of sludge hydrolysis is getting better and better.When the concentration of alkaline protease reaches 0.12 g/gtss,the organic dissolution is increased less.When the reaction pH is 11.0,the contents of SCOD,protein and polysaccharide in the sludge hydrolyzate are all maximum,and the organic matter is the most soluble.When the temperature is 55 ?,the contents of SCOD,protein and polysaccharide are all maximum,and the organic matter is the most soluble.In the first 0.5 h of the hydrolysis reaction,the contents of SCOD,protein and polysaccharide are increased significantly,and organic matter is eluted faster.After reacting for 0.5-4 h,the increase of organic dissolution become less.After reacting for 4 h,there is little increase of the contents of SCOD,protein and polysaccharide.In summary,due to the economic considerations,and the hydrolysis effect,the optimum conditions for alkaline protease hydrolysis of dyeing sludge are 0.12 g/gtss,pH=11.0,temperature of 55?,and reaction time of 4 h.After enzymatic hydrolysis,the particle size of the sludge is decreased,the surface become fuzzy,and the network structure become loose.It indicates that the alkaline protease destroyes the flocculation structure of the sludge and contribute to the dissolution and dehydration of organic matter.(4)The comparative study of alkaline protease hydrolysis of dyeing sludge and excess sludge shows that the dyeing sludge and residual sludge are separately hydrolyzed under the conditions of alkaline protease dosage 0.05 g/gtss,0.1 g/gtss,reaction pH=11,and reaction temperature of 55?.It shows that under the same hydrolysis conditions,the hydrolysis rate of excess sludge by alkaline protease hydrolysis is higher than that of dyeing sludge,but just a little.The reason may be that different types of dyes and auxiliaries in dyeing sludge have different effects on enzymatic hydrolysis.Some can promote the hydrolysis and some can inhibit the hydrolysis.