Study On The Transformation Rule Of Sulfonamide Antib Iotics In Enzymatic Hydrolysis Of Excess Sludge

Sulfonamide antibiotics(SAs)have been widely used in human and livestock husbandry.After the use of animals,67~90% or more will be excreted as animal excreta in the form of active compound or metabolites,of which only partially be degraded,mostly deposite in the sludge after various processing links of the municipal sewage treatment plant.If the sulfonamide antibiotics(SAs)in the excess sludge are not treated,they will enter the ecosystem,destroy the balance of ecosystem,and ultimately threaten human health.The enzymatic hydrolysis of excess sludge can accelerate the hydrolysis of EPS(Extracellular Polymer ic Substances)in sludge,causing damage to the biomass in the sludge flocculation structure,thereby increasing the contact area of the enzyme and the substrate,making the organic matter further hydrolysis in the sludge flocs and improving sludge digestion and dewatering capability.Predecessors have studied the effect and the role of migration and transformation of metal ions and some organic compounds in the sludge hydrolysis process.But there is no study on the effect of SAs pollutants on enzymatic hydrolysis and the distribution laws in solid phase and liquid phase in sludge hydrolysis process.So this paper selected sulfadiazine(SDZ)and sulfamethazine(SMZ)as the target pollutants,mainly studied the optimization test of SAs pollutants in excess sludge,effect of SAs on hydrolysis effect and transformation rule of SAs in the process of enzymatic hydrolysis in excess sludge.The main results of this paper are as follows:(1)Optimization of test method of SAs extraction from excess sludge: In this paper,ultrasonic solid phase extraction method was used as the extraction method of SAs.The single factor experiment was conducted to optimize the factors that affect the extraction method of SAs.The optimum conditions of solid phase extraction were obtained by orthogonal experiment,such as concentration of extractant agent(acetonitrile: water)1:3,shaking time 20 min,ultrasonic frequency 35 KHz,ultrasonic time 15 min.Under these optimal conditions,the recovery rate of SDZ and SMZ in the blank sample were respectively 93.4% and 91.8%;the recovery rate of SDZ and SMZ in sludge were respectively 75.50% and 72.79%.The research method is better than that in literatures,but also in line with national requirements that recovery rate range of 60~ 150% of trace organic compoundsis.(2)Effect of SAs on enzymatic hydrolysis: A small amount of SAs(less than 1 × 10-4mg/g)promote the enzymatic hydrolysis of excess sludge,while excess SAs(greater than 1 × 10-4mg/g)inhibite the enzymatic hydrolysis of excess sludge.As long as the content of SAs in excess sludge is less than 1 × 10-4mg/g(dry sludge),it needn't consider the inhibitory effect of SAs on the enzymatic hydrolysis of excess sludge.(3)When the amount of SAs is 1 × 10-4mg/g(dry sludge): With the increase of the amount of enzyme,alkaline protease hydrolysis effect was better and better,in which hydrolysis temperature was 40 ?,hydrolysis time was 4H and p H value was 9.5,there was no obvious effect on the enzymatic hydrolysis of excess sludge with SAs or without SAs,but it did not make for producing polysaccharides and organic matter.When the hydrolysis time reached 4h,the hydrolysis effect of excess sludge was the best,and the hydrolysis time was further delayed,but it went ill with the hydrolysis of excess sludge.When the hydrolysis temperature reached 40?,the hydrolysis effect of the excess sludge was the best,and then the hydrolysis temperature went ill with the hydrolys is of the excess sludge.The optimum temperature of hydrolysis of the excess sludge decreased from 55 to 40 ? by adding SAs.When the p H value reached 9.5,the hydrolysis effect of the excess sludge was the best,and then increasing the p H value went ill with the hydrolysis of the remaining sludge.The optimum p H value of the hydrolysis of excess sludge was increased from 8 to 9.5.by adding S As.(4)Transformation rule of SAs pollutants during enzymatic hydrolysis of excess sludge:The result shows(1)When the enzyme dosage was less than 6%,the percentage of SAs pollutants in hydrolysate increased continuously,and SAs transformed from solid phase to liquid phase with the increase of enzyme dosage,and afterwards the percentage of SAs in the hydrolysate was no longer changed.(2)When the hydrolysis temperature was less than 40 ?,the percentage of SAs pollutants in hydrolysate increased continuously,and SAs transformed from solid phase to liquid phase with the increase of hydrolysis temperature,but afterwards the percentage of SAs in the hydrolysate solution decreased.(3)When the p H value is less than 9.5,the percentage of SAs pollutants in hydrolysate increased continuously,and SAs transformed from solid phase to liquid phase with the increase of PH value,but afterwards the percentage of SAs in the hydrolysate solution decreased.(4)When the hydrolysis time is less than 4h,the percentage of SAs pollutants in hydrolysate increased continuously,and SAs transformed from solid phase to liquid phase with the increase of hydrolysis time,but afterwards the percentage of SAs in the hydrolysate solution showed a downward trend.