Investigation Of Excess Sludge Anaerobic Fermentation Hydrogen Based On Three-dimensional Fluorescence Spectroscopy

A large quantity of excess sludge is produced during the sewage treatment process,which will cause serious environmental problem without being treated properly, suchas serious harm to environment and human body, secondary pollution to water, airand land. The difficulty of the reasonable sludge disposal was increased as the highcost of sludge treatment. So the disposal of excess sludge has become an importantenvironmental task. With the increasing of social progress and the improvement ofindustrialization, the environment pollution and energy shortages are two most seriousproblems people face. Using the excess sludge to develop renewable energyeffectively is an environment and economic study. Hydrogen as a clean fuel, highenergy density and renewable energy, is an ideal fuel alternative energy sources. In allmethods of hydrogen production, bio-hydrogen by anaerobic fermentation is aneconomical, environmentally friendly and sustainable development of hydrogentechnology. But there are some problems of anaerobic fermentation hydrogenproduction, such as low rate, simple equipment et al. How to improve the utilizationand the rate of hydrogen production is a further study.In this study, a new multi-enzyme was added in the excess sludge to enhance thesludge hydrolysis and reduction, and the treated conditions of hydrolysis time, dosage,temperature of multi-enzymes were optimized. With the optimal dosage of multi-enzyme1.5mL per100mL excess sludge, the sludge was treated by5h, at30℃,andthe maximum concentration of soluble protein, carbohydrate and SCOD was obtained,which enhanced by3-4folds,2-3folds and3-4folds, respectively. At the sameconditions, sludge’s lysis rate was24.81%, and achieved the best effect of sludgereduction. Moreover, the VSS solubility was reached to27.62%, showing a goodeffect lysis of microorganisms, which contribute to the reduction of sludge. Highestactivity of multi-enzymes was obtained, the effect of solubility and reducing of sludgecan reduce the amount of sludge.The effect of excess sludge hydrolysis with multi-enzyme and S-TE (thermophilicbacteria) was studied. The change of substrate concentration, three-dimensionalfluorescence spectra of EPS (extracellular polymeric substances) and DOM (dissolvedorganic matter) was invested. The change of sludge EPS after hydrolysis, it can beseen that excess sludge was destructed, cell wall was broken, small moleculesdissolved in the solution. Substance concentrations of carbohydrates, protein andSCOD in sludge EPS reduced significantly. At the same time, it can be seen thatprotein in solution increased from the variation of sludge DOM. And the concentration of carbohydrates, protein and SCOD increased significantly. Thechange of sludge DOM after hydrolysis with S-TE, the tyrosine was divided intonon-flourescent molecules, indicating a more effective hydrolysis than multi-enzymehydrolysis.After multi-enzyme, microwave, heat, S-TE pretreatment, the hydrogen productionof excess sludge was conducted. The results showed that the maximum hydrogenyield of heat pretreatment was15.25H2mL/gVSS. Hydrogen yield from high to lowfollowed by microwave, S-TE, multi-enzyme pretreatment. The main type offermentation was ethanol-type fermentation, the propionic acid and ethanol had theimpact on the hydrogen production. In the stage of fermentation, because differentpretreatment methods has different choice of microorganisms, impacted the nutrients’using of hydrogen bacteria. And because the combined effect of conversion of sludgematerial, the microbial metabolic substrate, and cell lysis, the change of DOM, EPS,and the concentration of carbohydrates, protein, SCOD was different. Theconcentration of carbohydrates, protein, SCOD of EPS were reduced in the maximumhydrogen production by the using of hydrogen bacteria, and the substrateconcentration was the lowest, and has the best hydrogen production in allpretreatment. The using of protein was not obvious in the fermentation aftermulti-enzyme, which indicated that microbial activity was weak, and the effect ofhydrogen production. While the sludge after S-TE hydrolysis, the protein in DOMwas reduced and has better utilization, and the microbial metabolites were alsoincreased. But the advantages populations were more, so that the hydrogen yield waslower than microwave and heat pretreatment. Tyrosine, tryptophan and fulvic acids inDOM increased, microbial byproducts and fulvic were reduced, the utilization ofsubstrate of hydrogen bacteria was batter, and the hydrogen yield was the best afterheat pretreatment.In the anaerobic fermentation process of the heat, the anaerobic bacteria graduallybecame the dominant bacteria, including Cloctridium E. coli bacteria, Closteridiumand Anaerolineae bacterium as a major hydrogen production community. In theanaerobic fermentation process of the heat and microwave pretreatment, thecommunities (Cloctridium E. coli bacteria, Closteridium) of hydrogen productionwere more than the communities of S-TE and multi-enzyme pretreatment, so that theproduction of hydrogen were more than any other. There were also Thermophilic andGeobacillus sp in the process of S-TE pretreatment. And the advantages of bacteriawere weak after multi-enzyme, and the hydrogen yield was the minimal.