Enhanced Excess Sludge Reduction In AAO Process And Energy Production Based On Combined Ozone-ultrasoundpretreatment

Arbitrarily discharge of excess sludge seriously threaten people’s living environment. Based on excess sludge "minimization" and "resource utilization", scholars, at home or abroad, have already proposed many sludge treatment and disposal methods and technologies. The purposes of sludge disposal and treatment are to achieve sludge "minimization", "resource utilization", and "harmlessness". Due to the low excess sludge reduction performances and the low sludge utilization efficiency for anaerobic fermentation hydrogen, this study proposed an ozone/ultrasound pretreatment technology after compared the individual ozone and individual ultrasound pretreatments. A new combined bioreactor system constructed by an AAO system and an ozone/ultrasound technology was developed. The objective of this study is to study the performances of in-situ excess sludge reduction and nutrient removal efficiency in this combined ozone/ultrasound technique and AAO system. Simultaneously, 454 high-throughput pyrosequencing was applied to give anin-deep explanation for better understanding ofenhanced nitrogen and phosphorus removal mechanisms in this combined AAO system. Comprehensive study was conducted to propose the dominant bacterial communities and the regulation policies in this combined AAO system. Additionally, this study also examined the feasibility of using low-intensity ultrasound treatment sludge to stimulate the hydrogen production hydrogenase activity, and systematically analysis the effects of different pretreatments on hydrogen production in a biohydrogen system.Experiments were performed to investigist the effect of combined ozone/ultrasound pretreatment on slidge lysis efficient. Moreover, results also demonstrated that the optimal condition(ozone dose of 0.16 g-O3/g-TS and ultrasound energy density of 1.42 W/m L) was recommended by response surface methodology for this combined pretreatment, which this can achieve 39.9% sludge reduction ratio and 61.7% sludge disintegration degree(DD). Combined ozone/ultrasound can enhance the lysis efficient of sludge, which is favorable for sludge reduction.By applying the optimized ozone/ultrasound parameter, this study developed a combined ozone/ultrasound technology and AAO integrated weastwater treatment system. The mechanism of in-situ sludge reduction for this integrated system was microorganism cell lysis cryptic growth. Results showed that when control the sludge return ratio of 60%, the system could achieve the optimal sludge reduction(47.0%) and sewage treatment efficiency(COD removal rate of 91.0%, TN removal rate of 84.9%, TP rate removal of 78.0%). Comparing with AAO system, this integrated system could realize sludge in-situ reduction and enhanced nitrogen and phosphorus removal efficiency. This possible because that after the addition of the combined ozone/ultrasound reactor, the returned soluble carbon and nitrogen source would be increased, to some extent making up for the deficiency of carbon resource.This can provide more optimized control strategy and parameters for future practical application. On the view of microorganism community and structure, high-throughput sequencing method was employed. The denvisty of combined ozone/ultrasound technology and AAO integrated weastwater treatment system was higher than those of the convencial AAO process, which ensure the efficient operation. Moreover, the β-Proteobacteriaand γ-Proteobacteria of pretreatment system also were much higher. It can clearly be seen that the intergrated system enrich the organisms selectively, thus enhance the nitrogen and phosphorus removal efficient. The edficiency of oncencial sludge reduction was resolved effectively, which is that the effluent contains with high concentration nitrogen and phosphorus.Additionally, low frequency ultrasound(LFU) pretreatment was utilized to stimulate the bio-activity of hydrogen-producing hydrogenase(HPE). By using LFU pretreatment, this study successfully realized improved the anaerobic fermentation bio-hydrogen production. Results demonstrated that LFU pretreatment could effectively accelerate the microorganism cell growth or simulate the microbial synthesis metabolism. Under this optimum condition(an ultrasonic density of 125 W/L and a reaction time of 10 s), a maximum hydrogen yield of 13.0 m L-H2/g-TS was obtained by LFU pretreatment, which this was 18% higher than that seeding the raw sludge.By using these optimize parameters for subsequent bio-hydrogen production experiments, the maximum hydrogen yield was achieved at 9.3 m L H2/g DS under the optimal condition, which the hydrogen yield was 6.75 times higher than raw sludge sample(1.2 m L-H2/g-TS).This study proved that hydrogen production from NADH and NAD+ conversion by EEM. LFU make Directional metabolism was occurred and the NADH oxidation alao was increased via the addition of LFU. The investigation also indicact that the production of soluble substances(especially the contant of soluble Polysaccharide substances) was increased if the sludge was pretreated effectively, and those sludge could served as the substrate for bio-hydrogen production.