| 英文摘要 |
This study uses domestic small/middle size piggery farm as possible research target, main tasks including to explore the anaerobic treatment efficiency of the traditional three-steps piggery wastewater treatment system and to study the biogas waste reuse possibility. Four primary study sections are included. First, possibility and operational benefits of raised-temperature operation on the anaerobic treatment is proposed. By changing the operational temperature, methane production as well as solids decomposition rate will be evaluated. Second, a collection of biological desulfurization microorganism will be established. Using domestic samples as incubation source, collected microorganisms’ desulfurization ability will be analyzed and stored for future real system application. Third, the relationship of methane-production microorganism and co-existed microorganisms will be studied using molecular methods. Fourth, explore the possibility on using biogas wastes as replaced fertilizer by field tests and establish possible application conditions.
Current midterm results as followed:
This study uses domestic small/middle size piggery farm as possible research target, main tasks including to explore the anaerobic treatment efficiency of the traditional three-steps piggery wastewater treatment system and to study the biogas waste reuse possibility. Four primary study sections are included. First, possibility and operational benefits of raised-temperature operation on the anaerobic treatment is proposed. By changing the operational temperature, methane production as well as solids decomposition rate will be evaluated. Second, a collection of biological desulfurization microorganism will be established. Using domestic samples as incubation source, collected microorganisms’ desulfurization ability will be analyzed and stored for future real system application. Third, the relationship of methane-production microorganism and co-existed microorganisms will be studied using molecular methods. Fourth, explore the possibility on using biogas wastes as replaced fertilizer by field tests and establish possible application conditions. After checking the test site, the existing process is not good enough to perform the original tasks. Therefore, under the agreement of EPS, the field tests were replaced as lab-scale reactors in order to establish operating parameters for future application.
Major results as followed:
1. Based on the results of lab-scale experiments, the best methane production, either accumulated volume and concentration, is obtained when operated under 35 oC with a optimalized methane concentration of 60%. On the other habd, the highest TS concentration applied produced better gas production.
2. Diversity of eubacteria was identified in the anaerobic system including lactic acid producer, cellulose degrader, and desulfur bacteria. As for the methanogens, no significant difference was identified among different operation conditions. However, when operated under 45 oC, the cell number of methanogens dropped significantly.
3. For improving the traditional three-stage piggery wastewater treatment system, based on the batch and continuous flow experiments, optimized mixing (30 rpm) as well as controlling the reactor temperature at 35oC could potentially improve the system performance.
4. The chemical compositions of digestate various with time and unstable, making it difficult to estimate fertilizing quality and reuse amount. This limitation could be overcome by long-term accumulated usage.
5. Under the same nitrogen concentration, the effect of digestate addition on the growth and production of rice, watermelon, green onion, and cabbage are similar to chemical fertilizer. In particular for fast growing plant such as cabbage, digestate has significant effect on its biomass weights since digestate works similar to fast-utilization fertilizer.。
6. A strain of de-sulfur microorganism isolated from this study, Paracoccus sp. M6, processes outstanding sulfur removing ability in which its removing rate is better than what have been reported in the references. Another isolated strain, Thiomonas sp. M22 also processes sulfur accumulating ability. It works better under chemolithotrophic growt. These isolates could be used for bioaugmentation for future systems,
7. Using a mid-size piggery farm (2000 pigs) as example, its wastewater could produce methane gas 52.8 m3/d, generate 75.4 degree/d, and reduce carbon dioxide emission by 28.6 tons/year.
8. Transportation of digestate is the main cost concern. Therefore, it will be better to use it on the nearby farm land or minimize the transportation distance.
9. Currently the regulation on agriculture waste reuse requires case by case application for anaerobic digestate farmland usage. Example from England could be used as reference as it regulate waste source first and set regulation on pathogens, heavy metals, and volatile acids.
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