| Summary: | 碩士 === 國立中興大學 === 環境工程學系 === 90 === Abstract
For the study of continuous flow hydrogen photobioproduction, CSTR reactors w/o recycle were operated with seeded purple nonsulfur bacterium. Artificial substrate with glutamate as the nitrogen source was prepared to simulate the main organic composition in the effluent of anaerobic hydrogen production process.
Before the experiment of continuous flow, batch tests was performed for finding the optimum substrate concentrations for hydrogen production. Factors concerning hydrogen photobioproduction, such as alcohol and phosphate, was included in the batch tests. Optimum conditions obtained from batch study was then put in use for the continuous flow study.
The results from single substrate of batch tests indicated that the best C/N ratio was around 6.7 while butyrate was used as the only electron donor, glutamate as the nitrogen source. Highest hydrogen production was obtained when butyrate concentration was around 3000 mg/L. When applying complex substrate, acetate 280 mg/L, propionate 99 mg/L, butyrate 1200 mg/L and glutamate 500mg/L were resulted highest hydrogen production. The hydrogen production achieved 75.6 mmole/L after 60 hours cultivation under these conditions.
When ammonia was used as the nitrogen source, hydrogen productions were limited regardless the additions of glutamate or alcohol.
Under continuous flow experimentation, the results showed that CSTR reactor without recycle had a maximum hydrogen production rate of 0.504 mmole/hr when operated with a 20 hours hydraulic retention time (HRT). Propionate was identified to be the major electron donor. While operated under a 56.8 hours hydraulic retention time, acetate, propionate, and butyrate were found to serve as electron donor at the same time and the hydrogen production rate was around 0.35 mmole/hr.
The highest hydrogen production rate for operating under CSTR with recycle (HRT = 40hr, 100% recycle, MLSS=0.94 g/L and SRT = 7.5 days) was 0.967 mmole/hr. Hydrogen production rate went down to 0.648 mmole/hr when operated under HRT=30 hr, 50% recycle, MLSS 0.96 g/L and SRT=2.25 days. In the later condition, the system turned into using acetate as electron donor and the hydrogen concentration in the collected gas was down from 50% to 28%.
Sludge recycle improved hydrogen production in the continuos flow experiment.When feeding real effluent solution from anaerobic hydrogen production process as the influent for the same CSTR reactor used in this study, the resulted hydrogen production was unsatisfied. Methane gas was not detected in the collected gas. It was concluded that this hydrogen production was inhibited by the high ammonia concentration.
Maximum hydrogen production rate was 0.967 mmole/hr(HRT=40 hr, 100% recycle, MLSS=0.94 g/L, and SRT=7.5 days). In the biohydrogen production of applying real wastewaters, the manipulation of ammonia concentration could still be the limitation.
|
|---|
