| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 100 === Immobilization of microbial cells is an effective biological nitrogen removal technology that has many advantages over conventional activated sludge process including high organic carbon and nitrogen removal efficiency, low production of sludge, and small area of land use. The treatment and disposal of wasted sluge have remained as the primary challenge for conventional activated sludge process. The cost of disposing wasted sludge could amount to 50~60% of total operation cost. This research is believed to provide some insights on the potential of enhancing treatment efficiency, reducing land space requirement and minimizing wasted sludge disposal cost.
There are currently two main categories of material for microbial cells immobilization: natural (alginate and diatomaceous) and synthetic (polyvinyl alcohol and polyacrylamide). The advantage of natural material is that they are naturally made but the drawback is they are decomposed by microorganisms easily. Most of the syntheticmaterials are macromolecular polymer which is proven to be more robust to withstand decomposition, but the drawbacks are that they are more expensive and not environmental friendly.
For the purpose of sustainable development, we rely on an agriculture waste coagulant as the material for immobilization of microbial cells. This research is consisted of two parts: analysis of the material chraracteristic and the operating factors test. Analysis of the material chraracteristic consisted of compression test and solubility test for the purpose to realize the stability of the material. The operational aspect will focus on investigating nitrification, denitrification and total nitrogen removal efficiency under different operating conditions such as aeration mode, carbon to nitrogen ration (SCOD/N) and hydraulic retention time (HRT).
The compression test showed that the immobilized cells can withstand high pressure and stress, and stress enhance as the time. The immobilized cells elute COD, TDS, and were detected with conductivity and high pH in the early stage. However, the concentration of COD, TDS and conductivity decreased with time. The integrity of the immobilized cells stay intact throughout the entire experimental period.
The aeration mode appeared to impact significantly on the overall removal of nitrogen. Nitrficaion and TN removal efficiency were enhanced 36% and 28% respectivily when aereation ratio was adjusted from 1:1 to 1:0.5. Moreover, nitrficaion and TN removal efficiency were enhancedto 19% and 31% respectivily when SCOD/N was changed from 6 to 18. The variation of HRT did not demonstrtate noticeable effect on nitrification and total nitrogen removal efficiency: 80% of total nitrogen was removaed at HRTs of 12hr, 9hr, and 6hr. In conclusion, the optimum operating conditions is aeration ratio of 1:0.5, SCOD/N of 18, HRT of 12hr, which resulted in 96% SCOD removal efficiency, 98% nitrification, and 92% TN removal efficiency.
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