Masaaki KAWASHIMA
Deterioration and Recovery Process of Termophilic UASB Reactor Treatment Performance by Organic Shock Load
Akiyoshi Ohashi
Thermophilic UASB reactor has higher methane production activity which is 2-3 times as higher as that of mesophilic. But it has weakness that is sensitive to environmental fluctuation (influence of inhibit material, shock load). At same time, accumulated propionate has pointed out. To solute them, it is need to know detail behavior about deterioration and recovery of reactor. However, there is not a lot of reports. In this study, Thermophilic UASB reactor which was maintained in steady state was exposed artificial organic shock loads, and process of deterioration and recovery was studied.
In this study, Shock load test was studied seven times (experiment 1-7). This reactor was operated 7.3 kgCOD?m-3?d-1 in steady state. In experiment 1, sodium bicarbonate as pH buffer and all organic source of substrate (sucrose, propionate, acetate) was augmented five times (35kgCOD?m-3?d-1) and this shock load was exposed 0.5 day. In experiment 2, sodium bicarbonate and organic source was augmented ten times in the same way and shock load was exposed 0.25 day. In these two shock loads, pH don”Ēt decreased, so reactor deterioration don”Ēt occurred. This is because amount of buffer was enough. In experiment 3, organic source was augmented ten times in the same way but buffer don”Ēt augmented. Shock load was exposed 0.25 day. How ever, this experiment also couldn”Ēt decrease pH.
Consequently, in experiment 4 and 5, only sucrose was augmented to ten times organic load rate, in order to decrease pH by production proton originate in sugar degradation. Exposure time was 1.0 and 3.0 day respectively. As a result pH decrease until 4.95 and 4.54, COD decrease until 14.4% and 0.1% respectively. After exposure COD removal rate recovered over 80% at 1.9 day. On the other hand, COD removal rate recovered over 80% at 16.2 day in experiment 5 and propionate accumulated.
In experiment 6, pH substrate was decreased until 5.0 previously, and organic source was made by propionate solely. In this experiment process ability decrease earlier than experiment 4 and 5. COD removal rate recovered over 80% at 6.25 day. And then behavior of hydrogen partial pressure in experiment 4 and 5 was analyzed and 2 days exposure shock load test was studied in same OLR. 3 phase behavior in hydrogen partial pressure was found and linear relation ship was found in recovery time of experiment 4, 5 and 7.
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