Performance of UASB Reactor Treating Leachate from Acidogenic Fermentation of food Waste

음식물쓰레기의 산발효 침출액을 처리하는 UASB 반응조의 거동

Leachate from acidogenic fermentation of food waste was effectively treated by the UASB reactor at $37^{\circ}C$. The efficiency of COD removal was consistently over 96% up to the loading rates of $15.8g\;COD/{\ell}{\cdot}d$. The methane production rate increased to $5.5{\ell}/{\ell}{\cdot}d$. Of all the COD removed, 92% was converted to methane and the rest presumably to biomass. At loading rates over $18.7g\;COD/{\ell}{\cdot}d$, the efficiency of COD removal decreased due to the sludge flotation and washout in the reactor, which resulted from short HRT of less than 10.6 hr. The SMA(specific methanogenic activity) analysis showed that the VFA-degrading activity of granule was the highest for butyrate, and the lowest for propionate. This result was consistent with the observation that the residual propionate concentration was the highest among the VFAs in the effluent. Typical granules were found to be mainly composed of microcolonies of Methanosaeta. Though the original seed sludge contained 64.3% of particles smaller than 1.4mm, the sludge particles had been growing during the fermentation, and at the final step of this study, 75.1% of the particles were found to be larger than 1.4 mm in the UASB reactor.

음식물쓰레기의 산발효 침출액은 중온의 UASB 반응조에서 매우 효과적으로 처리되었다. COD 제거율은 부하율 $15.8g\;COD/{\ell}{\cdot}d$까지 96%이상의 효율을 유지하였으며, 메탄생성율은 $5.5{\ell}/{\ell}{\cdot}d$까지 증가하였다. 제거된 COD 중에서는 92%가 메탄으로 전환되었고 나머지는 미생물로 전환된 것으로 보인다. 부하율 $18.7g\;COD/{\ell}{\cdot}d$ 이상에서는 COD 제거율이 크게 감소하였는데, 이는 10.6 h 이하의 짧은 HRT에 의한 슬러지의 부상 및 washout에 기인한다. SMA(specific methanogenic activity) 값은 뷰틸산에 대하여 가장 컸고, 프로피온산에 대하여 가장 작았는데, 이는 유출수 중에서 잔류 프로피온산의 농도가 가장 높았던 사실과 일치한다. 대표적인 미생물은 Methanosaeta였으며, 운전기간 동안 슬러지의 입경이 증가하여 식종균에는 전체 양의 64.3%가 1.4 mm보다 작았지만 운전 후에는 75.1%가 1.4 mm 이상을 차지하였다.