Abstract
This study was conducted to evaluate the temperature effects on the nightsoil, anaerobic digestion, whether it could be operated with a higher organic loading rate at a higher temperature during summer months, or with a lower organic loading rate at a lower temperature during winter months. A laboratory completely mixed digester was continuously operated at 11 different temperatures from $18.5^{\circ}$ to $60^{\circ}C$ with 30 days of HRT. The study results indicated that the best efficiency occurred at a temperature range of $35^{\circ}$ to $40^{\circ}C$, at which BOD and VS removal efficiencies were respectively 71 and 53 percent, and gas production rate was $0.6m^3/kg$ VS fed or $16m^3/m^3$ fed. BOD removal efficiency would be increased to 78 percent if the digester effluent settled for 24 hours. Since the digester efficiency decreased beyond this temperature range, this suggested the digester need not to operate a higher temperature even during the summer months. The laboratory results were in good agreement with those of the existing digester operated at a temperature range of $32^{\circ}$ to $40^{\circ}C$. Application of septage or cow manure to the digester with nights oil at a rate of 1 to 1 did not greatly affect the digester performances. In addition, the digester effluent could be treated aerobically without any dillution water. BOD and SS removal efficiencies were greater than 90 percent in this case.
본연구(本硏究)는 다절기(多節期)에는 저온(低溫)으로 하절기(夏節期)에는 고온(高溫)으로 혐기성(嫌氣性) 소화조(消化槽)를 운전(運轉)시킬 수 있는지를 검토(檢討)하기 위한 것으로 실험실(實驗室) 완전혼합형(完全混合型) 혐기성(嫌氣性) 소화조(消化槽)를 $18.5^{\circ}C$ 부터 $60^{\circ}C$까지의 11단계(段階)의 온도(溫度)에서 유기물질(有機物質)의 제거효율(除去効率) 가스생산량(生産量)을 서로 비교(比較)하였다. $35^{\circ}{\sim}40^{\circ}C$ 내외(內外)에서 BOD와 VS 제거효율(除去効率)은 각각(各各) 71%와 53%였으며 이 온도(溫度)에 있어서 가스생산량(生産量)은 주입분뇨량(注入糞尿量)의 16배(倍) 또는 $0.63m^3gas/kg$ VS fed 였다. 화조(消化槽) 유출수(流出水)를 심전(沈殿)시키면 BOD제거효율(除去効率)은 78%까지 상계(上界)하였다. 본실험(本實驗)의 결과(結果)는 $32^{\circ}$에서 $47^{\circ}C$로 운전(運轉)시킨 기존(旣存) 분뇨처리장(糞尿處理場)의 결과(結果)와 $40^{\circ}C$까지는 비교적(比較的) 잘 맞았으나 $40^{\circ}C$ 이상(以上)에서는 실험실(實驗室) 결과(結果)가 처리효율(處理効率)이나 가스생산량(生産量)으로 볼 때 양호(良好)하였다. 분뇨(糞尿)에 정화조폐액(淨化槽廢液)이나 우분(牛糞) 혼합처리(混合處理) 가능성(可能性) 검토(檢討)하였는데 1:1로 혼합처리(混合處理)시켰을 때의 BOD제거효율(除去効率)이나 가스생산량(生産量)이 분뇨(糞尿)만의 처리시(處理時)와 별로 차이(差異)가 없었다. 한편 혐기성(嫌氣性) 소화조(消化槽)의 유출수(流出水)를 희석(稀釋)없이 호기성처리(好氣性處理)도 가능(可能)한지 알아 보았는데 이때의 BOD와 SS제거효율(除去効率)은 98% 이상(以上)이었다.