Stabnikova O, Liu X Y, Wang J Y
School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, Singapore.
Waste Manag. 2008;28(9):1654-9. doi: 10.1016/j.wasman.2007.05.021. Epub 2007 Sep 10.
The hybrid anaerobic solid-liquid (HASL) system, which is a modified two-phase anaerobic digester, is to be used in an industrial scale operation to minimize disposal of food waste at incineration plants in Singapore. The aim of the present research was to evaluate freezing/thawing of food waste as a pre-treatment for its anaerobic digestion in the HASL system. The hydrolytic and fermentation processes in the acidogenic reactor were enhanced when food waste was frozen for 24h at -20 degrees C and then thawed for 12h at 25 degrees C (experiment) in comparison with fresh food waste (control). The highest dissolved COD concentrations in the leachate from the acidogenic reactors were 16.9 g/l on day 3 in the control and 18.9 g/l on day 1 in the experiment. The highest VFA concentrations in the leachate from the acidogenic reactors were 11.7 g/l on day 3 in the control and 17.0 g/l on day 1 in the experiment. The same volume of methane was produced during 12 days in the control and 7 days in the experiment. It gave the opportunity to diminish operational time of batch process by 42%. The effect of freezing/thawing of food waste as pre-treatment for its anaerobic digestion in the HASL system was comparable with that of thermal pre-treatment of food waste at 150 degrees C for 1h. However, estimation of energy required either to heat the suspended food waste to 150 degrees C or to freeze the same quantity of food waste to -20 degrees C showed that freezing pre-treatment consumes about 3 times less energy than thermal pre-treatment.
混合厌氧固液（HASL）系统是一种改良的两相厌氧消化器，将用于新加坡的工业规模运营，以尽量减少食品垃圾在焚烧厂的处置。本研究的目的是评估食品垃圾的冷冻/解冻作为其在HASL系统中厌氧消化预处理的效果。与新鲜食品垃圾（对照）相比，当食品垃圾在-20℃下冷冻24小时，然后在25℃下解冻12小时（实验）时，产酸反应器中的水解和发酵过程得到了增强。产酸反应器渗滤液中最高溶解化学需氧量（COD）浓度在对照中第3天为16.9克/升，在实验中第1天为18.9克/升。产酸反应器渗滤液中最高挥发性脂肪酸（VFA）浓度在对照中第3天为11.7克/升，在实验中第1天为17.0克/升。对照在12天内产生的甲烷量与实验在7天内产生的甲烷量相同。这使得间歇过程的运行时间有机会减少42%。食品垃圾的冷冻/解冻作为其在HASL系统中厌氧消化预处理的效果与食品垃圾在150℃下热预处理1小时的效果相当。然而，将悬浮的食品垃圾加热到150℃或冷冻相同数量的食品垃圾到-20℃所需能量的估计表明，冷冻预处理消耗的能量比热预处理少约3倍。
