Yoshiyasu INOUE
Mesophilic and Thermophilic Anaerobic Co-digestion of Sewage Sludge and Rice Straw
Toshiya KOMATSU¡¤Shuji HIMENO
We investigated the feasibility of anaerobic codigestion of sewage sludge and rice straw. Laboratory-scale mesophilic (36¡î) and thermophilic (55¡î) digesters were operated with hydraulic retention times of 15 days. The feeding ratio of sewage sludge and rice straw was 1:0.5 based on TS. Before digestion, the rice straw was ground to ca. 5 mm in length (grinding pretreatment), ground and soaked in distilled water (water pretreatment), or ground and soaked in a hydrolytic enzyme solution (enzyme pretreatment). The effect of these pretreatments on the digestion performance was investigated. A digester fed sewage sludge alone was operated as a control. Both water pretreatment and enzyme pretreatment effectively reduced the TS and VS of rice straw. The addition of rice straw increased methane production by 76?98% in mesophilic digesters and by 37?62% in thermophilic digesters. The maximum methane production of 10.9 L/L-added-substrate was observed in the enzyme-pretreated thermophilic digester. In addition, a decrease in the ammonia-nitrogen concentration and an improvement in the sludge dewaterability were achieved by the addition of rice straw.
In this study the energy output was compared with the total input to determine the condition at which the best energy balance could be achieved in the co-digestion system. The experimental results were used in estimating digester performance, whereas the energy balances were calculated for full-scale systems. It was found that the best net energy output was obtained in the enzyme-pretreated mesophilic digestion system.
Please use "previous botton" to return the previous page