In this study, the horizontal automatic scum remover with buoyant type is developed to reduce the cost of facility and is suitable for unit-process automation. This system is consist of the scum collecting box, leveling device for scum collecting box, drive device for scum collecting box, water level sensor and indicator, departure prevention device of scum collecting box, setting monitor, main control panel, etc. Performance tests for the system such as the accuracy of the scum thickness measurement, horizontal degree of the scum collecting box, scum removal time, accuracy of an unmanned control have been performed. The performance of the prototype system satisfies all the objects of this study.

In this study, the horizontal automatic scum remover with buoyant type is developed to reduce the cost of facility and is suitable for unit-process automation. This system is consist of the scum collecting box, leveling device for scum collecting box, drive device for scum collecting box, water level sensor and indicator, departure prevention device of scum collecting box, setting monitor, main control panel, etc. Performance tests for the system such as the accuracy of the scum thickness measurement, horizontal degree of the scum collecting box, scum removal time, accuracy of an unmanned control have been performed. The performance of the prototype system satisfies all the objects of this study.

Response surface methodology (RSM) based on a Box-Behnken Design (BBD) was applied to optimize the thermal-alkaline pre-treatment operating conditions for anaerobic digestion of flotation scum in food waste leachate. Three independent variables such as thermal temperature, NaOH concentration and reaction time were evaluated. The maximum methane production of 369.2 mL CH4/g VS was estimated under the optimum conditions at 62.0°C, 10.1% NaOH and 35.4 min reaction time. A confirmation test of the predicted optimum conditions verified the validity of the BBD with RSM. The analysis of variance indicated that methane production was more sensitive to both NaOH concentration and thermal temperature than reaction time. Thermal-alkaline pretreatment enhanced the improvement of 40% in methane production compared to the control experiment due to the effective hydrolysis and/or solubilization of organic matters. The fractions with molecular weight cut-off of scum in food waste leachate were conducted before and after pre-treatment to estimate the behaviors of organic matters. The experiment results found that thermal-alkaline pre-treatment could reduce the organic matters more than 10kD with increase the organic matters less than 1kD.