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.

To slove the problems by the scum, which causes operational and water quality problems in water treatment plants, several researches were conducted based on the site investigations on twelve large water treatment plants, biological and chemical analysis of scum, analyzing raw water quality data. Two types of scum, which are from scum and floe scum, can be classified based on the analysis and site investigations. The major parameter generating floe scum was indicated as fine bubbles dissolved in the water. The fine bubbles dissolved in the water can be generated by over-saturated air in the water, adding aluminum surface as the coagulant, conducting the break point pre-chlorination and so on. The water spray method, which is one of the physical treatment methods for removing scum, was selected for conducting experiments on the removal efficiency in the flocculation basin of the real water treatment plant. The water spray method was successfully applied for removing scum with the advantages of using spiral nozzles in case of using the raw water rather than the cleaned water.