Hikaru Miyazaki

Research on business improvement by intensive co-treatment of sewage sludge

Syuji Himeno   Komatu Tosiya

This study investigated the impact of solidification and co-treatment of sewage sludge on current business research and improved the business feasibility of sludge heavy metals. In the current situation study, a public study was conducted using data on past cases of solid fuel conversion projects, and the status of prefectural and sewerage projects. Based on the amount of sludge generated in Niigata City, the cost and scale of the solid fuel conversion business, the scale of sludge treatment when co-processing sewage sludge in Niigata City, and the economic and environmental impact of sludge, It was evaluated and analyzed. At that time, pretreatment was performed according to the manual of the Ministry of the Environment, and tests were performed using high-frequency plasma emission analysis.
According to current research, in the solid fuel conversion business, economies of scale affect the unit price of sludge disposal.
In a business survey in Niigata City, sludge was converted into fuel at eight treatment plants in Niigata City and collected, and a calculation was made assuming joint treatment. As a result, the unit price of sludge treatment is currently 20,000 to 30,000 yen / t, but it can be reduced to 15,569 to 19,542 yen / t, indicating that 7381 tons of CO2 can be reduced annually.
Analysis of heavy metals in sludge showed that ash sludge from four treatment plants could exceed the arsenic elution threshold based on waste treatment methods. If the simultaneous burning rate of solid fuel and coal in use is the calorie assumed in this study, and the mass ratio exceeds 17%, it is necessary to pay attention to the adhesion of ash melted in the boiler. However, the mass ratio is 2.2% and has little effect on the boiler, but if mixed ash is used as cement material, it must be analyzed.
The integration and co-processing of sewage sludge by converting it to solid fuel has been shown to improve the business feasibility of the sewage business and contribute to reducing CO2.