Cutting edge of sewage system
Recycling of sewage sludge
Recently, Osaka city has started a new project that utilizes sewage sludge as an energy resource. Figure 1 shows effective energy recovery in a sewage treatment plant. First, electric power is generated using the digestion gas from the sewage treatment process and the generated power is used for sewage treatment.
Furthermore, the heat from the power generation process is used to promote digestion gas generation. Therefore, effective use of the sewage sludge leads to an effective treatment system which reduces the sewage treatment cost and CO2 emission at the same time.
Combined sewer overflow control
The first sewage system in Osaka city, was a combined sewer system, which flows stormwater and wastewater in the same pipe. This system was applied in order to reduce both the cost and term of construction so that it could become operational rapidly and widely. However, a combined sewer system has problems that occur especially in wet weather in which wastewater exceeding the treatment capacity is discharged directly and pollutes rivers. Therefore, we have been developing a sewage treatment method that has countermeasures against heavy rain and does not pollute rivers. Figure 2 shows the method for treating wastewater in wet weather to prevent direct discharge to rivers.