Current Situation of Johkasou Sludge Treatment
Sludge and scum accumulated in johkasou are withdrawn by a vacuum truck, and carried out by johkasou desludging vendors approved by mayors of municipalities. The situation of johkasou sludge treatment in FY 2006 is shown below.
Johkasou sludge has been mainly treated and disposed of in night soil treatment facilities (92.3%), sewerage treatment plants (5.2%), or by ocean dumping (1.8%), with a fragment of it disposed of via others means (0.7%). The weight of ocean dumping is decreasing year by year, and, in order to comply with the Treaty of London, which bans the dumping of sludge into the oceans, this dumping will be discontinued from 2007, while land-based treatment of sludge will be promoted.
The spread of sewerage system construction in large cities thanks to massive public works projects has also put many small municipalities in serious financial distress, thus further heightening expectations for johkasou systems and other small scale or decentralized systems in the future. To deal with the increase of johkasou sludge, it will be necessary for johkasou desludging vendors to introduce vacuum trucks with sludge thickening functions or dewatering trucks to make desludging work more efficient.
Utilization of Johkasou Sludge
Although it is not popular to use johkasou sludge directly as resource, some private companies have launched projects focusing on the sludge recycle business, such as sludge drying, compost fertilizer and sludge carbonization, etc.
Meanwhile, the traditional night soil treatment facilities have been evolving into Sludge Resource Recycling Treatment Centers that also possess the functions of recycling plants. Recycling technologies such as sludge composting, sludge carbonization, methane production, firework fuel, slag
production, cement admixture, and phosphorous recovery have been discussed. All of these recycling technologies should be adopted in the Sludge Resource Recycling Treatment Centers. Johkasou sludge, which has been treated and disposed of as waste, becomes an organic resource and is expected to be reused and recycled widely.
