The Whereabouts of Sludge Resounding on Shiga's Lakeshore: A Period of Intersection between Aging and Widespread Use Late 2000s to Early 2010s

The Whereabouts of Sludge Resounding on Shiga's Lakeshore: A Period of Intersection between Aging and Widespread Use Late 2000s to Early 2010s

The joint treatment of sewage sludge in Otsu City, Shiga Prefecture, was not simply an administrative collaboration between municipalities, but a symbolic effort born from the intersection of aging sewage infrastructure and sustainability issues that were progressing across Japan. Several decades after its construction, the Kosai Sewage Treatment Center in Otsu City had reached the point where its incineration and melting furnace was due for renewal. At the same time, Otsu City's final disposal facility was running out of capacity, and stable disposal of sludge was becoming difficult for the municipality to handle on its own. Therefore, the prefectural and municipal governments' interests coincided and they came to the conclusion that they would jointly dispose of the sludge.

This move was also in line with the national government's policy. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) was promoting the wide-area expansion and joint processing of sewerage projects against a backdrop of aging facilities, staff shortages, and declining rental revenues. It was believed that wide-area expansion would reduce the burden of facility renewal, enable efficient maintenance and management, and lead to more advanced water environment preservation. According to government data, wide-area expansion was important in order to cope with the increase in investment in the renewal of facilities and the decline in population.

Shiga Prefecture has a unique situation in Lake Biwa. Lake Biwa has long been a symbol of water environment preservation throughout Japan, and watershed management has been promoted against the backdrop of eutrophication prevention ordinances. Stable and safe sludge treatment is essential to protect the lake environment, and cooperation between the prefectural and municipal governments is a natural progression. The wide-area sludge treatment was positioned as a method to achieve both environmental conservation and infrastructure renewal.

The prefectural government was entrusted with the sludge treatment work by the city and began accepting a portion of Otsu City's sludge in FY2012, with plans to accept all sludge from FY2015 onward. A system has been established to reduce the environmental burden by distributing the burden of equipment renewal through a phased joint treatment system. Amid the nationwide challenges of increasing renewal costs and tight finances, the joint treatment by Shiga Prefecture and Otsu City was a pioneering effort to establish a sustainable treatment system as a concrete example of wide-area expansion.