The sewer facility (11 water reproduction center, 2 sludge exploitation of resources center, 26 pumping stations) of Yokohama-shi has enormous assets amounting to about 1 trillion yen, and, also, most are built based on old earthquake proofing design guideline in the Showa generation.
We may have a serious influence on citizen's hygienic living environment and society economic activities for needing long time for the restoration because most are constructed underground when we suffer damage for earthquake, and these sewer facilities not being able to use restroom when function stops once, and sewage of non-processing flowing out into river and the sea.
However, we need a great deal of time and expenses to reinforce all of these facilities against earthquakes.
Therefore it takes effort and investigates important element (bottleneck) which may become limitation of restoration at time, and go ahead through approach of chief earthquake measures to restoration and, in the case of large-scale earthquake, plan resumption of sewer service early.
Approach of earthquake measures
We push forward chief earthquake measures based on business continuity plan (BCP: Business Continuity Plan) of the sewer facility to plan improvement of processing function just after from shortening shop evil during period required for restoration at the time of damage of the sewer facility caused by large-scale earthquake.
We push forward approaches such as earthquake resistance of pumping facility drawing sewage to enable simple handling of gross quantity of inflow sewage (pumping, deposition, disinfection) at the time of damage.
We push forward approaches such as earthquake resistance of sludge digestion tank to enable gross quantity destruction by fire of sludge at the time of damage.
In addition, we are telling about information about earthquake measures pushing forward now.
Seismic strengthening (PDF: 1,275KB) of northern sludge exploitation of resources center sludge digestion tank
Seismic strengthening (PDF: 2,194KB) of southern sludge exploitation of resources center sludge digestion tank
☆The minimum sewerage treatment must continue at the time of damage caused by large-scale earthquake.
We plan improvement of rate of operation just after from shortening shop evil during period to need for recovery of rate of operation as we identify business that should carry out priority under the situation that the sewerage treatment facility made functional decline by large-scale earthquakes and show to restoration expectation curve of the chart below, and business continuity plan (BCP: Business Continuity Plan) in the sewerage treatment facility is plan for the purpose of minimizing influence on citizen's life, life.
In BCP, we push forward disaster occurrence "disaster prevention measures" (earthquake resistance on structure side of facility) not to let lower than maximum permissible level lower rate of operation just after that, and it is necessary to push forward "reduce disaster damage measures" (temporary measures to enable quick emergency correspondence after damage) to revive rate of operation after the disaster occurrence immediately in addition.
Restoration expectation curve
As for the functional decline in the sewerage treatment facility, it is necessary to push forward approach of earthquake measures based on BCP to have possibilities to have a serious influence on public sanitation and social economic activities by nonuse of restroom, outflow of non-processing sewage.
☆We aim at conduct of gross quantity simple processing at the time of damage.
It becomes possible to carry out gross quantity simple processing (deposition, disinfection processing) for quantity of inflow sewage which is usually at the same level as time at damage caused by large-scale earthquake if we almost find series of 1, pumping function, deposition function, disinfection function in each water reproduction center.
Conduct of simple processing
Therefore we advance earthquake resistance of pumping facility and earthquake resistance of chlorine rapid mixing basin (disinfection facility) by gross quantity at the time of damage for realization of taking a simple step. In addition, we push forward earthquake resistance of expansion joint (structure coupling) in cistern of facility (beginning sedimantation basin, reaction tank, the last sedimantation basin) to water-treat.
BCP of system to water-treat
☆Continuation of sludge processing is essential for continuation of the sewerage treatment.
Disposal of sewage is comprised of water-treating and sludge processing according to the flow of the chart below, and sludge processing function to process sludge occurring in process of the sewerage treatment is function that is essential to carry out water-treating.
Flow of water-treating and sludge processing
When concentration sludge and dewatering sludge which we cannot handle occur in large quantities, securing of disposal ground is difficult, and, at the time of damage, as for the sewage sludge, it is big problem for surrounding environment, public sanitation by bacteria and odor to include a large quantity of moisture, organic share.
Therefore we receive and, for realization of gross quantity destruction by fire of sludge at the time of damage, push forward earthquake resistance of mud facility and sludge digestion tank.
Sludge pro-processing BCP
The Yokohama-shi sewer business "medium-term management plan 2007"
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