A johkasou is a device for cleaning and discharging sewage from homes without using sewers.
The difference from the sewage system is that "factory wastewater" is not treated.
The difference from the sewage system is that "factory wastewater" is not treated.
johkasou to treat all sewageMerger processing johkasou(In the Johkasou Act, " Johkasou"It's called. ) and treat only sewage from flush toiletsSingle treatment johkasou(In the Johkasou Act, "Considered johkasou"It's called. ) are available.
The amended Johkasou Act, which came into force in April, Heisei 13, prohibited the establishment of new deemed johkasou, and now only johkasou can be newly established.
johkasou is installed in buildings of all kinds, including single-family homes, condominiums, residential complexes, schools, hospitals, offices, supermarkets, hotels, and pachinko parlors. The size of a johkasou is expressed in terms of human tanks (or number of people to be processed); tanks with 50 or fewer people are called small, tanks with 51 to 500 people are medium-sized, and tanks with 501 or more people are called large. By the way, the smallest johkasou currently installed is a ５-person tank (large enough to treat sewage for ５ people), and the largest is the 38,500-person tank at Kansai International Airport (planned to eventually be a 77,000-person tank). It is said.
The processing performance of johkasou isBODThe removal rate (ratio of amount removed to inflow) is over 90%, and the BOD of treated water is less than 20 mg/L, which is comparable to final treatment facilities for sewerage systems. Processing technology for johkasou is progressing day by day, and it is becoming more compact, and it is also attracting attention from overseas, including those that remove nitrogen and phosphorus as a countermeasure against eutrophication, those that can be used with a disposer, and those that utilize membrane technology.
In addition, since Heisei 20, the government has been actively promoting the development of johkasou, such as increasing the subsidy rate from 1/3 to 1/2 for eco-friendly advanced processing type and energy-saving compact johkasou.
The amended Johkasou Act, which came into force in April, Heisei 13, prohibited the establishment of new deemed johkasou, and now only johkasou can be newly established.
johkasou is installed in buildings of all kinds, including single-family homes, condominiums, residential complexes, schools, hospitals, offices, supermarkets, hotels, and pachinko parlors. The size of a johkasou is expressed in terms of human tanks (or number of people to be processed); tanks with 50 or fewer people are called small, tanks with 51 to 500 people are medium-sized, and tanks with 501 or more people are called large. By the way, the smallest johkasou currently installed is a ５-person tank (large enough to treat sewage for ５ people), and the largest is the 38,500-person tank at Kansai International Airport (planned to eventually be a 77,000-person tank). It is said.
The processing performance of johkasou isBODThe removal rate (ratio of amount removed to inflow) is over 90%, and the BOD of treated water is less than 20 mg/L, which is comparable to final treatment facilities for sewerage systems. Processing technology for johkasou is progressing day by day, and it is becoming more compact, and it is also attracting attention from overseas, including those that remove nitrogen and phosphorus as a countermeasure against eutrophication, those that can be used with a disposer, and those that utilize membrane technology.
In addition, since Heisei 20, the government has been actively promoting the development of johkasou, such as increasing the subsidy rate from 1/3 to 1/2 for eco-friendly advanced processing type and energy-saving compact johkasou.
Source: Ministry of the Environment booklet "Johkasou's Efforts to Improve Local Water Environments"
Contaminants in domestic wastewater are 40g of BOD per person per day. Since johkasou's BOD removal rate is over 90%, the amount of BOD in the treated water is less than 4g, and the dirt in domestic wastewater is reduced in 10 parts to less than 1 part.
On the other hand, in the case of deemed johkasou, the BOD removal rate is 65% or more, so the amount of BOD from flush toilets is 13g, but after treatment, it is less than 5g. Combined with 27g of untreated BOD from kitchens and bathrooms, a total of about 32g of BOD is discharged.
Due to the large amount of BOD emissions from deemed johkasou, the national government, prefectural and municipal governments provide financial support to promote conversion to johkasou for users of deemed johkasou.
On the other hand, in the case of deemed johkasou, the BOD removal rate is 65% or more, so the amount of BOD from flush toilets is 13g, but after treatment, it is less than 5g. Combined with 27g of untreated BOD from kitchens and bathrooms, a total of about 32g of BOD is discharged.
Due to the large amount of BOD emissions from deemed johkasou, the national government, prefectural and municipal governments provide financial support to promote conversion to johkasou for users of deemed johkasou.
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- BOD is a measure of how polluted the water is. The higher the number, the more polluted the water is, and the more likely it is to rot (and become a drain).
- Technological development of johkasou for single-family homes began around Showa 50, mainly at the current Japan Environmental Education Center, and installation began in Showa 59 based on the results. After that, in order to promote the spread of johkasou, a national subsidy system for installation costs was established in Showa 62, and in Showa 63, the Ministry of Construction (now the Ministry of Land, Infrastructure, Transport and Tourism) standardized the structure.
