Night Soil Treatment and Domestic Wastewater Centralized Treatment and Treatment Systems in Japan Decentralized Treatment Systems

There are three major domestic wastewater treatment systems in Japan, which can be classified into " system," "Rural To efficiently promote countermeasures for domestic wastewater, several kinds of domestic wastewater treatment facilities sewerage system" and "Johkasou system," according to the type of wastewater treated, the facility size and administrative have been constructed in accordance with regional characteristics in Japan. In urban areas and villages with high population support. Apart from these systems, there are two systems for night soil treatment: “Tandoku-shori Johkasou” and “Night soil density, centralized systems such as sewerage systems and rural sewerage systems are planned and constructed; decentralized storage tank.” New installations of Tandoku-shori Johkasou were forbidden from 2001, and night soil storage tanks are no systems such as Johkasou systems are constructed in rural areas with low population density. longer installed and are gradually being phased out. Sewerage systems are usually constructed in urban areas, where houses, factories and office buildings are concentrated, collecting wastewater through a piping network system and treating the wastewater in a centralized manner at wastewater treatment plants that are usually located in downstream areas of rivers or near the seacoast. A sewerage system is usually Sewerage system designed to serve tens of thousands to several hundreds of thousands people and includes the treatment of industrial wastewater and rainwater.

A rural sewerage system is introduced primarily in farming villages for domestic wastewater treatment. Under this system,

gully wastewater from each home is collected through a piping system and then delivered to a centralized treatment plant for wastewater treatment facility treatment. Rural sewerage system Johkasou systems are generally divided into ‘small-scale Johkasou,’ which are designed for treatment of the domestic wastewater of individual houses,and ‘medium to large scale Johkasou’, which are designed for treatment of the domestic wastewater of housing complexes, hospitals and other commercial facilities. However, more than 90% of installed Johkasou are small-scale Johkasou. gully

Night soil treatment facility Johkasou system Treatment plant for treating r capita collected night soil and Johkasou sludge. , pe

onstruction Balance point

r c Least populated area Rural sewerage system in fo Agricultural promotion area gully

Cost Decentralized d maintenance system

an Centralized system Tandoku-shori Johkasou Population density Decentralized treatment （Johkasou） Figure 12 Comparison of decentralized/centralized system costs Night soil treatment and (as of the end of FY 2016) gully organic 100 99.6 94.0 93.1 90 90.0

center , % 80 84.8 Night soil storage tank Treatment plant for treating 70 78.3 Centralized treatment 60 and recycling collected night n rates (sewerage treatment) Sum of major domestic wastewater treatment systems soil, Johkasou sludge and 50 40 other organic 30 19.5 20 15.2

isseminatio Densely populated area 7.6 9.5 D 10 5.9 gully 0.3 Johkasou system storage tank 0 More than 1,000 500～1,000 300～500 100～300 50～100 Less than 50 Size of municipality in population, thousand people Figure 13 Dissemination rates of domestic wastewater treatment systems Figure 14 Schematic of decentralized/centralized systems Figure 11 Major night soil and domestic wastewater treatment systems in Japan Table 2 Outline of major domestic wastewater treatment systems

Type of system or facility Sewerage system Rural sewerage system Johkasou system Night soil treatment facility

Purpose Maintain the water quality of natural Maintain agricultural water/wastewater Maintain good water quality of public Maintain healthy living environment and Column Evolution of vehicles used for night soil transportation water resources and improve the living clean/safe and improve the living water bodies and a healthy living promote public health by treating collected 4 environment by collectively treating night environment by collectively treating night environment and promote public health night soil and Johkasou sludge. soil,miscellaneous domestic soil,miscellaneous domestic wastewater by treating night soil and miscellaneous wastewater,industrial wastewater and and rainwater. domestic wastewater onsite. rainwater. Individuals,communities and Municipalities Municipalities Municipalities Responsible agency municipalities Applicable district Mainly urban areas Agricultural villages within specified Districts where Johkasou installations districts where agriculture is being are promoted –––––– promoted Applicable population Approx.1. 100,00,0000 or or m moreore UpUp toto abouaboutt 1,1,000000 –––––– –––––– Applicable wastewater Night soil (flush wastewater) Night soil ( wastewater), Night soil (flush toilet wastewater) and Collected night soil and miscellaneous domestic wastewater, miscellaneous domestic wastewater miscellaneous domestic wastewater Johkasou sludge industrial wastewater and rainwater and rainwater (6) A two-wheeled cart in 1950s The first small vacuum truck A normal vacuum truckA vacuum truck with Construction period Approx.5. 5 yeyeararss 3～5 years Approx.1 week up to 1 year 2～3 years in 1960s(6) concentrating function Competent authority Ministry of Land, Infrastructure, Ministry of Agriculture,Forestry Ministry of the Environment Ministry of the Environment Transport and Tourism and Fisheries 6 7