Living drainage and septic tank

For a general person, little being interested about the amount of sewage put out for myself while living and the purification is current state. I also hardly knew the thing until the septic tank management person's license was acquired. It was thought that it wanted a lot of people to have the concern more while studying being interested in water, and decided to introduce it with this HP.

Dirt and BOD of water

What is BOD(Biochemical Oxygen Demand) under an aerobic condition in the biochemical oxygen demand 20 degree C the amount of oxygen consumed in five days (mg/L) or(ppm) is said.

It is an amount of oxygen because it purifies water in a word consumed when dirt (organism) in water is resolved by the microorganism, and it is used as an index of pollution with the organism. It can be called water that the smaller this numerical value is, is the more beautiful.

It is considered that it is the same and cares about neither mg/L nor ppm like water when the specific gravity is almost one. It seems to be united to mg/L recently.

Example of typical BOD density

Night soil
(non-washing in clear water for toilet)
Night soil
(washing in clear water for toilet)
Polluted water to wash rice 3g/L
Soup of ramen 25g/L
Sake 200g/L
Abolition tempura oil 1000g/L
Water after processesed
single processing septic tank
0.09 G/L or less
Water after processesed
amalgamation processing septic tank
0.02 G/L or less

It is understood that the one other than the night soil include the one with high BOD density. Especially, the thing not thrown into drain because it is difficult for the abolition tempura oil to purify is important. Though you can do the soup etc. of the ramen and not throw into the river as it is.

How water becomes beautiful if the amalgamation processing septic tank is set up might be understood.

Amount of BOD of living drainage

  Amount of BOD Volume of water
Night soil
(washing in clear water)
About 13g/person and day About 50L/person and day
Miscellaneous drainage About 27g/person and day About 150L/person and day
Total of living drainage About 40g/person and day About 200L/person and day

The miscellaneous drainage understands than the night soil and it is understood that the amount of BOD is large even by the twice.

I think that the importance of the amalgamation processing septic tank from the single processing septic tank where only the night soil is processed from which all living drainage is processed is understood.

Difference amount of BOD after processesed by difference of septic tank

There are two kinds of septic tanks of the amalgamation processing septic tank where both a single septic tank, the night soil, and the miscellaneous drainage that processes only the night soil are processed. Neither production nor the installation construction of the single processing septic tank are done now. Therefore, when the septic tank is newly set up, everything becomes an amalgamation processing septic tank.

Because still a lot of single processing septic tanks that were produced in the past and set up are used, and it drips and the miscellaneous drainage is thrown, the river water doesn't become beautiful easily.

Especially, Okayama City is late the maintenance of drainage compared with other municipalities and becomes a problem. There is actually even no plan that becomes drainage in the place with my shop though it is an artificial center. It is not even in the district where maintenance is scheduled after 16 years the futures either. (April, 2007)

  Single processing
septic tank method
Amalgamation processing
septic tank method
Only Night soil has
been processed
Night soil +
miscellaneous drainage
BOD loading
(g/person and day)
About 13 About 27 About 40
Sewage quantity
(L/person and day)
About 50 About 150 About 200
BOD density of sewage
(mg/L) or(ppm)
About 260 About 180 About 200
BOD removal rate(%) 65 or more 0 90 or more
BOD remaining rate(%) 35 or less 100 Ten or less
BOD density (mg/L)
of waterafter
90 or less About 180 20 or less
Amount of BOD
after processes
(g/person and day)
4.6 or less About 27 4 or less
BOD amount total
after processes
(g/person and day)
About 32 4 or less

When it is only a single processing septic tank, it is understood that the amount of BOD after it processes it compared with the amalgamation processing septic tank is as much as eight times larger. If the performance is good, and management is good, a recent amalgamation processing septic tank can be assumed to be a treat water of 5mg/L or less.

The sewage plant of the amalgamation processing septic tank is the same as the standard of the exhaust water. Because construction that buries the sewage pipe is unnecessary, building the amalgamation processing septic tank can be fewer than that of establishing the sewage plant the cost of the total. Especially, there seem to be a lot of things that establishing the sewage plant in the region where the population density is not so high becomes wasteful of the tax.

Outline of septic tank management person examination


Japanese environmental maintenance education center   TEL 03-3635-4880
ZIP code 130-0024   Tokyo Sumida Kikugawa 2-23-3

Outline of

Maintenance check of septic tank (work to check, to adjust or to repair according to these).

The person who executes the maintenance check of the septic tank comes to be consigned by the septic tank manager when the person should receive the delivery of septic tank management person's diploma from the Minister of Health and Welfare the septic tank management.

However, when the septic tank manager manages voluntarily, septic tank management person's qualification is unnecessary. I can manage the septic tank at home even if unqualified though I acquired to manage the septic tank at home. However, I do not think that how I may manage when it is unqualified is understood.

ofcandidacy for
an examination

Neither the academic background nor the business experience, etc. are taken into account at all.


About October every year


Miyagi Prefecture, Tokyo, Aichi Prefecture, Osaka Prefecture, and Fukuoka Prefecture

Subjects of
  1. Septic tank outline
  2. The septic tank administration
  3. Structure and function of septic tank
  4. Septic tank construction outline
  5. The septic tank is checked, and it adjusts and it repairs.
  6. Water-purity control
  7. Cleaning outline of septic tank
-"Operation and maintenance of septic tank"
(septic tank management person recognition course text)
Edit and issue: (foundation)Japanese environmental maintenance education center
B5 size   four separate volumes It was about   20,000 yen. It doesn't sell it in the bookstore. There is only buying it when taking an examination by self-study.
-"Operation and maintenance of septic tank (supplement)"
It was B5 size (149 pages), and about 2,000 yen.
-Ohm 250 septic tank equipment person problem answer title company
This is a problem collection for the septic tank equipment person. However, it was able to know the tendency to the problem. Actual examinations seemed to be a little more difficult than these.
Problem collections of the septic tank management person examinations seem to be marketed now though at that time, at the time of took an examination by me there were no problem collections of the septic tank management person examinations.
Impression of
  • The testing body etc. had not announced the problem in the past, and the problem collection was not, and was ambiguous. After it had examined it, all examination papers were collected. This was surprised because it was thorough.
  • Quite a lot of examination papers are 100 questions and exist. If I understood the content of the book more than the formula was remembered, I thought that there were a lot of solvable problems though there seemed to have been a lot of computational problems, too. There are a lot official and everything is not remembered at all. It is feeling of unseen passage of mathematics and the chemistry. I think that there were a lot of quite good problems.
  • Because the ratio of successful applicantss were about 1500 examinees and 222 those who passed for Osaka, it was about 15%.
  • It aimed at one passing only by the problem collection of the above-mentioned reference book and the septic tank equipment person because time and cost were too good. It was impossible though it had aimed at the full marks passing. However, there was response of passing at once after it had taken an examination.

I took an examination in 1999. Passing might be possible once a year the examination if it studies ahead hard longer than half a year.