In Japan (other countries may also be used as reference) it’s said that wastewater from households is the cause of 70 percent of water pollution.  According to documents from the Ministry of the Environment, wastewater refers to drainage water from everyday life such as kitchens, toilets, baths, laundry, etc.  The amount of water used by a single person each day has reached 250 liters.  Wastewater can be broken down into miscellaneous household drainage (kitchens, baths, laundry) and human waste (toilet), with the former accounting for 70 percent.  Of this, the largest is wastewater from kitchens, with miscellaneous household drainage making up 40 percent. 

One indicator of the degree of water contamination is BOD (Biochemical Oxygen Demand).  BOD is the amount of oxygen used when microorganisms in the water breakdown wastewater.  Put simply, high BOD means we must be mindful of flushing water that is not dirty. 

For BOD value, the value where oxygen still exists of 10mg O2/L has been adopted as the minimum environmental standard.  In Japan, thanks to vault toilets, separate sewage treatment tanks, public sewage systems, rural community sewage, community plants, and individual sewage treatment tanks, one public body of water, a major river’s BOD value (from the Ministry of the Environment’s collection of environmental statistics) is continuing to decrease when compared to the previous year’s study.    Although the data is old, the numbers for the Tone River in Japan were 1.9mg in 1985, 1.7mg in 2000, and 1.5mg in 2002.  Even non-major rivers are showing improvement (reference: the Ministry of the Environment, public water quality measurements).

In recent news, Chinese investment firms and investors are said to be eyeing Japan’s water sources and purchasing or considering purchase.  Population growth is one reason, but the number one reason is apparently water contamination.  The main contaminants in Chinese rivers are organic materials and ammonium-nitrogen, as well as phenol and cyanogen, which are causing the pollution to progress.  These come mainly from industrial wastewater and miscellaneous household drainage, with the former slightly under 40 percent and most of the latter being released into the environment without being treated.  One of the six large rivers in China, the Yangtze and its tributaries, has relatively good water quality, however it is degrading and worsening (reference: the Ministry of the Environment website.)  Even though the maintenance and installation of public sewage and septic tanks is rapidly taking place, water quality improvement is likely to take a long time.  
Water contamination is undoubtedly a large problem for not only China, but also other emerging nations.    

As we are not researchers we don’t know if Japan is a good example, however if water quality has improved as the data shows, then as a country we should proactively carry out technical collaborations such as sewage treatment and septic tanks.  Recently, we often see the phrase “water business” so we think that perhaps actions are being taken.  However, wastewater improvements are not just talk about technical capacities, but also have a big influence on the country and the culture, as well as the way of living.  The topic is likely much larger than we can possibly imagine.


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