- Takashi Asano
Civil and Environmental Engineering,
University of California
In California, groundwater is pumped up in locations such as Sacramento and San Francisco to the north, and transported south via water channels to Los Angeles and San Diego, a distance equivalent to that from Aomori to Kitakyushu. However, California has suffered drought for three consecutive years, and as a result on average only 69% of the target volume is being sent nowadays. The next choice for remedying this water shortage is reuse. I usually divide water reuse into seven categories.
The first is reuse for agriculture. The second is golf course, freeway median, and other landscape irrigation. The third is industrial reuse. The fourth is water for recreational uses, the fifth, non-potable urban uses such as flush toilets. The sixth and seventh are groundwater recharge and potable water.
In California, agriculture accounts for about 75% of water reuse. Another 15% is used for artificially recharging groundwater. The next challenge is to reuse water in a way that is closer to potable water.
Since there are health risks involved, we need to think about the kind of water sources that could be used for such reuse. If we have epidemiological data, that is something to go on, but where endocrine disruptors and such like are concerned, we cannot tell what kind of medical conditions might result from ingestion. We need to consider the eventuality of discovering some years later that this or that turns out to be a carcinogen. It has already been shown that advanced membrane-based treatments can be used to produce cleaner water than natural or dam water. I hope that this Center will drive the development of innovative technologies in this area.
From now on, we need to think about turning wastewater into potable water rather than just treating it for disposal in rivers or the sea. In other words, we need to think about sound pre-treatment, and segregate industrial wastewater that cannot be treated from wastewater that can be reused in this way. For coming generations too, we need to develop innovative water resource technologies that pay greater attention to protecting this planet and the creatures that inhabit it.