Source: Bureau of Waterworks (1994).

One of the important tasks of today's purification plants is to produce water that is safe and tastes good, no matter how polluted the original supply. In particular, the Kanamachi Purification Plant, where the water comes from the Edo River, was no longer able to supply safe and palatable water with the use of the conventional rapid filtration system. A mouldy smell had been noticed in the water since around 1972, and filtering the water through powdered activated carbon had been tried without satisfactory results. Hence, an advanced water purification treatment system combining ozone, biochemical, and activated carbon treatments has been employed. This system is capable of treating 520,000 m³ (approximately one-third of the plant's total daily capacity of 1,600,000 m³). In order to cope with a similar problem that started in 1994 at the Misato Purification Plant, where the water is also taken from the Edo River, the same advanced water purification treatment system is under construction to exclude ammonia-based nitrogen gas, which is the cause of the smell of mould and bleach.

Since the pollution of river water has developed, advanced water purification technologies have been sought, and the cost of water purification has risen. Similar problems can be observed in Osaka's waterworks, where pollution is becoming serious in its water sources: Lake Biwa and the Yodo River.

In order to meet changes in the social environment appropriately and to respond promptly to diversified needs, new technology is developing. Currently, the most important areas are: the development of purification technology; improvement of the transmission and distribution system; improvement of the direct supply system; improvement of leakage prevention technology; and the effective utilization of resources and energy.