Nearly 23 percent of water in wells and mineral springs nationwide is undrinkable.
Particularly, water from about half of the wells in Seoul and Incheon contain more than the permissible amount of colitis bacteria.
The environment ministry sampled and tested water from 1,578 wells and springs that provide citizens with water, and 29 percent of samples exceeded the amount of bacteria allowable.
By city and province, Incheon showed the highest ratio of non-drinkable water at 46.2 percent, followed by Seoul, 45.5 percent; Daegu, 36.4 percent; Busan. 35.4 percent; Gyeonggi Province, 32.6 percent; and Ulsan, 32 percent, while all springs and wells on Jeju Island provided clean water.
Following the survey, the ministry closed 17 of the wells and springs, and has begun to sterilize some of them.
In the meantime, the ministry has proposed bills to improve the quality of water.