| Value | Category | Cases | |
|---|---|---|---|
| 1 | boiling | 169 |
4.2%
|
| 2 | chlorinating | 12 |
0.3%
|
| 3 | filtering | 131 |
3.2%
|
| 4 | without treatment | 3692 |
90.7%
|
| 5 | other | 31 |
0.8%
|
| 9 | not stated | 36 |
0.9%
|
| Sysmiss | 839 |