4 Water Sources ........................................ 149 Criteria ............................................. 149 Major types .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 . . . . . . . . . . . . Summary ............................................ 152 5 Water Treatment ...................................... 155 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 . . . . . . . . . . . . Materials ..............................................