After the water by b↕♥↔♣oiling, water can only kill most bact✔✔→∞eria and viruses, however, rust, sedi§&±✘ment, colloids, algae and o♦ש↓ther harmful substances still remain ®≠♠ in the water by boiling boil approach i¶&s not to remove these harmful substan©±÷ces a.