This video lecture from Environmental Chemistry (F.Sc. second year Chemistry) covers the disinfection of water by the addition of chlorine in the water treatment cycle. Chlorine works by producing hypochlorous acid with water which enters the cell membrane of the pathogens killing them and purifying the water from water borne diseases. The problems associated with chlorination are discussed and the complete water treatment and softening cycle is summarized at the end of the lecture. Find more e-learning material and educational video lectures in Urdu at maktab.pk. These videos are free to use for promotional and commercial purpose by keeping the credits to Maktab.