Water (rivers, seas and oceans) is our natural heritage. Recent developed technological society has become indifferent to water- 'the miracle of life'. Our drinking water today, far from being pure, contains many undesirable chemical and bacterial contaminants. Therefore water is an essential commodity today. The existing techniques employed for the disinfection of water are either energy intensive or their by-products are harmful to human health. Hence there is a need to review these processes and explore the possibility of novel technologies for water disinfection that are synergistic with the existing techniques. This Book gives a comprehensive review of various physical, chemical and hybrid techniques commonly used for disinfection of water in terms of its mode of action, scale of operation, efficacy, merits and demerits. Experimental data comparing different methods in terms of efficacy and economics are presented, which will not only be useful to students but also teachers and researchers in this field.