Removal of natural organic matter from source water: review on coagulants, dual coagulation, alternative coagulants, and mechanisms

Natural organic matter (NOM) represents a range of soluble and insoluble material which can have considerable impact on drinking water quality. In addition to creating problems with taste, odour, clarification, and colour, removal of NOM is problematic because it can initiate the formation of disinfection by-products, which can adversely affect human health. Numerous technologies and methods have been employed to remove NOM in water treatment, with the most common processes involving the use of coagulants and similar technologies. This paper provides an overview of the most widely studied coagulants, coagulant aids, dual coagulants, and alternative coagulants. The paper also investigates the effects of operating parameters such as temperature, coagulant dose, pH, use of inorganic salts, inorganic polymeric coagulants, and organic polyelectrolytes in terms of charge neutralisation, polymer adsorption, and polymer bridging. Finally, emerging technologies and the use of novel coagulants are investigated.