Disinfection by-products and their potential impact on the quality of water produced by desalination systems: A literature review

When chemical disinfection is applied before or after desalination systems, compounds may be formed that pose potential risks to the health of human and aquatic organisms or impact aesthetic quality of drinking water. The formation and speciation of disinfection by-products (DBPs) in desalination systems is affected by the elevated concentrations of bromide and iodide in seawater and desalinated product water. To gain insight into DBPs likely to be formed in desalination systems, DBP studies conducted in saline source waters, coastal power stations and existing desalination systems are reviewed. Chlorination is the most common disinfectant used in current desalination systems, with chloramines and chlorine dioxide gaining more popularity for disinfection of desalinated water. When seawater or reverse osmosis permeate is chlorinated, bromoform (CHBr3) and brominated haloacetic acids (e.g. monobromoacetic acid, dibromoacetic acid, bromochloroacetic acid) are found to be the prevalent DBP species. Under conditions typically encountered in desalination systems, concentrations of these DBPs in the product drinking water are below levels of concern set by regulating agencies. Less information is available on the formation of other haloorganic DBPs in desalination plants. Among DBPs identified in saline drinking waters, haloacetonitriles (HANs), mutagen X compounds (MX), halonitromethanes (HNMs) and cyanogens bromide (CNBr) pose potential concerns, especially when desalinated waters are blended with organic-matter rich source waters.