Fate of disinfection by-products & their precursors across reverse osmosis membranes when producing high quality recycled water

This paper investigates the fate of some regulated and emerging disinfection byproducts (DBPs) and their precursors across reverse osmosis (RO) membranes during the production of high quality recycled water (HQRW). Total organic halogen (TOX) and its speciation has been used as a holistic tool to measure the total concentration of halogenated organics in the water which can be compared to individually measured halogen-containing DBPs to determine a mass balance between "known" and "unknown" fractions. Results from TOX analysis show that more than 95% of halogenated DBPs generated at the plant are rejected by the membranes. However, the percentage of rejection is lower for some specific polar and low molecular weight DBPs such as chloroform (TCM), bromodichloromethane (BDCM) and N-nitrosodimethylamine (NDMA). NDMA precursors have been measured by means of the NDMA formation potential test. Results showed that while more than 98.5% of NDMA precursors are rejected by this system, almost 90% of NDMA generated during disinfection prior to the membranes pass through them. In general, results from the formation potential test performed on the RO feed water and its permeate support the statement that membranes are a good technology to decrease the formation of DBPs during water disinfection even when long contact times between water and the disinfectant are needed for distribution purposes. 201