Rejection Capabilities of RO Membranes to DHS Notification-level Chemicals and Selected Endocrine-disrupting Chemicals

The information regarding rejection capabilities of RO to non-regulated compounds such as "DHS notification level chemicals" and endocrine-disrupting chemicals (EDCs) is very limited. In this study, a pilot scale MF (providing pretreatment for RO) and a two-stage RO process receiving secondary treated wastewater effluent from Big Bear Area Regional Water Agency (BBARWA) WWTP was tested to determine the rejection capabilities of the RO membranes for specific non-regulated compounds and CDHS specified endocrine disrupter chemicals (EDCs). Due to limitations in analytical methods, the following EDCs have been tested: Acetaminophen, bisphenol A, caffeine, 17b-estradiol, EDTA, fluoxetine, gemfibrozil, ibuprofen, iopromide, 4-methyl phenol, polybrominated diphenyl ethers, progestrone, testosterone, triclosan and sulfamethoxale. Due to domestic nature of BBARWA wastewater and the degree of secondary treatment (extended aeration) provided, with the exception of boron and chlorate, all DHS notification (action) level compounds were below their detection limits in RO feed water. For the detected compounds, the RO exhibited 93.7 percent rejection capability to chlorate while rejecting boron only 44 percent. EDC testing results have shown that with the exception of 4-methyl phenol, the RO exhibited very good rejection capabilities to the tested EDCs. In this study a very good correlation between RO rejection and molecular size, polarity (charge) and solubility of the compounds.