AWWA MTC69696

This paper presents a study, funded by the Awwa Research Foundation (Water Research Foundation as of January 1, 2009), that explores the effects of organic nitrogen compounds (measured as dissolved organic nitrogen -- DON) on reversible and irreversible fouling of low pressure (LP) membranes as well as pretreatment conditions to optimize organic nitrogen removal and minimize membrane fouling. The paper presents initial data for experimental work with model nitrogen containing compounds. One critical aspect of this research is the study of the impact of DON on membrane fouling for a bench-scale system that imitates full-scale operation. Poly(vinylidene-fluoroethylene) (PVdF) based outside-in membrane samples were tested. The fiber has an inner diameter (ID) of 0.8 mm, outer diameter (OD) of 1.9 mm, and a nominal membrane pore size of 0.04 micron (manufacturer supplied data). The technique that was used allowed the lower ends of the fibers to be loose, and for one end of the membrane module to be open which obtained better removal of solids during backwashing. This potting technique also makes it easier to remove a small piece of the hollow fiber for surface analyses. An air bubble test was conducted to check for membrane leakage on assembled modules prior to testing. The membrane system was built so that either vacuum or pressurized operational modes can be utilized. In this initial phase, tests were conducted using the vacuum mode, which is the actual operation mode at pilot and full scales for the type of membrane utilized. Three separate pressure transducers were used to monitor the pressure at the inlet and outlet to the membrane module and the backwash pressure. The membrane system was operated at constant flux, dead-end filtration, with periodic backflushing and monitoring of TMP and permeate volume. Chemical washing was conducted periodically. Includes table, figures.