NAMS 2002 Workshop - ICOM 2008

Drinking and Wastewater Applications II – 1 – Keynote
Tuesday July 15, 2:15 PM-3:00 PM, Maui
Analysis of RO Membrane Performance for Municipal Wastewater
Treatment
C. Bartels (Speaker), Hydranautics, Oceanside, California, USA - cbartels@aol.com
R. Franks, Hydranautics, Oceanside, California, USA - rfranks@hydranautics.com
P. Gourley, Hydranautics, Oceanside, California, USA - pgourley@hydranautics.com
Reclamation of wastewater has become a key means to augment local water
supplies in water stressed areas. Reclamation technology varies from
conventional filtration and UV- advanced oxidation processes to membrane
processes combined with UV and advanced oxidation processes. The selection
of the type of process depends on the planned use of the reclaimed water. For
indirect potable and industrial use, reverse osmosis (RO) has proven to be an
essential wastewater treatment technology. RO membranes are a physical
barrier that can ensure the significant reduction of dissolved inorganic solids,
total organic carbon (TOC), pharmaceuticals, endocrine disruptor compounds
(EDC), and other potentially harmful chemicals. The effective pore size of RO
membrane is on the order of a few angstroms or molecular weight cut-off values
on the order of 70 Daltons. As a result of the large number of plants using RO,
there is a growing amount of detailed information about the removal rates of
these compounds. Experience has shown that there are two critical parameters
which determine if the effectiveness of the membrane system - stable water
permeability and high rejection of contaminants. This paper will present analysis
of these factors from a variety of operating plants.
A typical advanced wastewater treatment plant may consist of activated sludge
treatment process, UF or MF membrane treatment, RO, and then UV and/or
advanced oxidation process. To achieve stable RO operation, the plant must be
operated within certain defined guidelines. Some of the key parameters include
operating at a flux of 10-12 gfd, a recovery of 75-80%, maintaining a chloramine
residual of 2-4 ppm, and utilization of RO membranes that show resistance to
organic fouling. When the system is operated well, it is possible to achieve 3 to 6
years of membrane life.
Even when systems are operated with careful attention to detail and within
recommended guidelines, it is still certain that their will be fouling. Due to the
broad variety and complexity of organic compounds, there are many compounds