(715e) Integrated Membrane Bioreactor Process for Treatment of Reclaimed Water for Groundwater Recharge

Membrane separations promise to yield substantial economic, energy, and environmental benefits leading to enhanced global competitiveness by significantly reducing energy consumption, increasing capital productivity, and lowering waste generation.  Many challenges must be overcome before membrane technologies can be widely used in wastewater treatment, water reclamation and water reuse.  The technological barriers include membrane fouling, low permeate flux, low separation factors or selectivity, and poor rejection characteristics.  The membrane bioreactor (MBR) process has shown excellent potential for water reclamation and groundwater recharge.  In order to make the process more efficient, economical and versatile for water reclamation and reuse applications, superior membranes must be developed with better aqueous transport and anti-fouling characteristics to resist permeate flux decline attributed to organic and biological fouling attributable to natural organic matter (NOM), exopolymeric substances (EPS), and other macromolecules.  This would significantly reduce energy costs which represent a substantial portion of total operation costs associated with membrane systems.

In the realm of water reclamation and reuse, the MBR process with ultrafiltration can be made more energy efficient, economical and versatile than reverse osmosis or nanofiltration by using exhibiting better transport properties, higher permeate flux, and greater fouling resistance. The MBR process  is specially designed the control of membrane fouling and permeate flux decline by a combination of powder activated carbon (PAC) sorption and fluid management. Therefore, the present research was directed at overcoming these problems to develop superior foulant-resistant membranes that can be used in MBR process for treatment of reclaimed water to be subsequently used in groundwater recharge.  The batch-mode flat-sheet membrane tests represent an economic means for evaluating  the potential for membrane fouling and rejection characteristics.  These test were conducted in the Osmonics Sepa CF Type I  plate-and-frame test cells, generally recommended by the U.S. Environmental Protection Agency for performance membrane evaluations in water treatment and water reclamation systems.

Preliminary  flat-sheet membrane tests were performed as a prelude to evaluate the nature of fouling and the fouling potential of polymeric membranes, and  to obtain the best membrane material for the fabrication of superior foulant-resistant hollow-fiber membranes for use in MBR systems.  These membranes could involve the combination of polymeric materials impregnated with nano-materials.  In these tests,  the permeate flux and the effluent total organic carbon (TOC) were determined to evaluate permeate flux decline patterns.   The reclaimed water was obtained from a water reclamation facility in Southern California.  In these tests the conditions in a membrane bioreactor system were simulated using PAC, acclimated microorganisms, and the results provided insight into membrane fouling, permeate flux deterioration, and TOC rejection in a system containing a typical MBR feed.   Additionally. surface characterization techniques were  employed  for evaluating fouling potential and morphological details of membrane surfaces include atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and x-ray photoelectron spectroscopy (XPS).  These studies provided useful information on several aspects including the nature and extent of membrane fouling (and permeate flux recovery), and  alteration to membrane material caused by fouling.