Pilot-Scale Evaluation of Chemical Cleaning Protocols for Organic and Biologically Fouled Microfiltration Membranes Jonathan A. Brant 1 ; Pierre Kwan 2 ; Uzi Daniel 3 ; and Ralph Valencia 4 Abstract: The Edward C Little Water Recycling Facility ECLWRF is the largest high-purity water recycling facility in the United States. Here, microfiltration MF membranes play a critical role in treating the secondary effluent and serving as pretreatment to the downstream reverse osmosis systems. New chemical clean-in-place CIP formulations were evaluated through pilot-scale tests for their ability to improve the performance restoration for the Phase III continuous MF CMF membranes at the ECLWRF. Membrane autopsies found that the primary fouling mechanisms for the CMF membranes were biological and organic in origin. It was also determined that the current CIP protocol provided an incomplete removal of the biological and organic foulants. The cleaning test results found that the current CIP regime for the Phase III system performed better than the four commercially available cleaning solutions evaluated here. However, improved results were obtained when hydrogen peroxide was added to the current CIP regime consisting of caustic soda and the commercially available Memclean C cleaning solution. The effects of the addition of hydrogen peroxide to the standard cleaning procedure shows some promise; however, further research is needed to understand the cleaning mechanisms and long-term effects of using hydrogen peroxide as a cleaning additive. DOI: 10.1061/ASCEEE.1943-7870.0000192 CE Database subject headings: Membranes; Fouling; Water reclamation; Filtration; Organic matter; Water treatment. Author keywords: Membrane cleaning; Membrane fouling; Water reuse; Microfiltration. Introduction Water recycling has received increased interest as a result of shrinking freshwater supplies and greater demand from growing populations. Water recycling involves the treatment of secondary effluent to some standard so that it may be “reused” for some beneficial purpose. One of the largest high-purity water recycling facilities in the United States is the Edward C Little Water Recy- cling Facility ECLWRF in El Segundo, California, which pro- duces roughly 8 billion gal. of recycled water per year. The ECLWRF is owned by the West Basin Municipal Water District and treats secondary effluent from the Hyperion Wastewater Treatment Plant Los Angeles. Like other water recycling plants, the ECLWRF uses microfil- tration MF and reverse osmosis RO membrane processes to remove the biological, organic, and inorganic materials that re- main in secondary effluent Baker 2004; Durham et al. 2001. Membrane fouling is a commonly encountered challenge in water recycling membrane systems Nghiem and Schafer 2006; Safarik and Phipps 2007; Thompson and Powell 2003. Currently the ECLWRF is experiencing rapid fouling of their Phase III MF membranes, which is attributed to less than optimal membrane cleaning. Therefore, the ECLWRF is attempting to develop and evaluate new chemical cleaning procedures for their Phase III MF membranes. Accomplishing this objective requires that the mem- brane fouling mechanisms that are present be understood in order to develop targeted and optimized cleaning techniques for the membranes. Membrane Fouling Membrane fouling results from the accumulation of rejected sub- stances on a membrane surface, and/or within the porous mem- brane structure. It is a function of many factors, including the feedwater quality particle size distribution, inorganic/organic content, biological activity, membrane characteristics pore size, configuration, hydrophobicity, charge, and the process operating conditions water flux, pressureBrant and Childress 2002; Hoek et al. 2003; Lim and Bai 2003. The consequences of membrane fouling can include reduced membrane permeability, premature membrane module replacement, increased cleaning frequencies, and variations in permeate quality. All types of membrane fouling inorganic, organic, biological, and colloidal/nanoparticle may occur in water recycling systems as a result of the complex composition and chemistry of second- ary effluent Fan et al. 2008; Jarusutthirak et al. 2002. Neverthe- less, organic, biological, and colloid/nanoparticle fouling are the most commonly encountered in water recycling systems Lim and Bai 2003; Safarik and Phipps 2007. Organic and biological foul- ing are generally more recalcitrant relative to other forms of foul- 1 Assistant Professor, Dept. of Civil and Architectural Engineering, Univ. of Wyoming, 1000 E. University Ave., Dept. 3295, Laramie, WY 82071 corresponding author. E-mail: jbrant1@uwyo.edu 2 HDR Engineering, Inc., 500 108th Ave. NE, Suite 1200, Bellevue, WA 98004-5549. E-mail: pkwan@hdrinc.com 3 Senior Environmental Quality Specialist, West Basin Municipal Water District, 17140 South Avalon Blvd., Suite 210, Carson, CA 90746- 1296. E-mail: uzid@westbasin.org 4 Engineer, United Water Services, 1935 S. Hughes Way, El Segundo, CA 90245. E-mail: ralph.valencia@unitedwater.com Note. This manuscript was submitted on May 14, 2009; approved on November 2, 2009; published online on November 4, 2009. Discussion period open until October 1, 2010; separate discussions must be submit- ted for individual papers. This paper is part of the Journal of Environ- mental Engineering, Vol. 136, No. 5, May 1, 2010. ©ASCE, ISSN 0733-9372/2010/5-542–553/$25.00. 542 / JOURNAL OF ENVIRONMENTAL ENGINEERING © ASCE / MAY 2010