Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres Beneﬁcial phosphate recovery from reverse osmosis (RO) concentrate of an integrated membrane system using polymeric ligand exchanger (PLE) Manish Kumar, Mohammad Badruzzaman Ã , Samer Adham, Joan Oppenheimer MWH, 300 N. Lake Avenue, Suite 1200, Pasadena, CA 91101, USA article info Article history: Received 21 September 2006 Received in revised form 12 December 2006 Accepted 27 January 2007 Available online 26 March 2007 Keywords: Integrated membrane system RO concentrate Phosphate Ligand exchange Struvite abstract Phosphorus (P) discharge to surface water is a major environmental problem. Wastewater treatment is targeted towards removal of this nutrient to prevent degradation of surface water. Integrated membrane systems (IMS) are increasingly being considered for waste- water reclamation, and provide excellent removal of P compounds. However, reverse osmosis (RO), which forms an integral part of these IMSs, concentrates most dissolved substances including P-species such as phosphates in the RO waste stream. In this study, removal of phosphate from this stream using polymeric ligand exchange (PLE) resins was investigated. Further, the possibility of phosphate recovery through struvite (MgNH 4 PO 4  6H 2 O) precipitation was tested. Struvite has been promoted as a slow release fertilizer in recent years. This study demonstrates that PLEs can be successfully used to remove phosphate from RO-concentrate, and to recover more than 85% of the adsorbed phosphorus from the exhausted media and precipitated as a beneﬁcial product (struvite). The approach, presented in this study, suggests advantages of providing economic beneﬁt from a waste product (RO) while avoiding phosphorus discharge to the environment. Published by Elsevier Ltd. 1. Introduction The discharge of phosphorus (P) containing compounds to the environment is a signiﬁcant environmental issue (Farmer, 2004; WERF, 1994). The discharge of P into surface waters leads to eutrophication of lakes and difﬁculties with algal blooms in fresh, estuarine and coastal water bodies (Carpen- ter et al., 1998; Boesch et al., 2006). This is a primary reason for widespread use of chemical and biological P removal tech- nologies employed at wastewater treatment plants (Viessman and Hammer, 1998). A regulatory limit of phosphate discharge of 0.1 mg/L as P has been recommended for the usage of wastewater treatment efﬂuent for water reuse applications in the United States (US). In recent years, the use of advanced treatment processes utilizing membrane technologies has lead to great improvements in the water quality of treated wastewater (Adham et al., 2005). Such advanced wastewater treatment strategies are focused on reuse of the reclaimed wastewater for industrial, agricultural or in some cases indirect potable use. These advanced treatment systems are typically integrated membrane systems (IMSs) incorporating low-pressure membranes followed by reverse osmosis (RO) membranes. An environmental challenge is created due to the use of the IMS utilizing RO membranes. These membranes lead to production of a concentrated waste stream that could be from 5% to 25% of the feed stream in volume and bet- ween 4 and 20 times of the feed stream in concentration. ARTICLE IN PRESS 0043-1354/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.watres.2007.01.042 Ã Corresponding author. Tel.: +626 568 6013; fax: +626 568 6015. E-mail addresses: Manish.Kumar@us.mwhglobal.com (M. Kumar), Mohammad.Badruzzaman@us.mwhglobal.com (M. Badruzzaman), Samer.Adham@us.mwhglobal.com (S. Adham), joan.oppenheimer@us.mwhglobal.com (J. Oppenheimer). WATER RESEARCH 41 (2007) 2211– 2219