Chemical Security Program The Role of Chemistry and Materials Science in Advanced Water Treatment

The Role of Chemistry and Materials Science in Advanced Water Treatment

Materials Science is an Essential Part of Water Treatment Infrastructure Introduction Water treatment processes Materials science for water infrastructure Membrane technology- polymeric Micro and ultrafiltration (MF and UF) Nanofiltration and reverse osmosis (NF and RO) Recent RO membrane advances

Materials Science has a Dramatic Effect on Water Treatment Infrastructure Glass reinforced plastics - corrosion Pump coatings - friction reduction Pipe lining – trenchless technology Composite pumps – corrosion resistant Steel alloys (Duplex SS)- corrosion resistant Polymers, resins, additives- treatment Polymeric membranes- porous: water purification, nonporous: desalination- pressure driven Source : U.S. Filter

Membranes have Revolutionized Water Treatment http://www.gewater.com/products/equipment/mf_uf_mbr/zeeweed_500.jsp http://www.ionics.com/technologies/ro/index.htm#

Membrane Separation Spectrum Dissolved salts Nonporous Suspended solids/ DOM Porous Virus Bacteria Porous: Filtration by size - molecular weight cutoff (MWCO). Nonporous: Solution diffusion separation – hydrated ions. Removal: Salinity can be reduced only by RO/NF membrane treatment. The Future of Desalination in Texas:Texas Water Development Board 2,(2004) 137-154 Alyson Sagle and Benny D. Freeman,

Basic Water Treatment Removes Particles and Dissolved Organics Coagulation Flocculation Sedimentation and or filtration Coagulant Removal of particles and natural organic matter (NOM), color, disinfection byproducts (DBP), iron, manganese, arsenic, taste, odor. Granular activated carbon can be used as a filter and adsorber, but regeneration may be different than sand media.

Microfiltration (MF) and Ultrafiltration (UF) can be used Instead of Sand Filters Coagulant Microfiltration or Ultrafiltration concentrate Flocculation Coagulation Membrane filtration normally uses hollow fiber bundles that can be submerged or pressurized. These membranes can be air scoured , backflushed and cleaned and are not usually sensitive to chlorine.

Hollow Fiber Units Consist of Tube Bundles (UF-MF) Asymmetric membranes are formed by phase inversion and produces anisotropic material. Membrane Polymers Polysulfone (PSF), Polyethersulfone, Poly(vinylidene fluoride), Polyacrylonitrile, Polypropylene. Pressurized in housing Submerged in cassette Source : Pall Source: Zeeweed

UF and MF Membranes can be “Inside-out” or “Outside in” Mean pore size ~ size rating of filter (.01 -10 micron) Lumen Source: Koch Membranes Permeate Feed Porous membranes can be backflushed and cleaned. Skin

Primary Difficulty with Membranes is Fouling Dead-end membrane operation Cross-flow membrane operation feed permeate feed ∆P ∆P permeate Crossflow operation scours the surface and reduces stagnation near membrane surface.

Non-porous Membranes: Nanofiltration, Reverse Osmosis-thin Film Composite (TFC)* thin, dense polymer coating on porous support (composites) Surface morphology Journal of Membrane Science, 158 (1999) 143-153. Seung-Yeop Kwak, Dae Woo Ihm Thin (100 - 200 nm) polyamide membrane Porous support (polysulfone UF membrane) Woven mechanical support * Discussion will not focus on cellulose acetate asymmetric membranes

Spiral Wound Membrane has Multiple Flat Sheet “leafs” 2007 EDS Conference, Halkidiki, Greece Craig Bartels*, Mashiko Hirose, Hiroki Fujioka *Hydranautics

Reverse Osmosis Primarily Uses Polyamide TFC Membranes saline feed pre-treatment high pressure pump post- treatment fresh water concentrate disposal membrane RO Plant concentration dependent, membranes susceptible to fouling, pre-treatment required, polyamide membranes degraded by Cl2. dense polyamide membrane porous polymer mechanical support Thin film composite membrane polyamide

Reverse Osmosis Membrane Performance Measured by Four Factors Salt rejection, Water permeability, Fouling (multifaceted), Chlorine tolerance. Salt Rejection Normalized water permeability m3/(m2 bar day) Journal of Membrane Science, 370(2011) 1-22. Kah Peng Lee, Tom C. Arnot, Davide Mattia

Active Research Topics in RO Membrane Science and Desalination Modification of PSF substrate Increase hydrophilicity Control of interfacial polymerization Crosslinking Membrane thickness Increased chlorine tolerance Surface post treatment Modify surface charge Membrane morphology Surface roughness New thin film nanocomposite studies Polymer with zeolite, Ag, TiO2 Journal of Membrane Science, 370 (2011) 1-22. Kah Peng Lee, Tom C. Arnot, Davide Mattia J. Mater. Chem., 20 (2010) 4551–4566. Dan Li and Huanting Wang

Materials Science has Provided Major Breakthroughs in Water Treatment Energy consumption and membrane costs have been reduced by new membrane formulations. Journal of Membrane Science, 370 (2011) 1-22. Kah Peng Lee, Tom C. Arnot, Davide Mattia

Membrane Surface Hydrophilicity Enhanced by Surface Modification Surface modification leads to decrease in contact angle; Less fouling potential, somewhat reduced water permeability Contact angle (°) Coating solution (mg/L) Journal of Membrane Science 371 (2001)293-306. Sanchuan Yu, Zhenhua Lu, Zhihai Chen, Xuesong Liu, Meihong Liu, Congje Gao

Membrane Smoothness has an Effect on Membrane Fouling Smoother membrane surface leads to less fouling Journal of Membrane Science188 (2001)115-128. Eric M. Vrijenhoek, Seungkwan Hong, Menachem Elimelech

Membrane Degradation by Chlorine Thin film composite membrane dense polyamide membrane porous polymer mechanical support Membrane degradation proceeds by chlorination of the amide followed by ring chlorination Journal of Membrane Science, 300 (2007) 165-171. Guo-Dong Kang, Cong-Jie Gao, Wei-Dong Chen, Xing-Ming Jie, Yi-Ming Cao, Quan Yuan

Chlorine Tolerant Membranes Being Studied A new polymer formulation holds promise as a chlorine tolerant RO membrane. Angew. Chem. 120 (2008), 6108 –6113. Ho Bum Park, Benny D. Freeman, Zhong-Bio Zhang, Mehmet Sankir, James E. McGrath

Conclusion Polymer science and composite fabrication have lead to increased use of membranes and advanced materials in water treatment. Microfiltration and Ultrafiltration membranes have provided compact, efficient means of removing suspended solids and wastewater contaminants. Nanofiltration and RO membranes provide lower energy alternatives for water desalination.