Membrane Technology Review: Materials, Costs, and BenefitsVictoria Hernandez, Chemical Engineering, Class of 2018

Tirupalavanam Ganesh, PhD, Assistant Dean, Engineering EducationSchool for Engineering of Matter, Transport, and Energy

Membrane Materials Used to Treat Drinking Water and Wastewater: Pros and Cons

IntroductionThis research is focused on the Engineering theme of Sustainability and the Grand Challenge of Providing Access to Clean Water. Population growth and climate change both have an impact on global water supply[1]. Utilizing new sources of water is becoming increasingly important. Membrane technology allows for the use of previously untreatable water resources, as well as the recycling of wastewater to be used again as drinking water. Membrane technology has the potential to revolutionize the water treatment process, with minimal use of chemicals and energy[2], and preservation of the chemical and biological properties of materials in the water, [3] allowing for nutrient extraction.

Membrane MaterialsGoals[1]:• Maximize selectivity and productivity• Reduce fouling, therefore increase membrane life• Minimize cost to manufacture • Be operational on a large scale

Materials (See Table 1)• Polymer: Integrally Skinned and Thin Film Composite• Inorganic: Mesoporous Ceramic• Nanomaterials• Biomaterials

A Comparison of Membrane Pros and Cons for Different Membrane Materials (Table 1) [1]

ProsWell establishedStrongWithstands cleanings

Fouling resistant Long Life

Integrally Skinned

Membranes

Thin Film Composite

Reactive/Catalytic Surface

Zeolite Coatings Mixed Matrices

Nanoparticle Thin-Film

Composites

Zeolite Thin-Film

CompositesAquaporins Aligned

NanotubesBlock

Copolymers

Mesoporous Ceramic

Membranes

ConsExpensiveNot good for drinking water

Low packing density

ProsSmooth surfaces

fouling resistantCheapEasy to

manufacture

ConsLimited temp.

and pH rangeChlorine

intolerantBio-degradable

ProsFilm over polymer

membrane reduces fouling

Film is separate from membrane

ConsSimilar fouling

problems as with polymer membranes

ProsSelf-cleaningEnhanced

selectivity

ConsHigher costLow packing

densityEnergy

requirements

ProsThermo-chemical

stabilityFouling resistantTunable

selectivity

ConsThin coatings less

efficientDefect proneExpensive

ProsBest of both

organic and inorganic

Selective tuningBiofouling

resistant

ConsExpensiveRelatively newShort-lived anti-

microbial particles

ProsProductivity

increaseFouling resistantAntimicrobial

activity

ConsExpensiveReduced

selectivitySome types show

decreased permeability

ProsIncreased

permeabilityDecreased fouling

ConsExpensive (but

minimal material requirements)

ProsStrongerLower energy

costIncreased

selectivity and productivity

ConsExpensiveDifficult to

produce in large amounts

ProsFar superior

productivity and selectivity

ConsExpensiveDifficult to extract

large amounts

ProsCan be scaled upPotential for self-

cleaningSoftMore selective/

productive

ConsProne to defectsWeaker

Background• Tertiary water treatment[4] • Used in place of flocculation, sedimentation, adsorption, ion exchangers, extraction, distillation[2] (see figure 1)• Impacted by pressure and electrochemical gradients[2] • Operated under cross- flow and dead-end flow[3] (see figure 2)

Further ResearchStudy zeolite materials more closely and their potential uses in the water treatment process. Investigate the potential benefits zeolites can bring to membrane technology, including studying both their coatings and thin film composites.

References[1] M. Pendergast, E. Hoek. “A review of water treatment membrane nanotechnologies,” Energy & Environmental Science, vol. 4, pp. 1946-1971, April 2011.[2] “Membrane Technology,” Water Treatment Solutions, Lenntech, 1998-2015. [Website]. Available: http://www.lenntech.com/membrane-technology.htm. Accessed: March 30, 2015.[3] H. Friedrich, V. Mertsch. “Basics of Membrane Technology,” in Membrane Technology for Waste Water Treatment, 2nd Edition, vol. 2, Ministry for Environment and Nature Conservation, Agriculture and Consumer Production of the Federal state of North Rhine-Westphalia: 2003, pp. 27-55.[4] V. Gupta et. al. “Chemical treatment technologies for waste-water recycling – an overview,” RSC Advances, vol. 2, pp. 6380-6388, April 2012.

Dead-End Flow Cross-Flow

Microfiltration• Bacteria and some

viruses• Oil emulsions• Yeast and Fungi

Ultrafiltration• Viruses• Proteins• Polysaccharides• Colloidal Solids• Nucleic Acids

Nanofiltration• Antibiotics• Mercury• Ions (multivalent)

Reverse Osmosis• Organic Acids• Ions (univalent)

Figure 1: Stages of Filtration in which membranes are most commonly used (above) [3]

Decreasing Pore Size

Figure 2: Dead-end flow (left) vs Cross-flow (right)