Wastewater Treatment for Reuse: Membrane Filtration

Vocabulary practice flashcards covering terminology, classifications, materials, and module types for membrane filtration in wastewater treatment.

Membrane

A typically synthetic, semipermeable material less than $1\,mm$ thick that allows certain components in a feed stream to pass while retaining others.

Feed

The volume or mass of solution that enters membrane modules, typically measured in $m^3/sec$.

Flux

The number of moles, volume, or mass of a solution passing per unit of time through a unit of membrane surface area, measured in units like $m^3/m^2 \cdot sec$ or LMH.

Membrane Fouling

The accumulation of pollutants inside pores and on the membrane surface, causing flux decline and requiring module replacement, increasing energy and chemical costs.

Pressure Difference Processes

Membrane processes driven by pressure difference, including Microfiltration, Ultrafiltration, Nanofiltration, and Reverse osmosis.

Chemical Potential Difference Processes

Membrane processes such as Pervaporation, Pertraction, Dialysis, Gas separation, and Vapour permeation.

Electrical Potential Difference Processes

Membrane processes including Electrodialysis, Membrane electrophoresis, and Membrane electrolysis.

Isotropic Membrane

A membrane characterized by a symmetric structure.

Anisotropic Membrane

A membrane characterized by an asymmetric structure, such as the Loeb-Sourirajan structure or thin-film composite.

Organic Membranes

Membranes made from synthetic polymers like polytetrafluoroethylene (Teflon PTFE), polyamide-imide (PAI), and polyvinylidene difluoride (PVDF), or natural polymers like rubber, wool, and cellulose.

Inorganic Membranes

Membranes made from materials such as ceramic, steel, or glass; they are often autoclavable and resistant to high temperatures ($> 200\,^\circ C$).

Dead-End Filtration

A filtration regime characterized by higher fouling, lower flux, higher OPEX, and greater difficulty in cleaning compared to cross-flow filtration.

Cross-Flow Filtration

A filtration regime offering improved fouling tolerance, higher sustainable flux, less frequent back-washing, and lower OPEX.

Plate-and-Frame Modules

Flat sheet modules used in small-scale applications like pharmaceuticals and bioproducts, where membranes can be easily exchanged and sterilized with steam.

Spiral-Wound Modules

A variation of the plate-and-frame module where the membrane envelope is rolled around a perforated central collection tube; widely used in reverse osmosis and ultrafiltration.

Tubular Modules

Membranes constructed as a solid structure with channels, typically made of inorganic materials, featuring a packing density of $140\text{--}310\,m^2/m^3$.

Capillary Modules

A large number of membrane capillaries with an inner diameter of $0.2\text{--}3\,mm$ arranged in parallel within a shell tube.

Hollow-Fibers Modules

The most common configuration for water treatment, consisting of hollow tubes with outside diameters of $0.5\text{--}2\,mm$ and high packing densities of $1200\text{--}1700\,m^2/m^3$..