Membrane Separation Technology
Growing global demand for clean water and increasing environmental concerns make membrane filtration the technology of choice for industries seeking to reuse their wastewater and reduce their water footprint. Knowing which membrane system solution is best for your water treatment challenge can help you increase plant efficiency, while reducing operating and chemical costs, and complying with increasingly stringent discharge regulations. Membrane filtration also offers solutions for large‐scale municipal applications that produce potable water from a variety of source waters.
- Better Removal of Contaminants. Smaller, absolute pore sizes offer a 99.9999% (6 log) removal rating for many contaminants. Conventional treatment systems typically achieve 99-99.9% (2-3 log reduction)
- High Efficiency. Water produced/water fed ratios to the system reach as high as 98%.
- Integrity Assurance. Automated procedures allow in-place testing to quickly confirm that the membrane is not breached.
- Variable Filtration Ratings. Systems employing differing classes of membranes ranging from microfiltration to reverse osmosis allow for precise contaminant removal at the lowest total cost.
- Smaller Footprint. Membrane systems typically require 50-70% less space than conventional technologies.
- Easy to Operate. Automated controls enable consistent, trouble-free operation, far less operator attention, and automated alarms when attention is required.
- Long Filtration Life. Some membranes have a useful life expectancy as high as 10 years.
Types of Membrane Filtration Systems
Membranes provide physical barriers that permit the passage of materials only up to a certain size, shape or character. Napier-Reid offers four crossflow, pressure ‐ driven membrane separation processes for liquid/liquid and liquid/solid separation:
Microfiltration (MF) systems are widely used in process water and wastewater treatment industry. They are used as pre-treatment to ultrafiltration, nanofiltration and reverse osmosis; used for removal of suspended solids, insoluble metal hydroxide solids, and turbidity reduction.
Ultrafiltration (UF). Napier-Reid’s Ultrafiltration system is designed to remove turbidity, colloidal silica, iron, manganese, total organic carbons, bacteria, viruses, and chlorine resistant pathogens (giardia and cryptosporidium) from municipal drinking water. The system incorporates hollow fiber membranes.
Nanofiltration (NF) is a pressure related process, during which separation takes place, based on molecule size. N-R’s Nanofiltration systems operate in cross flow filtration mode. It is widely used in production of drinking water and softening. It removes bacteria, viruses and chlorine resistant pathogens such as giardia and cryptosporidium, dissolved organics, pesticides, heavy metal, nitrates, and colour.
Reverse Osmosis (RO) systems are used for the production of drinking water from seawater, production of boiler feed water and ultra pure water for municipal and industrial applications. These systems are capable of removing silica, dissolved solids and salts, dissolved organics, pesticides, synthetic organic chemicals (SOCs), and colour.
|Microfiltration (MF)||Ultrafiltration (UF)||Nanofiltration (NF)||Reverse Osmosis (RO)|
|Typical Operating Pressure (PSI)||3 – 100||3 – 150||50 – 450||75 – 1200|
|Typical Product Water Recovery||Greater than 95%||Greater than 95%||75 – 90%||30 – 90%|
|Retained Particle Size||> 0.1 µm (> 200,000 Da)||0.1 – 0.01 µm (200,000 – 20,000 Da)||0.01 – 0.001 µm (20,000 – 200 Da)||< 0.001 µm (< 200 Da)|
- Units are designed for automatic operation and can be supplied with an automated cleaning cycle if required.
- Ease of Installation: Stand-alone pre-packaged units and components for larger projects have been designed to be assembled in the factory to the greatest extent possible to simplify installation.
- Napier-Reid’s membrane filtration equipment is designed on a modular basis that gives a high degree of flexibility. The design of a system can thus be customized to meet any process needs and it is easy to expand if production requirements increase.
Electrodeionization (EDI) Systems
High purity water production has traditionally used a combination of membrane separation and ion exchange processes. EDI is a process which combines semi-impermeable membrane technology with ion-exchange media to provide a high efficiency demineralization process.
Napier-Reid’s Electrodeionization units eliminate the need for acid and caustic regenerants associated with traditional ion exchange. The units are modular in design such that a multiple of stacks can be configured to provide a variety of outputs.
The fundamental principle of EDI technology is the use of pressure and electrical current to separate soluble ions from water through a semi permeable material which includes both cationic and anionic membranes. Each cell incorporates specific ion exchange resin between the two types of membranes allowing negative and positive ions to only pass through one of the membranes.
The resulting product stream is high purity water and a concentrate stream which is usually recycled back to an upfront RO system for reprocessing.
EDI is a polishing technology and requires reverse osmosis (RO) as pretreatment. The combination of RO-EDI provides the customer with a continuous, chemical-free system.