Membrane Separation and Filtration: Tried and True Technologies

By Alan Murphy

Introduction
In reverse osmosis and nanofiltration membrane separation processes, membranes act as barriers against the normal hydrodynamic flow of water, thereby filtering liquids that contain high dissolved solids. This unique cross-flow filtration pattern separates solids out of water without the application of any heat. Microfiltration and ultrafiltration utilize specific pore size membranes to allow for separation of microorganisms, suspended particles and small colloidal particles, respectively, from the process stream. These are used for the removal of relatively large molecules, whereas nanofiltration and reverse osmosis are more popular for salts and lower molecular weight contaminants. High-salinity water, such as from the ocean, can best be processed using seawater membranes with an RO system (SWRO) or nanofiltration.

Changing membrane dynamics
Innovative techniques using membrane separation processes are constantly emerging to enhance or completely replace the conventional methods of separation (such as distillation, flocculation, sedimentation, extraction and others) due to reduced energy consumption and better process efficiency. Membrane filtration is becoming more popular as a green technology, specifically in water recovery and reuse applications, as industrial, municipal and oil & gas wastewater can be treated at a lower cost. This is due to minimum to no use of chemicals, low maintenance cost and high-quality clean water that can be produced to meet stringent discharge limits to release in to US surface waters, or reuse for other applications such as drinking or processing water for industrial and oil & gas markets. Other applications using membrane filtration are now becoming an economical alternative to the traditional methods of evaporation/distillation in various chemical industries, food, dairy, biotechnology and bio-refineries for extracting solids and recovering raw materials to produce valuable byproducts.

It’s amazing to consider just how far technology has improved over the years. In fact, current advancements in the water industry with newly emerging technologies using membrane filtration are now capable of treating almost any type of contaminated water, to purify it to any desired product-water quality. The final results often range from potable water standards to any type of industrial process water. For instance, have you ever heard of the phrase, toilet to tap? We are now able to take wastewater effluent that may contain high-organic loading, viruses, bacteria, micropollution from pharmaceuticals, high BOD, TOC and other contaminants and treat it using some of the most advanced membrane filtration methods, with a comparatively lower cost and lower energy consumption. One of such newly developed technologies is the above referenced toilet-to-tap application, which consists of an advanced oxidation process and ultrafiltration, with ceramic membranes combined with reverse osmosis and UV disinfection. This treatment process chain is able to remove any type of contaminants in wastewater effluent step-by-step and it does it in the most energy-efficient way possible.

Future demand to increase
In 2012, the global demand for membrane modules was estimated at approximately $15.6 billion (USD). With many researchers collaborating with new innovations, membrane demand increased dramatically and opened doors for a variety of new applications. (It is forecast that the membrane demand will grow about eight percent annually within the next few years and in fact, is expected to increase by 25 percent by 2018, according to Global Membrane Technology Market, Second Edition). China is expected to be the fastest growing market. Countries with large developing industrial bases and stressed local water resources are also front runners. If you combine China and the US, the two alone would make up 43 percent of market gains between 2012–2017, as the two largest individual markets for membrane demand. In the US, state authorities have already mandated cities to be more proactive when it comes to the conservation of water.

The increasing need for clean drinking water in the US calls for an economical solution, leaving few choices but to look for alternative sources of water. Desalination, with emerging innovations of membrane filtration processes, is one of the most sophisticated and cost-effective approaches to reclaim water by wastewater remediation for reuse to combat the increasing lack of clean drinking water. There is a tremendous amount of water found throughout the country, that while untreated and unused, represents a key opportunity for water treatment and reclamation. It’s up to the municipalities, business, organizations and political entities to not only identify these waters as an opportunity but work with water-solution providers to set a plan in motion.

Time for broader acceptance
A good question to ask is: with the population increasing and more municipalities and cities growing at an exponential rate, will we be able to keep up? The future is uncertain. With more and more developments in membrane separation technology, major advances are pivotal to combat the growing shortage of clean drinking water. This process gives hope with its highly effective procedures to produce clean water from previously unused resources that have always been available and are now at our disposal.

In the state of Texas, policy makers have already passed bills to make the approval process for desalination using membrane filtration (for treatment of brackish, high brackish and salt water) in conjunction with advanced oxidation pretreatment. They determined that it was the most cost-effective approach to identify, contribute and produce solutions for water scarcity in the state. Others from around the country and even the world will hopefully come to this realization and begin implementing similar technologies.

Conclusion
Treatment of seawater and brackish/high-brackish groundwater sources are key applications for membranes in all regions of the world. The ultimate goal of global process of water filtration is to produce water suited for its specific purpose, the primary one being to produce clean drinking water. With the emerging application of wastewater reuse becoming a more feasible tactic and a most promising process, membrane use will even further expand.

I, like many providing water solutions, believe there is a promising future. With the growing need for more membrane process systems, we should see more laws passed, regulations managed and a more structured government policy leaning toward the relatively low-energy membrane system. Other advantages of using and building membrane technology is that it creates jobs, boosts the economy and compared to many other processes, is easy to operate and requires less maintenance.

About the author
Alan R. Murphy, CEO and Chairman of the Board at STW Resources Holding Corp., is a native West Texan who attended Southwest Bible Institute. Murphy brings 20+ years of extensive water treatment industry experience with various municipal, industrial and commercial water and wastewater treatment facilities, including consulting, design, engineering, procurement, operations, management and complete project oversight and construction throughout Texas. He has vast knowledge on most up-to-date innovative technologies, which include membrane filtration systems, thermal technologies, freshwater recovery and reuse, brine discharge treatment systems and others.

About the company
STW Resources Holding Corp. is a quality provider of oilfield services, water reclamation and processing management services and rig cleaning services through three subsidiaries. STW Water is a total water solutions provider company offering turnkey design-build solutions for its customers, with out-of-the-box design solutions to meet their water needs. The company can provide complete oversight of various water and wastewater projects, with primary focus on engineering, regulatory permitting including public water systems (PWS), discharge permits, pilot exception and pilot study, equipment design and treatment process design, manufacturing and installation and full-scale commissioning and training for all types of oil and gas, industrial and municipal water and wastewater markets throughout the state of Texas.