A Cost-Effective Solution

Shortly before the Fall 2006 issue of Membrane Technology went to print, a report from Frost & Sullivan declared that the growing use of membrane filtration technologies for water purification and recycling is being driven in part by dramatic reductions in cost.

This is very good news for the water and wastewater industry, considering that many of you are currently incorporating membranes into your water treatment systems, while for others, the time has likely come to consider expanding your treatment systems.

Additionally, for those plant managers and engineers who are considering a membrane treatment system, there may be no better time than the present as the footprint of these systems is getting smaller; the treatment systems are customizable for a wide range and size of applications; and membranes consistently allow water and wastewater plants the ability to produce water to meet municipal drinking water and wastewater quality requirements, and water reuse specifications.

The dramatic reduction in the price of membrane water treatment technologies, specifically within the past few years, continues to evolve membrane-related technology as a cost-effective alternative for water treatment.

Aside from the various reverse osmosis, ultrafiltration and microfiltration technologies currently incorporated for water and wastewater treatment, a newer membrane-related technology soon may be growing in popularity.

Earlier this year, researchers at the Lawrence Livermore National Laboratory created a membrane made of carbon nanotubes and silicon that may offer an even less expensive desalination technology. The nanotubes, special molecules made of carbon atoms in a unique arrangement, are hollow and more than 50,000 times thinner than a human hair. Billions of these tubes act as pores in the membrane, allowing liquids and gases to rapidly pass through while the tiny pore size blocks larger molecules.

The research team was able to measure flows of liquids by making a membrane on a silicon chip with carbon nanotube pores, ideal for desalination. The membrane was created by filling the gaps between aligned carbon nanotubes with a ceramic matrix material. The pores are so small that only six water molecules could fit across their diameter.

“The gas and water flows that we measured are 100 to 10,000 times faster than what classical models predict,” said Olgica Bakajin, lead scientist for the Livermore nanotube membrane research project.

In regards to desalination, the process is usually performed using a reverse osmosis membrane process, which does require a large amount of pressure and energy. According to the research team, the more permeable nanotube membranes could reduce energy costs of desalination by up to 75% compared to current reverse osmosis technology.

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