Soaring oil prices and the boom in global commodity markets are serving to focus attention on the growing scarcity of a less-traded, but no less valuable, commodity: water.
Just as rapid industrialization and rising affluence in China, India, and other developing nations helped propel energy use to record highs, so too have they had the same effect on water consumption. And just as the massive growth in fossil fuel consumption is having an increasingly noticeable effect on the environment due to the release of carbon dioxide, so too is the growing volume of wastewater from residential, commercial, and industrial sites threatening an already delicate environmental balance in many areas.
In 2004, the U.K. charity WaterAid reported that a child dies every 15 seconds from easily preventable water-related diseases; often this means lack of clean drinking water.
Faced with high and rising costs to acquire water that is clean, and dispose of water that is dirty, many regions are looking into wastewater recycling as a means of addressing both issues at once. Those doing so are increasingly turning to a relatively new technology known as submerged membrane bioreactors that offer the ability to purify wastewater effluent well beyond existing drinking water standards, thereby increasing the supply of fresh water and decreasing the volume of waste.
Technological advances in recent years have made membrane bioreactors cost competitive with other types of wastewater treatment. Membrane bioreactors also offer some important benefits compared with conventional water treatment systems, including a greatly reduced need for land to house the treatment facility and less use of water treatment chemicals.
While other technologies such as treating wastewater with ozone or ultraviolet light have significant growth potential, "the market for membrane is particularly attractive," according to a December, 2007, report on the investment opportunities in the water industry by Zurich-based Sustainable Asset Management. The report cited estimates by consultants Global Water Intelligence that membrane equipment "sales in the drinking water segment are expected to be roughly eight times higher in ten years' time than they are today."
Conventional wastewater treatment techniques involve pumping pretreated water into a settling tank, where suspended solids drop out, then passing through a sand filter. It is then disinfected — either with ozone, ultraviolet light, chlorine, or other chemicals. These processes have drawbacks including using large amounts of energy or requiring large holding tanks — extremely large in the case of a major city. A membrane bioreactor works by adding bacteria or other organisms to the wastewater to reduce the water's organic content in a process known as activated sludge. The water is then sucked through a membrane that removes any remaining impurities.
Early membrane filtration systems suffered from significant problems. They clogged easily and therefore required large amounts of energy to operate, making them extremely expensive and limiting their use. During the early 1990s, a research program funded by the Japanese government came up with the idea of a submerged membrane bioreactor that sucked water instead of pushing it through the membrane. Just the right amount of aeration in the tank would dislodge solids that clogged the membranes in earlier versions. This advance greatly reduced the amount of the equipment needed and the system's energy use, and made advanced water filtration much more competitive on a cost basis, according to the MBR-Network, an information network sponsored by the European Commission.
As a result, more than 70 new membrane bioreactor facilities are expected to be built in Europe annually over the next three to five years, according to a 2007 study of the European market for membrane bioreactors sponsored by the Berlin Centre of Competence for Water.