Will Rogers once advised audiences to “drink upstream from the herd.” That usually worked in a thinly populated world. Running water and soil percolation remediated low bioloads. Heavy metal contaminants weren’t as widely distributed.
Today we have to help nature deal with high bioloads and pervasive industrial chemicals, but big sewage treatment plants are energy intensive. Nearly 4% of U.S. electrical consumption now treats wastewater. This percentage is expected to rise if we add process steps to reduce outgoing concentrations of heavy metals and non-soluble contaminants.
Energy costs associated with water – pumping, heating, cooling, cleaning – consume 20% of electrical power, and perhaps a bigger percentage than that of natural gas. Wastewater treatment is only part of it. For years the American Council for an Energy-Efficient Economy (ACEEE) has been mapping this energy-water nexus and proposing policy changes. Although this map needs more detailing, a mere sketch of it reveals a big, growing problem. One reason, as ACEEE notes, is that utility business models reward growth, not conservation. But utilities aren’t unique. Most other industries’ business models do the same, and everybody uses water.
If wastewater has both a big bioload and metallic contaminants, remediating it takes a lot of energy, and options are complex. However, microbial generators promise to reduce the energy to purify at least the bioload. Lab scale microbial batteries have existed for some time. Now Emefcy has begun to install commercial units to harness the bacterial potential in wastewater to generate enough power to purify at least its bioload; maybe with a little to spare. You can see a demo of the principle. Microvi is a bigger company with similar ideas.
Wastewater treatment is no technical backwater, and yet the scope of problems threatens to outrun it. Of course, the red alert wastewater problem today is chemically contaminated wastewater from hydraulic fracking. The industry recognizes major risks from using so much water and cleaning it up after use. Around 25% of injected water may return to the surface. Containing underground water is one risk. Dealing with surface return is another – storing it, trucking it, remediating it, and finally either purifying it for release or re-injecting it where it can do no harm (we hope). The water treatment industry has begun to develop portable systems to remediate flow-back water at the wellhead.
All this takes energy, of course, which saps the energy return from fracking. It seems obvious that if energy demand were not so high, the scope of the problems and risks would diminish. But that takes us back to the incentives of business models again.