Waste Not - Make Electricity Instead
by Francis P. Koster, Ed.D.
I bet that you do not often think about the role sewage treatment will play in the future of your family.
Starting around the time of the second world war a torrent of new medicines were added to the waste that the sewage treatment plants had to handle. Simply put, if you apply modern medicines to your skin, or put it in your mouth, some portion winds up at the plant.
Add to that the enormous increase in chemicals produced for use in industry, farming, painting homes, and even paving streets, and you can see that the very nature of sewage has changed. In 1940 about 1 billion pounds of synthetic (not found in nature) chemicals were produced. By 1990 that number grew to over 400 billion pounds consisting of over 70,000 different chemicals. This tonnage does not include pesticides that enjoyed similar and perhaps more spectacular growth.
Our future may also be impacted by these chemicals combining with each other in the environment and making new chemicals, a process known as “ecotoxicology.”
In most parts of the country, this chemical-laden sewage is run through treatment systems not designed to handle it. The American Society of Civil Engineers’ 2013 report card on the state of our nation’s 14,000 sewage treatment plants gave us a “D.”
When waste goes through the sewage plant, it basically splits into two sections. One is liquid, and the other is solid (called bio-solids). The treated liquids are dumped back into the river for the city downstream to make into drinking water. The treated bio-solids remain a local problem for the sewage plant operator to dispose of. For many years now, about half of all bio-solids produced nationally have been distributed to farmers for fertilizer under a system of state issued safety permits.
Scientific controversy continues to exist about how safe our current handling of bio-solids really is.
As medical science discovers a wider set of impacts from chemicals in the environment, the Environmental Protection Agency responded to rising safety concerns and in 2009 conducted a study of bio-solids, collecting 84 samples from representative sewage plants around the country. The EPA found 27 potentially harmful metals (like lead) in virtually every sample, three pharmaceuticals in all 84 samples and nine more pharmaceuticals in 80 of the samples. Three steroids were found in all samples. The majority of all samples contained flame retardants suspected of causing health issues.
Further scientific investigation is ongoing.
Taking a conservative approach, since the risk is not well known and bio-solids are not going away any time soon, the challenge is to figure out alternative ways to dispose of them.
One promising step is to take the solid waste from sewage treatment plants and burn it at very igh heat. Of the 1,400 sewage systems in the nation, only about 200 incinerate bio-solids. This is surprising, because burning has been shown to remove a significant amount of the chemicals and reduce the volume to a fraction of its former size.
Of the 200 facilities that have put such high-temperature incinerators in place, the more creative ones are actually using the burning process to generate electricity.
The Metropolitan District of Hartford Connecticut has adopted a plan to upgrade its current bio-solids incineration system so that the previously wasted heat will be used to generate electricity. The plant, coming on line in early 2014, will produce 40 percent of the electricity needed to run the sewage treatment facility.
The Northeast Ohio Regional Sewer District is in the final stages of a similar project. It will produce 25 percent of the electricity the Southerly Wastewater Treatment Center’s electrical needs.
Closer to home, the Water and Sewer Authority of Cabarrus County (WSACC) offers another example of a forward leaning operation. It owns an incinerator that is operating below 50 percent capacity due to textile plant closings in this region. To more efficiently use the incinerator, WSACC has constructed an “import bio-solids facility” to allow other sewage plants to bring their bio-solids to WSACC for incineration. This is part of a larger project to install a heat recovery steam generator and a steam turbine generator to produce electricity from the excess heat that would have been wasted. WSACC is now taking bio-solids, safely incinerating them, and by March 2014 will be using the heat from that process to make electricity and reduce demand on the power grid.
Think of this — instead of creating endless streams of possibly contaminated solid waste that might wind up fertilizing food-producing fields, the bio-solids are burned to create electricity, which reduces the demand for coal-fired generation (which has its own chemical waste to contend with). So the win-win is reduced potential risk in our food supply, decreased taxpayer cost for waste disposal, more electricity, and the environmental risk to future generations is reduced.
The choice will be made by local leaders and informed citizens like you. Are you going to waste this opportunity?