Biosolids = Sewage Sludge
In the past sewage was dumped directly into the nation’s rivers, lakes, and streams. Obviously this was not a very healthy way to dispose of waste.
Sewage treatment plants were built to remove the waste from the water before it was discharged. While this helped clean up the waterways, it created another problem. What to do with the sludge that’s left over? For a period of time it was placed on barges and dumped at sea. It was then discovered that the areas where the sludge was being dumped were becoming devoid of life.
In the 1990’s a ban was placed on dumping the sludge at sea. This left a problem of what to do with it all. To start with a change in the name was made from sewage sludge to biosolids. That certainly sounds less toxic, doesn’t it?
It was left up to municipalities to figure a way to deal with their sludge. Many municipalities began selling or giving away the biosolids as an organic fertilizer. San Francisco did this for a few years, distributing it to gardeners as free “organic biosolid compost”. Unfortunately, very little testing for toxicity was done. What little testing was done found several toxins. Crops that are certified organic can’t use biosolids for fertilizer.
The main solution for several years has been to put the sludge on farmlands as fertilizer. While this is probably not a very healthy solution, it is the cheapest. A few municipalities burn the sludge, but not many, and very few landfills take it.
So just what is in sewage sludge? Just about anything that can go down a drain or toilet from homes, businesses, industrial and medical facilities. It is treated in an attempt to remove pathogens. This still leaves many heavy metals and other toxic substances. There has been a great deal of controversy about the safety of using this composted sludge to fertilize crops and grazing lands. There has also been concern about the chemicals, metals, and other toxic substances leaching into ground water.
There has also been research done into turning the sludge into biodiesel. So far this has not been deemed as cost effective, however, this is a possibility for the future. There are also some treatment plants that use the sludge to create energy, but for now, at least in the US, land application seems to be the option of choice.