Not every utility that cleans wastewater views itself as a wastewater treatment plant.
Some utilities have started making the shift from saying we make clean water to saying we recover resources from water, said Matt Williams, an anaerobic digestion/biosolids expert from WesTech. They are seeing themselves as water resource recovery facilities.
These utilities are using anaerobic digestion to turn their biosolids into biogas — a renewable energy source. Williams shares five reasons why every wastewater treatment plant should consider doing the same.
1. Stop Wasting Resources
Traditionally, biosolids are thought of as something that needs to be removed, and the waste gas is flared into the environment. Utilities that do that are throwing potential money out the window, Williams explained.
That gas is a very valuable resource, he said. Utilities are just wasting it.
2. Power Alternative
Biogas can be used to power a variety of functions at the plant. Currently, the most popular use for it is to run plant heating systems, but it is also suitable for fueling process heating, sludge drying, cogeneration, vehicles, and other equipment.
One option, for smaller facilities in particular, is a combined heat and power (CHP) unit. Operations looking for a solution with very low emissions and the ability to use the gas with little to no scrubbing could consider a CHP unit with a Stirling motor.
3. Good for Any Size Utility
Ten years ago it didn’t make financial sense for a small plant to invest in an anaerobic digester. That is no longer the case.
The model is changing, said Williams. In many cases, yes — a small wastewater treatment plant can’t produce enough biogas on its own to warrant buying the equipment. But if they consider what else they can bring to their digester and think outside of the box, an anaerobic digester stands to really be worth the investment.
Plants now have the opportunity to collect food waste and fats, oils, and grease (FOG) from area businesses and add them to their digesters. This transaction is mutually beneficial for both area restaurants — as they are required to properly dispose of waste — and wastewater treatment plants that need additional fuel sources for their digesters.
By combining biosolids from the plant with FOG and food waste, some wastewater treatment plants have been able to go completely “off the grid.” Not relying on outside electricity saves utilities a significant amount of money and gives them more control over their energy efficiency. Some wastewater treatment plants produce more biogas than they need, which gives them an opportunity to make a profit by selling it to other facilities.
5. Reduce Odor and Sludge
Feeding biosolids to an anaerobic digester means there are fewer biosolids that need to be managed at the plant.
The amount of solids in the sludge is reduced when plants improve their digestion process, said Williams. That means there isn’t a lot of odor and the plant has less to haul away. That saves them money and time. It is a win-win.
Looking To the Future
As biogas technology expands, so will the incentives for utilities to take advantage of it.
No one knows what this industry will eventually look like because there are a variety of unconventional models out there, said Williams. Right now we are still in the infancy of this, but there is so much potential for growth.
Note: A version of this article was originally published by Water Online.