Green Innovation: How Bad Plus Bad Can Equal Good
One of the largest wastewater treatment facilities in Florida came up with an interesting way of reducing its environmental impact - add hazardous waste to the water! Their project, which looked at reducing nitrogen discharge into the St. John's River, won JEA an honourable mention for Best Project contributing to Green Innovation at Process Excellence Awards earlier this year. Arthur Nettles, Operations Coordinator at JEA, tells us more.
PEX Network: What's wrong with discharging nitrogen into the water system?
Arthur Nettles: When nitrogen is released into a waterway, the effect is the same as a fertiliser that you would put on your yard or your plants: it makes things grow. The problem when this happens in a waterway is that the natural algae and plants are in that waterway experience an explosion of growth. If there is too much nitrogen, you a get problems with algae blooms.
These algal blooms lead to depleted oxygen in the water system, which is bad for the fish and water ecosystem overall. As a result, the government regulates the amount of nitrogen that we can discharge in waterways. We're federally mandated, by 2013, to reduce our output and meet a limit of 720 tons per year.
PEX Network: What did you do to tackle the problem?
Arthur Nettles: The wastewater treatment process that we used is a biological process - that means we don’t add chemicals to achieve our goals to clean the water. Instead the process is strictly done by biological agents.
Clearly, to reduce the amount of nitrogen that is discharged we need to remove it from the water. De-nitrification is a way to reduce or remove nitrogen biologically without the addition of chemicals or filters. Essentially, the process involves stripping oxygen away from a certain type of bacteria and introducing a food source into the water. Once the food source is introduced, the bacteria require oxygen and they see the nitrates (the form of nitrogen in the water at this stage), which is one part nitrogen and three parts oxygen. When the bacteria see these nitrates and all the oxygen contained in the molecule they strip the oxygen off of the nitrates. What's left is nitrogen gas, and it bubbles into the atmosphere thus reducing the nitrogen discharge into waterways.
The food source that we used was the by-product from the manufacturing of biodiesel – i.e. it’s what's left over once you make biodiesel. This food source was considered a hazardous waste itself - it needed to be hauled to a landfill and disposed of properly. We had to do a lot of testing and lab work before we could get it approved by the State of Florida. But it turns out that what was in effect a hazardous substance turned out to be a perfect food source for this application.
Effectively we took one material that was a hazard and another that was bad for the environment and when combined together they effectively cancelled each other out so that the environment didn’t have to absorb the effects of either of them.
PEX Network: What affect did the project have on the cost of waste-water processing?
Arthur Nettles:I believe the total budget for this process was around $1,500 and most of that was just storage containers for this material and small chemical pumps to deliver it to the irrigation basins.
PEX Network: Is this something that other wastewater facilities can apply?
Arthur Nettles: Absolutely, that’s basically where I got the idea from, because it effectively mimics a chemical way of removing nitrogen from the water. That’s to say – a tried and true method of removing nitrogen is with the use of chemicals like pure methanol and certain other substances. Indeed, methanol is the secret ingredient in the biodiesel by-product that we are using as a food source. (That is why it’s considered a hazardous waste). The trick was that it had to be in low enough concentration so that it wasn’t flammable and there was no real hazard in using the product, which it was.
So I think that certainly, it’s an interesting innovation and I hope that it might inspire other wastewater treatment plants.