From the Desk of Waste Water Superintendent Sean Neeley
Hello Shipshewana, from Sean Neeley, your Waste Water Superintendent.
With the latest blast of cold weather upon us, several things have been on my mind. How much L.P. is in the tank? How long will the cold weather last? How can there be no such thing as cold? Yah, cold is the result of the absence of heat…tell that to my frost-bitten fingers. Last but certainly not least. How are my bugs doing?
I know right? You were probably thinking of the same thing? Truth be told my hard-working bacteria are in many ways just like us. When it is cold outside, they do not want to work very hard either. Especially my nitrifiers. What’s nitrifiers you ask? Well, I so very glad you asked.
Nitrifiers are a group of bacteria that work break down various stages of Ammonia and nitrogen. In the wastewater world I am mostly concerned autotrophic and hydrophobic nitrifiers. Let us dig in shall we.
Nitrogen has a cycle, similar to water but not entirely the same. Most of us are somewhat familiar to the water cycle. We generally talk about how water starts off in a stream, lake, or ocean, and then evaporates into a vapor, or is released through plants in transportation. This vapor rises in the sky where the cooler air causes the vapor to condensate into clouds, and when the conditions are right the droplets are big enough and heavy enough the water falls back to earth in the form of rain. Starting the process all over again.
Nitrogen is a gas that make up around 80% of our air. Nitrogen can be found in the soil, and in plants and animals where it is called organic nitrogen. This nitrogen returns to the soil when plants die and decompose or when an animal defecates or dies and decomposes. From here nitrifying bacteria convert various forms of nitrogen back into nitrogen gas (N2) that is released back into the air or back into the soil where it is reabsorbed into plants, and inadvertently back into animals. The cycle I deal with at the wastewater plant is organic nitrogen from fecal matter and urine to ammonia nitrogen (NH3), to nitrite (NO2), to nitrate (NO3), to nitrogen gas (N2).
Let’s, break this down a bit, throw it into the sorting hat and see what families we end up with. We have Nitrogen as Ammonia. This can be broken down into to two forms NH3 (gas) and NH4 (ionic or liquid). There is Nitrogen as Nitrite (NO2) and Nitrate (NO3), and there is organic Nitrogen in plants and animals. If we add them all together, we call this Total Nitrogen or TN. If we add the Ammonia as Nitrogen and the Organic Nitrogen, we call this Total Kjeldahl Nitrogen or TKN. Finally, if we add NO2, NO3, NH3, and NH4 (our Ammonia Nitrogen) we have Total Inorganic Nitrogen or TIN. I know so much fun, right?
So how does this affect us down at the wastewater treatment plant, and what does the cold weather have to do with it all?
Nitrogen is received at the wastewater treatment plant in a large part via urine. When urine mixes with the water in the distribution system it is mostly converted into Ammonium (NH4). From here the nitrifiers get to work. The first group converts NH4 and Oxygen into Acid (H), H2O (water), NO2 (Nitrite) and energy to grow and make more nitrifiers. Now we move onto the second part. Our second group of nitrifiers convert the NO2 (Nitrite) and Oxygen into NO3 (Nitrate) and energy. These guys are our autotroph nitrifiers.
Now we need to remove all this Nitrogen and Ammonia for our receiving stream, and lakes. If we don’t there is a strong possibility of fish kills due to Oxygen depletion, algae blooms, and general toxicity.
So, we have converted NH4 (very toxic) into NO2 (slightly less toxic) into NO3 (the least toxic), but we need pay some attention to NO3. Nitrate (NO3) left unchecked can lead to other problems, most notably Blue Baby Syndrome. Blue Baby Syndrome is a condition where a baby’s skin turns blue from lack of hemoglobin, the part of our blood that caries Oxygen.
Let’s, focus on getting some of that pesky NO3 out of there too. We will tackle this problem with a process called denitrification. Now, I know what you are thinking. Why would we want to go back to NH4? We just got all the way to NO3! Denitrification is not the reversal of the nitrification process. It is something entirely different.
Denitrification is the process of using a different type of nitrifier. One that has the sneaky ability to steal O2. What we need to do it get our wastewater into an area of very little O2, and anoxic zone. Anoxic zones have O2, it is just bound to something else, like NO3 perhaps. Do not get confused anoxic is not that same as anaerobic. Anaerobic means no O2. Anoxic means very little O2. We call our new bacteria heterotrophic nitrifier. This nitrifier uses NO3, and Food (BOD), and then turns it into Nitrogen gas (N2), Base (OH-) and energy. In this equation we use NO3, and other parts of the wastewater that we need to treat for, namely BOD. We also get a Base that helps combat the acid from the autotrophic breakdown. The byproduct is Nitrogen gas N2 that is release back into the air, and energy for the bacteria to survive and make more of themselves.
The cold weather that we have been experiencing slows this process way down in some instances as much as 50%. As a treatment plant operator, I need to keep this in mind. One useful trick is to slow down the flow through the plant. This increases the retention time, allowing the bacteria more time to do their job. Another trick is to increase the number of bacteria that I have at the plant. This allows more bacteria to do less work.
Now we can all stay warm by the fire in comfort, knowing that we are not the only ones that dislike the cold.
Sean Neeley
Waste Water Superintendent
Town of Shipshewana
