The Ins and Outs of a Septic System

How often to do you think about where the water goes when you flush your toilet? Maybe never until the toilet doesn’t flush or there is wastewater backing up into the tub. Many homes throughout the U.S. are connected to a utility but onsite wastewater disposal systems are also common. According to the Environmental Protection Agency (EPA), an estimated 4 billion gallons of wastewater nationwide is collected, treated, and released from onsite wastewater systems per day.

Onsite wastewater disposal systems can be effective in the removal of pathogens (bacteria and viruses) but can also be major contributors of nitrogen and phosphorous to groundwater and surface waters; a potential problem that is propagated due to septic systems not always being correctly sited, installed, or maintained. Groundwater represents about 97 percent of the earth’s fresh water resource and needs to be protected from potential sources of contamination. Nitrates in drinking water supplies may adversely affect public health and are linked with methemoglobinemia (blue-baby syndrome), increased risk of cancer, and other possible health effects. Excessive nutrients, such as phosphorous and nitrogen, in surface waters can lead to eutrophication and decreased dissolved oxygen leading to adverse effects on aquatic species.

The most common type of onsite wastewater system is a septic system which generally consists of a septic tank and soil absorption system. If a septic system fails to treat wastewater properly, namely complete denitrification, this may lead to contamination of groundwater and surface water. The focus of our Coggle is on nitrogen cycling through a septic system and the ultimate fate of nitrogen released to the environment.

After exploring the coggle, you should be able to answer the following questions: ?

What are the sources of nitrogen input to wastewater?
What makes the septic tank and anaerobic environment?
What types of microbes transform ammonia or ammonium to nitrite, and what do they gain from it?
What happens to nitrogen present in wastewater? Can it pollute groundwater?

Brought to you by Kimberly Fitzgerald, Aasne Hoveid, Ankur Sachan, and Tonya Bear  



It’s More than just Rotten Eggs, It’s the Sulfur Cycle!

The sulfur cycle is made up of 4 steps: mineralization, oxidation, reduction and incorporation.  Sulfur is one of the main constituents of many proteins, vitamins and hormones. Sulfur is   often found in oxidation states that can range from Sulfates to In the soil environment, sulfur can be produced in either an organic or inorganic form. The sulfur cycle contains both atmospheric and terrestrial processes. In the inside of the terrestrial portion, the cycle begins with the weathering of rocks, which is what releases the stored sulfur. It is imperative to learn about how exactly the sulfur undergoes mineralization in the sulfur cycle. For this case, sulfur is mainly cycled throughout the soil environment and sea water in the marine environment.
Oxidation is the process of losing an electron from an element or compound. In the sulfur cycle there is a sulfide oxidation and a sulfur oxidation, each of these processes are performed by microbes in anaerobic environments such as a hotspring.  Sulfate reduction is a process carried out by anaerobic microbes which transforms sulfate into sulfide. These microbes are a diverse and varied group both genetically and physiologically, and are typically found in aquatic environments, where they act as decomposers. However, they are also present in great numbers within sulfur springs, such as those in Yellowstone, where sulfate is abundant and continually replenished. Incorporation involves the process of changing sulfide into organic compounds. This can include metal-containing derivatives. Microorganisms have the ability to immobilize sulfur compounds, which ultimately results in subsequent incorporation of these sulfur compounds into the organic form of sulfur.. The sulfur cycle is important because of how abundant it is in our environment. Take a look at our interactive coggle to learn about each of these parts more in depth.

Scavenger Hunt-Find the answers to the following questions in the coggle

  1. What is one practical application for sulfate reducers?
  2. Where does oxidation in the environment occur?
  3. What exactly would happen to sulfide if it were to be incorporated after oxidation and reduction?
  4. What are the three major processes that control the amount of sulfate in the oceans?

Scavenger Hunt Answers click here

To go to the coggle click here  

Collaborators: Kirsten Veech, Connor Ito, Alisa Thiede, Zachary Snelson

Phosphorus Cycle in Soil

Phosphorus, an essential nutrient, is a key component of molecules necessary for life, including energy (e.g. ATP), lipids, and DNA. Phosphorus exists in both organic and inorganic forms in the environment, initially entering ecosystems through weathering of bedrock and then cycling through soil, water, and organisms. Microbes are integral to the cycling of phosphorus, as they mediate transformations many within the phosphorus cycle, including immobilization, mineralization, and solubilization. Within this interactive Coggle, we present the various transformations of phosphorus between inorganic and organic forms and describe how these are mediated by microbes. Multiple mechanisms can be behind each transformation, and there is an abundance of literature available for you to dive deeper and explore each process!

You might be wondering: why it is so important to learn about the role that microbes play in phosphorus cycling? In addition to being an essential nutrient that all organisms need to live, phosphorus in high concentrations can have negative impacts on biota within freshwater ecosystems, causing harmful algal blooms and eutrophication. With increasing food demand due to a growing human population, the use of fertilizers containing phosphorus has increased in recent times, impacting surrounding ecosystems. Use the scavenger hunt questions below to help guide your exploration of the phosphorus cycle.


Scavenger hunt questions:

  1. What process in the phosphorus cycle is the opposite of mineralization?
  2. What are three factors that can influence phosphate mineralization in soil?
  3. What kind of phosphite oxidation (BPO or APO) would occur in the following environments? (Top later of loosely packed soil? Lake sediments?)
  4. What is the main limitation of phosphate-solubilizing microorganisms?

Collaborators: Presley Coryell, Sophie Weaver, Taylor Seitz, Alex Wynne

The Ferrous Wheel: A Perspective on the Iron Cycle

While you won’t find the ferris wheel that is a staple of the county fair, this coggle will introduce you to a different kind of ferrous wheel- the cycle of the transition metal, iron. Iron naturally exists in two states: ferrous iron, Fe(II), and ferric iron (III). These forms can exist as ions, or minerals, where they are bound to oxides. Iron is not only important to human life where it serves as cofactors in chemical reactions, but also to many microbes, where it drives their metabolism. It is prevalent in terrestrial environments, in oceans, and even the atmosphere. Preservation of the iron cycle is critical to the fluidity of geochemical cycling, as it plays a role in nitrogen cycling and limits phytoplankton’s ability to perform photosynthesis.

In this coggle we describe how microbes facilitate the anaerobic transition between ferric and ferrous iron, how microbes covert ions to minerals, and how iron enters the cycle. We presented this research in the framework iron cycling in the ocean, (including the role of phytoplankton), but the microbial iron cycle is diverse, and one step can happen via multiple mechanisms. This leaves much more to learn and explore, and we urge you to use this project as your first step into the ferrous wheel.

Begin on the left side with the entry “Mineral Iron II Flux”, and follow the blue arrows around the ferrous wheel. Click and drag to view different parts of the coggle


Team: Ben Hedges, Bayli Mohl, Karen Biondich, Courtney Hill and Mark Velasco

Scavenger Hunt: challenge yourself to complete these by reviewing all of the posts

  1. What method of iron oxidation was likely the first, evolving in ancient oceans?
  2. How can diatoms uptake iron into their cell bodies?
  3. Do anaerobic iron reducers need to import the iron?
  4. What is it about sea water that allows for the rapid oxidation of iron?
  5. Which ocean experiences the greatest input of aerial dust from the Earth’s major deserts?