What We Do
We know we are doing our job well when our customers can "flush and forget". But, let’s learn how the Wastewater industry helps protect water quality and the environment!
What is Wastewater?
It’s not just flushing the toilet! Wastewater is any used water that goes down the drains in your home or business. When you turn on the faucet to wash your hands, wash your clothes, take a shower, run the dishwasher, rinse a cleaning sponge, etc., it is Wastewater (or sewage) once it’s in the drainpipe.
What is Wastewater Treatment?
Before Wastewater Was Treated Collecting and treating Wastewater is one of the most important ideas in history. Before modern Wastewater collection and treatment, wastewater went directly into streets, streams and rivers. The same streets that people lived along and streams and rivers where people took baths, washed clothes, and got drinking water. Because of this, many people suffered from disease caused by used water contaminated with waste (bad bacteria, viruses, chemicals, etc.). Diseases such as cholera, typhoid, and diphtheria were common.
The Clean Water Act Wastewater Treatment has been practiced in the United States for over 100 years. But, it was only since the 1970’s that strict standards for clean water, known as the Clean Water Act, were established. Two bills govern Wastewater Treatment plant activities nationwide and establish Treatment operation standards:
- Congress passed the 1972 Clean Water Act to restore and maintain water quality.
- Congress reauthorized the Clean Water Act in 1987 to further support water quality programs.
Wastewater Treatment Used water (wastewater) must be cleaned before it can be returned to rivers and streams. The used water cleaning process is called Wastewater Treatment. Treating wastewater is one defense against water pollution that helps make rivers and streams safe for people, fish, plants, and other living things.
The Process
Water left alone in a stream or lake will naturally clean itself but that can take a long time. Johnson County Wastewater (and other wastewater treatment organizations) clean used water in almost the same way that nature would but we speed up the process.
Wastewater Collection
The first step in the Process is to collect the wastewater and transport it to a wastewater treatment facility.
Wastewater leaves your home or business through a service line that collects waste from sources like toilets, sinks, dishwashers, floor drains. Flow from the service line enters to a larger sewer "main" that transports the flow to one of our wastewater treatment plants. The mains are usually made of PVC (a plastic), cast iron, or clay. Sewer manholes allow us to access the sewer mains to inspect and clean them. Manholes can be very dangerous. Only Johnson County Wastewater personnel should open and enter them!
Sanitary sewers are designed to carry only wastewater from homes and businesses and not to carry rainwater. Rainwater goes into storm sewers and creeks. You can see storm sewer inlets along the curb on many streets. Johnson County Wastewater uses pump or lift stations to help carry the wastewater to one of our plants. Lift stations are needed to pump the sewage to a geographic high point where gravity takes over and sewage flows to a treatment plant. After the wastewater reaches the plant, the treatment process begins!
Treatment
JCW treats wastewater each day to become the clean water you count on every day. Here’s our newest example of how!
Headworks Treatment
The used water (wastewater) goes through a bar screen in the first treatment step at at the Wastewater Treatment Facility. The bar screens remove larger items that find their way into the waste stream. Most of the debris that ends up on the bar screen is trash and shouldn't have found its way into the sanitary sewer. After the bar screens, the influent pumps lift flow to send it through the treatment system. The water then goes through a grit removal chamber which removes heavy things like gravel, seeds, and coffee grounds (grit). When the water enters the chamber, the “grit” settles to the bottom and is removed. The material removed by the screen and grit chamber is usually disposed of in a landfill. The water then flows to the next treatment stage - "Primary Treatment”.
Primary Treatment
Clarifier Treatment Unit
Large solid materials and grit are removed from the wastewater by bar screens and grit removal chambers, but, many smaller solid particles remain. The wastewater is sent through large circular tanks called "clarifiers" to remove these particles. Through the “sedimentation” process, flow moves very slowly through the clarifier where the small solid particles settle to the bottom and are removed. The removed material is called sludge. The sludge is treated separately from the liquid. The remaining wastewater contains mostly dissolved wastes and moves on to "Secondary Treatment”.
Secondary Treatment
Activated Sludge Aeration Basin
Secondary Treatment is a biological process accomplished by living microorganisms. Bacteria and other microscopic organisms use the waste for food. This is a common process which occurs in nature and we just speed up the process at the treatment plant. Wastewater treatment facilities create a microorganism utopia: optimal food, optimal oxygen, and plenty of space to grow. As the microorganisms feed on the waste we’ve flushed away, they grow and divide - very happily! The water is cleaned as the organisms feed and grow. The microorganisms that feed on the waste in the water are "bacteria", "protozoa", “rotifers” and “worms”. We sometimes call them “bugs”. The microorganisms also need lots of oxygen to grow. Since the wastewater itself doesn’t have very much oxygen, we make sure the environment has plenty of oxygen for them. Johnson County Wastewater uses three methods for creating a good environment for the microorganisms to eat, grow and, in turn, cleaning the water. Learn more about these amazing Microorganisms.
Trickling Filter Method At Nelson Complex, we use "trickling filters" where the wastewater is trickled over rocks (or other “media”) in treatment tanks. The microorganisms live on the rocks which are surrounded by air. As the wastewater trickles past the microorganisms, they eat the waste and grow. The trickling of the water also provides the oxygen the microorganisms need to thrive.
Activated Sludge and Biologic Nutrient Removal Methods At most of our treatment plants, the microorganisms (“bugs”) are grown in large aeration tanks. Large blowers blow air into the wastewater in the tanks to add oxygen and the bubbling air mixes the wastewater “food” and oxygen for the “bugs” to eat. Both the “Activated Sludge” and “Biologic Nutrient Removal” processes use this method to clean the water.
With the abundance of food and air, the microorganisms grow and multiply rapidly. It's not too long before the population of "bugs" is too large and some must be removed to make room for new "bugs" to grow. Excess "bugs" are removed by sedimentation in large circular “clarifier” tanks similar to the Primary Treatment process. The "bugs" sink to the bottom of the clarifier and are removed. The settled "bugs" and the sedimentation from Primary Treatment are referred to as "Activated Sludge”.
The cleaner water exits the top of the tank on its way to “Tertiary (third) Treatment” and the sludge is treated separately from the water.
After Primary and Secondary treatment, 85 percent or more of all pollutants in the wastewater have been removed.
Tertiary Treatment
Cascade Re-Aeration Structure at the Facility Discharge
Disinfection Before we release the treated water back to a stream or river, we kill any microorganisms that might cause disease. At some of our facilities, we use a solution that contains chlorine to kill them. Extra chlorine left in the wastewater is removed by another chemical. At other facilities, we use ultraviolet (UV) light to disable and kill the microorganisms.
Re-aeration As a final step in some processes, flow cascades down steps as it exits the facility. The turbulence and fall adds oxygen to the water making it safe for the aquatic life living in the stream.
Effluent Where does the cleaned water go when we’re done? We put the it back into a stream or river where it’s safe for fish to live and animals to drink. Wastewater that is cleaned and sent back to the streams is called "Effluent."