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Most water naturally has metals present in the form of dissolved ions. In surface water, such as lakes, rivers, and streams, the pH of water can greatly affect the concentration of metals found in it. Water at a lower pH can more easily dissolve metals. So, water with a low pH is more likely to contain larger amounts of dissolved metals like arsenic, lead, copper, and manganese.
The Environmental Protection Agency (EPA) has set limits and guidelines called maximum contamination limits (MCLs) that states use to monitor contaminants in their water. Because public drinking water is treated and regulated, there is a set MCL for many different contaminants, including metals, to keep consumers safe. This means that, if a public drinking water system is found to have a concentration of a contaminant above this set limit, action is required to remedy the issue. Private well owners are not required to follow these limits on metals. However, MCLs can be used as a guideline for well owners to help ensure the safety of their water. Wastewater effluent that is discharged has a set of limits similar to an MCL for drinking water, but the limits are set a bit higher because contaminants in wastewater do not pose as high a threat to humans as those in drinking water.
These limits are put in place to protect consumers and the environment.
| Contaminant | Issues Related to Contaminant | Drinking Water MCL(mg/L)* | Wastewater Effluent Limitations(mg/L) |
| Lead | Lead is harmful to children and adults. In children, exposure to lead in drinking water can lead to slower growth, learning/behavioral issues, and anemia. In adults, exposure can lead to cardiovascular issues, decreased kidney function, and reproductive issues. | 0.015 | 0.05 |
| Arsenic | Arsenic can cause skin damage and may increase a person’s risk for cancer. | 0.010 | 0.04 |
| Copper | Copper can cause gastrointestinal issues and, over time, it can lead to liver or kidney damage. High concentrations can cause water to taste metallic, and it can cause blue-green staining on laundry. | 1.0 | 11.0 |
| Manganese | Manganese can cause water to taste metallic and bitter, and it can cause black staining on laundry. | 0.05 | 0.2 |
* Reclaimed wastewater must meet these requirements in order to be used.
Water is an essential liquid for all life. Humans use it for many things like consumption and recreation. Freshwater is the source of our drinking water and includes surface water like lakes, rivers, and streams, as well as groundwater from aquifers.
If you are like most people, you probably do not enjoy drinking water that is contaminated. Luckily, public drinking water systems in the US are some of the safest in the world due to regulations set forth by the Environmental Protection Agency (EPA). However, no system is perfect, and contamination by various pathogens can still occur, even if it is rare.
Some water systems, such as water from private wells, are more prone to contamination than others. This is because private wells are typically not maintained as frequently as public water systems and are not subject to the regulations of the Environmental Protection Agency (EPA).
Bacterial contamination of water often causes people to experience gastrointestinal issues. These issues can include abdominal cramps, nausea, vomiting, diarrhea, and if the issues are severe enough, even death. However, many of the organisms that are considered contaminants also occur naturally in the digestive systems of animals, including humans.
How do drinking water systems become contaminated?
Actually there are several ways in which drinking water can become contaminated. These include:
The following are examples of organisms that can contaminate drinking water.
Escherichia coli (E. coli)
E. coli is naturally found in the digestive systems of animals. There are several strains of E. coli, many of which do not cause disease. A notable disease-causing strain produces Shiga toxin. The presence of this bacteria is an indicator of water quality issues in both drinking water and wastewater. No strains of E. coli should be found in drinking water samples. It is common, and probably unavoidable, to find some concentrations of E. coli in recreational surface water.
Salmonella
Salmonella is another common biological contaminant of water. While testing water for E. coli is required, testing for salmonella is not. There are many species of Salmonella. Many of them can cause disease, especially in children. Salmonella is also associated with fecal matter and can be introduced into a water system by animals.
Shigella
Shigella is a less common contaminant of drinking water. This group of bacteria is responsible for the broader diarrheal disease called shigellosis. A specific species of Shigella is for dysentery, Shigella dysenteriae. Fortunately, this species is not as common as others in the US. Most often Shigella is picked up by ingestion of contaminated recreational water during swimming. It can also be contracted by drinking contaminated water. Shigella is very contagious and can be spread further through contact with surfaces contaminated with stool from an infected person.
Great job disinfecting your work area! Even if the bench looks clean, microbes could be lurking. Using the appropriate cleaning solutions will kill any biological contaminants that might affect the success of your experiments. Curious to see what might happen if you don't clean your bench? Try it after you've completed all the stations in the lab, to see what happens to your results. Remember, once samples are contaminated, you have to restart from scratch.
Your plated samples have been placed inside the incubator. The temperature is set to 35.0° C and will prevent non-target organisms from growing, while allowing any total coliform or E. coli to grow.
Start the timer to continue.
Sample incubation is complete! Your samples are now ready to be analyzed in the UV light box.
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You've got mail! It looks like All Metals Lab Corp has completed their analysis of those samples. Go ahead and check out the results and record them in your project notes!
These samples need metal analysis; however, our lab is not equipped to analyze them, so they will need to be subcontracted out. Please mail your samples to All Metals Lab Corp.
Excellent, you've got your PPE on. Putting on your personal protective equipment before handling any chemicals – even those used to disinfect your bench – is very important! Gloves protect your hands, goggles protect your eyes (many of these even fit over glasses), and a lab coat will keep chemicals off of your clothes and skin. PPE will also help protect your samples from contamination. Now it's time to disinfect your station!
DoDo wear appropriate clothing.
Do become familiar with where safety equipment is and how to use it properly.
Do wear appropriate PPE.
Do ask questions if you are unsure of the requirements of the lab.
Do keep your lab bench and communal areas tidy and clean.
Do treat every chemical as if it is dangerous.
Don'tDon't eat or drink in the lab.
Don't take experiments home.
Don't mix chemicals unless specifically instructed to.
Don't touch, eat, or drink lab chemicals.
Don't run or roughhouse in the lab area.
Experiment. Fail. Learn. Repeat.
All recorded information and progress will be lost.
Be sure to put on your personal protective equipment (PPE) before using or handling any chemicals – even the ones you use to disinfect your work bench. If you don't, you could potentially injure yourself!
You need to prepare your assay plates before placing them into the incubator.
This tool is only used to test liquids, so you'll need to prepare that first. These probes are expensive, so we don't want to break them by using the incorrect matrix.
Be sure to prepare and incubate your samples before analyzing them, otherwise you won't be able to tell if something is growing in them.
Your samples have been sent to All Metals Lab Corp for additional testing. You can check your inbox as often as you like, but keep an eye out for a notification icon in the lower-left when new mail arrives.