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The effects of water impurities on plant growth

The effects of water impurities on plant growth

Introduction: (Initial Observation)

Water impurities generally include minerals, viruses, bacteria and other organic material. Sewer water from homes and industries contain a large varieties of such water impurities. Currently sewer water is going through some initial treatment to remove some impurities and then it is discharged in rivers and oceans.

If water impurities are not harmful to the plants, part of such water can be used for irrigation and watering gardens.

In this project you will study the effect of water impurities on plant growth. You will limit the impurities in your experiments to household sources of impurities and you only do the test on non-food plants. What I am concerned about is that some industrial pollutants may even help the plant growth, however if they are used for irrigating farms, some hazardous chemicals may enter vegetables and crops, causing disease for people who consume them. In other words for each industrial hazardous pollutant and each plant a separate study is required. As a result of such studies, we may discover that certain plants may actually be able to decompose and destroy hazardous impurities.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Information Gathering:

Gather information about plant growth and the factors affecting the rate of growth. Read books, magazines or ask professionals who might know in order to learn about nutrients needed by plants. Also study about the role of plants in water filtration. Keep track of where you got your information from.
If you search the Internet, use keywords such as “Fertilizers“, “Plant nutrients“, “Plant Filtration” and “Plant pollutants“.


BACKGROUND: Experiments can be done to show how a plume of dissolved materials can move through soil and enter a groundwater aquifer. But soil and plants have something of a dual role in this process. Depending on whether materials are dissolved or suspended in the water, soils and plant roots can remove some or all of this material as the water moves down through soil.

Most suspended materials will adhere to the soil. These may then be broken down and used as food by the plants. Dissolved nutrients, such as nitrogen or phosphorus, chemically bond with some types of soil particles. They are then taken up by plants, thus removing them from the soil before they can enter an aquifer. For the plants, these elements are food, for an aquifer, they are pollution.

Not all materials are absorbed by plants and not all water pollutants are food for plants. However, sediments from eroding soil, nutrients in human and animal wastes, and some components of household wastewater (“graywater”) are excellent plant nutrients.

Plants also use different nutrients at different rates, so that the amount of material they take up will depend on how much is dissolved in the water and how fast the water moves through.

The plant communities clean the land by removing impurities into their own system. This removes the impurities from the air and water. Kind of how trees breathe in carbon dioxide and breathe out oxygen. It is the same process. This is extremely important to our plant! Continue…

Every pool needs oxygenating plants to keep the water crystal clear and pure. These plants grow under the water just like plants you see growing naturally in ponds and lakes. They absorb impurities from the water and liberate oxygen.  Continue…

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to find out how do water impurities affect plant growth.

The impurities that we will test are soap, dish washing detergent, tea, coffee, sugar, vegetable oil and salt. You may also test water insoluble impurities such as wood dust, sand, hair, plastic, leather, wool, cotton, …

It is also possible to test a combination of many different impurities, however you will not know which specific impurity contributed to any possible effect.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Independent (manipulated) variable for this experiment is they type of impurity.

Dependent (responding) variables are the plant growth related variables such as plant height and number of leaves.

Controlled variables are light, soil type, amount of water, temperature and other environmental conditions that may affect plant growth.


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

I think that none of the impurities that I am testing have a negative affect on plant growth. My hypothesis is based on my previous studies and gathered information.

I think some of these impurities will decompose and be absorbed by plant. Others such as plastics will remain unchanged with no effect on plant.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”


This experiment is designed to test the effect of water impurities on plant growth. The results of this experiment may provide useful information on usage of polluted water in growing plants.

Materials and Method:

In this experiment, fifty Kentucky Wonder bean seeds are planted in starter cups. They are arranged in five rows and ten columns. Each cup is labeled with a letter for its column and a number for its row. Each cup is filled with one forth cup of soil. A bean seed is planted in each. Each column represents one type of impurity that we are testing. Last column will be for the control experiment. Pure water.

Prepare the impure water samples with the highest impurity that can happen. For example use coffee with the same strength that we drink and consider it as a water polluted with coffee.

Columns A through I are watered with water containing impurities that you select. Last column will be watered with pure water.

Continue watering for about 3 weeks. Make daily observations and record any unusual change in any of the plants. At the end record the final result in a table like this. If any plant is dead or shows any unusual change, record it in the comments section.

Results table: Plant heights on final day.



Liquid Detergent

Then calculate the average plant height in each column and record the results in the average row of the table.

Materials and Equipment:

List of material can be extracted from experiment design.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


No calculations are required for this project.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.