A non-partisan, neutral perspective supporting diversity in the color of water

Wednesday, January 30, 2013

Greywater to the Rescue

Eighth grade water reuse expert Avni Limdi is a follower of the Rainbow Water Coalition. She contacted both Waterwired and the RWC for advice on her science fair project a couple of months ago. Waterwired served as the online mediator of the information exchange posted here.

Avni contacted me two days ago with the following news:
Thank you so much for your help with my project. It really paid off, I made it to reigonals science fair! Attached is my science project report. Once again thank you for all your assistance!
Blogger does not permit attachments, so the RWC highlights another Great Greywater Student Project with some of the findings of her 30 page report titled "Greywater to the Rescue"  


Hypothesis

If grass specimens are watered with biodegradable graywater, graywater, and tap water over an approximate six-week duration, then all grass specimens watered with biodegradable graywater will grow at least 1 centimeter taller than those watered by graywater and tap water. If Dracaena Godseffiana (Indoor) plant specimens are watered with biodegradable graywater (BGW), graywater (GW), and tap water (TW) over an approximate six-week duration, then all Dracaena Godseffiana specimens watered with biodegradable graywater will grow at least 0.5 centimeter taller than those watered by graywater and tap water. The evidence to support this is that biodegradable detergent contains ingredients that will both enhance growth and not harm the specimens.

The independent variable is the type of water used to water the specimens: biodegradable graywater, graywater and tap water. The dependent variable is the height of the plant or grass specimen: measured in centimeters. The control group is the plants and grass that are watered with tap water. The constants are amount of water used to water all specimens, environment, and type of soil used for each specimen type.


Conclusion

The purpose of the experiment is to determine if different types of water affect plant growth. The  hypothesis of the experiment was if grass specimens are watered with biodegradable graywater, graywater, and tap water over an approximate six-week duration, then all grass specimens watered with biodegradable graywater will grow at least 1 centimeter taller than those watered by graywater and tap water. The hypothesis for the Dracaena Godseffiana (indoor) plant specimens was if plant specimens are watered with biodegradable graywater, graywater, and tap water over an approximate six-week duration, then all Dracaena Godseffiana specimens watered with biodegradable graywater will grow at least 0.5 centimeter taller than those watered by graywater and tap water. The evidence to support the hypothesis is that biodegradable detergent contains ingredients that will both enhance growth and not harm the specimens.

The hypothesis is partially supported across both plant and grass specimens. The results show that for both plants and grass, all specimens watered with BGW grew most, the specimens watered with GW grew second most, and the specimens watered with TW came last.

For grass, BGW grass specimens grew 1.33 centimeters more than TW grass specimens, thus proving the hypothesis (> 1 centimeter). On the contrary, for grass, total growth difference between the BGW specimens and GW specimens was only 0.78 centimeters, thus disproving the hypothesis (< 1 centimeter).

For plants, BGW plant specimens grew 0.83 centimeters more than TW plant specimens, thus proving the hypothesis (> 0.5 centimeter). On the contrary, the BGW plant specimens grew 0.37 centimeters more than GW plant specimens thus disproving the hypothesis (< 0.5 centimeter).

The scientific explanation for the results is that both biodegradable graywater and graywater contain organic matter in them, like suspended solids (food particles), dead skin cells, hair, bacteria, enzymes, and residue from kitchen and laundry sinks that could have spurred growth. Agricultural studies show that organic matter is a known reservoir of nutrients that can be released to the soil. Each percent of organic matter in soil releases 20 to 30 pounds of nitrogen and 4.5 to 6.6 pounds of phosphate. The increased nitrogen and phosphate availability and higher uptake would result in spurred plant growth. Scientific research shows that organic matter behaves in a sponge-like manner, with improved water absorption and retention and ability to release most of that water to plants. Additionally, organic matter improves soil structure by causing soil to clump and form aggregates. This causes the soil to have better water permeability, which in turn improves soil’s ability to take up and hold water. Organic matter presence also improves toxicity filtering, fertility and diversity of life. Tap water contains chemicals like chlorine and other disinfection by-products that could hinder growth and affect the results.

This experiment concludes that graywater and biodegradable graywater can be safely used to water grass, and in fact may be preferable over tap water. By the third week in the experiment, the GW plant specimens were losing leaves, and many leaves showed signs of wilting, several leaves were exhibiting leaf burn, but overall the plants were still showing growth. So it is important to note that for indoor plants, graywater may not be the ideal type of water to use.

Attempts to limit errors included, keeping the same type of soil, using the same amount of water, watering all specimens at the same frequency and time, and keeping the same environment (southwest sunlight exposure and 70 degrees temperature). Some possible sources of error were the inconsistent amount of dirt or soil on the clothes and dishes used to make graywater and biodegradable graywater.

Some improvements to the experiment could include monitoring dryness of each specimen soil, measuring soil water retention, measuring soil pH, ensuring on a regular basis that drain holes were not clogged, measuring presence of chlorine, disinfectants and harmful contaminants in tap water. An expansion of this experiment could be to study the effects of graywater on the soil as well as study different types of plant specimens such as outdoor trees, ornamental bushes and crops. Another expansion could be to test several other types of water, like greenwater and redwater, on plants.

In the real world, this information can be used to help the world in many ways. If graywater is used to water lawns and other plants, it will save a great deal of freshwater. Valuable freshwater will no longer be needed to water lawns and other plants, and graywater will not be drained into the sewer. By reusing graywater, we will conserve freshwater for future generations.

The Water Resources Graduate Program at Oregon State University awaits Avni's application to graduate school.
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Almost everything that is great has been done by youth. 
~Benjamin Disraeli 


2 comments:

  1. I think this experiment should be widely considered by cities not only for the fresh water that can be saved by using GBW and GW but also for the additional growth of plants. Many cities limit water avaliability for yards during the summer. In our city many lawns turn brown including the parks and college lawns. With the use of GBW and GW these lawns could be maintained and green while saving fresh water.

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  2. Very interesting. We discuss water conservation and more at our blog, where we deal with using greywater to cut down on waste. Go Green, Go Grey

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