The Effect of Greywater on Plants

Francis Lawton an 8th grader at St. Timothy School in Los Angeles, CA utilized microBIOMETER® in his science fair project titled “The Effect of Greywater on Plant Growth, Soil Microbial Biomass Carbon, and Soil Fungi to Bacteria Ratio. Francis took first prize at the fair and moved on to the Los Angeles County Science & Engineering Fair where he placed 3rd in his category of Ecology. He also received a special award from USAID (U.S. Agency for International Development). Francis then took part in the California State Science & Engineering Fair in the category of Earth & Environment (Air/Water) and placed 2nd!

Have a science fair project coming up and would like to incorporate microBIOMETER®? Please contact us!

Project Abstract:

This project was designed to find out if greywater and treated greywater can safely hydrate plants, and promote plant growth, just as well as tap water. I live in drought-prone California and it’s important to find different ways of conserving water. My experiment tested the watering of grass pots with three different types of water (independent variable): Tap water, Greywater, and Greywater treated with Activated Charcoal. Over the course of 8 weeks, I measured plant growth, soil Microbial Biomass Carbon (MBC) levels and soil Fungi to Bacteria (F:B) ratio (dependent variables). Many controlled variables ensured a valid experiment. I hypothesized that each of the water types would result in the same growth rate, soil MBC and soil F:B ratio. My hypothesis, however, was incorrect. Greywater resulted in stunted growth and spiked the F:B soil ratio so high that the pot sprouted 13 fungi heads. Tap water and Treated Greywater, however, were equally good in terms of healthy plant growth and both pots had the two best average F:B ratios closest to 1:1 (which is the best ratio for grasses). Neither of these pots produced fungi. Soil carbon levels (MBC) fluctuated for all three plants, however each plant maintained an “Excellent” level. This indicated that each water type was fine for watering grass if you don’t mind stunted grass growth and some fungi in your lawn. My experiment also proved that Activated Charcoal effectively “adsorbs” chemicals in greywater that alter a soil’s F:B ratio.

Leave a Reply

Your email address will not be published. Required fields are marked *