The Metropolitan Water District is calling on Southern Californians to cut back on water use in yards because of an expected water shortage, due in part to a third year of dry weather in the Sierra Nevada.
The district is recommending growing drought resistant plants, reducing the frequency of lawn watering and keeping barrels to catch rain water.
Also threatening the water supply is a reduced amount of water coming from the State Water Project because of state regulations to protect the endangered delta smelt.
A team of engineers at UCLA are finding ways to stretch water even further.
Their research site is the backyard of a house at the end of a cul-de-sac in Mar Vista. The “Gray2Blue” filtration system is about the size of a refrigerator. Tubes carry soapy water from the home’s sinks, showers and laundry – called greywater – into a collection tank.
The regulations that govern greywater usage are difficult to navigate, although city officials are working on making them easier. This system adds another level – plants. The system is covered in a layer of plants, which help filters the water. The researchers call it “vertical wetlands.”
“These are bamboo, here are also some succulent plants planted here,” said Zita Yu, the UCLA doctoral candidate overseeing the project. “We also wanted to experiment with what type of plant would be suitable to be used for this type of system.”
The water circulates through soil and a layer of bio-film, drips into the tank, and after a few hours it’s piped into the backyard to irrigate avocado and citrus trees and a vegetable garden. It can also be stored for later use. Homeowners would just have to clean the screen filter in the collection tank two or three times a week. The researchers estimate the system would cost between $500 and $1500, depending on the quality of the components and the monitoring system. They figure that cost can be recouped in a year or two.
“Roughly about 50 percent of the water that is used in a home ends up as greywater,” said UCLA engineering professor Yoram Cohen. “And if we can reuse that water, you can immediately see that the savings in water is going to be tremendous.”
Cohen and Yu also plan to present their data to local and state water, health and zoning officials, to inform their decisions on how to regulate the further use of greywater in Southern California.