West Texas A&M Residence Hall
Client: West Texas A&M
West Texas University was planning Phase 2 of its Underclassman Residences and was interested in saving water by harvesting and reusing greywater (graywater) from showers and sinks to flush toilets. Continued drought in Texas raises serious issues about the long term supply of potable water, and the University wanted to demonstrate its concern for water sustainability while making a real impact on its water use and water and sewer costs. Unlike rainwater systems, greywater (gray water) systems enjoy a highly reliable source of on-site water that can easily meet demand for toilet flushing and still have processed non-potable water available for irrigation.
System Type: Greywater for Toilets & Irrigation
Commissioning Date: August, 2013
Challenge: The university wanted to maximize water savings, but there was concern about water quality, especially since the raw greywater would be collected from dorm room lavatories that might contain some food waste.
Solution: Wahaso ran an analysis of supply and demand and found that the projected supply of greywater exceeded by several times the amount of processed non-potable water needed to flush toilets. We proposed storing excess processed greywater in a secondary 10,000 gallon tank to use for irrigation. A special pre-filtration step was included to separate out the excess waste coming from the lavatory sinks that would have otherwise fouled the filtration system. Chlorine was also added early in the process to stop bacterial growth in the raw greywater.
Results: The system can harvest over 10,000 gallons per day when school is in session, providing sufficient processed water to meet 100% of toilet flushing demand and over 600,000 gallons of irrigation water annually. Estimated annual municipal water savings will add up to nearly 1.2 million gallons.