Reclaimed Water: Grey is the new Green
Abrielle Chan
Tecumseh Elementary
Floor Location : J 211 V

During the summer of 2015, Greater Vancouver had a record breaking water shortage. Metro Vancouver was at a level 3 water restriction prohibiting us from watering our lawns with potable water. Due to this water shortage, greywater reuse must be reconsidered and implemented. Many people are reluctant to reuse their greywater such as bath water to water their edible vegetables because of a risk of potentially ingesting pathogens. My project’s goal is to show that pasteurization of light greywater along with a method of recapturing heat energy may be an efficient and effective way of reducing our domestic potable water consumption by up to 30 percent. In order for greywater to be safely reused, it must be treated to reduce the bacterial load. If the greywater is stored for example in toilet tanks, it must meet Canada Health Regulations of 200 cfu/100 ml of water. Different ways of sanitizing domestic greywater are available. These methods were evaluated based on the criteria: convenience, cost, effectiveness and energy efficiency. This project will demonstrate that pasteurization is effective in reducing the bacterial load of light greywater using Standard Plate Counts (SPC). Escherichia coli was used as an indicator organism for potential pathogenic bacteria. The model pasteurizing hot water tank that I engineered is energy efficient as it recaptures the energy from pasteurization and the residual energy from the greywater to heat up domestic potable water. By meeting Canada Health Regulations, greywater can be reclaimed to be used in place of potable water for irrigation of gardens and for storage in toilet tanks.