What is Net Zero Water?
Similar to Net Zero Energy, which produces energy on-site and doesn’t ever consume more than it produces, Net Zero Water is a standard that sets out to close the loop of a household’s water consumption. In order to achieve this goal, rainwater that falls on-site is collected and stored, and all wastewater produced by the building or its occupants is treated and re-used. Rainwater is the primary source of freshwater in many regions of the world and is the easiest to treat. Filtration followed by ultra violet sterilization can make rainwater potable. Greywater is wastewater produced by the bathtub/shower, washing machine, and bathroom sink. It is not potable, but it also doesn’t have all the pathogens and bacteria blackwater has. Blackwater is the murkiest of wastewater produced in homes. It comes from toilet flushes, the kitchen sink, and the garbage disposal. Blackwater is difficult to treat because it contains organic matter which must first be separated out from the wastewater.
Rainwater, greywater, and blackwater are treated differently to achieve different outcomes. For example, in order to supply potable [drinking] water to the house, rainwater or greywater must be treated thoroughly, and without the use of chemicals. In this case, rainwater is cleaner than greywater and therefore takes less energy to purify, but a household’s specific demands will determine how much water is necessary.
Why does this concept interest me?
Water is a precious resource and is absolutely vital to life. We’re not using water efficiently right now, and I don’t think it has to be that way. 80% of the wastewater we produce in our homes is greywater, while only 20% is blackwater. Instead of treating each separately, since greywater requires much less energy to treat than blackwater, we are mixing them together, which contaminates the greywater with pathogens, and we are then forced to treat everything as if it were blackwater. This inefficiency doesn’t cut it in today’s innovative and intelligent age.
Right now, potable water is used for pretty much all household demands – whether it be toilet flushes, drinking, irrigation, washing laundry, etc. This means that we’re spending a lot of extra energy treating water to a higher standard than is necessary. In places where there is no human contact, such as toilet flushes and sub-soil irrigation of non-edible crops, we do not need fresh, potable water. We can lightly treat greywater produced on site and return them back into the system for these types of uses.
What am I planning to accomplish by researching this topic?
It’d be great to see net zero water in action in Philadelphia, but I’m just curious at this point. I want to research what others are doing (such as Phipps & CCC) and get a true understanding of sustainable water use systems.
Water independence in homes would be a huge step forward in relieving the city’s treatment plants of a huge burden. Also, I think it’s important that people know where their water comes from, how it is treated, and how it can be used. That’s one thing a lot of us have lost sight of.
