You’ve probably heard the term Net Zero Energy before, but have you ever heard the term Net Zero Water? This up-and-coming concept is considered one of the most stringent goals laid out in the Living Building Challenge (LBC). Sure, the LBC requires a building to abide by Net Zero Energy rules, follow a strict materials list, have all goods and services produced locally, recycle all construction waste, maintain excellent indoor air quality, and more. However, probably the most abstract prerequisite of this challenge to us is the water independence aspect.
In order to achieve water independence, a building must capture all precipitation, manage all storm water runoff, and re-use all household wastewater. ”Wastewater” can either be considered greywater or blackwater, depending on the source and contact with organic matter. Greywater is not riddled with pathogens, but is still not clean enough to be used for potable (drinking) purposes. Greywater comes from places like the laundry machine, the bathroom sink, showers, and baths. Blackwater has come into direct contact with organic matter and/or human waste. Blackwater sources include the garbage disposal, toilets, and sometimes dishwashers.
It may sound a little disturbing at first, but you won’t be drinking your treated toilet waste or anything, that serves better to be treated and re-used to irrigate, flush toilets, or to cool HVAC systems. Different types of water require different types of treatment. For instance, rainwater can be captured, stored, and treated with a relatively insignificant amount of energy. This is because rainwater is fairly clean – it just requires ultra-violet sterilization to be used for drinking purposes.
Greywater can be naturally filtered in a constructed wetlands system, or a “Living Machine.” In order to treat this water, you simply let gravity carry it through each chamber in the Living Machine, where plants and animals naturally clean it as they would in nature. Here’s a diagram from a past project of mine showing how this system works:
Although there have been attempts (2, 3) at achieving the LBC standard, so far none have completed the task. Net Zero Water is an idea we’ve been kicking around at Postgreen, and it seems to be the main hurdle we’ll need to leap before achieving the stringent standard.
I’ve put a site up pertaining to net zero water, which aims to compile some of my thoughts and research on the topic, as well as provide a place for discussion and the sharing of information. Please check out NetZeroWater.com and feel free to subscribe to it for updates!
Related posts:
{ 1 trackback }
{ 8 comments… read them below or add one }
Some great suggestions, but where are the details? Is the roof area large enough of the average home in proportion to the occupant’s water demand? What does this do to the water table levels? Is the land(lot) area large enough to adequately filter black/grey water? If not, what does this do to the waste/waste-water that goes to the sewage treatment facility? What about water storage installation costs, requirements, and problems?
Why not implement current technology that is available and/or proven? How about adding a pressure tank to a current system so faucets can be stepped down from 2.0-2.5 g.p.m. in the bath/shower to 1.5-1.0 g.p.m.? How about a shower valve(remember the show “MASH”) that can be pulled by hand(or foot) to conserve water ON TOP OF an extremely low-flow showerhead?
I’m not trying to be confrontatial , but be a stone roller instead of a rolling stone! This is the most progressive blog/web-site in relation to the construction industry, I’m just asking that you provide a realistic solution.
A waterless urinal for the boys in the house.
In some states it’s illegal for you to store and reuse the rainwater. Just another law that needs changing.
Tom-
Valid points, there are a lot of water metering issues we’ll have to work out. We’re trying to evaluate water usage in the current Postgreen homes, as they tend to be a good amount different from an average home.
Blackwater treatment is difficult to install because it is pretty expensive to put in membrane bioreactors. However, on a project with 6-10 homes, there could be a community treatment area that all the homes have in common. UV sterilizers are relatively inexpensive and can be hooked up to the faucet itself.
As with almost everything of high-efficiency these days, the water storage and installation costs may seem steep, but achieving water independence will pay for itself over time.
As I stated, there are metering issues and statistics to be collected, so at this stage it’d be tough to say exactly how much water the super-efficient Postgreen homes will be using.
GreenBuildingDenverdotcom-
Waterless urinals are great, but as you’ve stated there are pretty high-profile problems with them in terms of code. There are also several code issues with collecting, treating, and re-using grey and blackwater from your home. In Oregon, several laws have been changed, and even in Pittsburgh right now they are being reviewed.
There will have to be regulatory changes in order to achieve a new level of green building, but with enough backing I am optimistic that it can happen.
Aside from waterless urinals, we’ve also been looking into compost toilets. This would take a huge strain off the amount of blackwater to be treated.
I am interested in getting closer to net zero water. To be independent of water and wastewater utilities would be great. Keep up the good work. Santa Barbara will be tough with only 18 inches of rainfall in an average year. We have had some with only 7 inches and others with 40 inches.
I may have mentioned this before, but in the late 70’s under the carter administration and all the subsidized evironmental programs, a book entitled “the Autonomous House” was published with the help of a governemtn grant. It is net zero everything. It has a similar system for water filtration, as well as passive and active solar, etc. etc.
This is 30 years old, before the term “Green” this is PreGreen.
What’s the point of having an individual house with zero net water? The city or town you live in is net zero water, just on a larger scale. The municipality already handles all the water treatment issues more economically than anyone’s house ever could.
Reducing water usage as much as possible is a worthy goal, but I’m skeptical that processing all your water on your site within a city would ever make sense for safety reasons.
Rainwater collection is also a worthy goal, since gallons cost dollars.
Water Legacy is a Colorado manufacturer of of greywater reuse system that should be considered in the Net Zero Water Initiative. The Company is new and has a number of interesting projects. PLease check out the web site and ask questions.
In MN there is a company called Equaris and they do this now, I believe.
I met this guy several years ago. Very interesting background and technology. One piece of trivia that has stuck with me: He told me after he retrofitted his house he re-purposed the well from pulling up water he no longer needed to the piping necessary for a geothermal system.