A non-partisan, neutral perspective supporting diversity in the color of water

Monday, March 15, 2010

Greywater and the Testing Trap

I have been late in postings about the recent Oregon Graywater Advisory Committee meeting held in Eugene, Oregon last week due to the last week of school challenges and glad tidings from my students.  As promised, the group addressed the dreaded kitchen sink wastewater issue.   One interesting surprise in the process was that a decision was not reached by consensus, but rather by consent, meaning that it was not a "slam dunk" to recommend to the Environmental Quality Council to treat kitchen sink wastewater. There was also an issue of a potential conflict of interest when it came to the voting, but what the heck, we are just an advisory group.

On the basis of the many postings in the Rainbow Water Coalition, it should come as no surprise that I voted against treating the kitchen sink wastewater.  No one in the group cared to ask why, but my reasoning has been clear from the onset of the advisory group process.  Where we will find the "greywater-o-meter" that will indicate the treated water is "safe"?  What processes will be acceptable, and what will be the "metrics of success" in the treatment process? All of this wrapped up in - "what will the casual greywater reuser be willing to do to ensure "safe" treatment?"

More importantly, it was never very clear what the risk was to "protect the public" - something that I was tacitly accused of not being sensitive to when I did not join the coalition in voting.  The advisory committee has a toxicologist from a state agency onboard to help with the process.  During past meetings, the toxicologist presented an interesting list of chemicals and microorganisms that have been documented in greywater derived from the peer-reviewed literature.  What was missing from the analysis was the apparent source of the various threats - our homes.  Yes, we are exposed to these threats in our homes - the greywater is simply the transport mechanism to move these threats from inside our homes to the outdoors.  Consider what I call the "Brita Filter Conundrum" - the Brita Filter is purchased by a consumer to "treat" the tap water for a variety of things they think are hiding in the tap water.  But the Brita Filters don't last forever.  If not changed on a regular basis, say every four to six months, bacteria become trapped in the filter.  So, what has been purchased to make water "safer" has actually caused the water to become less safe.  The Pogo Syndrome: "We have met the enemy... and he is us".

The second, and perhaps more important, facet missing from the analysis was a risk analysis or assessment; the bread and butter of toxicological work. The toxicologist was not asked to provide these analyses by the group so it was not an omission.  But it is an important next step in assessing whether or not greywater is truly a threat to our wellbeing since it comes from us to begin with. And some members in the audience also wanted some more "facts" regarding some statements they heard during the meeting.

What is the risk to our wellbeing from greywater, and specifically kitchen sink wastewater?  Art Ludwig of Oasis Design, perhaps one of the foremost experts in greywater reuse in the western US, and perhaps in the world has explored this issue.  Oasis Design asks the question - If you irrigate your fruit trees with kitchen sink water, how likely is a kid to get sick from eating the dirt under the trees?

I will paraphrase their analysis given that the answer they provide might offend those readers who are sensitive to the kitchen sink wastewater issue: "A risk assessment analysis of this scenario is viewable in the Arizona greywater study (can be viewed at the Oasis Design website). Note that they assume from the high level of indicators that there is a level of pathogens in the water corresponding to nearly a gram a day of fecal matter entering the kitchen sink. This could be accounted for by ten people (cleaning themselves after defecating) with their hands only and washing them off in the kitchen sink—an unlikely scenario, I dare say. (If nothing else, few houses have ten people in them!) Also, note that they assume that 100% of the dirt the child eats will come from the greywater-irrigated area, 365 days in a row." 

"Considering that even with these wild assumptions, the risk was on the order of 1 in 10,000 of the kid getting sick, the risk is probably not significant.

For comparison, let's look at the risk of attacks from the natural order compiled from How We Die:

Risk of death from botulism 1 in 2,000,000
Risk of death from fireworks 1 in 1,000,000
Risk of death from tornados 1 in 50,000
Risk of death from airplane crash 1 in 20,000
Risk of death from asteroid impact 1 in 20,000
Risk of death from electrocution 1 in 5,000
Risk of death from firearms accident 1 in 2,000
Risk of death from homicide 1 in 300
Risk of death from automobile accident 1 in 100

So, it appears that getting sick from eating dirt "contaminated"with kitchen sink wastewater is about on the same order as getting killed in an airplane crash or getting hit with an asteroid.  Taking it one step further, let's explore what the Center for Disease Control considers the National Health Objective for Campylobacter, one of the bacteria of concern - 12.30 per 100,000 - about the same number as the kid getting sick from eating dirt.  Other bacteria of concern are about one half this number.  There are no National Health Objectives for parasites such as Cryptosporidium.   

What is the problem?

Back to the testing issue.   Our new neighbors, Just Water Savers USA who attended the meeting to describe the Australian experience, shared an observation that overregulation is counter-productive.  People will go ahead and reuse greywater regardless of the regulations if they are overly burdensome, and the results can be contrary to the safe reuse of greywater.  

One the other hand, over regulation can also lead to no one reusing greywater even if it is legal.  According to this article, the State of Wisconsin is revising their greywater law (who knew they had one, apparently not even the residents!):  "The state technically allows for the use of graywater in homes, but State Rep. Spencer Black, D-Madison, who introduced the legislation along with Sen. Mark Miller, D-Monona, said the code is so confusing that most people are wary of installing systems. He added that, because of the strict language, some plumbers and local governments are under the false impression that graywater systems are prohibited under state law."

Kevin Masarik, outreach specialist with the University of Wisconsin-Stevens Point Watershed indicates "If you are going to be re-using the water to flush a toilet, it has got to have a certain pH, B.O.D. standard, and a certain chlorine residual so there is no harmful bacteria that will contaminate the water supply. That's kind of funny because you are just using it to flush down human waste.

So, it sounds like if someone is required to treat greywater before reuse, they are going to have to not only know something about microbiology, but also chemistry.  And that means that someone is going to have to use some sort of disinfectant such as chlorine (somewhat hazardous material), collect samples for regular testing (meaning - get near the "dangerous" kitchen sink wastewater with their hands, presumably in gloves, hopefully not spilling), testing with a BOD meter (usually takes a few days for the sample to be analyzed using the meter), and entering the data somewhere for later reporting in case there is a challenge from a regulatory agency, or gasp, a lawsuit.

Wisconsin determined that treatment of greywater was counterproductive to reuse - nobody thought they could do it based on complex regulations.  Australia found that overregulating of greywater reuse also lead to unintended consequences.

Later in the meeting, there was a discussion about what the site conditions need to be to permit greywater reuse, suggesting that the onsite septic tank siting criteria or the Underground Injection Control siting criteria, as a model.  Unfortunately, this leads to what I will refer to as the Site Testing Trap in a later posting.  A hint regarding the trap, though, is that greywater is not injected underground, but rather spread on the ground surface.  Installation of test pits or borings to learn more about the soil profile or depth to groundwater provide conduits of nearly infinite permeability to the same groundwater that one wants to protect.  The Canadians figured this awhile ago and that is why they consider poorly abandoned borings and poorly constructed wells as the greatest threat to their "buried treasure".  This observation should not be taken lightly given that Canada hosts the best groundwater school in the world - the University of Waterloo.  But I have been told that geology and science in general has a tendency to get in the way of good engineering projects and policy making.

Next posting, The Greywater Gauntlet....


  1. Did you ask a soil scientist? There's a real good chance that this kitchen sink water, with its organic constituents, is one of the best, or certainly not the worst, things we could do to the soil. As science will tell you, organic matter builds structure in the soil. Structure allows for maximum water retention, toxicity filtering, diversity of life, fertility....

    The kitchen sink water a threat to mankind?? Not likely is it. (unless we keep dumping it in the sewer!!)

    What's the old saying, "Don't eat yellow snow and don't drink grey water."

    I'm so happy to hear that the discussion is on the table! Hope is on the rise. Way to go guys!

  2. Anon:

    I will address the "soil science" issue in the next couple of postings, but you are correct, soil is a pretty remarkable substance when it comes to treatment of most of our "waste". Thanks for reading!

  3. Todd, it is great to read your blog on grey water. I have little to add to it. In South Africa we started using grey water irrigation systems 16 years ago and am yet to hear of a single incident of anyone getting sick from eating dirt or vegetables irrigated with grey water. I'll be awaiting your "soil science" issue.

  4. Thanks for the feedback, Alje. The Australians have been very vocal and creative about their success with greywater. But the South African story is not so well known (except we are discovering more from the Love and Mortar TV series). Thanks for sharing the news (or lack thereof) on sickness and greywater reuse. Thanks for reading!