EXTREME Do-it-Yourself Resilience: A Home Scale Waste Water Treatment Plant

Today’s extreme DiY example is a home scale water water processing plant designed and prototyped by Bob Crosby.  Bob is originally from Alaska, but I interacted with him while he was in Costa Rica, working on a resilient community that’s being built there.

Bob has spent a good portion of his life designing and tinkering with systems to turn homes into productive living systems.  Fortunately, he’s both a talented engineer and he’s willing to share the fruits of his efforts with those of us with the foresight to understand their value.

Why would you want to process waste water?  Lots of reasons.

Water is expensive or use is limited (rationed).  You live in a very arid location.  You live off grid.  Your well is going dry.  Your expensive home septic system is broken.

DiY Waste Water Treatment

The solution?  Build your own water processing plant and put it in your basement.

Bob’s waste water treatment prototype can turn about 100 gallons of sludge water every 24 hours into PH neutral, oxygen rich, and oderless water that is ready for irrigation – or – some additional treatment that will make it potable.

Bob’s DiY design requires about $300 for some simple materials and a couple of weekends to build.  This is in contrast to commercial systems that costs tens of thousands to build.  Additionally:

  • It’s modular.  The process is divided into three different modules that make construction, repair and recombination easier.
  • It doesn’t require much to maintain since it doesn’t have any moving parts or corrosive parts that come into contact with waste water.
  • It’s inexpensive to operate.  It uses only 17.5 watts continuously (about ~$0.05 a day).

Here’s what the completed system and some of the steps needed to build it looks like:

The system is divided into three parts:

  1. A surge tank that smooths and slows rapid inflows from the home’s septic system.
  2. A settling tank for letting the sludge sink to the bottom and serve as “sludge blanket” that filters and anaerobically composts incoming, low flow waste water.
  3. A bio-filter to filter and aerobically compost harmful biological contaminates.

Here’s what the schematic looks like and some of the steps in the construction process.



If you want more detail on how to build this system as well as its capabilities, please visit Bob’s site.


Your always excited to see innovative thinking solve everyday problems analyst,




PS:    If you need more help on building waster water systems, Bob’s available for consulting at info@biorealis.

PPS:  For more discussion on productive homes versus the boxes we live in how, read this: is your home a box or a dynamo?.

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  • pragmatic sustainability

    FYI, The Health Departments will lose their mind if you try this.

    However, having one ready to go is definitely a good idea.

    The Surfer’s Journal recently had an article on the New Zealand earthquakes and the 2 yr timeframe to repair the sewer system. It silted up during the earthquakes. They are pumping raw sewage directly into the ocean.

    In the event of a big natural disaster, this is a great piece of infrastructure.

  • http://www.sisconsecurity.com michael


    Great post!

  • http://www.blueherontexas.com Christian S

    John, when you say

    “A surge tank that smooths and slows rapid inflows from the home’s septic system.”

    At what point in the septic system does this inflow come?

  • Chris Lindstrom

    Hey John,

    What about good old fashioned composting toilets? Why use water at all when you don’t have to? For anyone in Miami, I’m about lead a composting toilet workshop in Little Haiti.


    • johnrobb

      Chris, Those work too. JR

    • http://pennypincherpersonalfinance.blogspot.com Penny Pincher

      Chris, the same people have plans for composting toilets, just visit their site.

  • http://Wolfeintransition.blogspot.com magnus wolfe murray

    This is a great post. And good to see your site. I’ve been wanting to start a resilient community design site for a year or two but don’t have time. I work in humanitarian aid / early recovery, post disaster. Currently in Pakistan but globally as per needs. There is huge need and scope for innovation in our response, and some funding for research. Would like to link aid world with these type of off-grid, low tech, low cost systems that offer people energy independence and durable water / waste water treatment, better building designs etc. Currently we’re funding reconstructon of about 30,000 home in south pakistan (flood afftected areas) so there are huge opportunities to incorporate better design. (We’ve already taken out xement and buened brick, majoring on earth and lime construction).


  • Carl Farnsworth

    An excellent, simple design that would most likely be achievable even with spare parts too (if you’re hard pressed for money). I’ve read the site you’ve linked to, but I’m still curious about the biofilter. I can see the geofabric (first time I’ve heard of it) and the furnace filter material filtering out all but the absolute smallest particles, but the micro organism colonisation intrigues me. I suppose that will be a question for Bob though.

  • doc

    Could this be set up to run on a gravity system. That is elevating progressively the containers allowing gravity to move water to the end point…..

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