A Low Cost Site-Built Wastewater Treatment System

Copyright © 2006-2009
Robert L. Crosby Jr
Biorealis Systems, Inc


UPDATED 8/11/2013: Added Surge Pump construction details and Paypal button.



There is tremendous worldwide demand for safe, reliable, affordable sanitation systems in locations where water supplies and wastewater disposal options are limited. The United Nations Environment Programme (UNEP) estimates that, world-wide, more than three billion people lack access to proper sanitation, with water-borne diseases accounting for some twenty-five thousand deaths a day, worldwide.

And these problems are not just limited to the developing world. According to the USEPA, almost half of all American rivers, lakes, and creeks are damaged or threatened by water pollution, much of it coming from untreated residential and commercial wastewaters. From chronic water shortages and rationing in the American southwest to polluted aquifers on Cape Cod, destruction of the Florida Everglades, depletion of the great Ogalalla aquifer, to cholera and hepatitis epidemics in rural Alaskan villages, clean water is clearly one of the major resource challenges of our time.

There are a number of existing "small flow" technologies capable of treating residential wastewater to a quality sufficient for safe reuse. A survey of currently available products indicates that the smallest of these units are sized to handle a minimum of 400-500 GPD, cost between $8,000 and $20,000 to install, require connection to 120 VAC power, and use between 2 and 10 KWH/day of electricity to operate. The market for these systems is well populated, but these products are clearly beyond the reach of those who need them the most.

Following is a description of a simple wastewater treatment system developed by Biorealis Systems, Inc., which can be owner-built from locally available materials at a fraction of the cost of typical existing commercial units, while providing performance equal to, or superior to systems costing far more. The complete system, capable of treating domestic wastewater to advanced water quality standards, can be built for less than $300 in materials and a couple of weekends' worth of labor. (Actual costs will vary depending on local availability and cost of used drums & buckets, etc.)


  • Modular: Design consists of three different modules which can be combined in a variety of ways to treat a variety of different wastewaters to any desired quality.
  • Simple Design: Can be locally built, using commonly available materials. Does not require specialized tools or skills to build, lends itself to local self-help solutions, creation of local jobs, small business opportunities.
  • Low maintenance: No moving parts to fail. Only non-corroding materials in contact with wastewater.
  • Low energy use: 17.5 watts continuous, Less than $0.05/day at typical rates, or suitable for use with off-grid, alternative energy sources.

Design Summary:

The complete system includes three modules, each made from a 55 gallon plastic drum. Other components include 1-gallon and 5-gallon plastic buckets and miscellaneous plastic pipe and fittings, available from Biorealis Systems, Inc., or commonly available at most hardware or building supply stores. The drums and plastic buckets can often be found used, available at little or no cost.

Modules/functions include:

    1. Surge Tank: Provides flow equalization, eliminating surges--and disturbance of settled sludge--in following stage. Flow rate varies, depending on depth of water in tank. Peak flow rate (when tank is full) is about 25 gallons/hour. Total surge capacity is about 40 gallons.

    2. Settling/Sludge Upflow: Anaerobic contact zone. The closely regulated ultra low flow velocities achieved in the previous stage allow accumulation of a sludge blanket which functions effectively as fixed-film media with exceptionally high biological contact surface area/volume at zero cost.

    3. Biofiltration: Aerobic contact zone (trickle filter). Water (with the larger solids settled out), is continuously pumped over aerated biofilter media, and then returned to the settling tank. Flocs sluffed from filter media add to and build up sludge layer.

    4. Optional (not shown): Foam fractionator (protein skimmer) with ozonation, in final stage.



Construction Details:
Surge Tank

What it does: Equalizes flow velocity, providing continuous very low flow (like in a natural wetland) to following stages, allowing solids to settle undisturbed in the following stage.

How it works: Air powered "percolator pump" works like an old-fashioned coffee percolator, but with an added twist. The air chamber (an inverted 1 gallon pail) allows a big "gulp" of air to rise up the pipe instead of a continuous stream of smaller bubbles, providing much more lift.

How to build it: (Quick summary)

  • Gather all tools & materials list.
  • Cut holes in drum top for 4" pipe and bucket. Drill 2-3/4" dia. hole in side of drum to accept 2" bulkhead fitting.
  • Build percolator pump (Details).
  • Assemble.
  • Build support blocking (as required).

Enter Discussion: Go to online forum where you can ask questions, find answers, and maybe contribute some of your own.

surge tank


Surge Tank Construction Photos

Drum modifications are similar for each module: cut openings in top of drum for 5 gallon bucket and for 4" pipe, then drill holes in sides to accept bulkhead fittings as shown in drawings.

Basic tools required include tape measure, marker, scroll saw, drill and hole saw(s). (And a saw, if you need to build a base)

drum top
drum 2 cutting top
surge tank with bucket




Note: Not all 55 gallon drums are exactly the same size and shape. Depending on the height of the different drums you are able to find (in case you can't find three that match), you might need to mount one a bit higher than another. See drawing above for height relationships.

Here is an easy way to make a simple support stand from a couple of pieces of 2x lumber. No fasteners required. If carefully cut, they slip together--and just as easily come apart. Preferably, use treated lumber, as it may end up getting wet from time to time. Choose 2x4, 2x6 or 2x8 (or even 2x10?) depending on the amount of height adjustment required.

blocking2 blocking3


Sludge Settling/Anaerobic Upflow Tank:

What it does: Removes settleable solids, and traps lighter floating particles and grease. Flow up through the settled sludge blanket removes all but the smallest suspended solids and dissolved BOD. Anaerobic decomposition reduces the volume of accumulated sludge.

How it works: The continuous very low fluid velocities made possible by the surge pump in module 1 allow solids to settle out and accumulate in the bottom of this tank. Sludge returned from the trickle filter (Module 3) also acumulates in bottom, creating an anaerobic contact zone through which incoming water slowly flows up. This sludge blanket functions effectively as fixed-film media with exceptionally high biological contact surface area/volume at zero cost.

How to build it:

  • Cut holes in drum top for 4" pipe and bucket. Drill hole in side of drum and 5 gallon bucket to accept bulkhead fittings.
  • Drill holes in 5 gallon bucket.
  • Assemble.

Enter Discussion: Search for terms Stokes law, sedimentation theory and Upflow Anaerobic Sludge Blanket. Then come over to Forum to discuss how this design applies those principles.

Surge tank


Settling Tank Construction Photos:

Bucket marked for drilling holes. (The holes make a "notched" overflow weir.)

marking bucket holes
Cutting handle tabs off of bucket so it will fit in hole cut in top of drum. Flange at top of bucket should rest flat on top of drum. cutting tabs

Assembled unit, 5 gallon bucket fit into opening cut in top of drum.






What it does: Aerobic contact zone. Removes dissolved BOD, returns sludge to module 2.

How it works: Surge pump (similar to stage 1) continuously pumps water over biofiltration media in trickle filter at a rate of about 1/2 gal/minute. Trickle filter provides aerated surface area for microorganisms to colonize.

How to build it:

  • Cut holes in drum top for 4" pipe and bucket. Drill (2) 2-7/8" dia. holes in side of drum to accept 2" bulkhead fittings.
  • Assemble surge pump (Details) and install in tank.
  • Make trickle filter
  • Assemble.



Construction Photos:

Trickle filter media: geofabric and furnace filter material...

...rolled up into a cylinder and fit into 5 gallon plastic bucket. trickle filter

Surge pump construction. Made from used 1 gallon paste bucket and PVC pipe and fittings.

surge pump



Finished, assembled unit. Inset shows samples of water taken from the first and third drums, respectively, after about 3 weeks of operation. As the sludge blanket grows, and bacterial populations mature, it continues to get better.

While the treated water is still not crystal clear, it is pH neutral, oxygen rich and odor-free -- well suited either as is, for secondary uses (e.g. irrigation), or for further treatment.

Additional treatment options could include ...


...inline cartridge filters, root zone filters (constructed wetlands), slow sand filters, etc. etc.

We have demonstrated in our experimental bioshelter, that it is entirely feasible to treat household gray water (which accounts for over 90% of total water use) to a quality suitable for full reuse, in a fully closed system.

whole house filter   pond

Complete details with step-by-step assembly instructions, fully dimensioned drawings and specifications, materials list, tools required, and larger format photos are being developed and will be made available for sale soon. If you wish to be advised when it is available click here.

Download a one page flyer (97K PDF)

Update, Aug 2013:

Information on this website is outdated. The how-to manual promised above was never completed, but I do have additional photos, larger scale printable pdfs of the drawings shown above, surge pump construction details (what most people have requested...) and a couple of videos which I am making available for $11.95 - to help keep the site alive...

Thanks for your interest and support,

Bob Crosby


Copyright © 2003-2006 Robert L. Crosby Jr; this information may be copied, distributed and/or modified under certain conditions, but it comes WITHOUT ANY WARRANTY; see the Design Science License for more details.