Hydroponic Bog Garden (Water Recycling)




This idea came from the work that we do with sewage. Our systems produce a clean water effluent that is clean enough to discharge to ditches ponds etc. we wanted to develop a tertiary treatment system that would allow us to re-use the water for irrigation purposes. Hence the idea formed to create a hydroponic bog garden.

It essentially uses the same techniques employed in aquaculture. Use bacteria that are attached to biomedia to clean the highly oxygenated water passing through the media. We use alfagrog media for this. It has a high surface area and good void capacity. The added bonus to this system is that by placing a gravel bed over the top of the media we have been able to produce an ideal environment for growing those difficult to propagate plants. The moisture loving ones that fail at the first sign of drought.

You can find out more about us and our other projects on our site:Biotank

Step 1: Dig a Hole

The bog garden starts life as a square hole with a level base and square sides. The shape was determined by the sleepers that we are using around the outside in the finished bog garden.

Step 2: Line the Bottom

Once the base is levelled out, it is time to line the bottom of the bog garden with a cushion to stop stones rising up and making holes in the liner.

Step 3: Level the Bottom With Sand

First of all a sharp sand coating is added to level the bottom completely... Not that the digger driver was not able to get it completely level!

Step 4: Cushion the Bog

The lining cushion is laid out in sheets and comes right up the side of the bog garden. It has to protect the liner, which is 0.75mm butyl from harm. This is the same liner as would be used in a garden pond.

Step 5: Line the Bog

The liner is laid out and pushed all the way to the side of the hole. The liner is preformed to the size of the bog garden on purchase. It was made to measure for us.

Step 6: Add Second Cushion

Once the liner is in place it too is lined with cushion in order to protect it from the alfagrog that we will be putting on the top. The solid oak sleepers are put in the tank to separate off the aeration pond and the final settlement pond from the actual bog garden itself.

In the background you can see our experimental sewage system. This is a see-through Biotank 6 on which we do all of our experimentation.

Step 7: Separate Garden From Aeration Chamber

The oak sleepers, green untreated oak, have small holes routed in the bottom to allow the water to flow through into the bog garden from the aeration chamber. As with most things we where unsure how many were required so it is really guesswork!

Step 8: Add the Alfagrog

Having completed the basic design we fill the actual bog garden part with alfagrog. This is a ceramic filter media used in Koi fish ponds to filter the water. It contains a huge amount of surface area in which our bacteria will live and clean up the water.

Step 9: Add Water

Once we have completely filled the centre section of the hydroponic bog garden we then start filling it with water and adding the rest of the sleepers around the outside of the system. This size of tank takes around 6 cubic metres of water to fill it to a level just above the Alfagrog. Filling it with water allows us to level the Alfagrog and ensure that when we add the gravel to it that it is all immersed in water.

Step 10: Support the Center Section

The finished wood work looks like this. Full of water and Alfagrog and awaiting the gravel to fill the middle. The cross section wood is to stop the centre section moving when the gravel is added.

Step 11: Add Gravel

Once filled with gravel the finished bog garden looks like this. The water level is raised so that at least an inch of the gravel is under water to provide the plants with moisture. The whole purpose of this is not only to filter the water but to provide constant water for herbaceous water loving plants such as Hostas and Astibes.

Step 12: Get Ready to Aerate

The section of the tank that will receive the water from the Biotank needs to be aerated. A small compressor provides this aeration via a rubber aerator. The dissolved oxygen level needs to be as high as possible if the bacteria in the Alfagrog are going to survive.

Step 13: Put in Some Plants

Once finished the final touch is to add plants. All of these are moisture loving plants provided by our local nursery.

Step 14: Enjoy the Bog Garden

The water from the Bog Garden is used to feed our ponds and to water the lawns.

Full results from testing of the water from the Bog Garden can be found on ourBiotank effluent standard page.

You can find out more about us and our other projects on our site:Biotank



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    40 Discussions

    then again (wish we could edit these posts) maybe the clogging is more severe in primary or secondary treated water.

    forgot to ask. this has been running for seven(?) years now. how is the gravel? how has the maintenance been?

    i see alot of designs for reed beds with gravel and a few folks that had to clean them and they say never again. i'm leaning toward a more hydroponics approach with just roots and water so cleaning is just pulling out a plant and into the compost. open a drain for sediment build up or pump it out. no gravel shoveling.


    11 years ago on Introduction

    that's beautiful! This seems more like a marginal wetland environment than a bog. Could you make this into a "real" bog? Bogs are low nitrogen, anaerobic environment which are home to specialized plants like carnivorous flytraps and pitcher plants, as well as some orchids.

    3 replies

    Reply 11 years ago on Introduction

    You are absolutely correct but you have missed the play on words... In the UK one sits on a bog to do number 2's!!! No idea where it came from but back in the mists of time it appeared in the English language. A bog lives in a Karssy... Thats an Indian word!

    Andrew BurgessBiotank

    Reply 3 years ago on Introduction

    i believe bog comes from literally a bog. go to the bog meant go out back to the boggy wetlands to relieve yourself. the word crap, btw, comes from the name of the manufacturer of an early toilet.


    Reply 11 years ago on Introduction

    Ahhh, I see. We don't have that saying here (US). Too bad, it's a good one. I always appreciate a good pun.


    6 years ago on Introduction

    Global wastewater programs are working to create efficient ways cities and towns can repurpose water. You can do your part by recycling lightly-used household water to reduce the amount you use every day. You can also get some more procedures of recycling water with existing hydroponic systems in your garden here.


    6 years ago on Step 14

    great, wish I had space for that. I was just wondering if there is enough circulation between the aerated open part and the gravel part of your bog


    9 years ago on Step 14

    Have you considered Mycofiltration to assist with the cleaning. www.fungiperfecti.com has all the tools to add it. Also there are fungi that work synergystically with your plants to make them grow better in a permaculture type way.

    1 reply

    Reply 7 years ago on Step 14

    Ron, Can you share with us some more information on the fungi you mentioned? Links to sources on the web, books, magazines, etc., any thing to get us pointed in the correct direction. I want to make our homestead as permaculture friendly as possible and using fungi is one thing I hadn't heard about before.



    mr fat

    7 years ago on Step 14

    Awesome set up! An inspiration


    7 years ago on Introduction

    i am a green experimenter -research and plan very carefully before u meet with the men and women who decide whether u may this. good luck any1


    9 years ago on Introduction

     Pretty nice Instructable.  Using a flood and drain system it could be used with not so water loving plants if that were an interest.  Aquaponics has been making use of that technique for some time now.  It would be nice to see a little more detail but overall well done.  BTW 30 cm seems to be a good minimum for biological filter/ root growth area depth when using gravel of a larger diameter, although your surface area probably offsets the numbers some.


    Reply 11 years ago on Introduction

    Not at all... A Biodigester that produces Biogas is an anaerobic environment. Biogas is methane and this is only produced by anaerobic bacteria without oxygen being present. It is a more efficient digestion process than aerobic digestion but aerobic digestion is better for cleaning up the environment in that it produces water, the bacteria themselves generate new water, and carbon dioxide which is recycled back to the environment... This is a carbon neutral process before anyone starts jumping up and down about climate change and global warming.


    Reply 10 years ago on Introduction

    hahaha, love your sense of humor! and talking about climat change... your system is also producing a very dangerous product that is the maine component of acidic rain: the dihydrogen monoxide ;)


    Reply 9 years ago on Introduction

    I heard athletes use it to increase their performance!  I also heard the you can died from an overdose! It's called hypotremonia.

    Lions and Tigers and Bears! Oh My!

    The chemical formula for Dihydrogen Monoxide, for those who don't get the joke, is: H2O


    9 years ago on Introduction

    I have a pond, ponds are cheap, liners....not so much.