Grey Water Clean Up With Azolla Update

Developments 1 Year after Start up

The final filtration of my grey water through an Azolla pond has been functioning extremely well for a little under a year. The Azolla had grown profusely over the entire surface, dominating over the Spirogyra, Wolffia borialis and Duck Weed.

In mid-December I travelled overseas for 6 weeks, during which time no grey water flowed into the filter. The weather during that time was fairly hot, with little or no rain.

The water level dropped about 100mm in total. Azolla was presumably getting too little nutrients. Spirogyra became dominant, with some Duck Weed.

Please click on the Link below for a very impressive account of Duck Weed: with many thanks to that author!


When Grey Water Flow Ceases

Water flow had ceased, level had dropped through evaporation.
Water flow had ceased, level had dropped through evaporation.
Spirogyra has taken over and smothered the Azolla.
Spirogyra has taken over and smothered the Azolla.
The shade cloth acts as a filter on the outlet.
The shade cloth acts as a filter on the outlet.

Smothering Mat Removed

6 Days Later

One Week More

2 weeks after smothering mat was removed
2 weeks after smothering mat was removed
Air Temperature
Air Temperature
Water Temperature
Water Temperature

Three Weeks After Rejuvenation

Just three weeks after removing that thick mat of algae and decaying Azolla, the surface of the pond is covered in an ecosystem of Duckweed, Spirogyra, Azolla and Wolffia. The water under this growth is not smelly. It has been oxygenated well by photosynthesis of the algae and two species of flowering plant.


The colour of the water is now a light brown, caused probably by tannins from the mulch filter upstream from the pond.

Small clumps of Azolla, Duckweed (Lemna minor and Wolffia borialis) the darker Spirogyra is visible with the oxygen bubbles poking through.
Small clumps of Azolla, Duckweed (Lemna minor and Wolffia borialis) the darker Spirogyra is visible with the oxygen bubbles poking through.
Clear water, from beneath the surface, with the brown colour produced by tannins in the water.
Clear water, from beneath the surface, with the brown colour produced by tannins in the water.

Conclusions so far

It would be useful now to get a test done on the water, to see if the BOD, e.coli and nitrogen levels have changed with the dominant species.

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3 comments

Jodah profile image

Jodah 2 years ago from Queensland Australia

Interesting hub jonny. I applaud you for attempting to filter/clean your grey water this way. Please let us know how the tests on the cleaned water turns out and if it is free of bacteria etc.


in4mative 2 years ago from Birmingham UK

I did a brief google search as grey water is completely foreign to me.

It seems to an interesting topic.


jonnycomelately profile image

jonnycomelately 2 years ago from Tasmania Author

Thanks you in4mative. It is an ongoing study and project. Still lots to learn but the journey of learning is so exciting and informative. It keeps my mind and enthusiasm alive.

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