DIG-L: AD Effluent Polishing

["Michael Chesshire" <greenfinch@burford.co.uk>]

   Dear all,

I previously wrote regarding thermophilic and mesophilic digestion
relating to the final composition of the by-products.  Thankyou for all
your replies and the following discussion.

As I mentioned, our company Greenfinch is currently researching the
possible re-use of by-products using aquaculture.  We currently use
aquatic plants as a filtrate media for the liquid fertiliser. i.e. Water
hyacinths, watercress, duckweed.  They utilise the nutrients growing
abundantly.  These plants are also used  as a food source for carp and
tilapia.  The fish are held in enclosed tanks which are fed only by the
treated effluent (polished water).

In the New Scientist (26.02, pg 20) there was a recent article entitled
"Foul fare for fish".  This article describes the use of tilapia to polish
water from sewage works.  A biologist (Ray Drenner) from Texas Christian
University, Fort Worth, has developed a waste-water purification system in
which algae utilises the polluting sewage effluent nutrients and the
tilapia consumes the algae.

Has anyone come across a similar system in use with AD technology.  I know
this is popular in the developing world but does this type of treatment
system exist elsewhere?  I would also be very interested to hear any
comments concerning the use of tilapia as a food source once reared in
these conditions.  (Our initial input of nutrients is source separated
household waste- food waste, grass cuttings, no human excretion.)

Thanks again,


Lisa Pritchard
Research Scientist
Greenfinch Ltd
Shropshire, UK. 

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