Dear Mr. Todd and Ms. Josephson

Thanks for an interesting introduction to the world of living machines and ecological engineering.  It seems as if the main challenges are to create a system that has enough minerals to stimulate catalysis, can deal with large flow, load shocks and is adaptable to cycles and equipment failure - in a word, robustness.

I wonder if the sludge from municipal applications would be usable for fertiliser, or whether heavy metal contamination would be too high.  Also, is there scope for treating biodegradable municipal waste, in addition to sewage, using such systems?

Yours sincerely,

Simon Proops
Centre for Exploitation of Science and Technology (CEST)
5 Berners Road, London N1 0PW, UK
tel +44 (171) 354 9942    fax +44 (171) 354 4301
www: http://www.cest.org.uk