John Todds Living Machine Technology

Design Objective

Include igneous, sedimentary, and metamorphic rocks to provide a foundation for complex biological chemistry

Provide nutrients in available forms in order to maintain balanced cycling

Connect subsystems with very different physical-chemical conditions

Maximize the surface area of living biomass that is exposed to wastewater

Pulsing in physical-chemical conditions leads to robust adaptations

Provide some degree of small-scale autonomy within the larger scale context by using cells as units of design

Incorporate at least a small number of linked subsystems to enhance stability

Encourage microbial diversity because of its critical role in overall performance

Utilize solar energy as an energy subsidy by incorporating photosynthesis in the design with plant populations

Incorporate many animal populations, especially filter feeding invertebrates, into the design for added control functions

Frequent seeding from different external sources adds adaptability to the design

Include different ecological scales in the overall design concept

Source: Adapted from Todd, J. and B. Josephson. 1996. Ecological Engineering. 6:109.

Much of the design knowledge on living machines is recorded in the book entitled From Eco-Cities to Living Machines (Todd and Todd, 1994), and some of it is included in Table 2.5. Even a children's book on living machines has been produced (Bang, no date). Overall, this is an excellent example of an ecologically engineered technology utilizing the principle of preadaptation early in the design. The aquaculture tanks were preadapted to be organized into a wastewater treatment system with each containing a different unit process.

A critical component of the living machine is the sequential nature of the treatment process. Possibly Todd was influenced by John Ryther's project combining aquaculture and wastewater treatment that started in the early 1970s at Woods Hole

(Figure 2.23) while Todd worked there. A tie between Todd's design work and Ryther's project might be indicated by McLarney's role with Ryther in a major text on aquaculture (Bardach et al., 1972). Although Ryther's project continued through the 1970s and was well documented (Dunstan and Tenore, 1972; Goldman and Ryther, 1976; Goldman et al., 1973; 1974a, 1974b; Ryther et al., 1972; Tenore et al., 1973), it apparently led to no commercial development unlike Todd's living machine concept. Todd's work has generated a design company named "Living Technologies," another company named "Ecological Engineering Associates" (Teal and Peterson, 1991, 1993; Teal et al., 1994), and most recently, "Ocean Arks International."

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