12 Principles for Designing Natural Wastewater Treatment Systems

1. The living engines of the planet are the autotrophic bacteria that derive food and energy from inorganic mineral sources. These bacteria are comprised of chemosynthetic and photosynthetic forms. Between them they facilitate entire food chains. Autotrophic bacteria are dependent on mineral diversity and availability and on the amount and kind of light.
2. Mineral diversity provides the long-term foundation for nutrient diversity. Microorganisms and plants require nutrients to be present in available form. If carbon is recalcitrant or nitrogen, phosphorus, and potassium ratios out of balance, or trace elements not readily available, subsequent ecosystems may be impoverished in key ways. Nutrient imbalanced systems become prone to disease and subject to biological impoverishment. Over time species in such systems die out.
3. The history of planetary biota has, at its core, systems that have evolved between steep gradients in which the biochemistry of life is "flipped" between different states. Steep gradients can be defined in terms of gases, like the aerobic or anaerobic states expressed by oxygen, redox potential, pH, temperature, humic, and ligand or metal related states.
4. In ecologically engineered systems the objective is to maximize the surface area exposed to the waste stream without hindering the through flow of the system or the metabolism of the contained communities. Higher plants floating on water surfaces develop root complexes that provide extraordinary surface areas for microbial communities, in some cases as much as ten thousand times greater than the surface areas of comparable conventionally engineered systems.  
5. Periodic and random pulsed exchanges improve performance. In the classic text, Perspectives in Ecological Theory, systems ecology pioneer Ramon Margalef discussed the significance of regular or periodic outside influences as well as that of random external events in shaping the structure and response systems of ecosystems. He suggested: "Direct reaction of organisms to environmental change is most useful if the environment is being altered in an unpredictable way." This suggests that internal self organization and self design in ecosystems can be heightened by exposure to periodic and predictable external influences (seasons for example) as well as to environmental shocks (cold or extreme winds) of more or less knowable frequency and distribution. Self-design to a high level of organization may be further enhanced by exposure to random or rare perturbations. Examples include the temperature differentials between night and day and the variations in the flow and loading of wastewater.
6. Cellular design is the structural model. Design in nature differs from human engineering in a number of fundamental ways. In life the organizing architecture is the cell. When a living system scales up or gets larger it does so by increasing the number of cells. By way of contrast, scaling up in a standard waste treatment facility usually involves installing larger sizes of clarifiers or aerated lagoons, and so forth. With the appropriate structural materials, the ingenuity of the natural world is worthy of imitation. A single living cell is engineered as a whole system, capable of division, replication, nutrition, synthesis of molecular materials, digestion, excretion, and communicating with adjacent cells.  
7. Incorporate a law of the minimum.
   Ecosystems do not exist in isolation. They are connected to and exchange with other systems through an array of couplings. Neighboring ecosystems mutually define each other. This process extends outward in a lattice-work of interconnections that, ultimately, is planetary in scope. In integrating this principle into the design of living technologies, the question is: how many sub ecosystems will create a viable, self designing/organizing system that can sustain itself over time measured in years or decades. In Ecological Engineering, Jorgensen and Mitsch recognize the problem and propose a general rule: "Ecosystems are coupled with other ecosystems. This coupling should be maintained wherever possible and ecosystems should not be isolated from their surrounding."  
8. Introduce microbial communities.
   That microbial communities are the foundation of living technologies is, by now, obvious. What is less obvious, if the potential of ecological engineering is to be optimized, is the diversity in communities of microorganisms required. Bioaugmentation, the addition of natural bacteria, increases this diversity.  
9. Photosynthetic foundations are essential.
   Ecological engineering was founded on an appreciation of the ecological importance of plants and photosynthetic activity. The use of plants, particularly a diversity of plants, can result in balanced ecosystems that require less energy, aeration, and chemical management. The root zones are superb micro-sites for bacterial communities and increase the available surface area for microbes by several orders of magnitude. Many plants oxygenate waste and water and take up nutrients directly.
10. Encourage phylogenetic diversity.
    The regulators, control agents, and internal designers of living systems are often unusual and unpredictable organisms. As well as plants, incorporate snails and a variety of indigenous species. Snails play a particularly important role in living systems, cleaning surfaces and consuming sludge.
11. Sequenced and repeated seedings are part of maintenance.
    For a living system to be optimally effective, it must be interlinked through gaseous, nutrient, mineral, and biological pathways to the external environment. It should reflect internally the intelligence of the seasons, and should be capable of responding to perturbations and random events. It should contain pathways that originate in varied terrestrial and aquatic ecosystems. Periodic genetic innovations should be orchestrated by the ecological engineer or operator.  
12. Reflection of the microcosmos is a fundamental of design.
    The concept of the microcosmos most relevant to the evolution of living systems lies in the Hermetic epigram "as above, so below." For purposes of ecological design, the miniaturization of nature - not with relation to the pieces but in scale - should echo the fundamental patterns of the macrocosm. The Earth and its atmosphere are relevant to the design of the living system if it is to be a true microcosmos.