conventional systems. Sewage Greenhouse waste treatment plants such as the ones John Todd has developed can yield clean water from sewage. Bacteria consume the organic sewage and turn ammonia into nitrates. The nitrates are used as food for algae and fertilizer for duckweed. Zooplankton and snails consume the algae. Fish eat the zooplankton. Floating plants soak up the leftovers. Bulrushes, cattails, and water hyacinths render the toxins harmless. Trees absorb heavy metals. The byproducts are decorative plants and minnows, both of which are sold. The minnows are sold as bait fish. Aquatic plants, raised in the system's open-air lagoons for sewer treatment, are used in California, Florida, and Mississippi. By enclosing such a system within a greenhouse, it becomes possible to do this in the colder northern climates as well. Projects Todd's waste treatment systems have been implemented for sites in at least nine countries, in both the industrialized and developing world. Sites include Australia, Brazil, Canada, Czechoslovakia, England, Hungary, India, Scotland, and the United States. A number of projects have been particularly noteworthy because of the introduction of new concepts or major achievements. The Cape Cod Ark Soon after its founding in 1969, the New Alchemy Institute began to develop its first experimental environment, eventually known as the "Cape Cod Ark", at their headquarters in Falmouth, Massachusetts on Cape Cod. Their goals were to process wastewater and to explore the potential for food production. A series of solar ponds, each with its own ecosystem, processes wastewater and uses recaptured materials to farm fish and to grow vegetables and fruits. These include papaya trees, eggplants, tomatoes, and herbs. Computers were introduced to monitor and study the processes of remediation, energy use, and food production. Heating and electricity needs were met using renewable energy sources. The system was enclosed within a greenhouse, designed by architects Sean Wellesley-Miller and Day Chahroudi, so that it could operate year-round. When the New Alchemy Institute dissolved in 1991, the Cape Cod Ark became the property of a private co-housing community. In 1999, it was taken over by Hilde Maingay and Earle Barnhart, two of the co-founders of the New Alchemy Institute. Working with architect Ate Atema, they upgraded the structure and added an energy-efficient house to the original greenhouse. Under their care, the 1800 square feet Ark became a self-sustaining home, supporting humans, plants, fishes and animals year-round. The Cape Cod Ark was still their