Classification of Ecotechnology

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Ecological engineering may be based on one or more of the following four classes of ecotechnology:

1. Ecosystems are used to reduce or solve a pollution problem that otherwise would be (more) harmful to other ecosystems. A typical example is the use of wetlands for wastewater treatment.

2. Ecosystems are imitated or copied to reduce or solve a pollution problem, leading to constructed ecosystems. Examples are fishponds and constructed wetlands for treating wastewater or diffuse pollution sources.

3. The recovery of ecosystems after significant disturbances. Examples are coal mine reclamation and restoration of lakes and rivers.

4. The use of ecosystems for the benefit of humanity without destroying the ecological balance (i.e., the utilization of ecosystems on an ecologically sound basis). Typical examples are the use of integrated agriculture and development of organic agriculture; this type of ecotechnology finds wide application in the ecological management of renewable resources.

The rationale behind these four classes of ecotechnology is illustrated in Figure 1. It is noted that ecotechnology or ecological engineering operates in the environment and its ecosystems. As already mentioned, it is this domain that ecological engineering employs as its toolbox.

Illustrative examples of all four classes of ecological engineering may be found in situations where ecological engineering is applied to replace environmental engineering, mainly because the ecological engineering methods offer an ecologically more-acceptable solution, and where ecological engineering is the only method that can offer a proper solution to a problem. Examples are provided in Table 1, where alternative environmental technological solutions are also indicated. This does not

Type 3: ecosystems are recovered

Environment /ecosystems/surrounding nature Type 1: ecosystems are used to treat waste Type 2: ecosystems

Society are constructed to treat waste

Type 4: ecologically sound planning of the use of ecosystems

Figure 1 An illustration of the four types of ecological engineering. Reproduced by permission of Elsevier.

imply that ecological engineering can replace environmental engineering. On the contrary, the two technologies should work hand-in-hand to solve environmental management problems, better than they could do if applied individually. This is illustrated in type 1 ecological engineering (application of ecosystems to reduce or solve pollution problems) by wetlands utilized to reduce diffuse nutrient loads to lakes. This problem cannot be solved by environmental technology. Sludge treatment can be solved by environmental technology, namely by incineration. However, the ecological engineering solution (i.e., sludge disposal on agricultural land, which involves utilization of the organic material and nutrients in the sludge) is a much sounder method from an ecological perspective. Figure 2 gives an example, where both ecological engineering and environmental technology are applied to solve an environmental problem.

The application of constructed wetlands to cope with diffuse pollution is a good example of type 2 ecological engineering. Again, this problem cannot be solved by environmental technology. The application of root zone plants for treating small quantities of wastewater is an example of type 2 ecological engineering, in which the environmental engineering alternative (a mechanical-biological-chemical treatment) cannot compete, when the waste volume is low and/or the area costs are moderate, mainly because it would involve excessive costs, relative to the quantity of wastewater (sewage system, pumping stations, etc.). A solution requiring fewer resources always will be a more ecologically sound solution.

Although recovery of land contaminated by toxic chemicals is possible using environmental technology, it will require transportation of the soil to a soil treatment plant, where biological biodegradation of the contaminants would take place. Ecological engineering will propose an in situ treatment with adapted microorganisms or plants. The latter method will be much more cost-effective, and the pollution

Table 1 Ecological engineering examples (alternative environmental engineering methods are given)

Example of ecological engineering

Type of Without environmental ecological engineering eng. alternative

With environmental eng. alternative

Environment engineering alternative

Sludge disposal on agricultural land Sludge incineration

Wetlands utilized to reduce diffuse pollution Constructed wetland to reduce Root zone plant diffuse pollution

Recovery of lakes Recovery of contaminated land in situ

Traditional wastewater treatment Transport and treatment of contaminated soil

Agroforestry

Ecologically sound planning of harvest rates of resources

Reproduced by permission of Elsevier.

Constructed wetland

Constructed wetland

Hypolimnion water is removed by siphoning

Figure 2 Control of lake eutrophication, illustrating a combination of (1) chemical precipitation for phosphorus removal from wastewater (environmental technology); (2) a wetland to remove nutrients from the inflow (type 1 or 2 ecotechnology); and (3) siphoning of nutrient-rich hypolimnetic water downstream (type 3 ecotechnology). The eutrophication abatement may also be combined in this case with biomanipulation. Reproduced by permission of Elsevier.

Hypolimnion water is removed by siphoning

Figure 2 Control of lake eutrophication, illustrating a combination of (1) chemical precipitation for phosphorus removal from wastewater (environmental technology); (2) a wetland to remove nutrients from the inflow (type 1 or 2 ecotechnology); and (3) siphoning of nutrient-rich hypolimnetic water downstream (type 3 ecotechnology). The eutrophication abatement may also be combined in this case with biomanipulation. Reproduced by permission of Elsevier.

related to transporting the soil will be omitted. Restoration of lakes by biomanipulation, installation of an impoundment, sediment removal or coverage, siphoning of hypolimnetic water (rich in nutrients) downstream, or by several other proposed ecological engineering techniques are examples of type 3 ecological engineering. It is difficult to obtain the same results using environmental engineering, because this requires activities in the lake and/or the vicinity of the lake.

Type 4 ecological engineering is based, to a great extent, on pollution prevention by utilization of ecosystems on an ecologically sound basis. Although it is very difficult to find environmental engineering alternatives in this case, it is clear that a prudent harvest rate of renewable resources (whether, e.g., timber or fish) is the best long-term strategy from an ecological and economic perspective. Ecologically sound landscape planning is another example of the use of type 4 ecological engineering.

Constructed subsurface wetlands may also be used to treat dairy farm wastewater, mine water pollutants, textile wastewater, and pulp mill wastewater.

See also: Wetland Models.

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  • NUNZIA
    How are the Ecotechnologies classified?
    4 months ago

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