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Technical proposal
Present-day engineering, biological, chemical and naturalistic
knowledge makes it possible to draw up an environmental
intervention plan that uses tools taken from nature
itself, consisting of plants, mycorrhizal fungi, rhizosphere
bacteria and zeolithic rocks.
In order to better understand how these instruments
can work together, we can now briefly summarise their
potential in terms of safeguarding the environment.
Plants are organisms that are able to interact with
the surrounding environment by means of their leaf system
and rootage. By means of their roots, plants absorb
their nutrients from the soil.
Symbiont mycorrhizal fungi are earth fungi that bind
to the roots of the plant, helping the plant absorb
nutritional substances and taking their own nutrition
from the plant without causing harm.
The action of absorption by plants is also facilitated
by PGP (Plant Growth Promoting) bacteria in the rhizosphere,
which are capable of transforming organic substances
in the soil into compounds that can be assimilated.
Zeolites are minerals classified as tectosilicates.
Their structure, characterised by cavities occupied
by large ions and molecules of water (both highly mobile),
is responsible for their main chemical-physical peculiarities:
structural and textural micro-porosity of a "real"
type (since the pores communicate with each other and
with the outside of the rock), high-capacity for cationic
exchange in a selective manner, mainly as regards K+,
NH4+ and Pb2+ (reaching values of up to 2-4 meq/g),
molecular adsorption of water molecules and other polar
molecules.
Zeolites are capable of absorbing 20% of their weight
in water, and act as a temporary container for pollutants
taken from the pollutants carrier and later absorbed
by the plants.
Chabasite is a type of zeolite able to exchange the
ammonia ion (NH4+) in a not overly selective manner,
which means it does not compete, in terms of absorbing
nutrients, with the roots of the plants, especially
if they are well protected by bacteria and mycorrhizae.
The extraction mechanism that takes place is caused
by the interaction between zeolite and plant, which
gives a twofold advantage:
- on the one hand the rock retains the ammonium from
the flow of water and makes it available for the roots
of the plant,
- while on the other hand the roots "regenerate"
the zeolitic grains, exchanging the ammonium with
the humic acid they emit.
A plant that establishes a symbiosis with mycorrhizal
fungi and bacteria of the rhizosphere improves its own
ability to absorb nutritional substances that are present
in the soil in small quantities. A bio-naturalistic
system designed to restore the microbiological equity
of the soil, respecting its biodiversity, can only use
plants, mycorrhizal fungi, earth bacteria and zeolites
as its substrate.
The root-fungus-bacterium-zeolite
system is a significant innovation in the field of water
and soil preservation and reclamation.
SCHEME
Making use of the characteristics of chabazitic zeolites,
together with the capabilities of plants and the metabolic
activity of bacteria and mycorrhiza of the rhizosphere,
leads to good results in the removal of pollutants from
the soil, and from waste water and leach water.
Recent experiments in Australia (Sakadevan et al. in
1997) have examined the adsorption capacity of phosphorus
(P) by industrial byproducts, to study the potential
use of adsorbent materials in wetlands, in order to
remove these pollutants from waste water. The results
obtained show that certain by-products from the iron
industry (BFS - Blast Furnace Slag) can be used together
with earth and zeolites to improve the performance of
wetlands.
Thanks to the chemical and physical properties of zeolites,
ecosystem filters are able to take the pollutants out
of water and release them into the roots of the plants
above, which share the bacteria and mycorrhizae introduced
with the zeolites in the rhizosphere.
The phenomenon of euthrophication
Description
The problem in lakes
Indicators of environmental quality
Phytodepuration
Description of the “purification” phenomenon
Components of a Phytodepuration system
System typologies
Typical depurative mechanisms in phytodepuration treatments
Innovative techniques: zeolite, mycorrhiza, metallurgical waste
Phytodepuration applications
Managing systems |
