FLOTATING MACROPHYTES FILTER TECNOLOGY
WATER TREATMENT USING MACROPHYTE SYSTEMS
Systems that use aquatic macrophytes are based on single-crop
or multi-crop farming of macrophytes in shallow ponds, tanks,
or canals. Although they are usually used for tertiary water
treatment, they are suitable for certain types of secondary
water treatment. The plants supply oxygen to the treatment
process, which develops in the root system. Plants degrade,
absorb and assimilate pollutants in their tissues and they
provide a large surface area on which bacteria can grow and
solid elements are treated.
different treatment systems that use aquatic macrophytes are
1. EMERGENT SUPERFICIAL-FLOW MACROPHYTE SYSTEM
This system and the next one make use of rooted plants. The
leaves of these plant species (Phragmites, Scirpus, or Typha)
dry out in winter and sprout in spring. In the superficial-flow
systems, contaminants are eliminated through reactions that
take place in the water and upper zone of contact. Little
wastewater circulates through the roots, which limits their
water treatment capacity.
2. EMERGENT SUBSUPERFICIAL-FLOW MACROPHYTE SYSTEM
As in the previous system, water circulates
by gravity through a layer of gravel or soil. The most important
drawback of the system is rapid clogging up of the terrain
over time with roots, rhizomes, and sediment solids. When
the system gets clogged up, it has to be destroyed to eliminate
3. FLOATING MACROPHYTE SYSTEM
These systems use species that float naturally,
such as Lemma, Wolffia, Spirodella, Azolla, or Eichomia. The
advantage of these systems is that the contact between roots
and wastewater is complete and a large surface area is exposed.
However, these species are small and their biomass production
is limited, which reduces their absolute water treatment value,
although they absorb large quantities of nitrogen and phosphorus.
They are very effective for low concentrations of organic
matter and diluted solids.
4. FLOTATING MACROPHYTES FILTER (FLOATING MACROPHYTE FILTER)
This LIFE project proposes to use floating macrophyte filter
systems and has arranged for the construction of different prototypes
system is based on emergent macrophytes that naturally root
to the soil, but in this case are converted into artificially
floating macrophytes. It is an innovative method that has
the combined advantages of floating and emergent macrophyte
systems, while eliminating or reducing their drawbacks. It
was developed by the Polytechnical University of Madrid and
is exemplified by three experimental treatment plants in the
Madrid-Barajas, Reus, and Alicante airports.
system is suitable for the tertiary treatment of secondary
effluents from conventional treatment systems, eliminating
eutrophicising elements, particularly phosphorus and nitrogen.
Secondary treatment processes occur in the system because
microorganisms attached to the roots of the plants decompose
organic matter. Finally, the system also reduces diluted solids,
which are retained by roots. Some species of emergent plants
can absorb large quantities of heavy metals and decompose
phenols, which makes the system suitable for treating industrial
system is based on a floating mat of plants that occupies
the entire surface of the pond or canals through which water
circulates. Their depth ranges from 25 to 75 cm. Plants should
be native species whenever possible and arrayed in such a
way that their roots, rhizomes and part of the stem are submerged.
Until now, the plants that have been used are Phragmites sp.,
Sparganium sp., Scirpus, Schoenus, Iris pseudocorus and Typha
sp. Typha species have shown the best results, with high growth
and treatment rates.
these plants are grown floating, they form a dense mat of
roots and rhizomes that occupy the entire collector volume
(pond or canal), thus forcing all the water to circulate through
the matted vegetation, which supports microorganisms that
degrade organic matter. Leaves pump oxygen to the roots, thus
favouring the process of contaminant degradation.
of the FLOTATING MACROPHYTES FILTER system
Economical and easy installation.
- Greater effectiveness than other systems, because the entire
volume of the effluent circulates through the treatment mesh.
- Easy harvest of the biomass, above and below the water surface.
Harvesting does not destroy the system, as occurs with rooted-plant
addition, once the system is stabilised, it produces a large
amount of biomass, which must be removed periodically. The
system produces annually 2.23 kg/m2 of dry material above
water in the case of cattails (Typha latifolia L.), which
can be used as livestock feed or as an energy source (a square
metre of canal has the same caloric value as a litre of oil).
FRAMEWORK DIRECTIVE OF THE EUROPEAN UNION
The Water Framework Directive was adopted, after a long debate
in the European Parliament and European Commission, on 22
December 2000. This initiative entailed an important challenge
for water management and comprises all the former directives
about this matter. It is considered to be one of the best
water legislations in the world, and its correct implementation
should improve the ecological situation of rivers, for example,
main principles of this Framework Directive are:
The river basin as a management unit that is equivalent to
the natural operating unit of the hydrological cycle.
2. Environmental externalities are to be included in the price
3. Achievement of a “good ecological state” (biological,
hydromorphological, and physical-chemical) of water and aquatic
ecosystems is the best proof of water quantity and quality
(making it an ecological approach to the sustainable use of
4. The main tools of this initiative are pollution control,
elimination of dangerous substances, restoration of ecosystems,
tax policy, water basin management planning, efficient water
use, prevention of the degradation of aquatic ecosystems,
public participation, and the designation of protected areas.
principles are vital for the conservation of aquatic ecosystems
in relation to water conservation and sustainable use of this
resource. This directive was transposed in 2003 and entails
commitments that must be met by Member States according to
a strict calendar.
A complete version of the Directive in Spanish.
- Calendar for application.
- A document in English about the principles of the Directive.
WATER TREATMENT IN SPAIN
Traditionally, there have been two main water-related problems
in Spain. The first problem is that water is a scarce resource
that is even more difficult to obtain in periods of prolonged
draught. The second problem is the deterioration of water
quality in some parts of our hydrographic network due to effluents
from urban areas.
Wastewater from Spanish urban areas (some
of them with thousands of inhabitants) is dumped into river
basins and the sea. Years ago, polluting agents were diluted
by the volume of water, but now, the increase in the load
of contaminants and the reduction in water flow make solutions
exclusively based on the self-treatment capacity of the hydrographic
system ineffective. This has raised the need for treating
wastewater before releasing it into the water network.
Spanish legislation includes various regulations
designed to guarantee the quality of our continental and maritime
waters. Act 46/1999 of 13 December, on the modification of
Act 29/1985 (now repealed), of 2 August, on Water; the revised
text of the Water Law, approved by Royal Decree 1/2001, and
Act 22/988, on the Coasts, establish, among other measures,
the need for previous authorisation for activities that can
cause pollution of public water resources or maritime and
terrestrial waters, especially the discharge of effluents.
There are many other dispositions and regulations related
with water quality and with the obligation to treat effluents
in suitable plants.
In 1991, the European Union, acknowledging
the need to ensure water quality in Member States, began their
journey on the path that Spanish authorities had taken when
drafting the legislation cited, with Directive 91/271/EEC.
Member States were asked to install water treatment plants
for urban effluents in all population centres with more than
2000 inhabitants before 2005, so that the necessary measures
would be taken to ensure the correct collection and treatment
of urban wastewater before discharge.
Fourteen years have passed by since the Directive
was adopted and at the beginning of 2004, one year from the
deadline for fulfilling the commitments with the European
Union, it is noteworthy how well work has progressed in Spain
as a continuation of the work that had been under way: from
the transposition of the Directive into Spanish legislation
to the preparation of a National Treatment Plan and execution
of most of the planned infrastructures. It is estimated that
the investment required to meet the demands of the European
Union was almost 2 billion pesetas (about 12,000 million euros).
According to agreements with Autonomous Communities,
the total participation of Central Government in financing
the Plan was about 3000 million euros during its period of
execution up to 2005. For example, since the creation of the
Ministry of Environment in 1996, the General Administration
contracted about 721 million euros worth of infrastructure
development, which indicates the strong support given to the
Plan. To that amount must be added calls for tenders through
participation in the European Funds for Autonomous Communities.
In 1998, almost 48% of the Spanish population
lived in areas with treatment systems that fulfilled satisfactorily
the requirements established by the European Union and it
was expected that an additional 16% lived in areas where water
treatment plants were soon to be developed.
A document available on the website of the
Spanish Ministry of the Environment presents in a systematic
way a summary of the Spanish National Treatment Plant and
its development and evolution since Directive 91/271/EEC was
prepared until its adoption and entry into force, describing
the works executed and results obtained. Another aim of the
document is to disseminate the action lines currently being
From this perspective, this document starts
with an abstract about European legislation related to this
issue and the Spanish legal provisions that have allowed its
transposition and application (contained in Annex III).
After this abstract, the document
briefly describes the main characteristics of the Spanish
Water Treatment Plan adopted in 1995 and in the following
sections it describes the advances made up to 2000.