Substrate for constructed wetlands and phytopurification systems

Phytopurification is a natural waste water purification system that uses a special filtering substrate and is based on exploiting the combined action of bacterial microorganisms and specific macrophytic plant types.

PRINCIPLE OF OPERATION: a phytopurification plant consists of a waterproofed basin filled with a filtering substrate that is planted with semi-aquatic macrophytic plants (constructed wetland).

The water to be purified is first pre-treated and then fed into the basin, where it passes through the substrate. The plant roots develop in the substrate, and set free part of the oxygen that the plants absorb through their leaves and stems. This oxygenation creates conditions in the substrate that enable bacterial flora (the biofilm) to proliferate.

The combined action of:

• the filtration of water through the substrate,
• chemical degradation by the bacterial flora, and
• the absorption of water by the plant roots

sets off physical, chemical, and biological processes that are both simultaneous and sequential and continue for so long as there is water in the system. This removes the most significant pollutants (nitrogen, phosphorus, suspended solids, heavy metals, organic substances, pathogenic microorganisms deriving from civil and industrial waste).

IDEAL AS A SUBSTRATE FOR CONSTRUCTED WETLANDS:

Laterlite Expanded Clay is the ideal substrate for creating the filter bed where the plant roots develop.

The main advantages of using Laterlite Expanded Clay in constructed wetlands are:

• it provides a large surface area for filtration because of its intergranular and intragranular porosity
• it is an ideal support for the biofilm to develop because the granules of expanded clay contain a dense network of cavities. The biofilm consists mainly of bacterial colonies and this is where the biological purification process actually occurs
• optimised development and anchoring for the plant roots, which grow easily in the intergranular spaces of the expanded clay
• durability: expanded clay will not rot, is not subject to chemical or physical alteration, does not degrade over time, and is resistant to acids, bases, solvents, and freeze/thaw cycles.
• it is extremely easy to lay and maintain because of its lightness and its suitability for pneumatic pumping.
• it makes possible low environmental impact solutions that integrate easily with the surrounding context and is ANAB-ICEA certified for sustainable building.
• it gives excellent control of the odours that result from waste water treatment.

Laterlite Expanded Clay is suitable for use in constructed wetlands that are associated with domestic, agricultural, or industrial applications, for instance for the environmental upgrading of parks, nature reserves, and protected areas; in the hospitality sector (for example holiday farms, holiday apartments, hotels, camping sites, bathing establishments, and mountain lodges) and for farms, wineries, and sports facilities.

Laterlite Expanded Clay can be used in open-air phytopurification plants of either subsurface or surface flow type, or in greenhouses where the vegetative activity of the plants can be fully exploited throughout the year.

One of the most advanced greenhouse phytopurification systems is the “Organica” ecological waste water treatment system. This recreates an authentic ecosystem both in the greenhouse and the substrate. Laterlite Expanded Clay can be used successfully in systems of this type.

The recommended size and type of Laterlite Expanded Clay for these uses will depend on the project requirements.