Recent years have seen an increase in water purification requirements in the light of growing environmental awareness. Existing treatment plants for removing organic material from water do not, however, remove phosphorus. To remove phosphorus additional purification is necessary in order to bring the amount down to an environmentally acceptable level.
Increasing attention is being focused on the phosphorus retention capacity of wetlands. Several attempts have been made to improve the reduction of phosphorus in wastewater by the use of constructed wetlands. One way of improving the phosphorus reduction capacity is to use efficient filter materials in the wetland.
It is also known to use Expanded Clay Aggregate (ECA ®) or Lightweight Expanded Clay Aggregate (LECA) to improve the hydraulic conductivity of the earth medium. These Expanded Clay Aggregates (ECA ®) have also been found to have a certain capacity for removing phosphorus, which is due in part to the fact that during production these balls are often powdered with dolomite in the firing zone for production-technical reasons. The phosphorus binding capacity of these clay aggregates is however not sufficiently great, thus making it is desirable to have a medium having greater capacity for binding phosphorus.
It is an object of the present invention to find a material for use as a filtration medium for purifying water which has a considerably greater capacity for removing phosphorus than the previous expanded clay aggregates, whilst having the same good hydraulic properties as this previously known material.
According to the invention, this is achieved by means of sintered Expanded Clay Aggregate (ECA ®) or Lightweight Expanded Clay Aggregate (LECA), characterised in that prior to expansion and firing carbonates of calcium and/or magnesium are added to the clay as flux material.
With the aid of the present sintered Expanded Clay Aggregate (ECA ®) or Lightweight Expanded Clay Aggregate (LECA), it has been possible to combine a high phosphorus binding capacity with very good hydraulic conductivity. The sintered Expanded Clay Aggregate (ECA ®) or Lightweight Expanded Clay Aggregate (LECA) are balls having a large specific internal surface in the form of internal cavities in the configuration of small cells which are interconnected. The reactive carbonates of calcium and magnesium contained in the matrix are spread over this large internal surface and provide a very large phosphorus binding capacity.
The sintered Expanded Clay Aggregate (ECA ®) or Lightweight Expanded Clay Aggregate (LECA) are ceramic matrices, which affords the material the strength to ensure that it retains its hydraulic conductivity. In this way it is ensured that the water which is to be purified has good contact with the reactive substances in the matrix and that the reactive substances are distributed in the system in an expedient and optimal fashion
The capacity of the present sintered light aggregates to bind phosphorus is also dependent upon a large specific surface, but this large specific surface is obtained in that the internal surface in the Expanded Clay Aggregate (ECA ®) or Lightweight Expanded Clay Aggregate (LECA) is also accessible to the water.
The sintered Expanded Clay Aggregate (ECA ®) or Lightweight Expanded Clay Aggregate (LECA) according to the present invention are made following a conventional method for manufacturing light, expanded clay aggregates, in that marine clay is treated by a process wherein the clay is fed into a rotary kiln where it is first shaped into clay pellets which are fired and finally expanded at a temperature increasing up to about 1200° C. in the firing zone. In this way an approximately ball-shaped granulate having a ceramic shell around a porous core is formed. The clay aggregates according to the present invention are prepared in essentially the same way except that prior to granulation and firing carbonates of calcium and/or magnesium, e.g., dolomite, are added to the clay making Expanded Clay Aggregate (ECA ®) or Lightweight Expanded Clay Aggregate (LECA) best fit to absorb phosphorus from contaminated water.
100 % Inert
Light in Weight
Reduction of 40-50% Load
Micro Porous Structure
Aids Better Aeration
Non-Toxic & Eco- Friendly
100% Eco-Friendly and Sustainable
Good Water Absorption
18 to 23 % of size
High Resistance to Water Absorption
Excellent Filtration Media
Unique structure suited to filter water
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