Living Bio-Filter: Cleaning water by Phytoremediation

Alternative ways of water treatment and purification

Besides our phenomenological examinations of the research about the memory of water under the darkfield-microscope we are also strongly engaged in alternative ways of water treatment and cleaning water.

We start with the exotic project of phytoremediation: In this particular case, the field of application is in the purification of mine water by water hyacinths and their filtering roots.

The water hyacinth in our research pond

The filtering roots in detail

Purification of mine water by water hyacinth

To keep water clean and healty is one of the most important tasks for the future of a country. Besides process water and fresh water cleaning the use of mine water plays an increasing role in the future. Mine water comes from the surface and increasingly fills mines after the end of coal production. It is geothermally heated to about 30° C. It is contrary to a direct use that mine water can be contaminated with various heavy metal ions and with sulfate ions.

Initiated by the legislature to shutdown all coal mines until 2018 this will lead to the flooding of the mines to below the groundwater level. This has the consequence that then the occurring mine water must be pumped out to below the groundwater level to protect drinking water. From the mines of the Ruhr region is thereby expected a burst of 40 million cubic meters per year. Since the composition and quantity of waste mine water is initiated anthropomorphic by the closure of mines, the mine water falls under the provisions of the Federal Water Resources Act and the EU Water Framework Directive and therefore under the obligation to treat mine water on the principle "b.a.t. - Best Available Technique".

Mine water under our darkfield microsope.

Tab water under our darkfield microsope.

A new TAO project for cleaning mine water

With the end of coal mining 2018 mine water is considered industrial wastewater, which is subject to the Water Framework Directive. The project idea is to combine bioremediation stages, mechanical and electrochemi-cal stages with an energy use and identify the most effective combinations of parameters with filter or adsorption in a pilot program. With this procedure, in addition to cleaning the geothermal resource the use of mine water as a catalyst is intended. Within this framework, new filter materials are developed, a selective adsorption of ceramics, a phytofiberfilter for adsorption, a textile filter with photocatalytic activity and graphene coated ceramic electrode. Portions of the biomass produced can be used for energy.

The chosen water hyacinth type has no resistance to winter coldness, so the plants can´t unintention-ally be emitted into the biosystems. The population can be controlled by water temperature. Without warm water – like used in our research project – the water hyacinth type is dying.

Project steps and innovations of the phytoremediation

A multistage process will be tested for the cleaning of mine. This consists of a biological stage (phytoremediation) with upstream and downstream mechanical filter stages. The biological plant-based treatment reduces the concentration of pollutants in the water by storing heavy metal ions in the root system of plants. This treatment uses the geothermal mine water as a growth booster in a quasi tropical milieu. A further growth booster of the biological stage is fertilization. The biological stage will remove the majority of the mine water pollution, but its performance is determined by external factors, so that the downstream filter stages to stabilize and reduce emitted substances are needed. The mechanical steps are relating to the testing of filtering and adsorption. For this matched filters are developed that replace or supplement the standard filters.

An attendant plant and a water monitoring are intended to show the performance of active biological processes with integrated technical filtering. The project aims to explore, which purity level can reasonably be achieved with the combination of methods applied here. The investigations will be carried out in a pilot plant to be drawn up with three or four pools of 4 per m width and 8 m in length, in which the parameter combinations can be studied systematically. The mine water flows through these pools until the final purification step and is held on temperature by imminent mine water. The basins are covered similar to greenhouses.


Sustainability by using biomass of plants

In addition to the conservation of resources it is a contribution to sustainability, that parts of the biomass produced should be used for filter production in this project and that the biomass produced can be used for energy and to gain material, so that a certain amount of the geothermal and solar energy can be used futhermore. In addition, the used forms of energy - geothermal and solar energy – are regenerative forms of energy with the lowest possible costs.

Use of water hyacinth fibers for basket production

A meaningful order of methods used could be as follows:

  1. The standard mechanical filter to eliminate the coarse solids and floating particles and phytoremediation to remove the heavy metals and sulfate and chloride ions form the basic stage of the process.
  2. The Phytofaser-adsorption filter forms the second stage, also to eliminate the heavy metals and / or sulfate and / or chloride ions. It serves as a first stabilization step of the process and is at this point due to the expected cost effectiveness.
  3. The textile fiber with photokatalytics forms the next stage only to eliminate organic radical molecules.
  4. The electrochemical stage serves as the second stabilization for the elimination of heavy metals and sulphate and chloride ions. It increases the energetic use and brings a high degree of safety by flexibility and effectiveness.
  5. The Ceramic adsorption stage is the final stage and serves as a final backup.

In detail: What is Phytoremediation?

It is the subject of international research for over 60 years and a wide range of plants was studied focusing on the suitability to hyperaccumulation regarding various chemical substances such as heavy metal ions, radionuclide ions and organic solvents. For the special task to remediate mine water which is contaminated with heavy metal using phytoakkumulation and extraction, the species of water hyacinths appeared suitable. Current summary publications on the potential of the plant come from Narang, Rahman, Sood 2015. Here it is shown that the water hyacinth is suitable for detecting and accumulating traces of arsenic, lead, cadmium, chromium, iron, copper, nickel, mercury, uranium and zinc. The results refer to laboratory research and practical field studies in tropical waters.


The water hyacinth-type chosen by TAO characterises

Water hyacinth in bloom
  • a size, which makes it possible to separate the polluted and submerged parts of the plant while harvesting and use these parts specifically,
  • a particularly high growth rate,
  • no resistance to winter coldness, so the plants can´t unintentionally be emitted into the biosystems. The population can be controlled by water temperature.
  • a high aptitude for accumulation of various heavy metal ions and chemical sub-stances,
  • the possibility of further use of parts of the plant which are not highly polluted.

Our new experimental approach for Phytoremediation

Our application for mine water in moderate climates is new and innovative and energy saving because of the use of geothermal heat as energy source.


Status of the TAO-Group project Phytoremediation:

In our laboratory and a participating institution currently first tests run on the growth of the selected types of water hyacinth and their behavior.

In parallel, the mine water has been examined regarding nature and content (pH, minerals, other contents).

Growth experiments in mine water with duckweed (the so-called Lemna test) were performed (Institute).

In a following second step, the insertion of water hyacinth in the prepared mine water and filtration tests took place.

In addition to the TAO Group Stuttgart (initiator) project - or research partners are (among others) the University of Hohenheim.

For interested inquiries about the project, please send us an email to: