Biocascade Water purification system - subpage

Charging phase
In general, biocascade water purification consists of a series of connected water basins. Dependent on the demand for purification, the intake water initially flows into a sedimentation basin, in which the sediment-bound nutrients can settle at the bottom. Alternatively, the water filters into an iron-rich base which has been planted with flood-resistant plants. The water then flows into the water basins containing helophytes. This stage primarily involves the removal of nitrogen compounds. The helophytes pump oxygen into the low-oxygen base via their stems and roots. This bridges the gap between nitrification and denitrification processes, allowing nitrogen (N) to disappear from the system into the atmosphere. After this stage, the water flows into another basin with submerged aquatic plants for post-purification. There may be a final stage in which the water flows through an ironstone filter in order to bond any remaining phosphorus (P) residue.

Discharging phase
When the soil in the biocascade contains phosphorus (P), which is an inevitable occurrence after some time, this will no longer bond phosphorus present in the water. In light of this, the plants will be the sole mechanism for removing phosphorus from the water. In practice, the primary production of plants is often too low to prevent or to compensate for a subsequent supply of nutrients from the soil into the layer of water. When measurements from the soil and water demonstrate this in practice, the system will be entirely submerged in surface water. This will mean that the system will quickly become anaerobic due to the presence of reactive organic material on the bottom. In these reduced circumstances, the phosphorus which has accumulated in the bottom is mobilised and enters the layer of water via diffusion. Floating aquatic plants facilitate this process by sealing the water surface. This in turn reduces the amount of oxygen in the water, meaning the build-up of phosphorus can continue. The floating plants can absorb the phosphorus present in the water. The phosphorus is eliminated from the system by regularly harvesting these plants. Then, after a desiccation period, the soil in the biocascade system is able to bond phosphorus contained in the water that is infiltrated into the system. This gives rise to a regenerative system which can be loaded and discharged via controllable changes in reduction potential and the related nutrient conversions.