Biochar in Constructed Wetlands

Enhanced Biochar substrate for Phosphorus Removal in Constructed Wetlandsbiochar for phosphorus removal


Phosphorus is an essential nutrient for all forms of life and is one of the three fundamental crop macronutrients. However, excess phosphorus from sewage, animal farms and leached croplands can contaminate waterways causing eutrophication. Reducing these nutrients from wastewater is essential to protect natural ecosystems.

Constructed wetlands are an efficient wastewater treatment device, however their long term phosphorus removal is generally poor. They are typically rectangular beds built with an impermeable liner filled with gravel and aquatic plants. Wastewater is treated as it passes through plant roots.

Adsorption and precipitation reactions are regarded as the primary long-term phosphorus retention mechanisms in constructed wetlands. These processes are highly dependent on the properties of the wetland substrate. Phosphorus removal can be maximised in constructed wetlands with substrates that can be replaced when saturated. Typically, phosphorus is bound in the substrate through reactions with iron, aluminium and calcium. The use of mineral-enhanced sorption substrates can provide a high level of phosphorus retention and recovery from for reuse wastewater.

A mineral-enhanced biochar was tested as a substrate to remove phosphorus from domestic wastewater in a constructed wetland system. The biochar substrate was compared to a commonly used gravel substrate. The study aimed to identify whether a biochar wetland is capable of reducing phosphorus concentrations to less than a typical gravel wetland.

For more information about bicohar, please contact Lise Bolton at Ecoteam ph. (02) 6621 5123 or email