AMREWAS
AMMONIUM RECOVERY AND PLANT-BASED WATER PURIFICATION FROM NITROGEN-RICH WASTEWATER
INTRODUCTION
​
The processing of nitrogen-rich wastewater with activated sludge treatment is characterized by a high energy need, production of nitrous oxide (a.k.a. laughing gas, a strong greenhouse gas) and excess sludge.
​
AMREWAS alternatively demonstrates the stripper-scrubber combination for ammonia recovery followed by an aerated reed bed as further purification.
​
During the project, the ammoniacal nitrogen was recovered in the form of an ammonium nitrate solution (25%), which can be applied locally by farmers.
​
Using an aerated reed bed as post-treatment greatly reduces operational costs and sludge production. Energy consumption, follow-up efforts and maintenance of this system are also significantly lower.
​
PROJECT GOALS
​
The main project goal was the demonstration of the treatment of a nitrogen-rich wastewater, i.e. thin fraction of manure and/or digestate, where ammonia is recovered and a plant-based purification is applied. The project aimed at and achieved to:
​
• Reduce the operational and investment costs associated with the current state of the art of constructed wetlands, by first stripping out the ammoniacal nitrogen
​
• Research the possibilities with the effluent for water reuse in agriculture because of the remaining potassium salts
​
• Establish a purification technology to treat other types of wastewater with high ammoniacal nitrogen concentration, such as landfill leachate or black water from residential areas, based on a "nature-based solution"
RESULTS
​
Although the ammonium content of the stream to be treated varied, the stripping/scrubbing ammonium removal efficiency was fairly constant at around 30%. This efficiency was achieved without additional energy for heating or chemical dosing at an operating temperature of 20°C to minimise ecological and financial impact. It is estimated that the efficiency can be greatly increased, up to 85%, by adding chemicals and heat.
The aerated reed bed achieved good removals for total nitrogen and chemical oxygen demand.
CONCLUSIONS
​
• Removal efficiencies were greater than 90% for suspended solids, biodegradable contamination, ammonium nitrogen and phosphorus
​
• Nitrate concentrations increase with higher loads, indicating that an optimum must be sought between adding extra energy during stripping or taking up more surface area for the reed beds
​
• Recirculation over the reed bed could help to lower the nitrate concentrations in the effluent to be able to meet the discharge criteria with smaller downstream flow fields