ThermoEnergy Ammonia Recovery Process for municipal and agricultural wastes

A New Process for the Recovery of Ammonia from Ammoniated High-Salinity Brine

This paper describes a new method for the recovery of high-concentration ammonia from water in the form of ammonium chloride, ammonium hydroxide and ammonium carbonate. The method was applied to the Solvay process, in which sodium bicarbonate is produced through the reaction of ammoniated brine and CO2 gas. The Solvay effluent contains ammonia in the form of soluble ammonium chloride. The proposed method is based on the recovery of ammonia using a high-alkalinity reactant, calcium oxide (CaO), in a closed electrocoagulation cell operating at a specific current density. The recovered ammonia is collected as a gas within a closed cell containing deionized (DI) water at room temperature. Afterwards, the collected solution (DI water–NH3 gas) is concentrated through a separate process, and is then reused in the Solvay process and other applications. The electrocoagulation process is applied to the treatment cell using aluminum electrodes and a current density of 5–15 mA/cm2. After 7 h of treatment using the electrocoagulation cell, a high reduction of the ammonia concentration—99%—was realized after ~9 h of the electrochemical treatment. The initial ammonia concentration in a Solvay effluent of 13,700 mg/L N was decreased to 190 mg/L N. Furthermore, an ammonia recovery of 77.1% in the form of ammonium hydroxide was achieved. Generally, this process, which starts at room temperature, can result in an energy reduction of 80%—from 7.8 to 2.3 kWh/kg NH3—compared to conventional processes, which entail heating the Solvay effluents to 160 °C. The proposed system and method were found to be suitable for the recovery of ammonia from ammoniated water, and can be utilized for the treatment of landfill leachate, and municipal and industrial wastewater.

Electrochemically-assisted ammonia recovery from wastewater using a floating electrode

This work presents and explores a novel methodology for the removal and recovery of ammonia from wastewater based upon two mechanisms: electrochemical oxidation and a previously unreported electrochemically-assisted surface transfer mechanism. Recovery of ammonia is enabled by placing a porous cathodic electrode at the wastewater-air interface. In this configuration, the cathode creates local alkalinity and an electric field that draws ammonium ions towards the wastewater-air interface, resulting in near-linear reductions of dissolved ammonium irrespective of concentration. This approach leads to significant ammonia recovery without the need for ion-exchange membranes. In addition, anodic reactions that simultaneously occur at depth in the wastewater induce ammonia oxidation in accordance with proven mechanisms. The floating electrode approach offers improved ammonia removal efficiency in comparison to electrooxidation. Trials conducted on synthetic wastewater (900 mg NH₄⁺-N l^-1) and filtered anaerobic centrate (560 mg NH₄⁺-N l^-1) demonstrated ammonia concentration decreases up to 216 mg l^-1 hr^-1 and 110 mg l^-1 hr^-1, respectively, under the application of 5 mA cm^-2 current density. The technology would be best used to treat municipal and industrial wastewaters possessing high ammonia concentration, including anaerobic digester centrate and urine, and offers potential to assist in removing ammonia from environmental waters.