Ammonia Recovery and Energy Generation

Located in the central region of the UK, the Midlands Living Lab, hosted by Severn Trent Water (STW), in collaboration with Coventry University, Organics Group, and Environmental Monitoring Solutions (EMS), has three streams of activity;

  • Leakage detection module – implementing smart meters and options to reduce leakage in distribution networks.
  • Smart wastewater management – demonstrating Intelligent Wastewater Networks in addressing hydraulic capacity.
  • Ammonia recovery and energy generation – ammonia scrubbing of centrate WW and evaluated electrolysis for renewable hydrogen.

STW has committed to research, explore, and develop opportunities for ammonia recovery and renewable energy generation to enhance environmental and financial performance. A recovery process would avoid process emissions from conventional biological treatment, instead generating an ammonia product which could replace conventional fertilizer and avoid energy consumption and emissions related to its production. STW is collaborating with Coventry University and Organics to deliver this activity.

Coventry University have been developing a lab-scale electrolyser that will convert recovered ammonia to hydrogen.  

Figure 1. Anion exchange membrane selection lay-out and lab-based electrolyser developed.

To date, various electrolyser cells have been designed, built and tested to obtain the most effective configuration of the pilot electrolyser.  

Organics Thermal Ammonia Recovery (OTAR) Technology

Organics has been providing thermal ammonia removal for over two decades to sites in Hong Kong. These sites have some of Asia’s most challenging contaminated wastewater issues, and are very restricted on land availability, with undulating topography, and highly populated areas. 14 landfills and one Anaerobic Digestion site in Hong Kong presently use the technology, some have been operating for 20 years, and there are two new sites coming online.

Figure 2 Organics Thermal Ammonia Removal Plant – Hong Kong

OTAR builds upon advances in energy efficiency developed over the last twenty years, making the thermal process more efficient and sustainable, using appropriately scaled and sequenced economisers and heat exchangers. OTAR can operate using various energy formats such as: biogas, natural gas, exhaust heat, and low-grade waste heat from jacket waters.

The OTAR plant for Severn Trent differs from the Hong Kong plant as, alongside the standard stripping and scrubbing columns, it includes a rectifier column, for ammonia concentration and recovery.

OTAR is based upon a ‘switch on and monitor approach’ using the skill sets of operatives and technicians familiar with standard electrical and mechanical plant, requiring very little intervention post start up, other than the recording of data for trials and the occasional visual inspection of the plant.

Figure 3 OTAR Process scheme.

Organics is also supporting Coventry University with the design and build of a pilot-scale electrolyser, as one option to recover energy through hydrogen from the recovered ammonia. The recovered ammonia solution will also be investigated as a source of carbon free fertilizer.

The assembly of the ammonia recovery system has been completed and the OTAR Pilot plant is presently being shipped to STW’s Resource Recovery Innovation Centre (R2IC) at Spernal, to assess its performance and the evaluate the options for the recovered ammonia.

Figure 4 OTAR Pilot Plant