
Comprehensive process audit and mathematical modeling were applied to evaluate various options of reducing energy use in the activated sludge process . Modelling results predicted savings in aeration costs of ~25% through implementing optimized aeration control and up to 52% through implementing both influent flow balancing and optimized aeration control. Site implementation of optimization of current control strategies through introduction of variable DO setpoints achieved immediate savings on aeration costs of 25% aeration costs without incurring substantial capital expenditure but only changes in control protocols. More complex measures such as implementing flow balancing within the collection system are under review for site trialsuSense Process Engineering was engaged by Yorkshire Water.


- SBR activated sludge plant
- Package plant activated sudge process
- Aerated and polishing lagoon plant
- Rotating biological contactor
- Oxidation ditch


The main tasks involved collection and analysis of data, energy audits and benchmarking, evaluation of aeration energy use reduction strategies through advanced modelling and simulation as well as financial analysis.
The Key findings from the project were:
- Identified aeration ECMs can potentially save 9-40% of aeration energy consumption and cost.
- Implementing the identified ECMs which include optimal process and aeration control results in improved biological nutrient removal and compliance with final effluent nitrogen and phosphorus limits.
- In order to realise these savings local authorities, need to develop a clear energy management strategy and put in place robust systems and structures towards achieving this strategy.
The project was undertaken in collaboration with the City of Tshwane and ERWAT who provided the case study plants as well as collection of wastewater data and analysis services




- Anaerobic Digestion (conventional and advanced)
- Thermal Gasification
- An innovative emerging technology, Polymeric Carbon Solid (PCS).
The study will involve a combination of desk top evaluation of full scale plants as well as laboratory and pilot scale studies for the PCS technology. By adopting this approach, the project will address the gaps in knowledge on sludge-to-energy technologies identified in previous research and provide valuable information on both established and innovative emerging technologies that South African municipalities can use to formulate long term sludge management strategies.
The project is being undertaken in collaboration with the University of Stellenbosch who are carrying out the laboratory scale investigation for the PCS technology and ERWAT who are providing the case study plants for anaerobic digestion and for the PCS pilot scale study.
