Optimised Renewable Mix for Energy Saving in Waste Water Treatment Plants

PROJECT DESCRIPTION

BACKGROUND

Across the EU, there are around 16 000 waste water treatment plants (WWTPs). Treatment of waste water is necessary to prevent pollution from being discharged into water courses. It can also provide water that is sufficiently clean for re-use in certain contexts, which can be particularly useful in areas suffering from water stress.

However, owing to the high energy demands of WWTPs treated water is often more expensive than drinking water and its use is therefore currently restricted. WWTPs in the EU consume around 10 000 GWh/year. Furthermore, the volume of waste water being treated in the EU is increasing by around 7% each year, creating an additional environmental burden. This energy in Europe is typically produced from the burning of fossil fuels. Energy consumption from WWTPs creates emissions of more than 27 million tonnes/year of CO2 in the EU. In Spain alone, WWTPs consume 2 213 GWh/year, emitting more than 6 million tonnes/year of CO2.

OBJECTIVES

The LIFE RENEWAT project aimed to demonstrate the use of sustainable technologies for reducing the energy demand of WWTPs. The goal was therefore to reduce both greenhouse gas emissions associated with the treatment of waste water and the costs of water treatment, making treated water a more viable option for a range of uses.

Specifically, RENEWAT planned to demonstrate an intelligent system for applying a renewable energy mix in WWTPs. The project would follow three main stages:

Adapting the WWTP process to a new energy input from a renewable mix, including, small-scale (less than 10MW) photovoltaic (PV) and wind energy sources;

Using the renewable sources (PV and wind) in the WWTP; and

Developing an intelligent system capable of managing the input of energy from the different sources.

The intelligent system would discriminate between the energy input sources PV, wind or grid aiming to provide the optimum energy mix according to the environmental and weather conditions. It would also regulate the overall energy input according to the precise demand of the WWTP at every stage of the process.

The project thus expected to reduce the consumption of electricity from the grid as much as possible and therefore reduce the carbon emissions. It would also reduce the price of treated water and represent a first step in terms of boosting the re-use of treated water, for example in agricultural and landscape irrigation.

RESULTS

The RENEWAT project carried out three main activities at Archena's wastewater treatment plant in Spain:

Optimisation of the biological reactor in the aeration stage by including new control algorithms and new efficient equipment replacement;

Development of an innovative hybrid system that does not require energy from the grid (formed by 100 kW of PV energy and 5kW of mini-wind energy generation); and

Creation of an intelligent management system for load consumption and energy generation control in the most optimum way.

These actions demonstrated that the cost per cubic meter of treated water can be reduced by 9.56% to bring it closer to the price of drinking water. The project methodology can potentially be implemented in 99% of the EUs 16 000 WWTPs. Virtual and augmented reality and artificial intelligence applied to WWTP management have progressed greatly in recent years, so potential for implementation is huge. The project also showed that energy consumption at these WWTPs can be reduced by 28.47%at the aeration stage with the intelligent integration of renewable energy sources. These actions also lead to a reduction in the carbon footprint of around 46.80 tonnes of CO2/year for every 100 kW from renewable sources.

Efficiency savings at the WWTP also represent a cost saving for the agricultural and industrial sectors, as well as the public sector, that use treated waste water for a range of purposes. The cost saving related to energy consumption will also offset any additional research and development expenditure. Farmers will also benefit from a reliable supply of water, especially in areas that are increasingly prone to water shortages, such as the Mediterranean coastal region.

The innovation of the system is the design of the control software to regulate energy input/demand balance, which will ensure that 100% of the renewable energy produced is consumed, while adjusting demand to meet its availability. This regulation of the energy demand is key to ensure a reduction in energy consumption from the grid.

Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).