Energy efficiency through self-consumption of electricity by solar energy and cogeneration in WWTPs

14 February, 2024

By Mr Fernando Díaz, Incatema's Director of Infrastructure.

The UN established World Energy Day on 14 February 1949. This global initiative invites us to reflect on the importance of producing and consuming energy resources responsibly, and to innovate in order to develop more efficient and less polluting production alternatives.

In this regard, it is interesting to take into account the evolution of the engineering design of new wastewater treatment plants (WWTP). These facilities can be a clear example of infrastructures that are geared towards energy efficiency and, therefore, environmental sustainability.

For the engineering design of new WWTPs, the energy efficiency of the plant itself is taken into account, since the viability and, therefore, the profitability of the infrastructure will depend to a large extent on it. The main objective is to optimise the water purification process so that, without losing quality in the treatment, the greatest cost of the process, which is electricity consumption, is minimised. There are different ways to achieve this. Among the main ones are the commitment to new purification technologies, which are more efficient, and the automation of processes, which leads to greater control of the plant and, therefore, the improvement of its operation and maintenance. Automation, for example, makes it possible to keep the debugging operation active 24 hours a day, detecting operating errors on the spot and resolving them automatically, thus minimizing downtime and restarts in the event of a breakdown.

At Incatema we are also committed to the design of self-consumption treatment plants through the installation of high-performance solar panels. These systems guarantee the availability of highly sustainable photovoltaic energy for plant operations. Adapting WWTPs to the climatology of the area where they are located is a necessity, and in this sense, using the resource of sunlight, unlimited and free, is one of the keys to the sought-after energy efficiency in line with sustainable development goal number 7 of the 2030 Agenda aimed at the use of clean and non-polluting energy.

On the other hand, the process of electricity cogeneration from the use of biogas produced in the anaerobic digestion of some WWTPs also undoubtedly contributes to environmental and energy sustainability. The energetic use of biogas generated in sludge treatment is very attractive both economically and environmentally since, on the one hand, waste management costs are reduced and, on the other hand, the valorisation of this by-product, converted into a resource, has a positive impact on the environment. The WWTPs, therefore, also reuse the thermal energy produced by the cogeneration process for their own consumption, since it allows them to maintain the appropriate temperature of the sludge inside the anaerobic digester. A further positive factor to consider is that, if more electrical energy is produced than is necessary for the plant self-operation, it can be made available to the general power grid.

Developing this type of increasingly sustainable facilities obviously requires greater financial investment. It may be a handicap at the beginning, but in the medium to long term it provides a return on investment that far outweighs the initial outlay. The winner of all this investment is not only the organisation in charge of its exploitation, but also the environment and the planet and, therefore, all of us.