26th October, 2017.- Acciona Agua has demonstrated today its commitment to sustainability and energy efficiency in the presentation of the results of its project LIFE RENEWAT -financed by the European Union- which has been developed between 2013 and 2017 in the Waste Water Treatment Plant (WWTP) of Archena (Murcia), where the company leads another European initiative in the line of efficient purification: LIFE CELSIUS.
The aim of the project was to reduce the electricity consumption of the WWTP by 30 per cent, as well as the cost per cubic metre of water treated by 24 per cent, as well as a significant reduction in CO2 emissions into the atmosphere.
“We have totally fulfilled the objectives in the phase of aeration, with a reduced energy consumption by 28 percent, while in the whole of the plant, that savings represents only a 10 per cent”, has recognized Carlos Egea, Acciona Agua Engineer.
CO2 emissions have also been reduced by 45 tonnes per year and the integration of renewables in the plant has been promoted, which means that “partial or total disconnection of the network is now possible”, he added.
The integration of renewables
However, a 9.6 percent saving in the cost of treated water has been achieved, compared to 24 expected at the start of the project, and in terms of installed wind turbines, the weather conditions in Archena have prevented an optimum operation and the generated energy only represents one year later 0.76 percent of the total (the rest corresponds to solar energy), explained Noelia Dafonte, Engineer of Acciona Agua.
The integration in the Archena plant of renewable energies has pursued since its inception the consumption, with a total of 143,000 kilowatts a year, which corresponds to the average consumption of 40 Spanish households.
“The project has sought to reduce energy consumption through different actions on the WWTP, prioritizing in the aeration phase of the biological reactor and the implementation of a system of management of renewable energies”, said Miguel Fajardo, of Acciona Industrial; in RENEWAT “we have combined our capacities in water and energy”.
Amador Rancaño recalled that the biological treatment “is the one that consumes most energy in the WWTP”, especially the aeration or oxygenation phase of the bacteria that intervene in the degradation of organic matter; so savings must be reached through the reduction of oxygen, air and heat requirements.
In the phase prior to the start-up in the Archena WWTP of the LIFE CELSIUS project, an anaerobic membrane bioreactor was installed in which the bacteria responsible for degrading the organic matter can do so without the need for an external heat source to reduce the needs energetics of the process.
This bioreactor was installed within the framework of the OptiAnMBR project, led by Acciona Agua, the Regional Wastewater Treatment and Purification Entity of the Region of Murcia (ESAMUR) and CETENMA (Energy and Environment Technology Centre).
In addition, the microorganisms present in this reactor do not require oxygen for their metabolic functions, which reduces the need for aeration, and also generates biogas, which can be used as fuel to generate energy.
LIFE CELSIUS, optimizing the plant
From the verification of the smooth functioning of the anaerobic membrane bioreactor, Acciona Agua has promoted in the WWTP of Archena a second stage to influence energy saving and reducing CO2 emissions.
Under the European project LIFE Celsius, the company tries to demonstrate the feasibility of a water treatment system for more efficient warm climates, by combining the system devised by OptiAnMBR and the use of bacteria capable of performing oxidation of ammonium in the absence of oxygen, a process that contributes to fix the CO2 and emits nitrogen gas to the atmosphere.
With the combination of both phases, Acciona Agua expects to exceed 90 percent of organic matter elimination and the same percentage of nitrogen compounds and save 60 percent of the energy needed in both processes.
María del Mar Micó, director of LIFE Celsius, explained today that the project has met its objectives and is already in the optimization phase; “the most complicated has been the control of partial nitrification”, she has acknowledged.
In conventional nitrification, two types of bacteria work together, the ammonia-oxidants, which convert ammonium into nitrites, and nitrite-oxidants, which convert it into nitrate, and both of them need oxygen for their metabolic functions.
“In our partial nitrification, we want the ammonium oxidizers to survive above the nitrite-oxidizers and we achieved this by reducing aeration as much as possible”, said Micó.
In another reactor, the anammox combine ammonium with nitrate and convert it into nitrogen gas without the need for oxygen.
Traducción: Carmen Gilson