This line focuses on developing sustainable wastewater treatment processes that meet stringent regulations regarding water quality in terms of nitrogen concentrations. In particular, we are advancing the use of nitritation and anammox processes to treat wastewater with low carbon-to-nitrogen (C/N) ratios such as those from anaerobic sludge digesters, landfill leachate, predigested effluents from the canning industry, etc. For these wastewaters, the conventional nitrification and denitrification processes are costly due to the need for external organic matter to complete denitrification.
Anammox (Anaerobic Ammonium Oxidation) process provides a cost-effective and efficient alternative solution by converting ammonia and nitrite directly into nitrogen gas without using organic matter. This process requires a preceding partial nitritation stage to oxidize half of the ammonia (the common form of nitrogen present in wastewater) to nitrite. The main advantages of partial nitritation-anammox processes over nitrification/denitrification processes include minimal sludge generation, reduced aeration costs since only half of the ammonia has to be converted into nitrite, and no organic carbon is required. These processes can be applied to wastewater systems using two configurations: a two-unit configuration (partial nitrification stage + anammox stage) or a single-unit configuration (simultaneous processes under micro-aerobic conditions).
Since 2000, Biogroup has been advancing anammox-based processes by developing systems with high biomass retention to counteract the slow growth of autotrophic microorganisms, applying anammox to the treatment of industrial effluents and sludge anaerobic digesters, and evaluating the effects of common industrial wastewater contaminants, such as salts and antibiotics. In this line, the ELAN® patent (Eliminación Autotrófa de nitrógeno) was developed in collaboration with Aqualia, and full-scale installations are already in operation.
Currently, the application of anammox-based processes in wastewater treatment plants (WWTPs) has taken a step forward in treating the mainstream of WWTPs to improve their energy efficiency. With this approach, organic matter will be valorized in an upstream unit, and then ammonia from these units will be removed in an anammox-based process in a two-unit system. The main bottleneck of the anammox-based processes application to the WWTP mainstream is to prevent nitrite oxidation to nitrate by nitrite-oxidizing bacteria at low temperatures. The developed process is currently being demonstrated in 30m3 reactors.
We also explored autotrophic denitrification, which uses reduced sulphur compounds (eg H2S) to convert nitrate or nitrite into nitrogen gas. This process is of great interest in treating wastewater containing nitrogen and sulphur compounds, such as effluents from the petrochemical and canning industries. In this line, the research carried out in the group is focused on defining the conditions that allow the stable application of this process to industrial effluents.
Projects
Positive Energy Waste Water treatment plant for combined treatment of wastewater and biowaste in small populations (LIFE ZERO WASTE).
This project has received funding from the European Union’s LIFE programme under grant agreement LIFE19ENV/ES/000631)
Innovative decision-making tool for defining the most suitable manure management strategies to achieve a sustainable livestock farming system during the whole value chain (NUTRITIVE)
HORIZON-CL6-2023-ZEROPOLLUTION-02
Completed Projects
The aim of this project is to expand the field of application of the partial nitrification-anammox processes to different types of wastewater at low temperatures. Problems arising from the scale-up of the reactor are also studied in order to reduce the start-up time of these processes at industrial level. The specific objectives of the project are:
A. Treatment of high ammonia concentrated effluents: application to pig slurry. The production of pig slurry is a serious environmental problem that requires an economically feasible solution. The organic matter removal in these effluents can be reached in anaerobic systems at room temperature. However, this technology eliminates mainly organic matter and requires a post-treatment system for the removal of ammonia. A two stage system (partial nitrification-anammox) and a one stage system (CANON) will be applied, at laboratory scale, to treat pig slurry.
B. Treatment of wastewater with low ammonia concentration: Application to urban wastewater. Among the weaknesses of the activated sludge technology (commonly used in the WWTP) is its limited ability to remove nitrogen. This means that in some cases it is necessary to extend the reactor to comply with the legislation, with a high economic investment. A CANON biofilter for the post treatment of the urban wastewater is proposed as an option to improve the economic performance of the plant.
C. Scale up study: Application to urban wastewater. The effect of scale change on stability and efficiency of the system and in the physical properties of the biomass is going to be assessed. A CANON reactor at pilot plant scale (100 L) will be used to carry out the post-treat of urban wastewater. The results will allow the design of reliable industrial units which will benefit the implementation of this technology.
D. Application plan of the proposed technology in different sectors. The obtained results will be analyzed from the economic and environmental point of view in order to know the feasibility of the proposed technology. A mathematical model to predict and optimize the operating variables effect on the performance of the systems will be developed. Finally, the more suitable implementation strategies and operating conditions will be deduced.