DS0102 - Innovation technologique pour analyser, remédier ou réduire les risques environnementaux

Next Generation of Wastewater Treatment Plants: Optimization of Treatment Performance through Online Monitoring of Holistic Sludge Properties – NEXT

To optimise the sludge treatment line of Water Ressource Recovery Facilities

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To provide relevant measurement and analysis tools to limit the energy expenditure and the chemical consumption of actual and future processes

The sludge is a by-product of the wastewater treatment. The sustainable management of this sludge is one of the major challenges of the 21st century: the total production of potential dry matter if all wastewaters produced on earth was treated is estimated at more than 80 Mt. In addition, the costs related to the treatment of these sludge represent more than half of the entire sanitation bill, due to the chemical consumption and the energy expenditure. Also, optimization is needed to limit these costs and environmental impacts. To this aim, engineers need tools to evaluate the performance of these processes with regard to the physical characteristics of the sludge produced but also to quantify the environmental and economic impacts.<br />The processes involved in these sectors are mainly based on the physical separation of solid and liquid phases, in order to limit the costs of storage and transport of these by-products, and to guarantee their stability. Also, the flow properties of these materials are one of the main parameters governing the performance of these processes. The rheological properties (defining the viscosity) cannot be measured continuously. Also, efficient measurement tools must be proposed in order to equip the treatment line and to allow the continuous measurement of these physical characteristics and to envisage their optimization.

To this aim, a multi-scale and multi-disciplinary approach has been developed. First, an experimental approach was conducted at the laboratory scale to accurately measure the rheological properties of biological sludges and their evolution as a function of sludge composition (dry matter content and organic matter ratio).
Different measurement techniques have been evaluated for their ability to propose descriptors correlated with the rheological properties of the sludge. These techniques include both optical spectroscopy tools (in the near-infrared and visible UV ranges), electrical measurement (electrical impedance spectroscopy) and imaging (microscopy and fast camera). Their evaluation was carried out on sludge of different origins, taken from sampling on industrial facilities but also for monitoring experiments conducted at the laboratory scale, simulating the different sludge treatment processes. For this purpose, a semi-industrial pilot, reproducing a sludge treatment line equipped with a filtration belt, was designed and used to test the impact of various operating parameters on sludge properties.
In a second approach, various data relating to sludge treatment lines were collected at industrial scale in order to develop tools for evaluating the performance of the systems, based on life cycle analyzes, the definition of performance indicators and the evaluation of best available techniques (BAT).

The main results consist in (i) significant advances in the knowledge of rheological properties of biological sludge, (ii) reliable methodological developments of experimental protocols (rheological measurement reference method) and tools for process optimization through multi-criteria performance analysis and treatment line selection using the best available techniques; and (iii) identification and evaluation of relevant descriptors for in situ monitoring of processes based on optical spectroscopy techniques.

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The scientific valorization of the project consists in two publications in international journals and eight conference papers, mainly on experimental aspects (rheology and optical spectroscopy). The valorization of the relevant databases will be continued. In addition, the various developed methodological tools will be disseminated within the technical and scientific communities, in order to express the need of data at industrial scale to allow the definition of optimization strategy of the treatment lines.

Sludge (also known as biosolids) treatment and management is a growing challenge for municipalities around the world. If all of the wastewater from the world’s urban population was collected and treated, 83 Mt of dry sewage sludge would be generated by 2017.The cost of biosolids treatment constitutes to approximately half of the cost of wastewater treatment, and the quantities continue to increase as new wastewater treatment facilities are built and the existing ones are upgraded to keep up with the growing population and stricter regulations. Sludge treatment and management is going to be a major challenge in the next decade.
The goal of this research is to investigate the in-line and real-time use of novel holistic sludge descriptors to measure, monitor, model and predict sludge behavior through sludge treatment processes and use this knowledge for the optimization of design and operation of treatment processes. Based on the knowledge generated from this research, our ultimate goal is to develop in-line and real-time optimization and automation systems for sludge treatment processes with support from our industrial partners. The research will help to optimize sludge treatment processes, improve their performance while reducing the operational costs and the environmental impacts. This will result in important savings for treatment plants.
Sludge rheology, far UV (FUV), near infrared (NIR) and electrical impedance (EIS) spectroscopies, and water activity will be used as holistic descriptors to capture the changes in sludge characteristics, flow, and behavior. These descriptors can be measured in-line and real-time, and they are non-destructive to sludge matrix. Therefore, they can be successfully used for optimization and automation of treatment processes. Both lab-scale and full-scale tests will be carried out in this study. The team will also complete an evaluation of environmental and economic impacts of treatment improvements and alternatives.







Project coordination

Yannick Fayolle (Institut National de Recherche en Sciences et Technologies pour l'Environnement et l'Agriculture)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Endetec-Pathogen Detection Systems Endetec-Pathogen Detection Systems
Real Tech Real Tech
Canada Research Chair in Wastewater Treatment Engineering
TetraTech Tetra Tech
ARMINES FAYOL ARMINES Institut Henri Fayol de l'Ecole des Mines de Saint-Etienne
Irstea Institut National de Recherche en Sciences et Technologies pour l'Environnement et l'Agriculture
BPR-France BPR France Inc.

Help of the ANR 470,605 euros
Beginning and duration of the scientific project: October 2014 - 36 Months

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