Innovative process implementing nanomaterials for the elimination of emerging micropollutants from aqueous effluents. – POLPHARMA

The implementation of existing technologies to treat drug residues in different types of wastewater and water treatment systems for human consumption is penalized by their cost, efficiency and technical difficulties. In addition, some drugs are not completely degraded by conventional processes applied in WWTPs and / or drinking water supply chains. On the basis of consumption, environmental presence, resistance to usual treatments and possible toxicity, amoxicillin, doxycycline, carbamazepine, ciprofloxacin, danofloxacin and sulfamethoxazole were chozen as priority substances by the POLPHARMA project consortium: BRGM, CREGE, IEM, SUEZ & UPMC. The originality of this project lies in the development of tunable nanocomposites for the elimination of certain pharmaceutical molecules by sorption and/or enzymatic degradation. The nanocomposites can be synthesized from available and inert commercial products (bentonite, silica nanoparticles or iron oxide) and enzymes. After retention of the micropollutants, the nanocomposites of micrometric size, can be extracted by flocculation followed by filtration or sedimentation. The most effective flocculant found for the present formulation is an organic reagent marketed and authorized by the Directorate- General for Health.

The comparison of the results of ciprofloxacin depletion in aqueous phase by the main industrial minerals typically used in adsorption and filtration highlighted the performance of a montmorillonite of Moroccan origin. The cation exchange capacity is a determining factor on the adsorption of amphoteric micropollutants. Apart from economic and technical constraints, activated carbon remains the best adsorbent medium capable of non-specific adsorption of all targeted micropollutants. Nevertheless, the nanocomposites developed in this project present specific adsorption behavior towards some pollutants. Irrespective of the type of water tested, danofloxacin, ciprofloxacin and doxycycline are eliminated. However, sulfamethoxazole which presents low or no adsorption is well removed by enzymatic degradation promoted by functionalized composites, while carbamazepine is only partially removed by adsorption on activated solids with enzymes.

Promising results on the trapping of metals by the new composite media have been highlighted in preliminary tests performed on urban wastewater. In this regard, the application of these new multifunctional media (adsorbent and ion exchange) for the treatment of particular industrial effluents (specific pollution, acidic pH, high content of organic compounds, etc.) should be confirmed in a second phase of qualification of these media.
Enzymatic degradation has been studied mainly using synthetic wastewater. It would be important to evaluate the performance of free and immobilized enzymes under real wastewater conditions. In this sense, testing with enzyme-mediator systems in real wastewater with very low levels of micropollutants, as usually found in these waters, is fundamental to assess the impact of actual conditions on treatment efficiency. Another important aspect to consider is the treatment up-scaling, since all the experiments were carried out at laboratory scale. In this sense, the design of a reactor (eg enzymatic membrane reactor, packed bed) would be the best option as it would also evaluate the treatment effectiveness in continuous operation. In addition, a technical-economic study would make it possible to evaluate the cost taking into account the life cycle of enzymes.

3 publications have done from first developments of POLPHARMA

POLPHARMA is an ANR project emerging from two industrial partners (SOLVAY & SUEZ) and four research institutes (BRGM, CEREGE, IEM & UPMC) that have complementary and multidisciplinary skills to reply to an emerging societal and technological problem. The consortium's fields of research are focused on the application of nanotechnology to the effluent water treatment, that combines synthsis of active phases, characterization of their reactivity, and interfacial properties, adsorption capacity, technical and economical approaches of the recycling and risk assessment). This project falls within the scope of the high-priority themes of the French National Action Plan for public health and the environment. It aims at developing innovative technological solutions that will make it possible to treat, under advantageous economic conditions, water impacted by the pharmaceutical micropollutants that are among the most resistant to conventional water treatment processes used in France and elsewhere. These contaminants pass mainly through wastewater treatment plants and health care centers (hospitals and clinics). They are among the emerging contaminants whose presence in the environment is, as yet, unregulated in Europe. The ultimate goals of the project are to produce clean water and reduce the risks associated with the discharge of drugs into the environment. Micropollutants have been chosen based on their high consumption, occurrence in the environment and behavior in a WWTP and their resistance to water treatment. In this regard, we propose to study: amoxicillin, carbamazepine, ciprofloxacin, danofloxacin and sulfamethoxazole. The originality of this project is the use of nanostructured pillared clays with various reactivity and with or without immobilized enzymes to develop an innovative and economical process that can be added to pre-existing treatment processes to remove or degrade micropollutants. The project will include five interrelated phases that will culminate in the industrial validation of the treatment process. These phases cover various scales – from the laboratory scale to that of a demonstration under semi-industrial conditions. The first task is devoted to the selection of typical effluents (urban wastewater, hospital waste, industrial waste, cattle manure) representing significant inputs into the environment of the five drugs selected by the consortium, for further evaluation of innovative treatment processes. In order to determine the ability of the nanostructured materials and immobilized enzymes to remove both high and low drugs levels, a drinking water resource will also be selected. Task 2 will be devoted to the synthesis and characterization of nano-structured active phases. They will be obtained by bridging montmorillonite by nanoparticles that act as pillars. Various particles of different size and reactivity will be used in order to produce nanostructured pillared-clay with varying porosity and intrinsic reactivity to optimize the sorption of the organic pollutants. These supports will also be used for the enzyme grafting in task 3 as well as membranes. After defining the most appropriate enzymes and method of immobilization of these enzymes, the enzymatic activity and influence of the reaction parameters will be studied in task 3.
In task 4, work will focus on i) optimizing the capture of pharmaceutical micropollutants with raw or functionalized pillared-clays based on the physicochemical and hydrodynamic conditions of the environment and ii) the development of specific solid / liquid separation processes to the newly formed products. A demonstration semi-pilot scale will be carried out to define a part of an industrial processing scheme and secondly, to conduct a technical and economic study. Task 5 aims at developing recycling strategy for both membranes and PILCs as well as a evaluating the risk associated with the use of pillared-clays.