Focus Energy & Environment : Chapter I : The latest French innovation in water treatment (06/30/2015)
Article rédigé le 30/06/2015
Environmental technology is the application of environmental science, green chemistry, environmental monitoring and electronic devices to monitor, model and conserve the natural environment and resources, and to curb the negative impacts of human activities. The term is also used to describe sustainable energy generation technologies such as photovoltaic, wind turbines, bioreactors, etc. Sustainable development is the core of environmental technologies. The term environmental technology is also used to describe a class of electronic devices that can promote sustainable management of resources.
The Government of the region of Hong Kong considers environmental technologies as an important topic for development of its territory. France, which host the largest companies worldwide in the environmental services (Veolia, Suez, Areva ...) is a country that has always been well positioned in innovative technologies for sustainable development. This series of focus about French technologies will consider the latest environmental technologies. Because this field deals too many concepts, the whole field will be roughly covered throughout 5 successive chapters:
I) Water treatment (Purification and Sewage)
II) Air purification
III) Renewable energy
IV) Solid waste management
V) Green building and energy conservation
Among all the themes exposed in this case, the first chapter will be devoted to the latest French innovations in treatment of water. The purpose here is not to give an accurate description of technologies, but to show which areas are currently explored by French research institutes.
I) Water treatment (Purification and Sewage)
France, because of its temperate climate, is subjected to cold and rainy winters. Water stress is very low compared to other places on the planet. Despite this abundance of water, French companies are very active in the field of new technologies for the treatment of drinking water and industrial effluents. A key reason for this is the fact that the regulation is much stricter in France than in many other countries. To comply with all the standards, researchers try to find out how to improve or innovate in water treatment. Below are display the mains lines of current researches or inventions in France:
- Chlorination and Chloramination
The physico-chemical chlorine-based treatment is the most used technical method in the treatment of drinking water. Chlorination (EU) and chloramination (USA) are the two most common oxidation techniques worldwide. On one hand, these techniques combine the advantages to be cheap, easily exploitable, effective but also to have the ability to disinfect water for several days after the treatment phase. On the other hand, more and more studies indicate that formation of toxic compounds with long-term carcinogenicity are formed during this kind of treatment .
The four most toxic common compounds in water are Trihalomethanes (THM) and their recommended limits by World Health Organization (WHO) are :
* Trichloromethane CHCl3 with recommended threshold of 200 μg/L
* Dibromochloromethane with recommended threshold of 100 μg/L
* Bromodichloromethane with recommended threshold of 60 μg/L
* Tribromomethane with recommended threshold of 100 μg/L
THM are chemical compounds in which theree of the four hydrogen atoms of methane (CH4) are remplaced by halogen atoms. In France, the concentration of THMs in the water drinking network is heterogeneous between the regions but remains lower than the limits defined by the WHO. Moreover, 98% of drinking water sources show concentrations of THMs lower than 30 μg/L, less than 1% of the French population is fed by water with THM concentration exceeding 100 μg/L.
None innovation using Chlorination have been released for many years. Recent studies are more inclined to find how by-products can affect the quality of the water and therefore the human health.
- Ultraviolet light and ozonation
Ultraviolet (UV) systems can destroy 99.99% of harmful microorganisms without adding chemicals or changing the water’s taste or odor. It is one of the four methods of disinfection approved by the United States Food and Drung Administration. UV has proven to be a quick, reliable and cost effective method of disinfecting water for both point of use and point of entry . Moreover, UV treatment is a safe, clean, easy-to-maintain method of assuring that water is free of bacteria. It is a proven technology that has no significant drawbacks.
UV germicidal irradiation (UVGI) is a disinfection method that uses short wavelength ultraviolet (UV-C) light to kill or inactivate microorganisms by destroying nucleic acids and disrupting their DNA, leaving them unable to perform vital cellular functions. The optimal wavelengths for disinfection are close to 260 nm. UVGI is used in a variety of applications, such as water and air purification. UVGI devices can produce strong enough UV-C light in circulating water systems to make them inhospitable environments to microorganisms such as bacteria, viruses, molds and other pathogens. UVGI can be coupled with a filtration system to sanitize air and water. Ultraviolet in sewage treatment is replacing chlorination due to the chlorine’s toxic by-products .
Similar to UV, one of the new methods to disinfect water is to use ozone. Ozone is an unstable gas composed of three oxygen atoms; the gas easily degradates back to oxygen and generating a free oxygen radical during this transition phase. This free oxygen radical is highly reactive and short lived : under normal conditions, it will only survive for milliseconds. Ozone is unstable, and it will degrade over a time frame ranging from a few seconds to 30 minutes. The rate of degradation is a function of water chemistry, pH and water temperature. The oxidizing properties of this radical confers greater disinfection effectiveness to Ozone, against bacteria and viruses compared to chlorination . In addition, the oxidizing properties can also reduce the concentration of iron, manganese, sulfur and reduce or eliminate taste and odors. Indeed, Ozone oxides the iron, manganese, and sulfur in the water to form insoluble metal oxides or elemental sulphur. These insoluble particles are then removed by post-filtration. Organic particles and chemicals will be eliminated through either coagulation or chemical oxidation.
- Adsorption on activated carbon and zeolites
A new process developed at the “Centre de Recherche sur la Matière Divisée”, a joint institute of the National Centre for Scientific Research (CNRS) and the university of Orleans, can trap micro-pollutants (pesticides, medicines, solvents, etc.) on activated carbon fabrics [6, 7]. This process was the subject of a French patent, which has been extended internationally and published on 21 February 2014. Thanks to the characteristics of the materials used (carbon fabric, carbon felt), the kinetics are fast, the regeneration is easy and the compact device maintenance is reduced. One other way in adsorption is to use zeolites. The purpose of using zeolite is to increase the biological activity of the cleaning process, improvement of sludge sedimentation characteristics and quality of treated wastewater. The content of iron and manganese is reduced, there is a reduction in total nitrogen content, and adjusting the pH. Zeolite is also used for cleaning waste water from ammonia in wastewater. The addition of zeolite for water purification positively affects the activation level of technological parameters such as production of excess sludge, volume load of substances and loads of sludge, age of sludge, sludge index.
- Membrane process:
The membrane technologies are becoming more prevalent in the world whether in the food industry, or in water treatment centers or in the treatment of industrial effluents. For example, for the desalination of sea water, more and more plants move from distillation technology (highly electricity consuming) to membrane processes combining nano filtration and reverse osmosis . Membrane filtration technology has been identified as "Key Technologies 2010" by the French Ministry of Economy, Finance and Industry .
In the water sector in particular, France is the second largest market in Europe for membrane filtration . However, in order to continue to innovate, new solutions will be developed thanks to micro and nanotechnologies. France is a leader in the membrane domain and must support an effective development of membrane technologies in highly value-adding activities. Recently, the french company chemistry Arkema, and the French SME Polymem, specialized in the manufacturing of filtration modules for hollow fiber membranes, have jointly developed a new ultrafiltration hydrophilic membrane technology to produce high quality water over the long term . This ultrafiltration technology using membranes manufactured by Polymem from a brand new nanostructured Kynar® PVDF polymer developed by Arkema, makes the treatment of water using membranes more effective and less energy-intensive.
- Biological treatment and phytoremediation:
The project european projet “BioFat Recovery” lead by the french companie Innova Europe tackles a thorny problem: wastewater containing fat from processing of dairy products or meat. Ambisys, one of the project partners from Portugal, has developed a reactor to reverse anaerobic sludge bed (IASB), which efficiently recover the fat found in wastewater and convert it into bio-energy, as biogaz form. This method of treatment is ideal for small installations and is therefore addressed in particular to SMEs. Under the “BioFat Recovery” project, IASB a reactor was installed and tested in a fish processing plant in Povoa de Varzim in northern Portugal and show promising results .
On the other hand, phytoremediation consists of mitigating pollutant concentrations in contaminated soils, water, or air, with plants able to contain, degrade, or eliminate metals, pesticides, solvents, explosives, crude oil and its derivatives, and various other contaminants from the media that contain them. This plant-based remediation systems are becoming increasingly common in small towns in France. Larger towns, such as Honfleur or Caen, are using Phytorestore-designed gardens to transform sewage water into clear water. It is interesting to note that efficient soil remediation processes are still at the research-and-development stage around the world. Generaly the aim is to fix pollutants in the contaminated soil, or to transfer to the upper part of the plant pollutants from the contaminated water.
- Catalytic oxidation
There are roughly four types of specific oxidants to ensure the oxidation of organic pollutants into CO2: oxygen, hydrogen peroxide, chlorine and ozone. Advanced oxidation processes (AOPs), characterized by the formation of hydroxyl radicals OH., involving hydrogen peroxide or ozone at a higher temperature and pressure. This process is souhaitable for the degradation of toxic organic pollutants and non-biodegradable contained in industrial effluents. In general, the use of catalysts improves the performance and reduces the cost of these technologies, increasing reaction rates, leading to a more efficient removal of pollutants and using more selective oxidizing agent . Public research laboratories, from Toulouse, Poitiers, or Villeurbanne, and French company (Anjou Recherche, Degrémont, TREDI) are very active in this area. The soluble catalysts having the major drawback of not being able to be separated easily from the solvant, current researchs are much focused on the development of stable heterogeneous catalysts for total mineralization. The heterogeneous catalysts used are generally iron, vanadium oxide, nickel, palladium, platinum, rhodium and carbon (active carbon nanotube, carbon powder) .
- New oxidation processes (CO2 et H2O)
The wet oxidation is a waste treatment, more or less watery and containing organic compounds by reaction (possibly catalyzed) with an oxidizing agent (usually oxygen), with pollutants in aqueous phase. The treatment takes place at high temperature and high pressure in subcritical conditions. This process is particularly used for treating some effluents of the chemical industry, food or grease or urban sludge treatment plants.
Athos ™ is a process of oxidation by Wet Way (OVH) developed by Veolia and that can turn organic sludge, with low dry matter content, in a solid essentially mineral. Operation is performed under pressure by injecting pure oxygen directly into the effluent sludge. A plant is currently in running in one of the sludge treatment plan operated by Veolia in Toulouse .
Much more recently, innovative processes have emerged, using higher temperatures and higher pressures, enabling to transform carbon dioxide and water into supercritical fluids. Supercritical water is, for now, mainly used at the laboratory scale with relatively few industrial applications. The fact remains that the main expected applications are focused on the treatment of aqueous effluents. Supercritical water will thus enable to carry out oxidation reactions. Water to be treated, which contain organic substances, will be submitted to 500 degrees Celsius and 250 bars in the presence of oxygen in order to completely oxidize organic matter into CO2. That allows to obtain in the end of the process, pure water.
Innoveox , a French company, brings a revolutionary technology to the problem of waste management: the Supercritical Water Oxidation. This guarantees clean treatment of organic waste with a 99.99% effectiveness rate. The French CNRS laboratory ICMCB based in Bordeaux is the world leader in research and development of Supercritical Water Oxidation of liquid waste . The Center has developed unique patents that protect all industrial applications of the technology, including the multi-stage injection of oxygen that triggers an exothermic reaction.
Innoveox holds an exclusive worldwide license for these patents. They are able to grant a significant competitive edge in terms of easiness of industrial implementation and economic viability (size of investment, operating and maintenance costs, etc.).
Water scarcity is among the main issues to be faced by many societies and the World in the 21st century. Whether for the treatment of drinking water or industrial effluents, French industries have been very innovating for many years and are today considered as world leaders. More and more specific processes have been developped to treat all different kind of pollution. Drinking water membrane seems to be the more promising technologies for the future allowing the treatment of water ranging from sea water to surface and ground water. Sewage and industrial effluents membrane but also new advances oxydation processes should open up opportunities for water treatment at lower cost and in a greener way.
Justin MONIER, Chargé de mission scientifique - Hong Kong