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R Grommen

Publications and source records attributed to R Grommen.

3 recordsLinked to original sources

Nitrate removal in aquaria systems: use of electrochemically generated hydrogen gas as electron donor for denitrification.

Nitrate, the end product of the nitrification process, tends to accumulate in aquaria systems. Removal of nitrate in these systems by means of biological denitrification requires the addition of an external electron donor. In this study, the possibilities for using hydrogen gas in aquaria systems as a harmless alternative to other electron donors such as sulphur or reduced organic carbon was investigated. To circumvent safety issues regarding the storage of large volumes of hydrogen gas, in situ generation of hydrogen gas by means of a separate electrochemical cell was chosen. A plug flow reactor filled with polyester cotton wool as carrier material for denitrifying bacteria received hydrogen gas in the headspace. Removal rates of 15 +/- 6 mg N per day were achieved with a hydraulic residence time of 3.3 hours. During the start-up phase nitrite peaks up to 3 mg N per liter were measured in the effluent of the reactor.

Electrochemistry↗

Environmental biotechnology: the ongoing quest.

Environmental biotechnology, until now, has primarily focused on the development of technologies to treat aqueous, solid and gaseous wastes. At present, the basic knowledge on how biotechnology can handle these wastes has been acquired and the focus is now on the implementation of these processes as 'best available technology not entailing excessive costs' (BATNEEC) in the framework of strict and transparent environmental legislation. New environmental challenges continue to evolve, as it becomes clear that waste streams should be tackled in an overall holistic way. New technologies to reach this goal are currently under development. Novel aspects with respect to the domain of water treatment are, for example, the biomembrane reactor technology and the newly discovered processes to remove nitrogen by means of anaerobic ammonium oxidation. Also, most challenging is the continuing strive for re-use of treated wastewater. Indeed, water shortage is emerging in an increasing number of countries all over the world and necessitates the short cycling of water. Finally, biotechnology has a key role to play in the novel approaches to design wastewater treatment based on decentralised sanitation and reuse (DESAR). Solid waste is a major challenge worldwide. The implementation of anaerobic digestion to treat biowastes has become a grown-up technology. New approaches in which biotechnological processes are linked to physical processes, such as plasma technology, certainly deserve special attention for the coming decades. Soil and sediment clean up by means of biostimulation/remediation/augmentation is now well established. Certainly, a number of prospects need to be further explored, such as the use of special energy sources to stimulate in situ the microbial community and the seeding of knowledge to the in situ community by means of horizontal gene transfer mechanisms. A number of waste gases can be handled by biofilter systems. Biological treatment of wastegases is also evolving, inasmuch as that besides conventional chemical pollutants, now also highly problematic chemicals (even dioxins) can be dealt with through proper biotechnological approaches. A remarkable new potential is the use of well designed probiotics to upgrade aquaculture and together with conventional biological water treatment processes, to guarantee the overall water quality of this domain of food production.

Air Pollution↗

Use of a nitrifying culture to shorten the activation time of biofilters for the removal of ammonium and nitrite in freshwater aquaria.

The removal of ammonia (NH3) through nitrification in intensive aquaculture systems is an important process as the total ammonia nitrogen (TAN, compromising NH4+ and NH3) concentration often is the key limiting water quality parameter in these intensive aquaculture systems. In this study, the performance characteristics of a suspension of nitrifying cells (named ABIL) have been explored This aqueous suspension contains a highly active, nitrifying microbial consortium and is stable for several months when preserved at 4 degrees C. Tests were performed in freshwater at lab scale (70 L, 20 - 24 degrees C). Results showed that the application of the consortium at a dose of 5 mg Volatile Suspended Solids (VSS) L(-1) assures a total removal of ammonium and nitrite species from 10 mg N L(-1) to below the detection limit within a period of four days. Experimentally, at a substrate level of 10 mg TAN L(-1), a rate of biological ammonium and nitrite conversion of the order of 0.3 - 0.5 g TAN g(-1) VSS(-1) d(-1) could be achieved by the consortium in the freshwater aquaria systems tested Provided adequate aeration and dissolved oxygen levels of 6 mg per L or more, no important intermediary nitrite concentrations were noticed Only a small amount of TAN was not found back as nitrate and might have been lost due to ammonia stripping After 12 months preservation of the inoculum at 4 degrees C, no important decrease in ammonium removal activity and only a minor decrease in the nitrite removal rate of the consortium were noticed.

Ammonia↗