Development and implementation of a robust deammonification process

Deammonification represents a short-cut in the N-metabolism pathway and comprises 2 steps: about half the amount of ammonia is oxidised to nitrite and then residual ammonia and nitrite is anaerobically transformed to elementary nitrogen. Implementation of the pH-controlled DEMON® process for deammonification of reject water in a single-sludge SBR system at the WWTP Strass (Austria) contributed essentially to energy self-sufficiency of the plant. The specific energy demand of the side-stream process equals 1.16 kWh per kg ammonia nitrogen removed comparing to about 6.5 kWh of mainstream treatment. Has this resource saving technology already approached state of the art? Deammonification has been operated in full-scale now for almost 3 years without interruption reaching annual ammonia removal rates beyond 90%. Biomass enrichment and DEMON-start-up in Strass took a period of 2.5 years whereas start-up period at the WWTP Glarnerland (Switzerland) was reduced to 50 days due to transfer of substantial amounts of seed sludge.

One-stage deammonification: nitrogen elimination at low costs

Biological nitrogen elimination used to purify wastewater with high nitrogen contents can become a major cost factor, in particular when the wastewater in question contains only little amounts of biologically degradable carbon compounds. The use of new biological conversion methods and the application of compact operation technology, however, does allow us to save operation and investment costs. Currently, the focus of scientific interest is on deammonification, that is the direct conversion of ammonia into elementary nitrogen by autotrophic micro-organisms, because in contrast to conventional nitrification/denitrification this method requires considerably smaller amounts not only of carbon, but also of oxygen. Moreover, the use of compact biofilm technology makes it possible to considerably reduce the reaction tank volume. In the following we will present the operation results of both industrial plants and laboratory-scale units for the treatment of wastewater with high nitrogen loads, results which unequivocally show the favourable cost-effectiveness of the mentioned method combination and thus the economic viability inherent in the purposeful industrial utilisation of this technology.

Kinetics of ammonia oxidation on cobalt catalyst II application of tubular reactor with catalytically active wall

The kinetics of ammonia oxidation on cobalt catalyst is described on basis of experimental data measured in the tubular reactor with catalytically active wall. In the temperature range up to 623 K, where the products of ammonia oxidation are nitrogen monoxide and elementary nitrogen, it is possible to describe the rate of formation of these components by empirical equations (5) and (6), at the temperature above 900 K, where the products are nitrogen dioxide and elementary nitrogen, by equations (7) and (8).

Interrelations of photosynthesis and assimilation of elementary nitrogen in a blue-green alga

In blue-green algae the hydrogen donors and carbon skeletons required in the fixation of elementary nitrogen may be supplied by the photosynthetic mechanism. Study of the kinetic relationships between the photosynthetic assimilation of carbon and the assimilation of nitrogen into the cell material of Anabaena cylindrica Lemm. has demonstrated correlations between the rates of the two processes consonant with the existence of such biochemical connexions. The effects of light intensity, carbon-dioxide concentration and nitrogen concentration were each studied at four different temperatures by determination of changes in amounts of cell carbon and cell nitrogen in cultures grown for 48 h. Temperature was found to have the most marked differential effect, both low and high temperatures depressing nitrogen assimilation to a greater extent than carbon assimilation. At any given temperature there was a close correlation between the rates of the two processes over a wide range of variation in other factors. Both carbon and nitrogen assimilation were found to be inhibited by relatively low concentrations of carbon dioxide. The rate of carbon assimilation per unit amount of cell nitrogen was found to be related in the usual way to light intensity, but to be reduced at low nitrogen concentrations. The relative rate of nitrogen assimilation was likewise found to be related in the expected way to nitrogen concentration but to increase with light intensity and to be reduced at carbon-dioxide concentrations limiting for carbon assimilation.