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Abstract
Purpose of the paper is to experimentally verify that a downstream nitrifying fixed-film reactor may effectively backseed an activated sludge (AS) system. The experiment was carried out at the Southpest Wastewater Treatment Plant in Budapest, Hungary, with two pilot-scale AS systems connected directly to the preclarified influent and to the stream recirculated from the nitrifying fixed-film reactor of the full-scale plant ensuring both the nitrate and the backwashed biomass recirculation. Effluent NH 4 -N level dropped down to near zero in the experimental systems whereas no significant nitrification occurred in the fullscale plant being operated at lower aeration intensity. Simulation model developed for describing the combined system supported that backseeding was the cause of the high nitrification efficiency having been limited by inadequate oxygen supply in the full scale system.
Highlights
Introduction and goalsDifferent technologies have been developed for the reduction of Solids Residence Time (SRT) required for efficient nitrification in activated sludge (AS) systems
11.1 11.3 11.5 11.7 11.9 11.11 11.13 11.15 11.17 11.19 11.21 11.23 10.24 10.26 10.28 10.30 11.1 11.3 11.5 11.7 11.9 11.11 11.13 11.15 11.17 11.19 11.21 11.23 the efficient seeding, the autotrophic biomass having grown in the N-filter was assumed to be fully efficient in the activated sludge unit, whereas in the case of simulating without seeding, the backseeded nitrifiers were considered to be inactive in the AS unit and regarded as suspended solids
The large difference between the effluent NH4-N values simulated with and without efficient seeding shown in Fig. 3., support the theory that backseeding may highly enhance nitrification in the given activated sludge system, especially in the temperature range of 18–20 °C
Summary
Introduction and goalsDifferent technologies have been developed for the reduction of Solids Residence Time (SRT) required for efficient nitrification in activated sludge (AS) systems. Head and Oleszkiewicz [7] investigated the effects of seeding Sequencing Batch Reactors (SBR) operating at low temperatures by nitrifiers cultivated at higher temperatures, in separate SBRs and observed that even at low temperatures (10 textdegree C) the required minimum SRT for nitrification could be considerably decreased through seeding. Another approach of enhancing nitrification has been the application of nitrifying fixed-film units supplementing the activated sludge system. It can be assumed, that microorganisms in this case would grow at considerably lower concentrations of these inhibitory substances in the biofilm in the activated sludge unit
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