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1

Removal of nitrogen compounds in aerobic activated sludge process

100%
Bernat K., Wojnowska-Baryla I., Dobrzynska A.
Biotechnologia
|
2005
|
issue 1
194-206
EN
In sequencing reactors without separate nitrification and denitrification zones, controlling of oxygen and organic compounds concentration influences activated sludge nitrogen removal from wastewater. Under oxygen limited conditions, autotrophic nitrifying bacteria are able to nitrate or nitrites reduction to nitrous oxide or gaseous nitrogen. However, denitrifying microorganisms can carry out heterotrophic nitrification or aerobic denitrification at high oxygen concentration. Constant amount of oxygen concentration was supplied to the sequencing batch reactor with activated sludge, which indicates that oxygen concentration could change during the reaction time. It was assumed that control oxygen supply on the level of 2 mg/dm3 covers an oxygen demand in organics, ammonium nitrogen oxidation and endogenous respiration. In the initial phase of the reaction, total oxygen exhaustion was observed. After the reaction of oxidation, there was an increase in oxygen concentration to the value of 2 mg/dm3. In the presented experiment, it was shown that permanent complete oxygen using and the accessibility of readily biodegradable organic compounds in wastewater stimulate simultaneous nitrification and denitrification in activated sludge. Nitrogen removal effectiveness under constant aeration depending on COD/N ratio in wastewater supplying to the reactor ranged from 30 to 70%.
2

Poly-beta-hydroxybutyrate (PHB) storage and degradation in activated sludge under aerobic conditions and at high ammonium concentration in wastewater

100%
Dobrzynska A., Wojnowska-Baryla I., Bernat K.
Biotechnologia
|
2005
|
issue 1
183-193
EN
Numerous studies confirm poly-beta-hydroxybutyrate (PHB) synthesis by activated sludge under anoxic/aerobic conditions at high COD/N ratio in wastewater. In the presented experiment poly-beta-hydroxybutyrate (PHB) storage and degradation were observed in activated sludge at low COD/N ratio ? 3 in wastes. The researches were carried out in a single-stage system with activated sludge under constant oxygen supplied conditions. Readily biodegradable fraction increased in municipal wastewater through the addition of 0,2 g/dm3 acetate. Moreover, ammonium nitrogen was added to the wastes on the level of 50 mgNH4+/dm3. During the reaction time, organic carbon compounds oxidation by activated sludge and intracellular poly-beta-hydroxybutyrate (PHB) accumulation were observed. Under aerobic conditions and at low COD/N ratio ? 3 in wastewater, activated sludge used accumulated polymer as endogenous carbon source for denitrification. The obtained results show that poly-beta-hydroxybutyrate (PHB) synthesis is possible under fully aerobic conditions and at low COD/N ratio.
3

Changes of the nitrifying biomass concentration in activated sludge under different substrate conditions

100%
Wojnowska?Baryla I., Bernat K., Dabrowska M.
|
EN
The mechanisms of nitrogen compounds transformation were investigated during four research series. The experiments were carried out at dissolved oxygen concentrations of 30% of air saturation depending on the retention time (24 h, 12 h) and substrate conditions in the reactor (SBR). Sodium acetate as carbon source and ammonium chloride as nitrate source were added to municipal waste. The activated sludge loading changed from 0,054 to 0,2 g COD/gd. Changes of nitrifying, autotrophic biomass concentration in activated sludge were observed. Addition of ammonium enhanced the increase in autotrophic biomass concentration from 10,6 to 19,3% of the whole biomass. The lowest nitrifying biomass concentration, 3,4%, was observed when the activated sludge loading was 0,2 g COD/gd under 12 h retention time.
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