Resistance of nitrifiers inhabiting activated sludge to ciliate grazing

Abstract

We monitored the succession of nitrifiers in a newly opened wastewater treatment plant for five weeks. After the first distinct decrease in total nitrogen, we began monitoring the appearance, size and number of nitrifying bacteria colonies using the fluorescence in situ hybridization (FISH) method. Ammonia oxidizing bacteria (AOB) colonies were visualized under green excitation as red, and nitrite oxidizing bacteria (NOB) colonies were visualized under blue excitation as green. The changes in protozoan community were monitored simultaneously. Ciliates were divided into four functional groups: predatory, bacterivorous free-swimming, bacterivorous crawling, and sessile. The results showed that at the time of the first distinct total nitrogen decrease, the mean length of both AOB and NOB were relatively low, but the colonies, especially those of nitrite oxidizers, were abundant. In time, the distribution of ammonia oxidizer colonies shifted towards larger sizes, but their quantity decreased. In the case of nitrite oxidizers, a similar trend was noticeable but less pronounced. These changes corresponded with an increasing number of crawling bacterivorous ciliates dominated by the "scavenger" genus Aspidisca. The increasing size of nitrifier colonies may have been due to the growing grazing pressure from crawling bacterivorous ciliates. The strong grazing pressure did not negatively affect N-NH(4)(+) removal effectiveness.

Impact of optical indices on particle size distribution of activated sludge measured by laser diffraction method

“…Other investigators focus their research on the prevalence of pathogenic organisms and their dormant forms or eggs in sludge and wastewater [7,8]. Others investigate the relationship between the presence of protozoa in sludge and the structure and morphology of flocs on the course of the wastewater treatment process [9][10][11]. An important and currently commonly discussed tasks in wastewater treatment technology are the ways of description of physiological activity of activated [12,13] and fractioning of the substrate to build and calibrate computer models of sewage treatment systems [14][15][16][17][18].…”

Community Composition and Abundance of Protozoa Under Different Concentration Of Nitrogen Compounds at “Hajdow” Wastewater Treatment Plant / Zbiorowiska Pierwotniaków I Ich Liczebność W Oczyszczalni Ścieków „Hajdów” Przy Różnych Stężeniach Związków Azotu

“…The increase of effectiveness was accompanied with considerable quantity increase of sessile bacterivorous, namely peritrichid ciliates (Ciliophora: Peritricha). This can be considered as proof of positive influence of nitrifying bacteria grazing on effectiveness of ammonium nitrogen utilization process [38]. Whereas it is quite complicated to interpret the reasons of Peritricha quantity surge inside the community that exist in stable environment and with no food deficiency.…”

“…On account of this, the process of nitrogen compounds removal (nitrification and denitrification process) as a component of general metabolic activity in bioreactors is under careful examination [8,[32][33][34][35][36][37][38]. In turn, various factors, interacting with each other in bioreactors, are able to considerably affect the structure of microflora, protozoa, and other hydrobionts [39,40].…”

The Influence of COD Fraction Forms and Molecules Size on Hydrolysis Process Developed by Comparative OUR Studies in Activated Sludge Modelling

“…Additionally, other studies regarding the development of wastewater treatment technologies and the optimization of the processes have been carried out and implemented. They have concerned issues related to the development of technologies that use activated sludge in various forms [7][8][9][10][11]; the bioaugmentation of reactors [12,13], biofilm, and hybrid techniques [14,15]; and the preliminary preparation and pre-treatment of sewage sludge and back-side waters [16,17]. New research has also covered alternative technologies, e.g., sorption which may be used for the removal of a big amount of organic and inorganic pollutants and which can be used in conjunction with several techniques (such as flocculation-coagulation) [18][19][20].…”