The influence of Aspidisca cicada on nitrifying bacteria and the morphology of flocs in activated sludge

Abstract

Crawling ciliates play important role in activated sludge as they improve flocculation and remove loosely attached bacteria from the flocs. However, there are discrepancies concerning their influence on nitrifying bacteria and nitrification efficiency. We conducted a five weeks experiment in six bioreactors simulating the Sequencing Batch Reactor (SBR) process using activated sludge from a plant in start-up phase. Half of bioreactors were inoculated with dense Aspidisca cicada culture and the remaining bioreactors served as control. The density of protozoa was regularly evaluated. Artificially increased density of A. cicada did not impair nitrifying bacteria abundance nor flocs structure. On the contrary, when A. cicada abundance was the highest, the total nitrogen in effluent was significantly lower in treatment in comparison to control. Most probably nitrifying bacteria occurring in form of dense colonies or hidden inside the flocs were inaccessible for ciliates.

The applicability of the Sludge Biotic Index in a facility treating sugar refinery effluents and municipal wastewater

“…abundance (R S = 0.64, p < 0.05), and sulfite-reducing bacteria removal and number of taxa (R S = 0.79, p < 0.01). Sobczyk et al (2020) recently reported a correlation between the highest abundance of A. cicada and lowest total nitrogen in effluent, corroborating our results. Negative correlation was determined between effluent parameters and certain taxa: effluent conductivity and Opercularia coarctata abundance (R S = −0.62, p < 0.05), total bacteria in effluent and number of taxa (R S = −0.68, p < 0.05), total N in effluent and Vorticella sp.…”

Ciliated protozoa from industrial WWTP activated sludge: a biodiversity survey including trophic interactions and redescription ofBakuella subtropica(Spirotrichea, Hypotrichia) according to Next Generation Taxonomy

“…In addition, Aspidisca cf. cicada is one of the most frequently reported species in WWTP receiving industrial inputs (Dubber and Gray, 2011;Sobczyk et al, 2020); its occurrence is in line with the characteristics of the studied plant where the high concentration of ammonia and toxic tannery wastewater is treated. Phialina sp., the free-swimming carnivorous ciliate, appeared five times out of six samples; its high occurrence might reflect another characteristic of the studied plant, that is the presence of a well-structured food web (see below).…”

“…Among them, Aspidisca cf. cicada, Euplotes spp., and P. calkinsi are known to have strong ecological tolerance, e.g., they can survive in highly polluted water bodies (Madoni et al, 1992;Madoni et al, 1994;Puigagut et al, 2005;Sobczyk et al, 2020) and develop high-density populations. In addition, Aspidisca cf.…”