Free nitrous acid and pH determine the predominant ammonia-oxidizing bacteria and amount of NO in a partial nitrifying reactor.

We investigated the effects of free ammonia (FA) and free nitrous acid (FNA) concentrations on the predominant ammonia-oxidizing bacteria (AOB) and the emission of nitrous oxide (NO) in a lab-scale sequencing batch reactor for partial nitrification. The reactor was operated with stepwise increases in the NH loading rate, which resulted in a maximum FA concentration of 29.3 mg-N/L at pH 8.

Biomass granulation in an aerobic:anaerobic-enhanced biological phosphorus removal process in a sequencing batch reactor with varying pH.

Long-term influences of different steady-state pH conditions on microbial community composition were determined by fluorescence in situ hybridization (FISH) in a laboratory scale reactor configured for enhanced biological phosphorus removal (EBPR). Chemical profiles were consistent with shifts in populations from polyphosphate-accumulating organisms (PAO) to glycogen-accumulating organisms (GAO) when pH fell from pH 7.5 to 7.

FACS enrichment and identification of floc-associated alphaproteobacterial tetrad-forming organisms in an activated sludge community.

A precise phylogenetic identity of the Defluviicoccus-related glycogen-accumulating organisms (GAO) observed after FISH probing in a novel activated sludge process removing phosphorus was sought with the aim of exploring the phylogenetic diversity of this important group. These organisms, whose sequences were not revealed in previously generated community wide 16S rRNA gene clone libraries, were identified using flow cytometry cell sorting of FISH-positive cells. Sequencing of a 16S rRNA gene clone library created from this sorted population identified the Defluviicoccus-related GAO as being highly related to previous identified GAO from enhanced biological phosphorus removal systems, despite a marked environmental difference between the two systems.

Transformation of phosphorus and relevant intracellular compounds by a phosphorus-accumulating enrichment culture in the presence of both the electron acceptor and electron donor.

This study was conducted to obtain a better insight into the metabolic behavior of denitrifying phosphate-accumulating organisms relative to the transformations of relevant intracellular compounds as well as phosphorus and nitrate for enhanced biological phosphorus removal under different combinations of electron acceptor (oxygen or nitrate) and electron donor (acetate). Under anoxic conditions, the amount of polyhydroxybutyrate (PHB) produced per acetate taken up considerably increased with the increasing amount of nitrate reduced whereas the amounts of nitrate reduced and phosphorus released per acetate taken up remained almost constant. However, glycogen utilization occurred during PHB production and then was again observed in response to the initial supplementation of acetate after glycogen accumulation was transiently observed during anoxic phosphorus uptake using nitrate as an electron acceptor.

Ecology of the microbial community removing phosphate from wastewater under continuously aerobic conditions in a sequencing batch reactor.

All activated sludge systems for removing phosphate microbiologically are configured so the biomass is cycled continuously through alternating anaerobic and aerobic zones. This paper describes a novel aerobic process capable of decreasing the amount of phosphate from 10 to 12 mg P liter(-1) to less than 0.1 mg P liter(-1) (when expressed as phosphorus) over an extended period from two wastewaters with low chemical oxygen demand.

Changes in respiratory quinone profiles of enhanced biological phosphorus removal activated sludge under different influent phosphorus/carbon ratio conditions.

Changes in the microbial community of an enhanced biological phosphorus removal (EBPR) activated sludge system under different influent phosphorus/carbon (P/C) ratio conditions were investigated through evaluation of population respiratory quinone profiles. A total of 13 types of respiratory quinone homologs consisting of 3 types of ubiquinones (UQ) and 10 types of menaquinones (MK) were identified in this study. The dominant quinones were UQ-8 and MK-7 throughout the operational period.

Characterization of denitrifying phosphate-accumulating organisms cultivated under different electron acceptor conditions using polymerase chain reaction-denaturing gradient gel electrophoresis assay.

To investigate the characteristics and the microbial diversity of denitrifying phosphate-accumulating organisms (DNPAOs) that are capable of conducting enhanced biological phosphorus removal (EBPR) using nitrate as electron acceptor, three sequencing batch reactors were operated under three different electron acceptor conditions, i.e., only oxygen, oxygen together with nitrate and only nitrate.