SEM-EDS for determining the phosphorus content in activated sludge EPS

Abstract

Not all phosphorus removed in activated sludge systems can be accounted for by polyphosphate accumulating organisms (PAO). A method for the qualitative and quantitative in situ characterization of PAO cell clusters and closely associated extracellular polysaccharides (EPS) is described. X-ray microanalysis was performed on samples from four activated sludge plants situated in Pretoria, South Africa. Analyses were done by means of Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectrometry (EDS). Cell clusters with associated EPS on average contained between 57 and 59% phosphorus, while EPS alone contained on average between 23 and 30% phosphorus. Results suggest that phosphorus removal in activated sludge might be due not only to PAO, but also by EPS acting as a phosphorus reservoir. Extraction of EPS from two different activated sludge plants yielded different amounts of EPS, which, in combination with SEM-EDS, may shed light on different phosphate uptake abilities of different activated sludges.

Investigating Activated Sludge Flocs using Microanalytical Techniques: Demonstration of Environmental Scanning Electron Microscopy and Time‐of‐Flight Secondary Ion Mass Spectrometry for Wastewater Applications

“…Characterization techniques used to investigate biological floc (e.g., morphology and composition) can be divided into three major categories: (1) visual, (2) compositional, and (3) a combination of visual and compositional. Analytical techniques used in visual examinations may include conventional light microscopy (CLM) ( Jenkins, 1992 ; Liss et al, 2002 ), scanning confocal laser microscopy ( Lawrence et al, 1991 ; Martin‐Cereceda et al, 2001 ), scanning electron microscopy ( Oosthuizen and Cloete, 2001 ), and transmission electron microscopy ( Droppo et al, 1996 ; Jorand et al, 1995 ; Liao et al, 2002 ). These techniques can provide quality images for understanding floc morphology and structure but are not capable of determining composition.…”

“…Studies that combine visual and compositional techniques can be quite powerful in understanding floc structure, especially when in situ observations are performed. Typically, the combined studies couple a specific staining protocol ( Jorand et al, 1995 ; Martin‐Cereceda et al, 2001 ) or detector ( Oosthuizen and Cloete, 2001 ) with one of the above visual techniques.…”

Appraisal of suspended growth process for treatment of mixture of simulated petroleum, textile, domestic, agriculture and pharmaceutical wastewater

“…The composition of the simulated MWW used in the study is presented in Table 1. The domestic, textile, and petroleum were simulated following previous studies [16][17][18][19]. Among the different therapeutic classes of pharmaceuticals antibiotics, analgesic, and anti-epileptics are of great concern due to their high frequency of use and detection in the environment.…”

“…The surface morphology of the biomass was examined with high resolution scanning electron microscope (SEM) (JSM -7100F), Department of Mechanical Engineering Sciences, University of Surrey, UK. The sludge samples (seed sludge, biomass in reactor 1 and reactor 2) were pre-treated following the method stated in previous study [19]. 1 ml of sludge sample was introduced into 3 ml of Eppendorf tubes and washed 4 times with distilled water by centrifugation at 13000 rpm for 2 min using (eppenddorf Centrifuge 5415 C).…”

Acinetobacter haemolyticus MG606 produces a novel, phosphate binding exobiopolymer

“…EBPR is achieved through polyphosphate accumulating organisms (PAOs) present in sludge, which accumulates phosphate intracellularly in the form of polyphosphates (Oehmen et al, 2007). Although the role of EBP present in activated sludge and its participation in EBPR through phosphate sorption has been realized in the recent years, however, studies were either restricted to quantitative analysis of total phosphorus bound to EBP (Li, Ren, Wang, & Kang, 2010;Oosthuizen & Cloete, 2001) or mostly focussed on phosphorus speciation in EBP extracted from activated sludge (Zhang et al, 2013a,b). In the related reports, phosphate binding was studied in EBP produced by a community of PAOs and the role of specific microorganism producing the phosphate-binding EBP was not considered; also, the composition of phosphate-binding components and the mechanism of phosphate-EBP interaction were not completely elucidated.…”