The need to reduce energy input and enhance energy recovery from wastewater is driving renewed interest in high-rate activated sludge treatment (i.e. short hydraulic and solids retention times (HRT and SRT, respectively)). This process generates short SRT activated sludge stream, which should be highly degradable. However, the evaluation of anaerobic digestion of short SRT sludge has been limit...

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 Af...

A membrane bioreactor (MBR) and an activated sludge process (ASP) were operated side by side to evaluate the change of sludge supernatant characteristics and the evolution of the sludge fouling propensity. The MBR sludge had a higher organic concentration and more biopolymer clusters (BPC) in the supernatant compared with ASP. BPC increased in both concentration and size in the MBR. The results...

Sewage treatment works with percolating filter beds are known to provide profitable foraging areas for insectivorous birds due to their association with high macroinvertebrate densities. Fly larvae developing on filter beds at sewage treatment works may similarly provide a valuable resource for foraging bats. Over the last two decades, however, there has been a decline in filter beds towards a ...

Thesis submitted in fulfillment of the requirements for the degree of Doctor (Ph.D) in Applied Biological Sciences Proefschrift voorgedragen tot het bekomen van de graad van Doctor in de Toegepaste Biologische Wetenschappen op gezag vanSummary The activated sludge process is one of the most widespread biological wastewater purification technologies. Especially during the last two decades modell...

The high order of a two-input-two-output activated sludge system is reduced using Gawronski and Juang’s frequency limited reduction technique. The manipulated variables are the concentration of nitrate and dissolved oxygen (DO). A reduced fourth order system is obtained within the frequency band of 0.7 rad/s to 1.0 rad/s. The reduced system is compared with a fourth order activated sludge proce...

A method for quantifying bacterial populations introduced into an activated-sludge microbial community is described. The method involves extraction of DNA from activated sludge, appropriate dilution of the extracted DNA with DNA extracted from nonintroduced activated sludge, PCR amplification of a gyrB gene fragment from the introduced strain with a set of strain-specific primers, and quantific...

The integrated fixed-film activated sludge (IFAS) system is a variation of the activated sludge wastewater treatment process, in which hybrid suspended and attached biomass is used to treat wastewater. Although the function and performance of the IFAS system are well studied, little is known about its microbial community structure. In this study, the composition and diversity of the bacterial c...

The overuse or misuse of antibiotics has accelerated antibiotic resistance, creating a major challenge for the public health in the world. Sewage treatment plants (STPs) are considered as important reservoirs for antibiotic resistance genes (ARGs) and activated sludge characterized with high microbial density and diversity facilitates ARG horizontal gene transfer (HGT) via mobile genetic elemen...

In the activated sludge process, the share of filamentous bacteria is crucial for proper settlement and high sewage treatment efficiency. Disequilibrium of the microbial community may be a reason for the appearance of bulking episodes. During 19 months (August 2007-February 2009) activated sludge samples were collected and analyzed by physicochemical, microscopic, and molecular methods. Amplifi...