Removal of bacterial and viral indicator organisms in full-scale aerobic granular sludge and conventional activated sludge systems

Abstract

The aim of this study was to evaluate the effectiveness of the novel aerobic granular sludge (AGS) wastewater treatment technology in removing faecal indicator organisms (FIOs) compared to the conventional activated sludge (CAS) treatment system. The work was carried out at two full-scale wastewater treatment plants (WWTP) in the Netherlands, Vroomshoop and Garmerwolde. Both treatment plants have a CAS and AGS system operated in parallel. The parallel treatment lines are provided with the same influent wastewater. The concentrations of the measured FIOs in the influent of the two WWTPs were comparable with reported literature values as follows: F-specific RNA bacteriophages at 106 PFU/100 mL, and Escherichia coli (E. coli), Enterococci, and Thermotolerant coliforms (TtC) at 105 to 106 CFU/100 mL. Although both systems (CAS and AGS) are different in terms of design, operation, and microbial community, both systems showed similar FIOs removal efficiency. At the Vroomshoop WWTP, Log10 removals for F-specific RNA bacteriophages of 1.4 ± 0.5 and 1.3 ± 0.6 were obtained for the AGS and CAS systems, while at the Garmerwolde WWTP, Log10 removals for F-specific RNA bacteriophages of 1.9 ± 0.7 and 2.1 ± 0.7 were found for the AGS and CAS systems. Correspondingly, E. coli, Enterococci, and TtC Log10 removals of 1.7 ± 0.7 and 1.1 ± 0.7 were achieved for the AGS and CAS systems at Vroomshoop WWTP. For Garmerwolde WWTP Log10 removals of 2.3 ± 0.8 and 1.9 ± 0.7 for the AGS and CAS systems were found, respectively. The measured difference in removal rates between the plants was not significant. Physicochemical water quality parameters, such as the concentrations of organic matter, nutrients, and total suspended solids (TSS) were also determined. Overall, it was not possible to establish a direct correlation between the physicochemical parameters and the removal of FIOs for any of the treatment systems (CAS and AGS). Only the removal of TSS could be positively correlated to the E. coli removal for the AGS technology at the evaluated WWTPs.

Pathogen removal in aerobic granular sludge treatment systems

“…coli reactor was within the range previously reported for E. coli in full-scale AGS systems. However, the MS2 bacteriophage removal (0.7 Log10) was lower than reported [98]. It is worth mentioning that full-scale AGS systems contain both a large granular sludge fraction and a smaller flocculent sludge fraction [75].…”

“…Besides a good treatment performance concerning the water quality parameters, two recent studies showed the capability of the AGS technology in removing bacterial and viral indicator organisms from sewage. Barrios-Hernández, Pronk [98] and Thwaites, Short [85] compared removal efficiencies in AGS and CAS full-and pilot-scale WWTP. The AGS full-scale systems can just as effectively remove indicator organisms as the CAS process.…”

Performance Efficiency of Conventional Treatment Plants and Constructed Wetlands towards Reduction of Antibiotic Resistance

“…It can be inferred that WWTP do provide a suitable environment for the proliferation of ARBs containing a high proportion of resistant bacteria. Berrios-Hernandez [ 113 ] inferred that the removal of fecal indicator organisms is not correlated to water quality parameters but is generally dependent upon the treatment technology used. In the case of E. coli , total suspended solids have been positively correlated with its removal, supporting the efficacy of primary and secondary treatment units for the removal of the microbial population.…”

New Advances in Aerobic Granular Sludge Technology Using Continuous Flow Reactors: Engineering and Microbiological Aspects

“…Alternatively, viral removal can be promoted by physical procedures, mainly by biomass adsorption, because viruses are adhered to the surface and subsequently microbial inactivation occurs [33]. Despite efforts to increase knowledge about the removal of pathogens, few studies have concluded that AGS is able to remove F-specific RNA bacteriophages such as E. coli, Enterococci and thermotolerant coliforms as efficiently as CAS [34]. However, there is a clear need for further studies to determine if the removal mechanisms in the two systems are comparable.…”