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Aerobic granulation in sequencing batch reactors is widely reported in literature and in particular in SBAR (Sequencing batch airlift reactor) configuration, due to the high localised hydrodynamic shear forces that occur in this type of configuration. The aim of this work was to observe the phenomenon of the aerobic granulation and to confirm the excellent removal efficiencies that can be achieved with this technology. In order to do that, a laboratory-scale plant, inoculated with activated sludge collected from a conventional WWTP, was operated for 64 days: 42 days as a SBAR and 22 days as a SBBC (sequencing batch bubble column). The performances of the pilot plant showed excellent organics removal. COD and BOD removal efficiencies were respectively, 93 and 94%; on the contrary, N-removal efficiency was extremely low (5%-45%). The granules dimensions increased during the whole experimentation; change of reactor configuration contributed to further improve this aspect. The experimental work confirmed the essential role of hydraulic settling time in the formation of aerobic granules and in the sludge settleability and the need to find an optimum between granule size and oxygen supply to achieve good N-removal efficiency. [ABSTRACT FROM AUTHOR]

The growing increment of the urbanization and, on the other hand, the even more strict effluent limits imposed by the Water Framework Directive for the receiving water body quality state have led to the need for upgrading several existing WWTP. With this respect HMBBR systems are an innovative solution since they allow to upgrade existing high loaded WWTP without building new tanks. However, some uncertainties in their design, maintenance as well as performance have to be addressed due to their recent acquisition compared with well consolidated technologies such as activated sludge systems. In this light, a data gathering campaign on a HMBBR pilot plant has been performed. The aim was to detect the performance of such new technology as well as to survey the influencing effect of the carrier media filling ratio. Indeed, there may be problem of competitiveness between attached and suspended biomass that jointly operate in the same system for carbon and nitrogen removal. Such competitiveness may lead to a worsening of the system efficiency. The results are interesting and the gathered data in the experimental period show a slight difference in terms of performance behaviour, between the two systems (35 and 66%). Such result leads to address the filling ratio choice towards the 35%. [ABSTRACT FROM AUTHOR]

A semi-empirical mechanistic model able to simulate the dynamics of a stabilization reservoir was developed incorporating both settling of particulate components and chemical/biological processes. Several factors affecting the reservoir effluent quality were taken into account: hydraulics and hydrology, solar radiation, atmospheric reaeration, algae, zooplankton, organic matter, pathogen bacteria, and sediment-water interaction. The model quantifies the specific influence of each factor on effluent quality, evaluating the correlation between the different considered factors. State variables included in the model were: algae, dissolved oxygen, organic matter, zooplankton and indicator bacteria. The model was transferred into a computational code in order to provide a useful and versatile tool for water resource planning management issues. The model was verified by comparing simulated results with full-scale data collected from a small reservoir (Sicily, IT) filled with partially treated wastewater. The reservoir has a volume of 11,000m³, a maximum depth of 6.3m and a mean depth of about 5m. The monitoring period lasted four months during which the reservoir operated in different hydraulics conditions: as a standard batch reactor and as a continuous flow reactor. The model was able to reproduce the behaviour of the principal simulated parameters thus representing a potential tool for the management and performance optimization of these peculiar storage/treatment systems. [ABSTRACT FROM AUTHOR]

The present study has aimed to quantify the role of pore blocking and cake layer in a laboratory scale hollow fibre membrane module in submerged configuration. The membrane reactor (MBR) was fed with raw wastewater, only screened with a 2-mm sieve, collected from the Palermo WWTP. The MBR was characterised by an operating volume of 190 L and equipped with an aeration system located on the bottom of the reactor. The MBR operated for 65 days. The permeate was extracted by imposing a constant flux through the membrane (21 Lh-1m-2). The results confirm the importance of pore blocking control during start-up. In particular, it provides a rapid irreversible fouling that takes place at the beginning of the filtration process, before the deposition mechanism. Therefore, low suspended solids concentration in the initial phase causes a fast irreversible fouling. This circumstance creates the need for more frequent chemical cleaning after start-up without inoculum. Finally, the results underline that the cake has a mainly reversible feature. [ABSTRACT FROM AUTHOR]

In recent years there has been an increasing interest in the development of hybrid biofilm reactors, especially in the upgrading of existing WWFP that are no longer able to respect concentration limits. In fact, today's challenge is the achievement of a good aquatic state for the receiving water bodies according to the Water Framework Directive requirements, which indeed limit even more the continuous emissions, i.e. coming from WWTP. This paper presents the setting up of a mathematical model for the simulation of a hybrid MBBR system; the model calibration/validation has been carried out considering a field gathering campaign on an experimental pilot plant. The main goal is to gain insight about MBBR processes attempting to overcome main shortcomings in particular referring to the modelling aspects. The model is made up of two connected sub-models for the simulation of the suspended and attached biomass. The model is mainly based on the concepts of the activated sludge model No. 1 (ASM1) for the description of the biokinetic process both for the suspended and for the attached biomass. The results show a good agreement between predicted and observed values both for the attached and for the suspended biomass moreover they are encouraging for further researches. [ABSTRACT FROM AUTHOR]