There are various types of hybrid system in use based on the carrier material. These systems, which are termed as hybrid systems have advantages of the both systems. Overall, the optimal DO concentration was suggested as 4.5 mgL −1 for the IFAS system as it not only achieved high organics removal efficiency and but also minimized the sludge production with high sludge retention time.Īerobic hybrid systems exhibiting both suspended and attached growth have been widely in use. Moreover, activated sludge characterization results revealed that the dominance of micro fauna (ciliated protozoa) and microorganisms (gram characteristics) was different at different DO levels. The macromolecular composition) of activated sludge was also determined in terms of lipids, proteins and polysaccharides content. Insignificant variation in SVI values (190–245 mLg −1) was observed at different DO phase experiments. Biological phosphorus removal (BPR) efficiency of pilot deteriorated significantly at high DO (4.5 mgL −1) levels. The optimal DO concentrations for the efficient removals of organics, nitrification, denitrification, and total nitrogen were recorded as 4.5, 4.5, 2.5, and 2.5 mgL −1, respectively. Results obtained from experimental revealed that the DO concentrations of 0.5, 2.5, and 4.5 mgL −1 affected significantly the performance of IFAS reactor. In the present study, assessment of a single stage integrated fixed film activated sludge (IFAS) reactor treating municipal wastewater and subjected to various dissolved oxygen (DO) stresses, is done in terms of treatment performance and changes in biochemical characteristics of activated sludge. Fractional error plot for the NH(4)(+)-N data sets showed that the difference between observed and predicted values are insignificant at 5% level of probability for NH(4)(+)-N. It is found that the model validated well with the experimental results which was supported by the R(2) value of 0.79, further the statistical analysis between the observed and predicted values for various experimental conditions showed that the model tends to under-predict at high removal efficiency, whilst a slight tendency towards over-prediction at low removal efficiency values. The model thus developed is solved numerically and validated with the experimental results obtained on a laboratory scale AS-biofilm system. Monod kinetic equation and Fickian diffusion principles are coupled to derive the model. This paper deals with deducing a mathematical model for the simulation of ammonical nitrogen in such systems starting from the basic mass balance equations. Key words: biofilm, model, modified expressions, steady state, substrate flux.Īlthough activated sludge (AS)-biofilm system has many advantages, it lacks in the mathematical concepts for its design. Moreover, the exact solution from this study can be used to establish the biofilm kinetics instead of using the curve-matching technique. The proposed expressions and the present study may be useful to simplify the description of biofilm in many systems such as completely mixed or fluidized-bed reactor for treatment of water or wastewater as well as the biofilm-activated sludge reactors. Applicability of the developed expressions has been demonstrated through an illustrative example. In addition, the proposed expressions and solution can be used instead of the graphical solutions, which are commonly used to solve the original models. The modified expressions and the exact solution are short, simple, easy to use, and give reliable results in comparison to the original models. Thus, modified expressions were developed for the first one, while the exact solution of the second one could be obtained. Models of Suidan and Wang (1985) and Sáez and Rittmann (1988, 1992) were selected for the present study. The present study was carried out to simplify existing biofilm one-dimensional models, which consider a single substrate as the limiting factor.
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