No abstract

A B S T R AC TFew studies have been carried out to correlate the infl uence of temperature on the fi lterability of different mixed liquor fractions, i.e. suspended solids, colloidal matter and soluble organic matter. It is known that temperature has a big impact on the fl ux in microfi ltration processes. The aim of this research was to fi gure out the impact of temperatures in the range of 10ºC to 40ºC on fouling, especially in terms of the release of particles and soluble microbial products (SMP). Results based on the contribution of each fraction, namely mixed liquor (>1 μm), supernatant (1 μm to 1 nm) and soluble (<1 nm), to fouling, suggest that the colloids present in the supernatant are affected by temperature changes. Low and high temperatures result in defl occulation and formation/release processes respectively, resulting in a release of submicron particles and were observed due to retention changes. Similar values of the cake resistance for all the fractions and for the range of temperatures studied, indicate that all submicron/colloidal particles within the range 0.05-0.4 μm have a similar infl uence in terms of fouling. No correlation was found between the concentration of EPS and the cake resistance, which indicates that (an)other foulant(s) could contribute to the cake resistance. Finally, low retentions of both polysaccharides and proteins were observed at 40ºC.

Not many studies have been carried out in order to correlate the temperature influence on the filterability of different mixed liquor fractions, i.e. suspended solids (SS), colloidal matter and soluble organic matter. It is known that temperature has a big impact on the flux in the microfiltration processes, which is directly proportional to temperature. In this paper, a comparative filtration study at four different temperatures (10, 20, 30, 40ºC) is presented. The contribution of the different fractions that comprise the mixed liquor of a Membrane Bioreactor (MBR) is analyzed in sequential steps. In the first step, the resistance offered by the mixed liquor and its dependence on temperature is addressed. In the second step, the mixed liquor is centrifuged in order to remove the suspended solids and analyze the combined resistance offered by both the colloidal matter and the soluble organic matter. In the last step, the colloidal matter of greater than 1 µm is removed via filtration, and the effect of dissolved organic matter on filtration is analyzed. Specific oxygen uptake rate (SOUR) and Particle Size Distribution measurements were also carried out in order to complement the data analysis. The mixed liquor used was sampled from a submerged Kubota flat sheet membrane bioreactor situated in the sewage plant of Rincón de León, Alicante, Spain. The variables of this MBR were monitored in order to appreciate any change in parameters that could affect the sludge properties.