Production of sanitary safe water of high quality with membrane technology is an alternative for conventional disinfection methods, as UF and MF membranes are found to be an effective barrier for pathogenic protozoa cysts, bacteria, and partially, viruses. The application of membranes in water treatment enables the reduction of chlorine consumption during final disinfection, what is especially recommended for long water distribution systems, in which microbiological quality of water needs to be effectively maintained. Membrane filtration, especially ultrafiltration and microfiltration, can be applied to enhance and improve disinfection of water and biologically treated wastewater, as ultrafiltration act as a barrier for viruses, bacteria and protozoa, but microfiltration does not remove viruses. As an example of direct application of UF/MF to wastewater treatment, including disinfection, membrane bioreactors can be mentioned. Additionally, membrane techniques are used in removal of disinfection byproducts from water. For this purpose, high pressure driven membrane processes, i.e. reverse osmosis and nanofiltration are mainly applied, however, in the case of inorganic DBPs, electrodialysis or Donnan dialysis can also be considered.

A number of inorganic compounds, including anions such as nitrate(V), chlorate(VII), bromate (V),

arsenate(III) and (V), borate and fluoride as well as metals forming anions under certain conditions, have been

found in potentially harmful concentrations in numerous water sources. The maximum allowed levels of these

compounds in drinking water set by the WHO and a number of countries are very low (in the range of µg/l to a

few mg/l), thus the majority of them can be referred to as charged micropollutants. Several common treatment

technologies which are nowadays used for removal of inorganic contaminants from natural water supplies, represent serious exploitation problems. Membrane processes such as reverse osmosis (RO), nanofiltration (NF),

ultrafiltration (UF) and microfiltration (MF) in hybrid systems, Donnan dialysis (DD) and electrodialysis (ED)

as well as membrane bioreactors (MBR), if properly selected, offer the advantage of producing high quality

drinking water without inorganic anions.

I

The main goal of the present study was to examine the operating characteristics and mechanisms of membrane fouling in integrated membrane bioreactors (IMBRs) at diff erent temperatures. Two IMBRs, each with identical dimensions and confi gurations, were used in the study using synthetic domestic sewage at a low temperature (10°C) and high temperature (25°C). The results indicated that the removal effi ciency of chemical oxygen demand reached 93–96%, but the membrane contribution rate of IMBR2 (10°C) was higher than that of IMBR1 (25°C). The separation burden of the membrane on organic compounds increased at low temperature, which may have sped up the rate of membrane biofouling. The absolute rate of trans-membrane pressure build-up was faster at low temperature, leading to shorter IMBR operating times. Soluble microbial products (SMPs) and extracellular polymeric substances (EPSs) in the IMBRs signifi cantly increased at low temperature. These substances intensifi ed defl occulation, with an accompanying reduction of fl oc size and the release of EPSs at low temperature, which facilitated the formation of cake foulants on the surface, covering the entire membrane area. The protein and polysaccharide concentrations of SMPs and EPSs in the IMBRs were correlated with the concentration of C8-HSL. It was demonstrated that temperature aff ected the concentration of C8-HSL, which controlled the excretion of EPSs and SMPs and thus the membrane biofouling process.