engleski

Removal of aromatic surfactants from municipal wastewaters – comparison of membrane bioreactor and conventional activated sludge treatment

A pilot scale MBR facility, consisting of a 200 L primary settling tank and a 40 L aerated bioreactor equipped with an immersed hollow fiber microfiltration membrane (ZW-10, Zenon, Canada) was used to study removal of aromatic surfactants from municipal wastewaters. The MBR was situated in the vicinity of the main sewage outlet for the south part of the city of Zagreb, which allowed direct pumping of the feed wastewater from the sewer into the primary tank of the MBR-system. The study of the conventional activated sludge process was performed in the sewage treatment plant (STP) of Velika Gorica (Croatia), which included both mechanical and biological treatment. The samples were collected at the outflows from the primary settling tank (primary effluent) and secondary clarifier (secondary effluent). The elimination efficiency of nonylphenolic compounds using MBR-unit was significantly higher than that in the conventional treatment, exceeding 80 % for the overall removal for alkylphenolic compounds. The parent compounds were removed at a very similar rate like in the conventional STP (93 %). Nevertheless, as opposed to conventional treatment, NPnEO were the dominant class of nonylphenolic compounds even in treated effluents. Since, the concentration of lipophilic metabolites was rather low, it could be concluded that the effluent, resulting from the MBR-treatment, was probably ecotoxicologically more favourable than the conventional one. This was, probably, a consequence of lipophylic adsorption on highly concentrated activated sludge (about 10 g MLSS/L) in the aeration tank, followed by an efficient removal of particles by microfiltration.

-

nije evidentirano