Sequencing Batch Reactor systems treating artificial wastewater were operated. The systems were designed to study the effect of various components on biological phosphorus removal (BPR) process. In order to avoid nitrification the systems were operated at purposefully low sludge age (ca. 4.0 d). The characteristics of artificial wastewater was adequate to the composition of municipal wastewater with the exception for suspended matter (no solids added) and total phosphorus (high phosphorus content was set in order to avoid full biological dephosphatation - P=22 gP/m3). The behaviour of SBR activated sludge intoxicated with heavy metals was examined. Three SBRs were operated - one as reference reactor, the second with cadmium chloride (CdCl2) added to the influent and the third one with zinc chloride (ZnCl2) in the influent. All reactors were fed from the same source, except for the heavy metals dosed separately. Heavy metals were applied with the increasing doses - the lowest dose of cadmium was 0.2 mgCd/dm3 and zinc 0.5 mgZn/m3, and the highest 2.0 mg/m3 for both metals. It was observed that even the lowest doses of both metals influenced BPR negatively. Both metals caused sludge bulking and for the same heavy metal doses the effect was more intense for zinc. The decrease in active sludge total solids was observed for both metals' salts. Also the decrease of sludge phosphorus content was observed testifying that PAOs were being continuously washed out of the system. The solids phosphorus content was between 6.2 and 9.0% in reference reactor and it dropped to 3.3% and 3.0% for zinc and cadmium respectively with the highest metal doses. Effluent phosphorus concentrations were gradually increasing with higher metal doses. The lowest heavy metals' doses that caused the deterioration of BPR are lower than the concentrations permitted by Polish regulations for the discharge to the sewage system (0.4 mgCd/dm3 and 5.0 mgZn/dm3). According to our results the permissible concentration of zinc may cause severe sludge bulking and deteriorate the BPR completely.
Podstawowym procesem stabilizacji osadów w oczyszczalniach powyżej 20 tys. mieszkańców równoważnych jest mezofilowa lub termofilowa fermentacja metanowa z odzyskiem gazu fermentacyjnego. Ponieważ w obecnie budowanych lub modernizowanych oczyszczalniach stosuje się technologie do zintegrowanego usuwania związków węgla, azotu i fosforu ze ścieków, stąd w osadzie nadmiernym występuje podwyższona zawartość fosforu. Fermentacja tego osadu z osadem wstępnym może powodować nadmiarowe wydzielanie fosforanów do cieczy nadosadowych.
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