VERIFICATION OF ANOXIC PHOSPHATE-UPTAKE AS THE MAIN BIOCHEMICAL-MECHANISM OF THE DEPHANOX PROCESS

The phenomenon of anoxic phosphate uptake with simultaneous denitrific ation was studied. For this purpose kinetic batch tests have been carr ied out by using the activated sludge samples from three modifications of nutrient removal activated sludge systems: two based on an anaerob ic-anoxic-oxic (A2/O) system and a third on an anaerobic-oxic (A/O) sy stem. The results showed significant differences in anoxic phosphate u ptake rate between activated sludge which was alternatively exposed to anoxic conditions and activated sludge from the A/O arrangement. Thes e differences were also accompanied by different denitrification rates . Simultaneously with batch experiments the microscopic observation of activated sludge samples was carried out. Neisser and Gram stained sa mples showed clear differences in shape, size and distribution of poly phosphate accumulating bacteria between A2/O and A/O Processes. Moreov er, experiments performed using genetic probes confirmed the differenc es in microbiological composition of activated sludge samples from dif ferent nutrient removal system arrangements. (C) 1997 IAWQ. Published by Elsevier Science Ltd.