Simultaneous nitrogen and phosphorus removal from wastewater at anoxic conditions

Abstract

Cilj istraživanja bio je istražiti aktivnost DPAOs za uklanjanje N i P sa NO2-N kao elektron akceptorom u anoksičnim uvjetima sa acetatom kao izvorom ugljika. U aktivnom mulju aklimatiziranom za procese uklanjanja N i P, FISH metodom su dokazani mikrobni klasteri odgovorni za procese nitrifikacije, denitrifikacije, (anoksično) uklanjanje fosfora, i pohranjivanje glikogena. Dokazani su unutarstanično pohranjeni polimeri, poliP i PHA. U anoksičnim uvjetima sa NO2-N kao akceptorom elektrona, u procesu denitrificirajuće defosfatacije 15 mg PO4-P/L pri omjerima N/P 1-4 omjer ΔC/ΔN/ΔP je izračunat pri minimalnom omjeru C/N za postizanje potpune denitrifikacije za vrijeme ustaljene brzine uklanjanja P, i iznosi 14,3/1,3/1 pri N/P 1 i C/N 5, pri čemu je ostvareno 78% uklanjanje P; 15,9/1,8/1 pri N/P 2 i C/N 4, pri čemu je postignuto 77,1% uklanjanje P; 15,2/3,0/1 pri N/P 3 i C/N 3 uz 74,5% uklanjanje P, i 14,6/2,7/1 pri N/P 4 i C/N 3, uz 71,2% uklanjanje P. U anoksičnim uvjetima sa NO2-N kao akceptorom elektrona, u procesu denitrificirajuće defosfatacije 30 mg PO4-P/L pri omjeru N/P 0,5 postignuto je uklanjanje P 61,9% (C/N 4) i 67,6% (C/N 5), uz izračunati omjer ΔN/ΔP 0,8, a pri omjeru N/P 1 i C/N 5 postignuto je 78,6% uklanjanje P, uz izračunati omjer ΔN/ΔP 1,2. U anaerobno-anoksičnim uvjetima sa NO2-N kao akceptorom elektrona, u procesu denitrificirajuće defosfatacije 15 mg PO4-P/L pri omjeru N/P 2 i 4 omjer ΔC/ΔN/ΔP izračunat za period ustaljene brzine uklanjanja P, pri minimalnom omjeru C/N za potpuno uklanjanje N, pri N/P 2 i C/N 3 iznosi 11,6C/2,2N/1P uz 75,8% uklonjenog P; a pri N/P 4 i C/N 3 iznosi 17,9C/3,8N/1P uz 68,3% uklonjenog P. U procesu denitrificirajuće defosfatacije uz NO2-N kao akceptor elektrona postiže se neznatno bolji učinak uklanjanja P u anoksičnim uvjetima pri minimalnom potrebnom omjeru C/N za potpuno uklanjanje N, u usporedbi sa anaerobno-anoksičnim uvjetima.The aim of this research was to investigate DPAOs activity for N and P removal with NO2-N as an electron acceptor under anoxic conditions with acetate as a carbon source. By use of the FISH method in the activated sludge acclimatized on N and P removal process, microbial clusters responsible for processes of nitrification, denitrification, (anoxic) phosphorus removal, and glycogen storage, were proven. Intracellular storage polymers, polyP and PHA, were also proven. In the process of denitrifying dephosphatation 15 mg PO4-P/L under anoxic conditions with NO2-N as an electron acceptor at ratios N/P 1-4, a ratio of ΔC/ΔN/ΔP was calculated at minimal C/N ratio required for complete denitrification during constant P uptake rate and amounts 14,3/1,3/1 at N/P 1 and C/N 5, with 78% P removal; 15,9/1,8/1 at N/P 2 and C/N 4, with 77,1% P removal; 15,2/3,0/1 at N/P 3 and C/N 3 with 74,5% P removal, and 14,6/2,7/1 at N/P 4 and C/N 3, with 71,2% P removal. In the process of denitrifying dephosphatation 30 mg PO4-P/L under anoxic conditions with NO2-N as an electron acceptor, at a ratio of N/P 0,5 P removal of 61,9% (C/N 4) and 67,6% (C/N 5) was achieved, with a calculated ratio of ΔN/ΔP 0,8, whereas at a ratio of N/P 1 and C/N 5 P removal of 78,6% was achieved, with calculated ratio of ΔN/ΔP 1,2. Under anaerobic-anoxic conditions with NO2-N as an electron acceptor, in the process of denitrifying dephosphatation 15 mg PO4-P/L at ratios of N/P 2 and 4, a ratio of ΔC/ΔN/ΔP was calculated for the period of constant P uptake rate at a minimal ratio of C/N for complete N removal, and at N/P 2 and C/N 3 amounts 11,6C/2,2N/1P with 75,8% P removal; at N/P 4 and C/N 3 amounts 17,9C/3,8N/1P with 68,3% P removal. In the process of denitrifying dephosphatation with NO2-N as an electron acceptor a slightly better P removal under anoxic conditions was obtained, at a minimal required C/N ratio for complete N removal, compared to anaerobic-anoxic conditions