Abstract

The aim of this study was to determine the effect of enhanced primary treatment on: increasing primary sludge production for increased biogas production; reducing the organic load on downstream biological treatment processes and thereby reducing energy consumption for aeration; denitrification and enhanced biological phosphorus removal (EBPR) rates in the activated sludge system. For this purpose, three commercial organic polymers (termed flocculent 1, 2 and 3) and ZnSO4 were selected for batch experiments, including two-phase tests (anaerobic P release (PRR) followed by anoxic P uptake (PUR) and anoxic N uptake (NUR)). The samples of raw wastewater and activated sludge were collected from three municipal wastewater treatment plants in Gdansk, Gdynia and Slupsk located in northern Poland. The experiments were carried out with the raw wastewater after two-hours sedimentation and raw wastewater after sedimentation with dosing the above mentioned reagents. The obtained results showed that the maximum removal of COD was in the case of flocculent no. 3 (61.63±7.96% with respect to raw wastewater and 37.47±11.68% with respect to wastewater after two-hours sedimentation). The experimental tests revealed that the addition of flocculent no. 3 could provide a reduction of nitrogen (N) and phosphorus (P) above 15.52±8.35% and 29.25±6.53%, respectively. It was found, that there were no substantial discrepancies on biological nutrient removal (BNR) processes in the two-phase experiments without and with addition of the organic polymers. In experiments without addition of organic polymers, the NUR, PRR and PUR were 1.31±0.49 gN.gVSS-1.h-1, 7.28±2.59 gP.gVSS -1.h-1 and 1.19±0.97 gP.gVSS -1.h-1, respectively. For comparison, in experiments with flocculants, the NUR, PRR and PUR were 1.63±0.65 gN.gVSS -1.h-1, 7.29±3.65 gP.gVSS -1.h-1 and 1.46±0.79 gP.gVSS -1.h-1, respectively. The experimental results confirmed that CEPT can be used as an alternative for the treatment of wastewater to traditional biological processes.

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