Long term outdoor operation of a tubular airlift pilot photobioreactor and a high rate algal pond as tertiary treatment of urban wastewater

530L high rate alga pond (HRAP) and 380L airlift tubular photobioreactor (TPBR) were operated and compared in a urban wastewater treatment plant (WWTP), with the main purpose of removing nitrogen and phosphorous from the effluent of the WWTP while generating a valuable biomass. The photosynthetic activity in TPBR was during entire experiment higher than HRAP. The maximum areal productivity reached was 8.26 +/- 1.43 and 21.76 +/- 0.3 g SS m(-2) d(-1) for HRAP and TPBR respectively. Total nitrogen (TN) removal averaged 89.68 +/- 3.12 and 65.12 +/- 2.87% for TPBR and HRAP respectively, while for total phosphorus (TP) TPBR and HRAP averaged 86.71 +/- 1 0.61 and 58.78 +/- 1.17% respectively. The lipid content showed no significant differences (p<0.05) between HRAP and TPBR averaging 20.80 +/- 0.22 wt%. The main operating disadvantage of TPBR versus HRAP was the sever biofouling which forced to stop the experiment. Under the same conditions of operation TPBR was more limited at low temperatures than HRAP, and HRAP was more light limited than TPBR. (C) 2013 Elsevier B.V. All rights reserved.