cultivation of chlorella zofingiensis and nutrients removal in dairy wastewater were investigated in bench-scale outdoor ponds in winter, south china. the impacts of the two types of ph regulations, 5 similar to 6% co2 and acetic acid (hac) on this process were studied. after 6 days cultivation, the removal rates of total nitrogen (tn) and orthophosphate (po43-) using co2 regulation were better than those using hac. the removal rates of po43- and tn were 97.5% and 51.7%, respectively using co2 regulation; 79.6% (tn) and 42.0% (po43-) were obtained using hac regulation. higher biomass, protein, sugar content, and stable ph control were found using co2 regulation. however, significantly higher lipid content (31.8%) was observed using hac regulation. the dominant differences of fatty acids were the content of c18:1 and c18:3. the growth characteristics and environmental conditions especially during the typical logarithmic phase were also analyzed. (c) 2012 elsevier ltd. all rights reserved.