Abstract:In this study, three carbon sources (CO2, acetic acid and glycerol) were added to the pretreated molasses wastewater, and then the growth of Coccomyxa subellipsoidea C-169 in a symbiotic algal-bacterial system cultured in such enhanced wastewater and the outcome of such an enhancement were examined. Compared with the results related to aeration with air, supplementation with 2% CO2 could significantly increase the average cell growth rate and biomass yield by 6.49 and 10.4 times, respectively, and remarkably increased the total nitrogen, total phosphorus and ammonia nitrogen (p<0.05) but reduced the removal rate of COD (chemical oxygen demand) of wastewater. It was found that Coccomyxa subellipsoidea C-169 could use glycerol as its carbon source. At a glycerol concentration within 0~20 g/L, an increase of glycerol concentration led to an increased cell growth rate, and total nitrogen and total phosphorus removal rates. At 20 g/L, the highest dry weight of biomass reached 8.80 g/L, the average specific growth rate was 2.07 times as high as that without glycerol (the biomass yield, 0.70 g/(L·d). When the glycerol concentration was above 15 g/L, the removal rates of total nitrogen and total phosphorus were over 85% and 95%, respectively, which significantly increased the wastewater COD (p<0.01). Addition of 1~4 g/L acetic acid would inhibit the growth of Coccomyxa subellipsoidea C-169 and reduce wastewater purification efficiency. Therefore, when C-169 is used to purify wastewater with a high COD, glycerin can be added as a carbon source for its growth.
