| Chlorella can use of CO2 and solar for autotrophic growth, also use of organic carbon and nitrogen for high-density mixotrophic or heterotrophic growth. This feature makes chlorella can be used in organic wastewater treatment, and recycling of wastewater resource and achieving chlorella biomass, is an economical, environmentally friendly, sustainable wastewater treatment. Yeast wastewater is a kind of refractory wastewater of high organic load, high color and low biodegradability, severely restricted the cleaner production of yeast industry. This paper studies heterotrophic- photoautotrophic joint culture method of chlorella pyrenoidosa, which can quickly harvest high-cell-density biomass in six days to inoculate yeast wastewater. Analyzes the basic properties of yeast wastewater, investigated Chlorella tolerance to yeast wastewater, and compared the effects of different culture methods on Chlorella growing in the yeast wastewater. Systematically studied the absorption properties of activated carbon on yeast wastewater pretreatment, compared the effects of activated carbon pretreatment on Chlorella growing in the yeast wastewater.The main experimental results were as follows:1. In the process of heterotrophic-photoautotrophic joint culture, glucose concentration of Basal medium significantly(P<0.05) affect heterotrophic growth of chlorella pyrenoidosa, and nitrate does not significantly affect heterotrophic growth of chlorella pyrenoidosa. When the glucose concentration was 50g/L and nitrate concentration was 3.75g/L, chlorella pyrenoidosa achieved the highest biomass 21.31g/L under heterotrophic culture in four day. After heterotrophic chlorella into autotrophic culture, with the increase of initial cell density, the night biomass loss is less under the light/dark cycle culture. Nitrate concentration had no effect on the growth of heterotrophic chlorella in the autotrophic culture, but had a significant effect(P<0.05) on chlorella’s intracellular protein and chlorophyll content. When the initial cell density of 11.09g/L, nitrate concentration is 3.75g/L, and illumination intensity is 6411 lux, the chlorella get the highest protein content 54.1% and chlorophyll content 3.14%, achieving simultaneous accumulation of protein and chlorophyll.2. Characteristics of yeast wastewater were analyzed and found yeast wastewater contains PO43ˉ、NH4+、Mg2+、Ca2+、K+, whose content were 140.8 mg/L、455 mg/L、299 mg/L、827 mg/L and 5044 mg/L, respectively, which can be used for chlorella absorption and utilization, and COD, TN, TP, residual total sugar of yeast wastewater were 2.24×104 mg/L,3.35×103 mg/L,284 mg/L,6.80g/L, respectively, that is to say, yeast wastewater is a high load of organic wastewater. Studies have shown that chlorella can tolerate Basal medium at a concentration of 70g/L sucrose, and chlorella achieved the highest biomass 3.37g/L in third day under heterotrophic culture, which proved that chlorella can utilize sucrose.3. Load of yeast wastewater was raised by adding molasses(mainly composed of 30-40% sucrose), and the tolerance of chlorella to different load yeast wastewater was examined, found the chlorella pyrenoidosa can tolerate the yeast wastewater of COD, TN,TP up to 2.89×105 mg/L,1.39×104 mg/L,1.12×104 mg/L and achieving the highest biomass 1.95g/L and the average specific growth rate 0.43d-1, those proved that chlorella has good application in yeast wastewater treatment. Chlorella pyrenoidosa can grow continuously under the mixotrophic culture of yeast wastewater whose COD,TN,TP were 2.24×104 mg/L、3.35×103 mg/L、2.84×102,in the sixth day, chlorella pyrenoidosa get the highest biomass and COD,TN,TP removal rates, which were1.33 g/L、20.03%、21.28% and 24.53%,respectively.4. Yeast wastewater was pretreated by the activated carbon, and the results showed that activated carbon 200 was the best material. With increasing doses of activated carbon, purifying effect is enhanced, but TP increase, considering the cost and effectiveness, 3% doses is the best. Under acidic conditions(p H 3.0-6.0), activated carbon for wastewater COD, TN and color removal rates is better than those under neutral and alkaline conditions(p H 3.0-6.0), and TP of yeast wastewater was almost completely removed under alkaline condition. Taking into account the culture pyrenoidosa after pretreatment, we choose the p H 3.0 is the optimal. Under the above optimum conditions, the removal rate of COD, TN, color of yeast wastewater could reach 54.50% 、 46.75% 、98.96%,respectively, and the increment of TP of yeast wastewater is less(13.7%).5. After the pretreatment of the activated carbon, the COD, TN, TP of yeast wastewater were 1.16×104 mg/L、980 mg/L and 305.2 mg/L, respectively, which is better for growth of chlorella pyrenodisa and achieved the highest biomass 2.29g/L in 7th day after mixotrophic culture. This study showed the COD, TN, TP removal rate of yeast wastewater and chlorella growth was significantly correlated. Combined with activated carbon pretreatment and Chlorella growth, removal efficiencies of COD,TN,TP and color of yeast wastewater can reach 87.82%、68.26%、78.57%、98.96%,respectively. |
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