Mixed Culture Of Chlorella And Yeast For The Treatment Of Yeast Wastewater From Molasses

Chlorella is a unicellular green algae with various trophic modes,rapid growth rate and strong environmental tolerance ability.It can use carbon,nitrogen and phosphorus in wastewater for breeding and purify water quality.There are more than 600 kinds of yeast,of which some species can effectively remove the organic matter in the wastewater.Its growth rate is fast and culture period is shorter.These features make the mixed culture of Chlorella and yeast used in wastewater treatment,which can make full use of the advantage of the two microbes and at the same time harvest comprehensive utilization value of microbial biomass,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 optimizes the condition of mixotrophic growth for Chlorella pyrenoidosa and creates a method of rapid plant expanding for large-scale cultivation outdoors.By exploring the growth characteristics of Chlorella pyrenoidosa and Rhodotorula glutinis in yeast wastewater and the effect of purification on wastewater,and assessing the operability of activated carbon for pretreatment of wastewater,the mixed culture of Chlorella pyrenoidosa and Rhodotorula glutinis in tubular photo-bioreactor outdoors with yeast wastewater as the medium was investigated,establishing an effective treatment method for this kind of wastewater.The main experimental results were as follows:1.Glucose and sodium nitrate could significantly promote the growth of Chlorella pyrenoidosa.The maximum biomass of 14.32 g/L was obtained after 5 days cultivation,with the salinity of 15 ‰,30 g/L glucose and sodium nitrate concentration of 3.75 g/L.When sodium nitrate concentration was 5.00 g/L,Chlorella pyrenoidosa could achieve the highest content of protein,total chlorophyll and total carotenoid,which were 40.38%,3.79% and 1.06%,respectively.Glycerol could promote the growth of Chlorella pyrenoidosa and fatty acid accumulation in the cell,but the efficiency was much lower than glucose.Acetic acid,sodium acetate and 2% CO₂ could promote biomass growth of C.pyrenoidosa,but total fatty acids and pigment content in the cell decreased when adding acetic acid and sodium acetate.Using 2% CO₂ as carbon source,the biomass of 3.38 g/L could be obtained with salinity of 15‰ and sodium nitrate concentration of 3.75 g/L after 8 days cultivation,which was far more than autotrophic culture.And at the same time total fatty acids and pigment content in the cell were significantly higher than that of autotrophic control group.2.Chlorella pyrenoidosa could grow in summer with strong light outdoor and the optimum temperature was 33 ?,higher than indoor shake flask culture.With ammonium bicarbonate as carbon source,the highest biomass yield reached 1.00 g/L,a 1.98-fold increased compared with before the feeding.The content of total chlorophyll and carotenoid in the cell reached as high as 5.09% and 1.32% respectively.By adding urea in the autumn,the maximum biomass of 1.25 g/L could be obtained.And the highest content of total chlorophyll,total carotenoid and protein in the cell were 4.69%,1.04% and 55.32%,respectively.3.By comparing the growth of C.pyrenoidosa in original wastewater,nanofiltration wastewater and ultrafiltration wastewater,the original yeast wastewater was proved to be more suitable for the cultivation of C.pyrenoidosa and water quality purification.Adding glycerol to original yeast wastewater could significantly promote the growth of C.pyrenoidosa?p<0.05?.After 6 days cultivation with the glycerol concentration of 15 g/L,the removal rate of COD,TN and TP could reach 57.51%,52.18% and 91.37%,respectively.The biomass concentration and wastewater purification effect were higher in mixed culture of C.pyrenoidosa and Rhodotorula glutinis compared with that of pure cultures.The COD,TN,TP and NH3-N removal by the mixed culture with ratio of Rhodotorula glutinis to C.pyrenoidosa 1:3 were 57.33%,55.44%,88.99% and 75.13%,respectively.The highest biomass yield and the average specific growth rate were 8.0 g/L and 0.37 d-1 when added 20g/L glycerol to the mixed culture,which were 1.68-fold and 1.19-fold compared to the mixed culture without glycerol,respectively.The removal rate of COD,TN,TP and NH3-N reached 69.29%,59.08%,96.20% and 71.43%,respectively.4.At the optimum condition of the dosage of active charcoal T-80 3%?w/v?and initial pH of 3.00,the removal rate of COD,TN,NH3-N and color were 55.69%,39.44%,37.80% and 98.12% respectively.The content of PO43-in the wastewater significantly increased after pretreatment,which was more suitable for the growth of C.pyrenoidosa and yeast.But the active charcoal was difficult to remove when enlarged the pretreatmen and the processing efficiency was very low.It was not suitable for large-scale wastewater pretreatment.5.With sand filter,activated carbon filtration,ultrafiltration tertiary pretreated yeast wastewater as the medium,the mixed culture of C.pyrenoidosa and Rhodotorula glutinis was investigated in 700 L tubular photo-bioreactor outdoor.By gradually adding wastewater for amplification,the total removal rate of COD,NH3-N,TN and BOD5 of wastewater through the whole process could reach 80.98%,78.54%,83.21% and 87.76%,respectively.Using two-step cultivation,the mixed culture of C.pyrenoidosa and Rhodotorula glutinis was studied in 1300 L tubular photo-bioreactor outdoor.In the whole process,the total removal rate of COD,NH3-N and TN of wastewater reached 81.57%,67.27% and 67.27%,respectively.The removal rate of TP and PO43-of yeast wastewater could reach 100% in different volume of photo-bioreactors.