Study On Treatment Of Soy Sauce Wastewater By Fungi-Microalgae And Its Resource Utilization

Soy sauce is a common condiment in daily life.Its output is increasing year by year.But the wastewater produced in the process of soy sauce processing is a kind of high-concentration organic wastewater.It will cause serious water pollution if soy sauce wastewater is discharged directly.There are still some problems in the treatment of soy sauce wastewater by traditional activated sludge method.Therefore,developing a new efficient soy sauce wastewater treatment technology is of great significance to water environmental protection.In recent years,microalgae have been widely used in the wastewater treatment due to its numerous advantages,but study which focus on the treatment of soy sauce wastewater by microalgae have rarely been reported.In this paper,the pollutant-resistant microalgae（identified as Chlorella pyrenoidosa）was screened from landfill leachate,and the filamentous fungi（identified as Penicillium）was isolated from activated sludge.The microalgae,fungi and fungi-microalgae system were studied for soy sauce wastewater treatment potential;the effects of different initial inoculation of microalgae/fungal spores and initial inoculum ratio of microalgae and fungal on soy sauce wastewater treatment efficiency by different systems were investigated,and the resource utilization of fungi,microalgae and fungi-algae system biomass after wastewater treatment were explored.The main conclusions are as follows:The study on the treatment of soy sauce wastewater by Chlorella pyrenoidosa showed that Chlorella pyrenoidosa could better adapt to soy sauce wastewater and remove nutrients from wastewater.The highest biomass of Chlorella pyrenoidosa was1.86 g/L and 2.20 g/L in 50%concentration wastewater and original wastewater respectively,and it grew better in original concentration wastewater.The removal of nutrients in original concentration wastewater by Chlorella pyrenoidosa was much greater than 50%concentration wastewater.The removal efficiency of COD,NH₃-N,TN and TP in 50%concentration wastewater were 60%,95%,70%and 80%respectively,while those in original concentration wastewater were 70%,80%,70%and 80%respectively,and the removal effect of chromaticity in the original concentration wastewater was also higher than 50%concentration wastewater.The biomass of Chlorella pyrenoidosa and removal effect of NH₃-N and TN in wastewater were affected by different inoculation amounts,while removal effect of COD is not obvious,and it has little effect on the removal of TP and chromaticity.The study on the treatment of soy sauce wastewater by Penicillium showed that the removal efficiency of COD was obvious,and NH₃-N,TN and TP were also reduced in varying degrees,while the removal of chromaticity in wastewater was the most significant.The higher inoculation of fungal spores,the more final biomass obtained in wastewater.The final removal efficiency of nutrients in wastewater were nearly similar under three inoculation concentrations,with the maximum removal efficiency of COD,NH₃-N,TN and TP,which were 45%,30%,29%and 50%respectively;the removal efficiency of chromaticity in wastewater was significantly higher than that of treatment by microalgae;the initial inoculation of spores had little effect on the final removal efficiency of nutrients in soy sauce wastewater,but had an effect on the removal rate,and the higher the inoculation of spores,the faster the removal rate.The study on the treatment of soy sauce wastewater by fungi-microalgae system showed that the final biomass of the fungi-algae system was close to 2.5g/L under different initial inoculation ratios of fungus spores and microalgae.The fungi-algae system performed a good removal effect on the nutrients in soy sauce wastewater.Under the three inoculation ratios,the nutrients in the wastewater decreased obviously.The removal efficiency of COD,NH₃-N,TN and TP reached 75%,75%,67%and83%,respectively.The chromaticity of the wastewater also decreased significantly,and the removal efficiency reached higher than 50%.The growth of fungi-microalgae system and final removal efficiency of COD,NH₃-N,TN,TP and chromaticity in soy sauce wastewater were almost not affected by different initial inoculation ratios of fungal spores and microalgae,but the removal rates of nutrients were affected by the initial inoculation ratios.Fungi-microalgae system with an inoculation ratio of1:5000 had the fastest removal rates of nutrients in wastewater.Compared with the treatment by microalgae,the fungi-microalgae system improved the removal efficiency of COD,NH₃-N and TN in soy sauce wastewater,and the removal efficiency of TP was not lower than that of microalgae treatment.In addition,the removal of chromaticity in wastewater was greatly improved by fungi-microalgae system.Utilization analysis of fungi and microalgae biomass showed that Chlorella pyrenoidosa cultured in soy sauce wastewater could be used not only in biofuel production,but also in feed and other fields,while biomass of fungi and fungi-microalgae system could be used in biofuel production.