Treatment And Resource Utilization Of Monosodium Glutamate Wastewater Based On Microalgae

As a difficult-to-handle food wastewater,monosodium glutamate wastewater has the characteristics of high concentration of COD,ammonia nitrogen,salinity,acidity and low p H.However,monosodium glutamate wastewater contains abundant nutrients such as carbon,nitrogen,and phosphorus elements,which play an important role in the growth of microalgae.Therefore,the scientific utilization of monosodium glutamate wastewater can reduce production costs and achieve resource utilization.Firstly,the optimal dilution concentration of monosodium glutamate wastewater suitable for microalgae growth was tested to ensure that microalgae can grow normally in the wastewater.Secondly,microalgae strains suitable for monosodium glutamate wastewater treatment were screened,and the cultivation conditions in the wastewater were optimized to obtain the best growth and wastewater purification effects.Finally,microalgae cultured in the wastewater were added to wheat culture solution as a biological fertilizer,and the growth of wheat was evaluated,and the following conclusions were obtained:（1）In order to explore the growth of microalgae in monosodium glutamate wastewater and the optimal dilution concentration,the experiment used Chlorella sorokiniana GXNN-01 as the research object,and inoculated it in monosodium glutamate wastewater at different dilution concentrations.After the experiment,it was found that the biomass of microalgae reached the highest value at a dilution concentration of 1000 times,so monosodium glutamate wastewater diluted 1000 times was chosen as the culture medium for subsequent microalgae cultivation and wastewater treatment experiments.（2）Six kinds of microalgae were selected for adaptive screening.C.sorokiniana GXNN-01,C.sorokiniana FACHB-275 and Chlorella sp.FACHB-30,Chlorella sp.FACHB-9,Chlamydomonas reinhardtii FACHB-479,Tetradesmus obliquus FACHB-416.In order to shorten the adaptation time of microalgae,microelements were added to the wastewater,and the control group without adding or using ordinary medium was set up for comparison.The results showed that Chlorella sp.FACHB-9and Chlorella sp.FACHB-30 could adapt to the environment of monosodium glutamate wastewater well,and the biomass of FACHB-9 and FACHB-30 did not show significant difference（P>0.05）.In terms of removal rate,the removal performance of total phosphorus and chemical oxygen demand of FACHB-30 was significantly higher than that of FACHB-9（P<0.05）.After screening,it was found that Chlorella sp.FACHB-30 had a good wastewater removal effect,including total phosphorus removal rate of 69.10%,total nitrogen of 26.93%,ammonia nitrogen of 51.91%,and chemical oxygen demand of 61.50%.Therefore,FACHB-30 was selected to carry out wastewater purification experiment in the following experiment.（3）In order to optimize the purification effect of Chlorella sp.FACHB-30 in wastewater,three conditions including light intensity,iron ion concentration,and initial inoculation amount were optimized through experiments.In the light intensity optimization experiment,it was found that with the increase of light intensity,the growth and removal rate of Chlorella sp.both increased.Between the light intensities of 100μmol m^-2s^-1and 150μmol m^-2s^-1,the removal rate of COD continued to increase,but the removal rate of other nutrients did not show a significant difference（P>0.05）.In the iron ion concentration experiment,several groups with iron ion concentration lower than 1×10^-5mol L^-1showed an increasing trend of purification effect with the increase of iron ion concentration.However,when the concentration was higher than this,iron ions would cause oxidative damage to the cell photosynthetic membrane,thereby reducing the growth and removal effect of Chlorella sp.In the initial inoculation amount experiment,the highest growth rate was achieved when the inoculation concentration was 1×10⁵cells m L^-1.However,when the inoculation concentration exceeded 5×10⁶cells m L^-1,the removal rate decreased due to limitations in space and light conditions.After single-factor optimization,the removal rate of various nutrients was significantly improved.Among them,the removal rates of TP,TN,NH₄⁺-N,and COD were increased by 26.77%,152.69%,46.20%,and 26.76%,respectively,compared to the values before optimization..（4）The experimental results of cultivating Chlorella sp.in monosodium glutamate wastewater as a biofertilizer showed that the combination of Hoagland’s nutrient solution and living algae biofertilizer had the greatest growth-promoting effect on wheat seedlings.Compared with using only H nutrient solution,the growth of roots increased by 102.45%,the growth of stems increased by 12.53%,and the dry weight of stems increased by 14.98%.This indicates that cultivating Chlorella sp.in wastewater can produce a certain biofertilizer effect,and this new form of biofertilizer has good development prospects.At the same time,we also found that the performance of the living algae biofertilizer was better than that of the inactivated algae solution.This may be because living algae can improve the living environment around wheat roots,thereby promoting root growth.