Research On Rapid And Harmless Treatment Method Of Vegetable Wastes

With the rapid development of China’s vegetable industry,a large amount of vegetable wastes was generated during the harvesting,refrigerated transportation,and storage processes.Vegetable wastes was prone to degradation and decaied rapidly,randomly dumping will cause serious harmness to the environment,soil and water,so it is urgently needed for treatment.The existing large-scaled treatment systems for vegetable wastes generally consider vegetable wastes as high moisture content wastes,and use extrusion and sewage treatment processes,which not only have high treatment costs but also result in resource waste.In order to reduce the cost of vegetable wastes treatment and achieve the recycling of vegetable waste resources.This article proposed a rapid and harmless treatment method for vegetable waste based on the composition and degradation characteristics of vegetable wastes,as well as the existing problems in the large-scaled treatment systems of vegetable wastes.This method combines thermostatic temperature anaerobic digestion and thermostatic temperature aerobic treatment.Firstly,vegetable wastes(VW)and pressed vegetable wastewater(PVW)were subjected to 30 days of thermostatic temperature anaerobic digestion in a 0.56m~3 anaerobic digester.Secondly,the treated biogas slurry was subjected to 48 hours of aerobic treatment.Finally,heavy metals,pathogenic bacteria,pesticide residues,and other indicators in the treated biogas slurry were tested and compared with current standards to verify the feasibility of the treatment method.In addition,on the basis of feasibility verification,explore the effects of different mixed materials and temperatures on the anaerobic digestion biogas production characteristics and organic matter degradation characteristics of vegetable wastes and pressed vegetable wastewater.Analyze the impact of aeration amount and aeration temperature on the aerobic treatment process of biogas slurry,and ultimately obtain the conditions for rapid and harmless treatment of vegetable wastes.The main research conclusions of this article are as follows:(1)According to the composition and degradation characteristics of vegetable wastes,as well as the existing problems in the large-scale treatment system of vegetable wastes,a vegetable waste treatment method combining thermostatic temperature anaerobic digestion and thermostatic temperature aerobic aeration is proposed,and the feasibility of this treatment method is verified through experiments.The research results indicate that the methane production of pressed vegetable wastewater during anaerobic digestion is0.409m~3/kg VS,which can achieve its resource utilization;during the 31 days treatment process,the chemical oxygen demand(COD)of pressed vegetable wastewater decreased from the initial 15687.5mg/L to 1018.4mg/L,with a removal efficiency of 93.51%;the germination rate of the treated biogas slurry seeds is greater than 80%.After testing,it was found that there are no harmful substances such as pesticide residues,heavy metals,and pathogenic bacteria,and it can be returned to the field without harm.Therefore,the above experiement results prove that in the 31 days of treatment,vegetable wastes can realize the recycling and harmless return treatment,which proves the feasibility of thermostatic temperature anaerobic-aerobic treatment method.(2)To investigate the effect of mixed materials on anaerobic digestion of pressed vegetable wastewater,the experiment used a single digestion of pressed vegetable wastewater as a blank group,and compared the biogas production performance and organic matter degradation characteristics after added vegetable wastes and maize straw.The material group with the fastest degradation rate was determined.The research results show that the methane production of the group with added vegetable wastes and maize straw are0.491m~3/kg VS and 0.523m~3/kg VS,respectively,which are 20.05%and 27.87%higher than that of the single digestion group with pressed vegetable wastewater;the COD removal efficiency of three experimental groups were 83.07%,79.45%,and 79.15%,respectively.The volatile solids(VS)removal efficiency of the single digestion group for pressed vegetable wastewater was 89.05%,which was14.52%and 19.66%higher than the added group.Therefore,the degradation rate of the single digestion group for pressed vegetable wastewater was the fastest.(3)To determine the optimal aerobic treatment conditions for pressed vegetable wastewater,the aerobic treatment effects of biogas slurry under different temperatures(20℃,30℃)and aeration rates(0.5L/min,1.0L/min,1.5L/min)were compared,and the optimal aerobic treatment conditions were evaluated.The research results show that under the same aeration rate(0.5L/min),the COD removal efficiency at 30℃is 59.35%,which is 9.85%higher than that at 20℃,the ammonia nitrogen removal efficiency is 13.52%higher than that at 20℃,in addition,the seed germination of the 30℃treatment group is significantly better than that at 20℃.At the same aerobic treatment temperature(30℃),the removal efficiency of ammonia nitrogen is1.0L/min>1.5L/min>0.5L/min,and the removal efficiency of COD is1.5L/min>1.0L/min>0.5L/min,The seed germination rate is greater than 80%under three aeration rates.The variation trends of other parameters are similar under aeration rates of 1.0L/min and 1.5L/min,while aeration rate of 1.0L/min can reduce its treatment cost and energy consumption.Therefore,when the temperature is 30℃and the aeration rate is 1.0L/min,the aerobic treatment effect of biogas slurry is the best.(4)Based on the combination of the fastest degrading materials and the optimal aerobic treatment conditions,the effect of temperature on the rapid treatment of pressed vegetable wastewater was explored.Firstly,the biogas production characteristics and organic matter degradation characteristics of pressed vegetable wastewater during anaerobic digestion at 26℃、37℃and 52℃were compared.Secondly,the treatment effect was explored under the optim al aerobic treatment conditions.Finally,determine the treatment conditions and whether the treated biogas slurry can achieve harmless return to the field.The research results show that the methane production in the 52℃group is 2034.2L,which is 15.95%and 101.16%higher than that in the 37℃and 26℃groups;the COD decreased from 15687.5mg/L to 2201.1mg/L,with a removal efficiency of85.97%,which was 3.99%and 22.29%higher than 37℃and 26℃groups;in addition,during the aerobic treatment process,the COD of the 52℃group biogas slurry decreased from 2201.1mg/L to 902.7mg/L within 24 hours,with a removal efficiency of 58.99%and a seed germination rate of 123.4%,which is1.39 and 1.96 times higher than that of the medium and low temperature groups.During the 31 day treatment process,the COD of the 52℃group decreased from15687.5mg/L to 902.7mg/L,with a removal efficiency of 94.25%.Therefore,the 52℃group showed a higher degradation rate.After testing and analysis,it was found that the parameters of the biogas slurry treated at 37℃and 52℃meet the standard requirements and can be returned to the field.(5)After analyzing and summarizing the conditions for rapid and harmless treatment of vegetable waste and pressed vegetable wastewater,it was found that after 30 days of anaerobic digestion(37℃and 52℃)and 24 hours of aerobic treatment(30℃and 1.0L/min),both vegetable waste and pressed vegetable wastewater can meet the standard requirements and be returned to the field harmless.