Concurrent Production Of Volatile Fatty Acids And Hydrogen Accompany With The Odor Emission Control During Anaerobic Digestion

Proper management of food waste is crucial to city manager especially the large and medium-sized ones in China recent years.Anaerobic digestion has been widely used as an effecitive alternative treatment method for its technical maturity and high valued-added products.Aimed at the further deep utilization of food waste and odor emission control,this thesis systemically provides an optimization research on parameters which influence the anaerobic digestion process and its effect on substance release,studied the effect of sonication treatment from two dimensions?ultrasonic density and ultrasonic time?,investigated the inhibition effect of typical component oil/salt on anaerobic digestion.Meanwhile interpretation the long volatile fatty acids?LCFA?mechanism during anaerobic process.Furthermore,a potential efficient method of odor control is developed by the dosage of activated carbon?AC?using response surface methodology was put forward firstly.Thus,Concurrent production of volatile fatty acids and hydrogen accompany with the odor emission control during anaerobic digestion is realized.The main conclusions derived from the thesis listed as follows:Due to the aim of interpreted the interaction of VFA and hydrogen production,we applied response surface methodology?RSM?to optimize the concerned parameter including total solids?TS?,pH,and reaction time based on the previous research.The maximum volatile fatty acids?VFA?and hydrogen reached 26.17 g/L and 160.1 mmol respectively under the condition of pH 7.0;TS 100 g/L and reaction time 3 d.The result suggested that the observed hydrogen production maximum accounted for 32.3%to theoretically hydrogen production caused by the VFAs inhibition.After introduced the sonication pretreatment prior to anaerobic process,The results observed a 71.4%enhancement was achieved of soluble chemical oxygen demand?SCOD?,what's more,a 65.3%and 59.1%increase was reached for VFA and hydrogen production,respectively.And the required time for reach its maximum production was reduction by50%.In addition,95%of food waste particle was disintegrated lower 50?m which facilitated to the subsequent digestion.The relative abundance of concerned microbial including Firmicutes,Proteobacteria,Bacteroidetes and Chloroflexi were also increased with sonication density and time increased.Due to the restriction of food waste typical component oil/salt on digestion process,we demonstrated the sole and interaction effect of vegetable oils,animal fats.The inhibition effect was observed regardless of the oil content.Afterwards,salt and sonication pretreatment was introduced prior to the anaerobic degstion to evaluate both effect to the anaerobic digestion.The VFA production and hydrogen ratio increased 16.4%and 8.4%,respectively in the appearance of 6 g/L salt which caused by the bonding effect of oil content by ions.Under the optimal ultrasound conditions,the VFA production was 59.1%higher than that of the oil alone,and the hydrogen ratio was increased by 29%.The result implied that both the salt and the sonication pretreatment were effective means to alleviate the inhibition of oil.Moreover,the transformation of long chain fatty acids was also studied.Due to few literatures have been done on the odor control during anaerobic digestion,we proposed an efficient method for odor control for the first time by the dosage of activated carbon?AC?into the anaerobic system.Considered the olfactory threshold,the threshold diluton factor?ratio of mass concentration to olfactory threshold?was used to analysis the contribution of each single odor components.Four species of odor component containing hydrogen sulfide,ethanethiol,dimethyl sulfide,dimethyl disulfide was comfirmed.Considered the olfactory threshold and AC characteristics,we systemically studied the contribution rate of each single species based on threshold dilution multiple.In all,the optimized batch condition is nutshell charcoal activated carbon which its particle size over 2 mm with 30%TS_addeddded dosage.