Study Of The Critical Organic Load Of Hogwash Waste Grease On Semi-continuous Anaerobic Digestion Process

Hogwash waste grease renewable energy technology was less involved at home and abroad.The anaerobic digestion experiment was processed with different organic loading at35℃.The test selected waste grease of the hogwash as the experimental materials and pig manure as inoculum,which mixed in a CSTR reactor with an adopted semi-continuous operation mode. The experiment studied the anaerobic digestion regularity and the limiting organic load of hogwash waste grease, by monitoring and analyzing the pH value, volatile fatty acid (VFA), ammonia nitrogen, alkalinity, gas production and gas composition. The results indicated that:(1) The bacterial got high adaptability to the reacting environment when adding the pig manure to the self-made CSTR reactor for acclimatization,and then putting the hogwash waste grease to the system affter a succesfully domestication.The hydrolysis acidification and methanogenic process run orderly.The whole system went well, and the grease could be degraded effectively.(2) When the organic load gradually increased from0.5gVS/(L.d),0.75gVS/(L.d),1gVS/(L.d) to1.25gVS/(L.d),the pH, VFA concentration, alkalinity and ammonia nitrogen kept at7.3,450mg/L,9500mg/L and1100mg/L,respectively. The cumulative gas production and gas production rate increased constantly.The gas productions were90.21L,136.24L,196.64L,and the average production rate were1.36L/gVS,1.4L/gVS,1.5L/gVS, respectively. The results showed that low organic loading environment was suitable for microorganism growing and the system remained steady. When the organic load was1.25gVS/(L.d), the system run best and the gas production was stable.The maximum gas production per day was17.6L, the average gas production ratecould reach1.78L/gVS and the content of methane occupied60%of the gas.(3) When the system ran at high organic load,the pH was falling.When the organic load was1.5gVS/(L.d), the pH dropped to7.1, when the organic load reached1.75gVS/(L.d), the pH decreased from7.0to6.6, the VFA concentration increased from809mg/L to3697mg/L,gas production reduced to167.6L, the methanation of the system is inhibited, the content of methane fell to10%or even lower.(4) The methane generating ability of hogwash waste grease is better than the common food residue.However the anaerobic digestion of waste grease was more likely to appear acid inhibition, therefore, the anaerobic digestion system of this test required a higher organic load resistance to the waste grease.