Force Conditions Promote The Formation Of Structured Aerobic Granular Sludge And Process Operation Control

Aerobic granule sludge exhibits diverse characteristics of excellent settleability,high biomass retention,dense structure,and ability to withstand at high organic loading.Because of the unique granule attributes,the aerobic granulation technology was recently developed for treating high strength wastewaters containing organics,nitrogen,phosphorus,toxic substances and xenobiotics.However,popularization of aerobic granule sludge is restricted due to unclear formation mechanism,cultivation of granules and the issue of structure stability.In view of the high ammonia nitrogen wastewater,how to develop stable aerobic granular sludge and the process operation regulation have important significance.This paper established sequence batch reactors and cultivated structured aerobic granular sludge by regulating nitrogen load to study the formation of granules,using molecular biology techniques(PCR-DGEE,high-throughput sequencing technology),high performance liquid chromatography,scanning electronic microscopy.Regard to difficulty of cultivation and long granulation time of aerobic granules,this study enhanced aerobic granulation by applying the mode of fuctuant nitrogen loading.When the temperature was controlled at 3 0℃ and influent ammonia concentration was rapidly alternated from 600mg/L to 300mg/L,to 100mg/L,and then back to 600mg/L,aerobic granular sludge with regular shape appeared after 15 days operation.It showed that regulating nitrogen loading is an efficient method for cultivation of aerobic granular sludge.The aerobic granular sludge has the characteristics of obvious layered structure,great strength of granules and good substrate metabolism ability.Its fairly significant to maintain structural stability of aerobic granular sludge during the process operation.In this paper,the mature aerobic granular sludge was inoculated,removing organic carbon source to culture for 10 days and adding organic carbon source again to culture for another 10 days,then the effect of heterotrophic metabolism on the micro-instability of aerobic granular sludge was investigated.COD removal rate of mature granule can reach 92.1%,after cutting off organic carbon source and recovering supply of organic carbon source,COD removal rate was 96.6%.Substrate metabolism ability and apparent structure of structured granular sludge were not affect by the lack of organic carbon source,but the microstructure has been unstable,strength of granules decreased significantly.Glycoprotein molecule exist in structural granular sludge,whose molecular weight is 1778688.92.The compound is key to maintain the apparent structure,meanwhile strength of granule depends on polysaccharide.This research investigated the aerobic granules under rapid modulation of nitrogen loading,focusing on the impact of nitrogen fluctuation,temperature,inorganic carbon source input,and ratio of carbon to nitrogen.Nitrogen fluctuation was revealed to be the main causation of structured aerobic granules.When carbon source input was deficient,granulation process stayed unaffected with constant ratio of carbon to nitrogen at temperature below 20℃.But the strength and bacterial community of granules altered in that case:Temperature below 20℃ and constant C/N went against their growth and stability.Deficiency of carbon source could benefit the rapid growth but reduced their strength.Besides,the abundance of microbial populations was found to be another key factor.When temperature was higher than 30℃,Thauera,Leucobacter was abundant in the system.While Pseudomonas and Arthrobacter preferred lower temperature below 20℃.