The Choose Of Solid Organic Carbon Source In Biological Denitrification Of Wastewater

Biological nitrification and denitrification was widely used in nitrogen removal of municipal wastewater.Nowadays,There is presently the ubiquity of insufficient carbon source as electron donor,which is the most important restrictive factors of the efficiency of biological nitrogen removal in urban sewage treatment plant escepcially in southern China.So external carbon addition that meet the requirement of electron donor need to be considered.For high cost of low molecular organic compounds and carbohydrate which used in sewage denitrification process as liquid carbon source,using cheap solid carbon source to replace thetraditional ons has become a focus recently.Current research mainly focuses on papers,cotton,rice husk,rice straw, wheat straw and sawdust,but there still exist some good solid organic carbon source (SOC) which has not been studied.Microbial denitrification of pulluted water was studied in conical flasks packed with peanut shell,walnut shell' bamboo,receptaculum nelumbinis and luffa which were seldom researched as SOC to contrast with cotton wool and rice hull in order to find cheaper and more ideal materials.The results showed that luffa and cotton wool have high nitrate removal rate than others.The average removal rate of nitrate was 83.08%with luffa inl 3 days and 99.07% with cotton in17 days under the conditions of temperature 27℃and 90 r/min of rotation speed during 35 days.Although the average removal rate of nitrate with luffa is lower than cotton,we still choose luffa to experimentally study the effects and influencing factors as filler of anaerobic bioreactor for its attractive price and porous structure which could favor the overflow of N₂.The 4 months research shows that the bioreactor has such main advantages as rapid start,high impact resistance,little influence by pH and DO,relatively higher denitrification rate and high removal rate of nitrate to 92.79%under the conditions of the influent concentration of nitrate is 22.6mg/L,temperature 25±1℃,hydraulic retention time(HRT) is 11.7h.Although,there exists the disadvantage of lgreat influence by temperatuer and HRT,but overall,it has certain practical value for the main advantages what had mentioned above.The accumulation of No2-N as intermediate product is related to the amount of electron donor.When the bioreactor has deficiency of electron donor,the removal rate of NO₂-N drops sharply.The 4 months research also shows that denitrification rate of the bioreactor with luffa basiclly lies between slow rate biodegradable organic compounds and cell substances under high influent concentration of nitrate(81.55～102.57mg/L).The higher concentration of nitrate,the higher denitrification rate,when the influent concentration of nitrate is 102.57mg/L,and the HRT=11.7h,ternperature 25±1℃,the denitrification rate is 7.33 mgN/(L·h).After 4 months' operation of the reactor,the surface of the iuffa is more rough with wavy trace.