Study On Screening And Physiological Character Of Aearobic Denitrification Bacteria

Recent years, the content of nitrate in the waste water discharged into thewater is becoming higher and higher that have caused the water nourishment,the water smelt fishy, the quality of water depravation or the lake degenerate,seriously the water become black and olid. Most water systems are becomingvery fragility because the long time pollution of nourishment, Sometimes, thenourishment water will hurt the people health as the water source.Generally, nitrogen removal technology can be disparted two kinds:physical chemistry method or biology method. Physical chemistry methodincludes air blowing off, adding chlorine, flocculating and deposition, manualmarsh. Now the biology method is the main method to remove the nitrogen intreating the waste water which is recognized the most economic, effect anddevelopment future method. Traditional removing nitrogen theory considersthat ammonia nitrogen can be wipe off through nitrify moment anddenitrification moment, which can not happen in the same time because thenitrification bacteria and denitrify bacteria has different environmental request.Nitrification reaction always happens in aeration condition, the homoeroticbacteria can use the oxygen as the electron acceptor to turn the NH4+ into NO2-and NO3-. Denitrification reaction always happens in anoxic and anaerobiccondition, the heterophic bacteria can use NO2-and NO3-as the electronacceptor to turn the NH4+into N2.Recently, the new nitrogen removal technology is Shortcut nitrification-denitrification and Shortcut nitrification denitrification. Shortcut nitrification-denitrification use the physiological characteristic of the nitrify bacteria and thedenitrifiaction bacteria, control the nitrification in the NO2-moment, then thedenitrification. Shortcut nitrification denitrification use the impersonalityphenomena that the oxygen can not be supplied asymmetry, control thereaction dynamics balance to make the nitrification reaction and denitrificationreaction happen in the same time and space. While the traditional technic likeA/O has the anoxic and anaerobic reaction section, then the nitrification anddenitrification happens in different time.But as the development of the technic, scholars found the TN would alsolose in aeration condition. The first study about denitrification bacteria begin1980s, Robertson and Kuenen in the first time separated the Paracoccuspantotropha, Pseudomonas spp. and Alcaligenes faecalis in the effluent fromthe removing sulfur system and denitrification system. Then many scholarsseparated the aeration denitrification bacteria that can has the denitrification inanaerobic or aeration condition. Lone Frette, Shwu Ling Pai and Naoki Takayaused the aeration denitrification bacteria in practice and made the good effect.Aiming at the aeration denitrification bacteria, the experiment discusseshow to domestication and filter the aeration denitrification bacteria, and makethe more study about the physiological character.In the first moment,the experiment study the possibility of acclimatingaerobic denitrifying bacteria by activated sludge using the SBR reactor withintermission aeration, and let the aerobic denitrifying become the superiorybacteria. During the 60 days to acclimating aerobic bacteria,the experimentimprove the aeration time, influent burthen, the rate of HY in the influentbecause the sludge is from the normal sludge, the bacteria existing in that areconventional nitrify bacteria and denitrify bacteria. Through improving theaeration time, the rate of HY in the influent and aeration intension, thecapability of sludge to remove the TN in aeration condition can be improved,and we can get the aerobic denitrifying bacteria. At the end of the first moment,the aeration time is 23 h, ammonia is 115mg/L higher than the fires. Thoughthe aeration intension is very strong, but the removing rate of TN of system ishigher than 50%, even can get the 80% during the acclimating period. Last,weare sure that the sample to screen the aerobic denitrifying bacteria can be gotafter the aeration 1~1.5h by tracing the change of nitrogen.During the second moment, we get the 30 strains aerobic denitrifyingbacteria from the sludge, among 20 of 30 strains exhibit high TN remove ratesof more than 50%,that can be regarded as the aerobic denitrifying bacteria. Wego on the next experiment by picking out 3 strains.The 3 strains aerobic denitrifying bacteria are all negative through thedyeing. The experiment study the 3 effect genes of the aerobic denitrifyingbacteria :temperature, pH, C/N. The result is that growth temperature of the 3strains aerobic denitrifying bacteria is 25℃～35℃,the best growth temperaturefor FR4 is 30℃～35℃,while for FW3 and FW6 is 30℃, the quantity of NO2--Nproduced by 3 strains aerobic denitrifying bacteria would accumulate whengrowth curve get the logarithm period, however the condition of FW6 isdifferent, the quantity of NO2--N does not accumulate all the time when thecondition temperature is 25℃～30℃;The growth pH of the 3 strains aerobicdenitrifying bacteria is different, the best growth pH for FR4 is 7,while forFW3 and FW6 is 7~8,the quantity of NO2--N produced by 3 strains aerobicdenitrifying bacteria would also accumulate when growth curve get thelogarithm period, however the condition of FW3 is different, the quantity ofNO2--N does not accumulate all the time when the growth pH is 8;The C/N isnot the pivotal factor for the growth, but is importance from the economic view,when the growth carbon is amber acid salt, the best quantity of C/N is5.The 3strains aerobic denitrifying bacteria exhibit the high capacity of removingnitrogen, the last produce is N2 that the rate of N2 in the reactor is 10% higherthan that in air.Considering the actual condition, we think that mixing bacteria will havehigher capacity to remove TN, We do another experiment. The result is thatthough the single bacteria has higher capacity to remove nitrogen, but is notgood for TN, while the mixing bacteria not only have the long aerobicdenitrifying time,but also the higher capacity to remove the TN. So facing theindustry waste water, we should not only have the aerobic denitrifying bacteria,but also other different kinds of bacteria to complete the aerobic denitrifyingcourse.