Study On High-concentration Ammonia-nitrogen Wastewater Treatment Of Iron Oxide Red Plant

The treatment of precipitating with alkali could recycle Fe2+form iron oxide redwastewater effectively and turn the character of iron oxide red wastewater form acid toalkalescence, but could not remove ammonia-nitrogen (the concentration of ammonia-nitrogenin iron oxide red wastewater reaches up to an average of580mg/L). Ammonia-nitrogen is oneof the main pollutants in waters, it not only impacts water quality but also endangers human’shealth, needs to be strictly controlled.The wastewater which is discharged from the treatment of precipitating with alkalicontained high concentration of ammonia-nitrogen and low organic matter (CODCris less than50mg/L). Using traditional nitrification-denitrification process will cost large quantity ofcarbon resource and the cost of struvite method is also high. This study took thehigh-concentration ammonia-nitrogen wastewater which came from a iron oxide red plant inJiangmen city as research object, explored the feasibility of shortcut nitrification-denitrificationtreatment for this wastewater with A-O-O-A process, confirmed the optimal technologicalparameters of struvite method and realized cyclic utilization of struvite.The sludge which came from an aerobic tank of a sewage treatment plant in Guangzhouwas used as strains to domesticate the shortcut nitrification-denitrification sludge. By addingflour and controlling aeration rate, the microbial biomass in the reactor increased significantlyafter4days and the sludge also shows good settleability. Under the condition of25~28℃,DO=2.0~3.0mg/L, pH=7.0~8.0, nitrobacterium is domesticated by gradually increasingconcentration of ammonia-nitrogen in the reactor. Nitrobacterium is well domesticated after6days with rising ammonia-nitrogen removal rate, up to80%and TN removal rate is about40%.TN is mostly removed in anaerobic tank A1.During16days operation, CODCrwas mostly removed in anaerobic tank A1with anaverage removal rate of90%, the average removal rate of TN is about50%for influent withCODCr=750mg/L and it would increase with addition of carbon resources. NO2-N was mainlyproduced in aerobic tank O1and low dissolved oxygen tank O2with a low nitrite accumulationratio. The sludge in the reactor is with good activity and without sludge bulking.With the same CODCrconcentration of influent, when using only flour or flour and glucosewhich mass ratio is1:1as carbon resource, ammonia-nitrogen and TN removal rate are bothlower than using simplex glucose as carbon resource.Based on response surface analysis, the optimal technological parameters of highammonia-nitrogen wastewater treatment using struvite method were confirmed. When the pH value was adjusted to9.40, mole ratio of n(N):n(Mg):n(P) attained0.8:1:1and mixing reactiontime reached15min under the stirring rate of240r/min, the removal rate of ammonia-nitrogenreached98.91%.Compared with direct pyrolysis, struvite pyrolyzed under alkaline condition could acquirea higher denitrification rate. When the mass ratio of struvite precipitation and sodium hydroxidewas8:1and pyrolysis time reached90min under the temperature of90℃, the denitrificationrate of struvite precipitation reached94.33%.The optimal technological parameters of high ammonia-nitrogen wastewater treatmentusing pyrolysis product under alkaline condition were confirmed. When the pH value wasadjusted to9.40, mass ratio of struvite precipitation and sodium hydroxide was6:1, pyrolysistime reached90min under the temperature of90℃, mixing reaction time reached40min and thedosage of pyrolysis product under alkaline condition was1.20g per liter wastewater, theremoval rate of ammonia-nitrogen reached90.04%.The pyrolysis product of struvite under alkaline condition could be cyclic used to treat highammonia-nitrogen wastewater, the cycling times could reach four while the removal rate ofammonia-nitrogen was always more than80%.