Investigation On The Nitrogen Removal By Partial Nitrification-Anammox Of Livestock's Wastewater:Controlling Strategies,Modelling,and Processing Design

The livestock wastewater is characterized by the high concentrations of COD,suspended solids,ammonia nitrogen and phosphorus,and high biodegradability.Anaerobic digestion is frequently adopted to treat the livestock wastewater to remove organic carbon while recycling energy.However,digestate still contains high concentrations of suspended solids,ammonia nitrogen,and phosphorus.This research focuses mainly on the Partial Nitrification-Anammox techniques for removing ammonia from digestate from livestock wastewater.The conclusions drawn from this research are presented as follows.(1)Firstly,a partial nitrification process treating digestate from livestock wastewater regulated by p H was investigated.Compared with the conventional p H regulation strategy,the strategy proposed in this study can reduce the requirement of acid and alkali by approximately 33.8% without significantly affecting the activity of partial nitrification.Additionally,this strategy can lead to a p H value 6.8,which is lower than the value if the conventional strategy is adopted,and reduce the cost for p H regulation for the subsequent anaerobic ammoxidation.(2)Secondly,the distribution of bacteria inside Anammox granular sludge is investigated,which is then introduced into the mathematical model of Anammox reaction including substrate diffusion and biological reactions.The difference in the particle size of Anammox granular sludge causes the variation of the activity of anaerobic ammoxidation.The Anammox granular sludge with a particle size of 0.5 to 0.9 mm could reach the optimum activity of anaerobic ammoxidation15.7±0.5 mg N/g VSS/h.When the particle size of Anammox granular sludge falls within this range,there are 97.7% of Anammox bacteria distributed within 300?m of the outer layer.Based on these findings,a novel mathematical model is constructed for the Anammox granular sludge to produce satisfactory simulation results.(3)Finally,a new technical process is developed where the PN/A technique is applied to treat thedigestate from livestock wastewater.Moreover,a laboratory scale test is conducted to simulate the entire process of deammonification treatment.At the flocculation and precipitation stages,the maximum removal rate is 60.87±2.05% for SS,48.16±0.27% for total phosphor but merely 4.34±0.78% for ammonia nitrogen.For this stage,the optimum amount of PFS applied is 200 mg/L,and the optimum time of precipitation is 2 hours.At the partial nitrification stage,the percentage of ammonia nitrogen being oxidized reaches 97.78±0.75% while the activity of ammonia oxidation rate hits 47.05 mg N/g VSS/h at maximum.Besides,over the course of experiment on anaerobic oxidation,the maximum activity of ammonia oxidation reaches 9.27±0.52 mg N/g VSS/h,while the ratio of ammonia nitrogen to nitrate nitrogen is 1:1.37,which is close to the theoretical value.Based on the aforementioned results,a novel process is developed.This study provides a novel design scheme of partial nitrification-Anammox process for livestock wastewater.