Low-Carbon Nitrogen Removal For Iron Oxide Red Wastewater Based On Nitritation By Zeolite Sequencing Batch Reactor

After the sedimentation treatment with NaOH,the iron oxide red wastewater still contained high concentration ammonia and sulfate as well as lacked carbon source and alkalinity.The operation cost of process will directly determine whether it can be applied to the practical projects.In this study,two low-carbon nitrogen removal biotechnology:nitritation and denitritation process and partial nitritation-ANAMMOX process,were constructed to achieve the low consumption and high efficiency treatment of iron oxide red wastewater.Because stable nitritation was the key and difficulty step of the two combined processes,this study first carried out the research based on Zeolite Sequencing Batch Reactor?ZSBR?through controlling the factors of Free Ammonia?FA?and aeration strategy.As a result,Ammonia Oxidizing Bacteria?AOB?was enriched,and stable and efficient full nitritation and partial nitritation was achieved,respectively.Then the actual wastewater was treated by coupling denitrification reactor and ANAMMOX reactor of Anaerobic Upflow Sludge Bed?A-USB?respectively with ZSBR in order to provide theoretical support for low-carbon nitrogen removal of iron oxide red wastewater.The study results are as follows:Full nitritation:Under the conditions of exchange ratio of 2/3,external reflux ratio of 2/1and aeration rate of 1.3 m³/h,ZSBR aerated for 6.5h and the NAR was more than 95%as well as NPR could reach 0.48 kg/?m³·d?.The reflux alkalinity of denitrification was fully utilized in ZSBR in following experiment,so the alkalinity dosage ratio of Na₂CO₃ was only4.5-4.9/1.Partial nitritation:Under the conditions of NaHCO₃ basicity dosage of 4.3/1,exchange ratio of 1/2 and aeration rate of 1.0m3/h,ZSBR aerated for about 8 hours until pH was 7.0-7.3,which could control the effluent ratio of NO₂^--N/NH₄⁺-N to 1.1-1.5 accurately with NAR more than 92%and NPR reaching 0.72 kg/?m³·d?.The ammonia conversion in all stages of the experiment accorded with zero-order reaction,and the ammonia removal rate in stage I-IV accorded with the fitting equation of Grau model?v=0.30158×1200×S₀/S_e?.Nitritation and denitritation process:full nitritation effluent of ZSBR was used as denitritation influent in this process.In parallel experiments with different carbon sources,glucose and ethanol were considered to be the best carbon sources,of which the optimum C/N ratios were 2.5/1 and 2/1,respectively.What's more,glucose was used as carbon source in denitritation experiment.When Hydraulic Residence Time?HRT?was 1.5 h,the average TN Removal Rate?TRR?was about 2.87 kg/?m³·d?,and the TN Removal Efficiency?TRE?was more than 85%.In addition,the strategy of low HRT,regular sludge discharge and regular aeration could effectively inhibit the Sulfate Reducing Bacteria?SRB?and therefore effectively avoid the collapse of denitritation process.The operation cost of this process is about 24.74 yuan per ton of wastewater,which saves more than 22%of the cost compared with the nitrification and denitrification process?32.00 yuan cost per ton of wastewater?.Partial nitritation-ANAMMOX process:partial nitritation effluent of ZSBR was used as ANAMMOX influent in this process.When the influent TN concentration was 300 mg/L in the ANAMMOX section,the TRE was more than 70%,and the maximum TRR was 0.50kg/?m³·d?,while high concentration SO₄^2-in wastewater had no adverse influence on ANAMMOX.The operation cost of this process is only about 10.16 yuan per ton of wastewater,which should be the best biological treatment process.