Simultaneous Removal Of Multi-pollutant From Nitrogenous Fertilizer Wastewater With Low Consumption

Nitrogen fertilizer wastewater is a typical low C/N ratio wastewater which is difficult to be treated.the consumption of carbon sources and energy will be very high if treated with traditional nitrification and denitrification process.therefore,the combined process of anaerobic digestion and autotrophic nitrogen removal process was adopted in this study.the main contents were as follows:start-up of reactor,influence of toxic matters on anaerobic digestion and autotrophic nitrogen removal system and the performance of reactor in treating real fertilizer wastewater.Up-flow anaerobic sludge blanket?UASB?,Anaerobic sequencing batch reactor?AnSBR?and Anaerobic membrane bioreactor?AnMBR?were adopted in the start-up of anaerobic digestion.UASB achieved a high Total nitrogen removal rate?TNRR?of 2.44 kg COD m^-3 d^-1 with a temperature of 25³0?,pH of 8.0⁸.5,an Hydraulic retention time?HRT?of 4.5 h and a reflux ratio of 15.The TNRR of AnSBR and AnMBR were 0.54 and 0.36 kg COD m^-3 d^-11 respectively,with an HRT of 16 h and 11 h.the dominate genus of anaerobic digestion process was Methanothrix in this study.A biofilter and Membrane bioreactor?MBR?were adopted for the start-up of Anaerobic ammonium oxidation process?ANAMMOX?and Completely autotrophic nitrogen removal over nitrite?CANON?process.ANAMMOX reactor achieved a Total nitrogen removal efficiency?TNRE?and TNRR of 87.8%and 0.80 kg N m^-3d^-1 respectively with a temperature of 25³0?,pH of 7.8⁸.2 and an HRT of 11.5 h.CANON reactor was operated under a low to high aeration strategy,and successfully start-up with a temperature of 25³0?,aeration rate of 0.20⁰.25 L d^-1,pH of 7.6⁸.0 and an HRT of 7.5⁸.0h.The TNRE and TNRR were maintained at 84.9%and 0.55 kg N m^-3 d^-1,respectively.In autotrophic nitrogen removal process,the dominate genus of Aerobic ammonia-oxidizing bacteria?AerAOB?and Anaerobic ammonia-oxidizing bacteria?AnAOB?were Nitrosomonas and Candidatus Kuenenia.Considering that nitrogen fertilizer wastewater may has a lot of toxic matters such as heavy metals,sulfate and sulfide,and some nanoparticles and antibiotics which may be introduced during the pipeline transportation.The stability of anaerobic digestion and autotrophic nitrogen removal process under these toxic matters were investigated.For anaerobic digestion process,heavy metals concentrations in a range of 1⁵0 mg L^-1 didn't present obvious inhibition.The performance of COD removal also maintained in a stable level with the stress of sulfate concentrations in a range of 200¹600 mg L^-1.But the production of biogas was significantly improved.It suggested that the cooperation-competition relationship of anaerobic digestion and sulfate reduction can improve the removal of COD and then achieve the simultaneous removal of carbon and sulfur from wastewater.The short-term and long-term inhibition threshold of sulfide on anaerobic digestion were 5 and 50 mg L^-1,respectively.Significantly suppression was observed with the sulfide concentration of 50¹00 mg L^-1,but the system showed a good self-adaption ability.When the stress of sulfide was removed,the system can totally recover with a short time,which indicated the inhibition of sulfide was reversable;For autotrophic nitrogen removal process,ANAMMOX system was easily suppressed under 1 mg L^-1 Zn???and Cd???.But CANON system presented a good stability under the stress of 1 mg L^-1 Zn???,Cd???,Pd???and Hg???and the joint inhibition of these four heavy metals.The sulfate concentration in 500 mg L^-1 presented slight inhibition on CANON process,the high removal performance of reactor may due to the secretion of Extracellular polymeric substances.As for the impacts of sulfide,CANON process was slightly suppressed when the concentration of sulfide was 5 mg L^-1.The system was significantly inhibited when the concentration of sulfide went up to 50 mg L^-1,but the inhibition was reversable.Besides,Sulfur based autotrophic denitrification was also induced under the long-term stress of sulfide,it confirmed the feasibility of simultaneous removal of nitrogen and sulfur from wastewater with low consumption.The activity of AerAOB was improved with the addition of 1 mg L^-1 nanoparticles,while the AnAOB was obviously suppressed.Besides,a synergetic inhibition of nanoparticles and antibiotics was also observed when they simultaneously exist in autotrophic nitrogen removal system.Finally,Real fertilizer wastewater was gradually introduced to the combined process.the COD and total nitrogen concentrations in effluent was 2.0 and 10 mg L^-1,which was much lower than the limit values in the relative wastewater discharge standard.In this period,the dominate process of reactor transformed to Simultaneous partial nitrification,anaerobic ammonium oxidization and denitrification from CANON,the cooperation of denitrify bacteria,AerAOB and AnAOB achieved the simultaneous and efficient removal of carbon and nitrogen.Compared with traditional process,the combination of anaerobic digestion and CANON can reduce the consumption of resources and energy,and can recover part of energy.