| With the rapid development of China's aquaculture industry,the annual production of feces reached 243 million tons and the urine production reached 163 million tons.,becoming one of the major sources of surface-source pollution,and the COD,TN,and TP account for 96%,38% and 56% of agricultural pollution sources,respectively.According to the "Chongqing Environmental Bulletin" of 2014 Chongqing's annual chemical oxygen demand discharge amounted to 386,400 tons in 2014,of which emissions from agricultural sources were 119,700 tons,accounting for 30.98% of Chongqing's total discharge of chemical oxygen demand in 2014.Ammonia nitrogen emissions of 51,300 tons,of which agricultural sources emissions of 12,200 tons,accounting for 23.78%,has become one of the major sources of agricultural non-point source pollution,the environmental situation is grim,efficient and economic solution to livestock and poultry farming wastewater pollution is imminent.According to statistics,the treatment of most aquaculture wastewater in Chongqing mainly uses the treatment mode of “pretreatment + anaerobic treatment system + aerobic treatment system + natural treatment system” or the treatment of “pretreatment + anaerobic treatment system + natural treatment system” directly.The model has low efficiency for nitrogen removal and is directly used in irrigation,which easily leads to high nitrogen load and becomes one of the major sources of agricultural non-point source pollution.It cannot meet the needs of areas with high environmental protection requirements or insufficient land consumption area;To achieve a higher degree of processing,the investment is high,operating costs are high,the breeding industry is a niche industry,and the large and small-scale small and medium-scale breeding industry is unable to withstand its economic pressures.Therefore,it is urgently necessary to take into consideration the requirements of environmental protection and construction operating costs.The nitrogen removal technology of economically applicable organisms and the use of resources(water,nutrient elements).The SHARON-ANAMMOX(nitrosation-anaerobic ammonia oxidation)process is a novel biological nitrogen removal process that simplifies the denitrification process compared to the traditional denitrification technology,shortens the reaction time,reduces the reactor volume,and has oxygen consumption.Less,no additional carbon source and other advantages.Based on this condition,combined with the actual treatment of wastewater(biogas slurry)in aquaculture enterprises in the city,the development is based on the principle of nitrosation-anaerobic ammonia oxidation,utilizing rural mountain topograpHy,cascade arrangement of biogas slurry storage tanks,and gravity discharge utilization characteristics,Some biogas slurry cascade storage and utilization systems will be appropriately modified to form a quasi-natural method for the treatment of biogas slurry.It can reduce the effluent TN concentration in the aquaculture wastewater(biogas slurry)treatment system,reduce the risk of non-point source pollution caused by insufficient land consumption area in the culture area,reduce the wastewater treatment cost of aquaculture enterprises,and better solve resource utilization,pollution control,and cost reduction.The contradiction between the parties promotes the sustainable development of aquaculture enterprises.Therefore,the technology developed in this project has a good application prospect.In this paper,the A/O semi-nitrosation-EGSB anaerobic ammonia oxidation combined process was established based on the actual project to conduct a pilot study to demonstrate the feasibility of the combined process for treating aquaculture wastewater.The following work was carried OTU:(1)Study on A/O semi-nitrosation1)By controlling the DO of the A/O process,the partial nitrosation is achieved,and the ratio of the nitrous nitrogen and ammonia nitrogen in the O-water effluent can reach 1-1.32 to meet the requirements of the anaerobic ammonia oxidation process on the substrate,and at the same time,a good COD removal effect can be achieved.Follow-up anaerobic ammonia oxidation process stable operation,obtain the corresponding working condition parameters.2)The operating conditions of A/O nitritation under low temperature conditions were studied,and the feasibility of semi-nitrosation to maintain normal operation under low temperature conditions was verified by adjusting the DO conditions.3)The drop-recovery and reoxygenation device was made and tested,and the effects of falling water and reoxygenation were studied by changing the three factors of drop height,drop depth,and drop slope to verify that the A/O system achieved semi-nitrosation under quasi-natural conditions.Feasibility.(2)Anaerobic Ammonia Oxidation Test of EGSBStrictly control the environmental conditions such as low dissolved oxygen,complete darkness,and 25-35°C,and start the EGSB anaerobic ammonia oxidation reactor under artificially prepared wastewater with low nitrogen load.After the reactor is successfully started,the sludge acclimation is gradually carried OTU during the five periods of N load inease period,HRT deease period,internal reflux ratio inease period,DO lift period,and COD rise period until the inlet nitrogen load and reactor HRT.,DO,COD load can reach the level equivalent to the front-end A/O semi-nitrosation effluent,so that the EGSB anaerobic ammonia oxidation reactor can stably and efficiently process the artificial water distribution that is basically consistent with the experimental engineering aquaculture wastewater,and lays a foundation for the subsequent treatment of the culture wastewater.basis.(3)Study on the treatment of aquaculture wastewater by the SHARONANAMMOX combined process.To master the regulation technology and control parameters of SHARONANAMMOX combined process for the treatment of aquaculture wastewater(biogas slurry),and provide basic data for the operation and promotion of the process.To investigate the removal of COD and nitrogen from aquaculture wastewater by the combined process and analyze the contribution of each reactor to COD and nitrogen removal,in order to study the effect and feasibility of combined treatment of aquaculture wastewater,and to provide a theoretical basis for this combined process engineering application.Technical Support.(4)Using electron microscopy scanning combined with high-throughput gene sequencing methods,the bacterial morphology and colony composition of activated sludge in EGSB anammox reactor was analyzed from a microscopic perspective.The conclusions reached by the paper are as follows:(1)Start-up and run test of A/O half-nitrosation alone,at DO 0.3-0.4mg/L temperature 25-35°C,DO 0.5mg/L temperature 25-35°C and DO 0.5mg/L The effect of A/O heminitrosation was studied under four conditions of temperature 15-25°C and DO 0.6-0.7mg/L temperature 15-25°C.It was found that DO 0.5mg/L temperature was 25-35°C.Anaerobic ammonia oxidation is more compatible.Under this condition,the concentration ratio of nitrous nitrogen to ammonia nitrogen in the A/O effluent can reach 1.21,which satisfies the theoretical value of anaerobic ammonia oxidation(1-1.32).At the same time,the COD removal efficiency is good.89.87%,successful initiation of seminitrosation and provides guarantee for the operation of the combined process.(2)In this study,we investigated the three factors of falling height,falling depth,and falling slope.We found that the height of the falling water was 100 cm.The bottom edge of the drop disc was opened and the drop plate slope was set to 0.05.Under the conditions,the reoxygenation effect was the best,and the reoxygenation rate was 3.89.Under this condition,when the device was used in combination with the A/O system,it was found that there was a certain reoxygenation effect and the influent DO was 0.19 mg/L.After the water treatment,the O tank reaches 0.35 mg/L.(3)The anaerobic ammonium oxidation of EGSB was tested separately for start-up and acclimation.The anaerobic ammonia oxidation of EGSB could well adapt to the inease of nitrogen load at 25-35°C(influent TN concentration 172.6mg/L-517.82 mg /L),inease of reflux ratio(100%-300%),deease of HRT(1d-0.25d),inease of DO(0.2-0.4mg/L),inease of COD(0-200mg/L),and finally The average removal rates of TN and COD were 87.2% and 86.0%,respectively.(4)The A/O nitrosation and anaerobic ammonia oxidation reactors are jointly operated.The water quality of the effluent after the pilot-scale reaction system is abOTU COD 50 mg/L,and the total nitrogen is 40-60 mg/L,satisfying the livestock husbandry industry.The standards for pollutant discharge(GB18596-2001)and Water Quality Standard for Farmland Irrigation(GB5084-2005)are safe and reliable.They not only achieve the purpose of controlling surface source pollution,but also realize resource utilization and meet the requirements of sustainable development.The feasibility of the combined treatment of aquaculture wastewater was demonstrated,laying the foundation for the application of process engineering.(5)Through electron microscopy observation and high-throughput sequencing,it was found that with the start-up and operation of the EGSB reactor,the seed sludge mainly composed of filamentous fungi gradually became spherical and ellipsoidal bacteria and formed on the surface of the sludge particles.Biofilms of Candidatus genus with anaerobic ammonia oxidation function increased from less than 1% of seed sludge to 16.58% and were enriched by anaerobic ammonia oxidation. |
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