| With the large-scale development of livestock and poultry breeding, biogas slurry after anaerobic digestion of pig waste caused serious pollution. Biogas slurry has the characteristics of high ammonia nitrogen, difficult to biodegrade, and it can not be removed effectively by directly using conventional biological methods, such as SBR process, A/O process. According to the different targets, several biological and physical & chemical methods were adopted to process the biogas slurry of pig waste.On the basis of the conventional SBR process, coconut shell and coal activated carbon powder were added respectively to the 1#,2# reactor. Aerobic and anaerobic mode were alternately operated, COD of water inflow:1000-1600 mg/L, ammonia nitrogen:200-1000 mg/L, after 68 d, the average removal rate of COD was 59.09%(1# reactor),53.13%(2# reactor), and that was superior to the literatures; the average removal rate of ammonia nitrogen was 36.08%(1# reactor),32.26%(2# reactor), and ammonia nitrogen removal effect of two reactors was poor, also, nitrate nitrogen had high accumulation in water only at the beginning of the operation and when supplying the sludge. During the running of the whole system, the nitrification was very poor, because free ammonia generated by ammonia nitrogen (444mg/L) in water could inhibit the activity of nitrifying bacteria.In cases of water inflow:0.5 L/h, sludge load of aerobic pond:0.06 kg COD/(kg MLSS·d), organics removal effect of the aerobic pool of A/O system was obviously improved by adding the coconut shell powder activated carbon, but there was no obvious strengthening effect on ammonia nitrogen removal, and the removal rate fell below 20% later; Catalytic ozonation pretreatment can improve the removal efficiency of biogas slurry, and also stabilize the water effluent quality to some extent. The average COD of aerobic pond effluent was about 1000 mg/Lbetween 80-104 d.The removal rate was about 50%.The study of the degradation of biogas slurry by Fenton’s reagent was conducted.On the basis of single factor experiment, three factors and three levels orthogonal experiment was carried out, and the best experiment condition:mole ratio of hydrogen peroxide and ferrous ions is 6, t=40 min, pH=4. According to the effect graph and orthogonal experiment, the optimized validation test was carried out. The removal efficiency of biogas slurry without flocculation by Fenton’s reagent method was 87.43%, effluent COD:491.57 mg/L.By static adsorption experiments that simulate wastewater (ammonia nitrogen content is 1500 mg/L) was treated by artificial zeolite, granularity, dosing quantity, pH and initial concentration of ammonia nitrogen were studied. According to the synthetic zeolite adsorption data of different concentration of ammonia nitrogen wastewater, Langmuir, Freundlich isothermal adsorption equation were fitted, R2 of two equations were both above 0.99, and the Langmuir model can describe the adsorption law of 445-1485 mg/L ammonia nitrogen wastewater very well, the amount of ammonia nitrogen adsorbed by per gram of synthetic zeolite was 28.32 mg; By investigating the adsorption of practical biogas slurry, after fitting the data, the quasi secondary dynamics can describe the behavior of artificial zeolite adsorption (R2> 0.99).79.0% of ammonia nitrogen in pig biogas slurry can be adsorbed by artificial zeolite, ammonia nitrogen of effluent:333.92 mg/L, equilibrium adsorption quantity:17.95 mg/g.Under different conditions of circulation flow rate, cycle time, natural zeolite particle size and dosing quantity, dynamic adsorption experiment was carried out. The best conditions of adsorption ammonia nitrogen in pig biogas slurry by natural clinoptilolite:cycle reaction 90 min, velocity of 18 mL/min, the particle size of 1-2 mm,250 g (volume of sample is 100 mL) of natural clinoptilolite.23.99% of ammonia nitrogen in biogas slurry can be removed under optimum conditions. |
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