Study On The Effect Of Coagulation And Adsorption Processes On Swine Wastewater Treatment

With the rapid development of large-scale pig farms in China,the increasing amount of swine wastewater has become one of the main sources of agricultural pollutions in our country,causing significant harm to the water,air,soil and health of residents.Anaerobic treatment has been widely used to treat the swine wastewater,but it has disadvantages of long hydraulic retention time,large volume,high initial investment cost and poor removal efficiency of NH3-N.In this study,a combined process of enhanced coagulation and zeolite adsorption has been used to study the effect of treatment on swine wastewater.The research have showed that four inorganic flocculants(PAC,PFS,PAFC and PSAF)and three organic flocculants(APAM,NPAM and CPAM)all have good treatments on turbidity,COD and TP in piggery wastewater,but poor removal efficiencies of NH3-N and TN.The optimum inorganic and organic flocculants were PAFC and CPAM,respectively.The optimal dosage of 100 g/L PAFC was 11 mL,and the dosage of 2 g/L CPAM was 5 mL,when treating with 1 L piggery wastewater.When pH was 5,the coagulation effluent was most clear,and got the highest removal efficiencies of turbidity and COD,but it cost too much acid to adjust pH,and the TP removal was also poor in acidic conditions.When in the original pH,the removal efficiencies of turbidity and COD were a little worse,but TP removal was greatly improved.It is more economical not to adjust the pH of wastewater in coagulation.The optimum sedimentation time for inorganic flocculants was 15 min and 5 min for organic flocculants.By the orthogonal experiments,we got the optimum hydraulic condition in jar test for PAFC,which was fast stirring for 30 s with 350 r/min in the mixing stage and then slow stirring for 20 min with 40 r/min in the reaction stage.In addition,for CPAM it was fast stirring for 30 s with 350 r/min and then slow stirring for 30 min with 60 r/min.In the use of inorganic and organic flocculents together treatment of swine wastewater,we should first add inorganic flocculant PAFC and then organic flocculant CPAM,and keep the interval time at 60~90 s.The best conditions for enhanced coagulation were as follows: the dosage of PAFC(100 g/L)was 8 mL,the dosage of CPAM(2 g/L)was 3.5 mL and the precipitation time was 5min.In this condition,the removal rates of turbidity,COD and TP could reach 89.39%,84.85% and 89.93%,repectively,but the removal efficiencies of NH3-N and TN were not satisfied.We compared the adsorption effect of two kinds of natural zeolite(FS1 and FS2)on NH3-N in simulated wastewater,and selected the better zeolite particles(FS2KL)to synthesize a new type of filler(FS2TL)for nitrogen and phosphorus removal.The isothermal adsorption characteristics of these 4 materials on NH3-N well followed Langmuir and Freundlich curves,and the saturated adsorption capacity was 13.95 mg/g,13.98 mg/g,9.94 mg/g and 8.02 mg/g,respectively.The dynamic process of 4 materials on NH3-N showed a “rapid adsorption,slow balance” feature,including dynamic curve of FS1,FS2,FS2 KL were better fitted by pseudo second-order kinetic equations,while FS2 TL followed the pseudo first-order kinetic equation better.At pH 5~7,the adsorption capacities on NH3-N were no affected by pH.While pH?7,the adsorption capacities decreased slightly,and pH increased to 9,the adsorption capacities decreased significantly.With zeolite dosage increased,the removal rates of NH3-N increased rapidly at the early stage and then became steady slowly and the trends of adsorption capacities on NH3-N were opposite.The adsorptions of these 4 materials on NH3-N increased with the increase of temperature,which indicates that the adsorptions on NH3-N are endothermic.The saturated adsorption capacity of FS2 TL on NH3-N in coagulation effluent was 5.71 mg/g,which was significantly less than 8.02 mg/g in simulated water.In the dynamic adsorption experiment of FS2 TL to treat the effluent,the adsorption column had a good effect on the treatment of NH3-N,TN and TP in wastewater,while COD removal was poor.With the increase of influent velocity,wasterwater stayed shorter in the column,the breakthrough and saturated time were advanced.With the increase of the height of packing layer,the amount of absorbent increased,the hydraulic retention time got longger,the breakthrough and saturated time were delayed.Therefore,properly decreasing the influent velocity or increasing the height of packing layer would effectively improve the removal efficiencies of NH3-N,TN,TP and COD.