Study On Advanced Treatment Of Swine Wastewater By Enhanced Biological Nitrification-dentrification And Paddy Field

Swine wastewater was generally characterized by high concentration of nitrogen and phosphorus,and low ratio of carbon to nitrogen(C/N).The quantities of swine wastewater are increasing rapidly,causing a serious threat to our environment.In this study,we investigated four swine farms and analyzed swine breeding wastewater.On the one hand,the combination of membrane bioreactor(MBR)and solid denitrification system has been set up.On the other hand,biogas slurry was irrigated into paddy field to reduce the nitrogen and phosphorus.We studied the removal rates of nitrogen and phosphorus in the MBR and solid denitrification system.And the solid carbon was selected by comparation of denitrification rate and cost accounting.The biofilm of three solid carbon was detected by Illumina high throughput sequencing analysis.We also studied the removal rate of nitrogen and phosphorus in the paddy field,the influence of different slurry irrigation residence time on the growth and yield of rice,and the soil fertility and the content of heavy metals.The main results of this study were drawn as follows:(1)The swine breeding stock of four investigated swine farms was between 500-20000.Wastewater treatment mode was biogas engineering&oxidation pond.The concentration of ammonia nitrogen and total nitrogen in original wastewater and biogas slurry were more than 999 mg/L and 1397 mg/L,respectively.The concentration of dissolved phosphorus and total phosphorus were over 13.9 mg/L and 29.2 mg/L,respectively.The concentration of COD was more than 1500 mg/L.The quantities of swine wastewater in oxidation pond were huge.The wastewater index of three swine farms was below the local standards in Zhejiang Province.(2)When the ammonium load at 0.048 g NH4+-N/(gVSS·d),the concentration of NH4+--N and COD in MBR were below 14 mg/L and 79 mg/L,and the removal rates of NH4+-N and COD were generally more than 94%and 97%,respectively.But the concentration of NO3--N began to accumulate.Membrane fouling began to increase at day 27.In solid denitrification system,the removal rate of nitrogen was 99%,but the removal rate of nitrogen in PCL system changed into 50%.PHBV system's rate was between 20%and 60%.The internal molecular functional groups in PBS were changed.Based on the denitrification rate and cost accounting,PBS had the potential to function as carbon source in denitrification system treating nitrified swine wastewater under the conditions in this study.(3)The reduce rates of ammonia nitrogen and total nitrogen in paddy field water were 155 mg/(L·d·ha)and 226 mg/(L·d·ha),respectively,and the reduce rates of dissolved phosphorus and total phosphorus were 19 mg/(L d ha)and 31 mg/(L·d·ha),respectively.Different slurry irrigation residence time had litter influence on SPAD,plant height and the yields of rice.Thousand seed weight increased.The organic matter,available nitrogen and phosphorus of the soil were stable.Different slurry irrigation residence time had a significant influence on available k.The concentration of Ca,Fe and Pb remain constant in the solid.The concentration of Mg,Cr and Ni increased after biogas slurry irrigation,while Mn,Zn,Na,Cu,Cd and As concentration decreased.The content of heavy metals were below the standard of the GB15618-2008.Soil pollution didn't take place after biogas slurry irrigation.