Effects Of Irrigation With Livestock And Poultry Wastewater Treated By Modified Ultrafiltration Membrane On Quality Of The Pakchoi

In this thesis,a high-performance modified ultrafiltration membrane was developed.The modified membrane was used to advanced treatment for the secondary effluent of livestock wastewater（WW）.The treated wastewater was then used for hydroponic culture of pakchoi.The performance of the modified membrane on the wastewater was detected,and the effects of the treated wastewater（TWW）on the heavy metals content and quality of pakchoi were analyzed.The conclusion were as follows:（1）The fouling resistances and antifouling properties of the modified membrane were significant improved.The pure water flux of the modified membrane was 312 Lm^-2h^-1,the rejection rate of BSA was 98.6%,which was 13.9%higher than that of the unmodified membrane.After UV irradiation,the flux recovery rate of the modified membrane was95.8%,and the bacterial survival rate was 0.34%.（2）The reclaimed water treated by modified membrane meets the water quality standard of irrigation water.Except for total phosphorus,other indicators meet the class I standard of comprehensive wastewater discharge standard.The removal rates of chroma,turbidity,COD and BOD₅ by modified membrane were 56.3%,62.2%,54.5%and 51.3%,respectively.The removal rates of TP and TN were 45.7%and 77.4%.The retention rate of modified membrane for various metal ions in wastewater was as follows:Fe²⁺>Zn²⁺>Cu²⁺>Ca²⁺>Mg²⁺>Na⁺>K⁺.（3）There was no significant difference in K,CA,Na and Mg between WW and TWW irrigation treatment.The content of Cu in TWW irrigation group was at a low level,which may promot plants grow.WW irrigation group was more prone to Cu pollution than TWW irrigation group.The high Zn content in WW irrigation group may affect the normal growth of pakchoi.（4）The absorption and enrichment of Cu and Zn in the WW irrigation group were higher than those in the TWW irrigation group.The Hazard Quotient（HQ）indicates that,compared with the tap water（TW）irrigation group,TWW irrigation group showed no greater potential risk of heavy metal enrichment.The single type of heavy metals in pakchoi of WW irrigation group and TWW irrigation group had lower health risks for adults,and the health risks of TWW irrigation group were lower than those of WW irrigation group.The Hazard Index（HI）indicates that,eating TWW irrigation group of pakchoi will not affect the children’s health,eating cabbage cultivated by the WW group may endanger human health and pose a greater health risk to children.（5）The fresh weight of the leaves in WW and TWW irrigation groups was greater than that in TW irrigation group,and the moisture content of leaves in TWW irrigation group was the highest.The content of total chlorophyll and vitamin C in TWW irrigation group was higher than that of the other two groups,the content of soluble protein was 18.7%higher than that of the WW irrigation group,124.9%higher than that of the TW irrigation group,and the content of soluble sugar was 28.3%higher than that of the WW irrigation group and 91.5%higher than that of the TW irrigation group.The nitrate content of pakchoi in the WW irrigation group was 60.6%higher than that in the TW irrigation group and 93.3%higher than that in TWW irrigation group.Comprehensive above indicators can be seen,TWW irrigation group of pakchoi quality is the best.The separation performance of the modified membrane is greatly improved,the antifouling and scale resistance are significantly improved.The advanced treatment of the secondary livestock effluent by the modified membrane can be reused in hydroponics,and has a positive effect on the quality of pakchoi,which reduces environmental pollution and alleviates the pressure of agricultural water.Therefore,the modified membrane technology can be used for advanced treatment of agricultural wastewater and realize the reuse of agricultural wastewater,which has a very broad application prospect.