Investigation On Piggery Wastewater Pretreatment And Nitrogen Removal By Anammox Process

In recent years,nitrogen removal had become a major focus in piggery wastewater treatment since nitrogen was the nutrient causing eutrophication.Anaerobic ammonium oxidation?Anammox?process was considered a promising process for ammonia-rich wastewater because of its high efficiency and low cost.However,due to the large amount of organic matter and suspended solids?SS?in piggery wastewater had a negatively effect on Anammox process,the application of Anammox process for treating piggery wastewater was limited.This paper firstly studied the pretreatment of coagulation-flocculation and anaerobic digestion process on piggery wastewater Secondly,the effect of organic matter in piggery wastewater on Anammox process was studied.Finally,to investigate the flexibility of using PN/A process to treat digested piggery wastewater in a sequencing batch reactor?SBR?.?1?The pretreatment of piggery wastewater was investigated.Firstly,the pretreatment effect of flocculant polyacrylamide?PAM?and polyferric sulfate?PFS?on piggery wastewater were studied.When the PFS 1000mg/L was added in piggery wastewater,the removal efficiency of SS and SCOD in piggery wastewater reached69.7%and 30.2%,respectively.When 750mg/L PFS and 80mL PAM were added in piggery wastewater,the removal efficiency of SS and SCOD was 87.1%and 31.5%,which indicated that PFS and PAM had better removal efficiency of SS and organic matter in piggery wastewater.However,the required flocculant dose was larger and the cost was higher.The anaerobic digestion process can effectively separate SS and SCOD in piggery wastewater.After 19 days of anaerobic digestion,the removal efficiency of SS in the anaerobic digestion,the anaerobic digestion with PFS and the anaerobic digestion with iron ions was 52.4%,62.1%and 70.0%,respectively.And SCOD removal efficiency was 50.3%,56.7%and 60.3%,respectively.Which shown that the anaerobic digestion process can effectively remove the organic matter and SS in the piggery wastewater,and flocculant and iron ion can increase the removal of organic matter and SS in the anaerobic digestion process.?2?The effect of organic matter in piggery wastewater on Anammox process was studied.The organic matter in digested piggery wastewater was difficult to biodegrade.In the second stage,the organic matter in piggery wastewater was mainly inert organic matter,and the average removal rate of ammonia nitrogen and total nitrogen were 77.2%and 71.6%,respectively.The activity of Anammox bacteria is inhibited,but the Anammox system can remain stabilize.The results also showed that the inert organic matter in the piggery wastewater had a limited impact on the Anammox process.In the third stage,sodium acetate was added to the piggery wastewater,and the removal rate of ammonia nitrogen and total nitrogen decreased to 47.7%and48.8%on the 132^thh day,which indicated that the Anammox process was gradually deteriorated.High throughput sequencing results analyzed the changes in the abundance of functional microorganism in Anammox process.Candidatus Kuenenia and Candidatus Brocadia were two functional bacteria in the Anammox process.When there were insufficient biodegradable organics in the piggery wastewater,the bacterial community abundance of Anammox decreased from 5%on day 104 to1.41%on day 131.Meanwhile,the denitrifying bacteria Thaurea increased from0.07%on day 28 to 1.91%on day 104 and continued to increase to 4.77%on day131.The results showed that the Anammox process can be used to treat piggery wastewater under the condition that the wastewater contains limited biodegradable carbon sources.?3?The feasibility of partial nitrification-Anammox?PN/A?process for treating piggery wastewater was investigated.In this chapter,the low concentration of dissolved oxygen?0-0.2mg/L?and intermittent aeration were studied to start the PN/A reactor.The digested piggery wastewater with the gradient dilution was fed into the reactor,corresponding to gradually increasing the ratio of chemical oxygen demand?COD?to ammonia?COD/N?to 0.8,1.33 and 1.67.The PN/A system had achieved ammonia and total nitrogen removal efficiencies remained around 90%and 70%,respectively.However,the ratio of COD removal value(COD_removed)to ammonia(COD_removed/N)ranged between 0.1 and 0.3,which indicated the influent organic matter was difficult to biodegrade.The presence of low biodegradable organic matter did not affect the operation of the process.Our study confirmed the PN/A system could maintain good nitrogen removal performance as long as the low COD_removed/N ratio even if the influent digested piggery wastewater at a high COD/N ratio.By means of the 16S-rDNA technique,the abundance of Candidatus Brocadiacese was decreased from 8.61%on day 125 to about 4.56%on day 173 and remained a stable proportion?3.41%on day 235?.Our study showed that the PN/A process was a promising alternative way to remove nitrogen of digested piggery wastewater.