Study On Treatment Of Piggery Wastewater With Microalgae Immobilized By Based On Cellulose System

The immobilization of microalgae can simplify the separation process of microalgae in wastewater treatment and resource utilization,and reduce the cultivation cost.It has a practical significance in the resource utilization of treatment of aquaculture wastewater by microalgae.Bacterial cellulose?BC?has become a popular immobilized carrier material due to its ultra-fine nanoscale three-dimensional network structure,high mechanical strength,high porosity and abundant active hydroxyl groups in the molecule.This study explored the feasibility of immobilizing microalgae by adsorption or embedding with bacterial cellulose,and preliminarily studied the removal efficiency of organic matter and metal ions in aquaculture wastewater by these two immobilized carriers.And comprehensively evaluated the possibility of microalgae fixation by bacterial cellulose carriers in purification treatment of piggery wastewater.The experimental results are listed as follows:?1?Taking the Scenedesmus obliquus,Chlorella vulgaris,Chlamydomonas reinhardtii,and as experimental subjects,the immobilization effects of two kinds of ceramic materials and three different fiber materials on microalgae were preliminarily studied.It was found that the adsorption capacity of ceramic materials for microalgae cells was weak.There is no difference in the adsorption of microalgae by coarse or fine pore ceramics.The adsorption capacity of absorbent cotton fiber and non-woven fabric on microalgae cells is better than that of ceramic materials,while it is lower than bacterial cellulose.The nanoscale bacterial cellulose has good surface adsorption properties on these three species of microalgae cells.Three microalgae cells can be embedded and immobilized in the crosslinked network of bacterial cellulose which was produced in situ by the co-culture system of G.xylinus-microalgae.The immobilized carrier for microalgae was successfully obtained by adsorption or entrapment of bacterial cellulose.?2?The results of purification treatment of piggery wastewater by immobilized microalgae with adsorption of bacterial cellulose showed that the removal rates of NH₃-N,TN,TP and COD by S.obliquus were higher than those of free microalgae cell culture by 9.54%,10.45%,6.08%and 11.75%,respectively.The removal rates of those by adsorption-immobilized C.vulgaris increased by 5.68%,9.47%,16.55%and 15.07%than free cell culture,respectively.But the removal rate of adsorption-immobilized C.reinhardtii decreased by 10.78%,16.99%,17.43 and3.12%.These results indicated that bacterial cellulose adsorption of S.obliquus and C.vulgaris immobilized carrier can significantly improve the purification efficiency of poultry wastewater,and the removal indexes have achieved good efficiency.The removal rate by adsorption-immobilized C.reinhardtii was reduced,especially decreased in total nitrogen and total phosphorus by 16.99%and 17.43%,respectively.These indicated that the microalgae species had a certain effect on the efficiency of wastewater treatment by adsorption-immobilized microalgae with bacterial cellulose carrier.?3?The results of bacterial cellulose-embedded immobilized microalgae on the treatment of piggery wastewater showed that the removal efficiency of S.obliquus,on NH₃-N,TN,TP and COD decreased by 45%,20%,30.8%and 11%,compared with its free cell culture respectively.Those removal efficiency of embedding-immobilized C.reinhardtii decreased by 8.4%,18%,22%and 2.3%,respectively.Embedded by bacterial cellulose reduced the sewage treatment efficiency of S.obliquus and C.reinhardtii.There was no significant difference in the removal efficiency of organic matter between the embedding-immobilized C.vulgaris and its free cell culture.?4?The purification of metal ions in cultured piggery wastewater by immobilized microalgae with adsorption or embedding with bacterial cellulose were studied.The results showed that removal efficiency of metal ion Cr⁶⁺by two kinds of immobilized C.reinhardtii and its free cell culture was obvious.The two immobilized carriers of three microalgae had no significant effect on the removal efficiency of Cu²⁺ions in wastewater.The three free microalgae culture had good removal ability to Pb²⁺.The adsorption method immobilized S.obliquus promoted the removal efficiency of Pb²⁺to 89.91%.The removal efficiencies of Zn²⁺were different among the three free microalgae cultures.Two immobilized carriers promoted Zn²⁺of S.obliquus,while the removal efficiency of Zn²⁺by adsorption immobilized C.vulgaris and C.reinhardtii with bacterial cellulose carrier in wastewater treatment has little change.But the removal rate of Zn²⁺by three algae embedded in bacterial cellulose carrier decreased.Microalgae immobilized by bacterial cellulose adsorption can promote the removal efficiency of organic matter in piggery wastewater by S.obliquus and C.vulgaris,while the embedding method of immobilization reduces removal ability of S.obliquus and C.reinhardtii.Two kinds of immobilized carriers of bacterial cellulose that adsorpting and embedding microalgae showed high removal efficiency for Cr⁶⁺,Cu²⁺,Pb²⁺and Zn²⁺ions.These process operation were easy to carry out in piggery wastewater treatment.The present research provides basic data for microalgae immobilized by bacterial cellulose in treating and resourcing piggery wastewater.