| Due to the chemical stability and light stability of dyes,dye-wastewater has beome one of the most difficult industrial wastewaters to treat.Biosorption was shown to be one of the most promising method for dye-containing sewage treatment.Fungal mycelial pellet,which possesses strong survival ability,fast settling velocity and good reusability,has been noticeably exploited as a new kind of biosorption material.Marine fungi has a great application potential in sewage treatment since its strong resistance,especially the good salt tolerance.In our research,a strain of marine-derived fungi Aspergillus niger ZJUBE-1,isolated by ourselves,which can form mycelial pellets,was utilized to the treatment of wastewater.The pellet-forming mechanism and open cultivation process were also studied.Firstly,the experiment of mycelium passage showed the mycelium fragments seeded in a new medium would agglomerate,grow and eventually formed into a new mycelium pellet,which demonstrated that the formation of mycelium pellet can completely not rely on spore aggregation.Thus,beyond the traditional model of spores agglomeration,we put forward another point of view:the formation of the mycelial pellets is not dependent on the spores and the necessary condition is the agglomeration properties of hyphae.Although spore aggregation may not be essential,it is likely an enhancing factor for the mycelial pellet formation.Secondly,due to the references of mass production and morphology control for mycelial pellets were very few,this paper carried out the comprehensive research for the preparation technology of marine-derived A.niger.It was found that by changing the medium initial pH or mycelium inoculation quantity can both control the size of the diameter of the pellets,while the later one had a higher feasibility.The two-step scheme of open cultivation was formulated:(1)The marine-derived A.niger was pre-cultivated in shake flask for 12 h to form the hyp ha agglomerations;(2)The shake flask cultivation content was then added into a open culture vessel,and the influence of bacterial pollution was lowered by limiting the C/N source,adjust pH and timing replacement the culture medium.According to the preliminary results that the 15 L open container can produce mycelial pellets of 3.47 kg wet biomass,it is showed that open cultivation has great application potential.Thirdly,The biosorption of eight common dyes with mycelial pellets of A.niger were studied.Results showed that the mycelial pellets had a good biosorption ability for these dyes.The decolorization rate of five dyes(Eriochrome black T,Congo Red and so on)could reach 96%.Fourthly,in order to deeply research the effect of external factors on mycelial pellets decolorization efficiency and its biosorption mechanism,Congo Red was taken as a model dye for the follow-up study.The pellets have strong salt and acid tolerances in biosorption process.The biosorption capacity was quite steady among pH 2.0 to pH 5.0,always staying above 98.7%.The decolorization percentage was still at 87.6%even though NaCl concentration reached to 300 g L-1.Batch decolorization study shows that mycelial pellets could possess an efficient and continuous decolorization ability with the supplement of certain amount of C,N source or through a re-culture process between every two batches.Fifthly,A semi-continuous airlift reactor was designed and the reusability of pellets was verified to be excellent and still more than 85%dye was removed in the seventh batch.The utilization of pellet biomass in the first batch was relatively low and a re-culture process undernon-sterile condition successfully achieved the maximize utilization of mycelium biomass.In general,the airlift reactor combining with mycelial pellets can be used as a promising high-efficiency mode for the removal of dyes from aqueous solutions.At last,the mycelium cake which has a capable of quickly "gathered-scattered again"were preparation by mycelial pellets through the method of vacuum filtration.The mycelium cake could achieve the rapid decolorization process for Congo Red solution.In the case of higher temperature,the decoloring rate would be slightly lower,but the speed of passing time would also increased greatly.This method has great industry application potential in the rapid treatment of wastewater containing dyestuff. |
PDF Full Text Request