| The ballast water convention has officially entered into force on September 8,2017.However,the existing ballast water treatment technology still has some problems such as low efficiency and instability.Meanwhile,algae wastes after the ballast water treatment cannot be effectively treated which brings great hidden dangers to the Marine environment.In this paper,the high gradient magnetic filtration system combined with UV/TiO2 system(HGMS-UV/TiO2)was used to remove microorganisms in ballast water stably and efficiently,and the productivity of algal waste after ballast water treatment was studied,so as to realize the recycling and innocuity of ship waste.In view of the present situation that the common filter has little effect on organisms smaller than 20 ?m,this paper established HGMS-UVC/TiO2 system and invented magnetic seeds of modified wheat straw,which replaced traditional magnetic seeds and without flocculan added.The pretreatment of HGMS could realize a single purification of many kinds of pollutantsa and increased removal rate of suspended substance and escherichia coli in ballast water by 29.8%and 0.4 log,respectively,compared with the magnetic seeds before modification.And the sterilizing capacity of the secondary treatment system of UVC/Ti02 was given full play,it made the e.coli cell membrane severely damaged,lipid peroxidation products MDA content increased,SOD enzyme activity abated,intracellular K+and protein leaked,the structure and the DNA of e.coli cells produced irreversible double damage and kill,inhibited bacteria resurrection of light and dark repair ability.The application of magnetic straw HGMS system combined with ultraviolet photocatalysis has a certain synergistic ability,and it has a significant effect on the removal of escherichia coli in artificially prepared seawater.In order to improve the removal effect of HGMS-UVC/TiO2 system on microalgae with tough cellulose cell wall,this paper established the novel long and short wave ultraviolet photocatalysis(UVA/UVC-TiO2)system.Compared with the photocatalytic system with long wave or short wave as the light source alone,the algae elimination rate increased by 0.31 log and 0.19 log respectively.The combined action of long and short wave ultraviolet photocatalysis aggravated the damage of microalgae cell membrane and its permeability,while the short wave ultraviolet radiation damaged the metabolism and genetic material in cells.Compared with the single-wavelength ultraviolet catalytic system,UVA/UVC-TiO2 system could increase the content of lipid peroxidation products in microalgae cells by 40%,reduce the activity of superoxide dismutase by 40%,and increase the amount of intracellular substances leakage by 25%in a relatively short reaction time.UVA/UVC-TiO2 system gave full play to the high catalytic activity of UVA to TiO2 and the high damage of UVC to cells,thereby achieving efficient inactivation of micro-organisms in ballast water.In view of the factor that ballast water algae waste have high utilization value but cannot be effectively treated and reused,the effects of different kinds of sludge and pretreatment methods on the productivity of selective fermentation and degradation of ballast water algae waste were investigated.Results showed that the FP pretreatment technology of waste water ballast algae,if inoculated aerobic sludge(AS)could generate the most volatile fatty acid(VFA),and the inoculation of anaerobic sludge(ANS)could retain more fat,this might be due to the Sphingomonoadaceae,Other Bacteroidales and Clostridiaceae dominant population in AS group,which leaded to waste of ballast water algae had good biodegradable properties.And a large number of families related to biohydrogenation were found in the ANS group,so typical biohydrogenation occurs that preserves fat and produces more methane.In the study of roductivity effects of different physicochemical pretreatment methods,AS was used as selective fermentation seed sludge,the results showed that the hydrolysis rate of the non-materialized selective fermentation was slightly slower than that of the pretreatment group in the early stage of fermentation,but the indexes of the latter stage of fermentation were significantly improved,41%unsaturated fatty acids were saturated the physicochemical properties of biodiesel were improved.In addition,selective fermentation is a green anaerobic fermentation technology with low energy consumption,no need to add chemical reagents,and no secondary pollution.Therefore,the degradation capacity of algae waste in ballast water can be improved without pretreatment.Instead,selective fermentation technology is used as the best method to break down algae and improve the efficiency of fat extraction. |
PDF Full Text Request