Pilot Study On The Treatment Of Algae Micro-polluted RAW Water By On-line Coagulation-ultrafiltration-ozone Activated Carbon Process

In this paper,the in-line coagulation-ultrafiltration-ozone activated carbon process was used to treat the Taihu raw water in depth.The results are summarized as follows:?1?The algae is rich in the lake Taihu and algae cells concentration can reach up to355/L in summer during the experiment.Plenty of algal toxins and odorants will be released which makes conventional treatment process of drinking water often fails to meet the national standard if Excessive algae exist in water.The concentration of turbidity,ammonia nitrogen and organic matter was greatly influenced by the change of seasons and the characteristic of organic matter is mainly hydrophilic,and the molecular weight is mainly distributed in0.5-10K Da.According to the three-dimensional fluorescence analysis,the content of aromatic protein in soluble organic matter is the highest,and the integral volume accounts for55.8%of the total integrated volume.?2?Raw water filtrated directly by UF process can reduce turbidity to below 0.2 NTU,but the removal of organic matter is limited,while on-line coagulation-UF can effectively improve the removal rate of ammonia nitrogen and organic matter,and effectively slow down UF membrane fouling.The whole process can also run stably for a long time,even the UF membrane flux was set for 90L/m²·h.On-line coagulation-UF,compared with direct filtration,increased the total integrated volume of ammonia nitrogen,COD_Mn,TOC,UV₂₅₄,algae and three-dimensional fluorescence by 9%,9%,23.4%,7%and 13.43%,respectively.?3?Through the removal of ammonia nitrogen,organic matter and algae and the process operation,the optimal operating parameters of the online coagulation-ultrafiltration-ozone activated carbon process are:Coagulant dosage 4mg/L(Al³⁺),ozone dosage 1mg/L,ozone contact time 15minutes,carbon layer depth 1m,activated carbon filtration rate 6.5m/h and empty bed contact time was 10 minutes.By comparing the conventional process-ozone activated carbon process and on-line coagulation-ultrafiltration-ozone activated carbon process,the turbidity of the on-line coagulation-UF-O₃-activated carbon process can be decreased below 0.1 NTU in terms of turbidity and algae removal.The average removal rates of ammonia,COD_Mn,UV₂₅₄,TOC and fluorescent substances in the on-line coagulation-UF-ozone activated carbon process were 81.30%,63.55%,70.20%,62.05%and 91.28%,respectively.The removal of algae was higher,and the average removal rates of chlorophyll a and phycocyanin reached 99.53%and 96%,respectively.In the following,chlorophyll a was detected as 0,while the conventional process-ozone activated carbon effluent turbidity was about 0.8 NTU,chlorophyll a was 0.25 ug/L on average,and the effluent stability was poor.In terms of the removal of ammonia nitrogen,COD_Mn,UV₂₅₄,TOC and three-dimensional fluorescence,the two processes have comparable removal capabilities.?4?Study on irreversible pollution of UF membrane by different water influent indicating that there is no correlation between influent turbidity and UV₂₅₄54 and ultrafiltration irreversible pollution index,but a certain correlation with TOC,and strong correlation with fluorescent substances.Correlation.Through the analysis of chemical cleaning solution,the main irreversible pollution of the UF membrane is calcium,potassium,manganese,iron and aluminum.The Ca²⁺content is the highest,the average is 31.79mg/L,and the K⁺and Fe²⁺content are higher,the average value is5.39 mg/L and 3.44 mg/L,while other ion levels are low.The fluorescent substances mainly causing irreversible contamination of the ultrafiltration membrane are aromatic protein substances II,soluble microbial metabolites and aromatic protein substances I.Organic matter is mainly small and medium molecular organic matter.