Pilot Study On The Raw Water Of Taihu Lake By Pre-ozonation–Conventional Treatment–Ozone Biological Activated Carbon Process

With economic development and people's demand for high-quality drinking water,ozone biological activated carbon?O3-BAC? has become the best choice of advanced treatment processes. This study was carried out for Taihu raw water, mainly on the influence of organics' removal, which is caused by ozone dosage with conventional treatment process and BAC, and activated carbon types with BAC. According to the experiment results, several conclusions are obtained as follows:?1? Taihu raw water is characterized by high concentrations of organic matter, large seasonal changes of ammonia and turbidity. It's mainly formed of hydrophilic organics,whose most molecular weight is 0.5¹0KDa.?2? When the pre-ozone dosage was less than 2mg/L, the pre-ozone had no effect on the removal of turbidity, COD_Mn, UV₂₅₄. The highest removal rates of ammonia, DOC were5.32%, 15.65% respectively. The organic molecular weight of raw water declined after pre-ozone, which enhanced the hydrophilic, weakened the hydrophobicity. There was positive linear correlation between AOC of water after pre-ozone and the pre-ozone dosage,when the dosage was 2mg/L, AOC was increased by 66.07%.?3? When the pre-ozone dosage was 0.5mg/L, the highest turbidity removal rate of coagulating sedimentation was 81.89%, when 1.5mg/L, the highest ammonia removal rate was 47.69%. The removal rate of turbidity and ammonia declined with increasing the ozone dosage. When the dosage was 2mg/L, the removal rate of organics achieved a higher value,COD_Mn, UV₂₅₄, DOC were 29.35%, 18.59%, 26.48% respectively. The removal rate of AOC is about 20% in coagulating sedimentation process.?4? When the main ozone dosage was 0²mg/L, there was almost no effect on organic removal. There was positive linear correlation between AOC of water after main ozone and the main ozone dosage, when the dosage was 2mg/L, AOC was increased by 40%.?5? The main ozone dosage had no affect on the removal of turbidity and ammonia in ozone-BAC. The turbidity after carbon filtration was under 0.5NTU, the removal rate of ammonia was about 63%. In ozone-BAC, BAC tends to remove macromolecular and intermediate molecular weight?10³KDa? protein organics first, followed by macromolecular and intermediate molecular weight?10³KDa? humic organics, again is micromolecular?3⁰.5KDa? fulvic acid organics, finally is micromolecular?less than 3KDa?protein organics. When the main ozone dosage was 2mg/L, the removal rate of AOC was44.90% in BAC.?6? The removal rate on COD_Mn, UV₂₅₄, DOC of coal carbon is higher than wood carbon, increased by 14.93%, 8.61%, 29.67% respectively. The best retention time of coal carbon is 12 min, wood carbon is 18 min. The best thickness is 180 210 cm on carbon layer of both coal carbon and wood carbon.