Formation Of Disinfection By-products From Algae After The Pre-oxidation And Coagulation

Two kinds of algae, representing blue-green algae (Microcystis aeruginosa) and diatom algae(Cyclotella meneghiniana), were used to investigate the disinfection by-products (DBPs) formation during chlorination and preoxidaiton (KMnO4 and NaClO)- coagulation disinfection process. The results were concluded as followed:(1) During the chlorination, Microcystis aeruginosa showed higher DBPsFP than Cyclotella meneghiniana. Five DBPs such as TCM, DCAN,1,1-DCP,1,1,1-TCP and TCNM were detected after chlorination of two algae under different conditions. The formation of TCM and TCNM from both algae increased with the increasing the reaction time and the chlorine dosage. Otherwise, DCAN,1,1-DCP,1,1,1-TCP were increased at the eailer reaction stage and then decreased with the increasing of reaction time. All of these five kinds of DBPs increased with increasing concentration of algae cells when the dosage of chlorine was excess for oxidation reaction.(2) The yield of DBPs varied with components of algae cell. The order of DBPs formation for different components of Microcystis aeruginosa was Cell Suspension (CS)≈ Intracellular Organic Matter (IOM)> Extracellular Organic Matter (EOM)> Cell Debris (CD). IOM of Microcystis aeruginosa was the main DBPs precursors; The yield of these five DBPs from different components of Cyclotella meneghiniana was in the order of Cell Suspension (CS) > IOM≈Cell Debris (CD)≈EOM. The Exicitation-Emission Matrix Flourescence Spectrophotometer(EEM) results showed that the amount of organic compunds containing in two algae cell were different. However Soluble Microbial Products (SMP) and aromatic protein-like were the main cellular components and also contributed to the DBPs precursors in the algae cell.(3) The yield of TCM decreased with increasing potassium permanganate dosage after KMnO4-preoxidation-coagulation-disinfection, but increased with increasing chlorine dosage after prechlorination-coagulation-disinfection. After KMnO4-preoxidation-coagulation, DOC and SUV254 could decrease, but not for turbidity. Prechlorination-coagulation treatment decreased DOC and turbidity with the increasing of chlorine dosage, but could not remove SUV254, which might contribute to the DBPs precursor in later disinfection.(4) Preoxidation by potassium permanganate and chlorine caused the damage to two algae to some extent. The cells of Microcystis aeruginosa after KMnO4 and chlorine still kept the whole shape of cells compared with those of Cyclotella meneghiniana. The preoxidation of Cyclotella meneghiniana led to the lysis of cells and the releasing of the cellular cytoplasm, which increased the DBPsFP during the water treatment process.