The Formation Process And Impact Factors Of Haas Upon Chlorinating Blue-green Algae

Control the formation of the Disinfection By-Products (DBPs) in drinking water is one of the most important task for safety of drinking water. It is necessary to study the formation process of haloacetic acids (HAAs), a kind of typical DBPs during the treatment of raw water.In this thesis, four general blue-green algae in fresh water are regarded as target. Chlorella vulgaris and Scenedesmus obliquus are selected as the representative of general green algae respectively, while Microcystis aerugrinosa and Spirulina platensis are regarded as the representative of geferal blue algae respectively, the formation process and the impact factors of the HAAs upon the chlorinating of blue-green algae were investigated. Furthermore, the characteristics of the formation of HAAs during the chlorination of the raw water in Xiangjiang River was studied. The main conclusions were achieved as follows:(1) The yields of the HAAs increased with the reaction time and reached steady after 24 h, and HAAs first increased and then reached steady with the rised pH. At pH 8.0, the yields of DCAA and TCAA from the chlorinating Chlorella vulgaris were 34.5μg/mgTOC and 41.9μg/mgTOC at 24 h. Compared with Chlorella vulgaris, the yields of DCAA and TCAA upon chlorinating Scenedesmus obliquus increased by 25.2% and 3.12% respectively, the yields of DCAA and TCAA upon chlorinating Microcystis aerugrinosa increased by 57.9% and 47.3% respectively, the yield of DCAA and TCAA upon chlorinating Spirulina platensis increased by 16.8% and 19.2%, the highest capacity of the formation of HAAs is Microcystis aerugrinosa in the four tested blue-green algae. Compare of the biochemical compose of the four blue-green alage, the formation of HAAs was direct proportion to the content of Bovine Serum Albumin(BSA) in algal cell.(2) The yields of DCAA and TCAA increased with the rising of temperature. For example, DCAA and TCAA reached 38.2μg/mgTOC and 42.3μg/mgTOC at 20 oC to 25 oC. The presence of Cu²⁺ promoted the formation of DCAA, whileras significantly inhibited the formation of TCAA and this inhibitation ratio was enhanced at high pH. The yield of TCAA was decreased by 25.0μg/mgTOC at pH 8.0 with the addition of 1.0 mg/L Cu²⁺, and the similar result was showed when chlorinating BSA, one main component of chlorella vulgaris. In the presence of F-, the yield of DCAA and TCAA first decrease and then increased, while SO₄^2- and NO₃^- have little influence on the formation of HAAs upon chlorinating chlorella vulgaris.(3) The results showed that the yields of HAAs in summer were maximum, while the minimum occured in winter. DCAA and TCAA are 33.5 and 31.0μg/L in summer respectively,, but was 16.8 and 18.0μg/L in winter respectively.