銅綠微囊藻生長階段對加氯程序生成消毒副產物之影響

Effect of Microcystis aeruginosa growth phases on disinfection by-product formation in chlorination process

余雄鐛(Aldeno Rachmad Ika)

指導教授 ： 林志麟

中原大學/工學院/環境工程學系/碩士(2020年)

https://doi.org/10.6840/cycu202000924

摘要

水庫原水藻華現象發生會造成淨水場水處理操作負擔加重，因混凝程序不易去穩定藻類細胞，導致藻類有機物(AOM)殘留，對產水水質具有負面影響。當藻類細胞不易經混沉程序中移除會造成後續加氯程序中消毒副產物(DBP)大量形成，例如三鹵甲烷(Trihalomethane, THM)和鹵乙酸(haloacetic acid, HAA)，其濃度有時會超過飲用水法規限值。本研究旨在探討銅綠微囊藻(Microcystis aeruginosa, MA)生長特性及次氯酸鈉氧化對藻細胞特性影響及加氯程序消毒副產物生成潛能(DBPFP)。氧化實驗前，利用高效能液相層析儀分析藻類胞內物(Intracellular organic matter, IOM)及胞外物(Extracellular organic matter, EOM)光學特性及分子量分布，以及細胞大小、活性及細胞完整性，以評估NaOCl對MA細胞之氧化行為。
研究結果顯示，MA化學性質在生長期內隨時間變化，IOM及EOM特性會隨生長期而有所不同。AOM衍生之DBP前驅物由高分子量的溶解性微生物產物(soluble microorganism products, SMP)及類腐植酸(Humic acid-like substances)組成，含有類多醣體有機質、多醣體或類蛋白質物質等生物聚合物(biopolymer)。在指數生長期，IOM及EOM具有之鹵化消毒副產物生成潛能相似，但從後指數生長期至死滅期IOM加氯生成之THM較HAA多。在加氯程序中自由餘氯會先與DOM產生反應，再與MA細胞反應造成細胞損害或破裂(尤其是在較長的氧化時間)。自由餘氯會與指數生長期生成的MA細胞及DOM反應，造成細胞破裂及DOM性質改變，但死滅期生成之MA細胞幾乎沒有破裂，此時自由餘氯主要與DOM產生反應。加氯與指數生長期及死滅期生成之藻類有機物(包括溶解性微生物產物、類腐植酸及類黃酸)即時反應過程，THM產生量較HAA多。在加氯氧化銅綠微囊藻過程中，鹵化消毒副產物生成多寡取決於會生成不同有機物特性之生長階段。

關鍵字

藻類有機物 ； 氧化 ； 消毒副產物 ； 次氯酸鈉

並列摘要

Algae bloom in raw waters from reservoirs results in undesirable effects such as increases burden of treatment plant where poor destabilization of algal cells by coagulation increases residual algal organic matter (AOM), which causes negative changes in the quality of final treated water. As poor algal cell removal from water by coagulation-sedimentation frequently results in the significant formation of disinfection by-products (DBP), such as trihalomethane (THM) and haloacetic acid (HAA), during post-chlorination with concentration occasionally exceeds the limit regulated by drinking water standard. This study aims to investigate the growth properties of Microcystis aeruginosa (MA) and the effects of sodium hypochlorite (NaOCl) oxidation towards MA cells characteristics and the corresponding DBPFP. Before chlorination test, the intracellular organic matter (IOM) and extracellular organic matter (EOM), separated from the MA cells at different growth phases, were characterized, by spectroscopy methods, and fractionated, by high-performance size-exclusion chromatography (HPSEC) to determine their molecular weight distribution. Cell integrity, cell size, cell viability and fluorescent features as indicators were determined to evaluate the behaviors of chlorination on MA cells using NaOCl.
The results have showed that the chemical properties of MA changes over time with its growth. The composition of IOM and EOM are different respectively to its growth phases. DBP precursors from AOM origins are predominantly consist of soluble microorganism products (SMP)- and humic acid (HA)-like substances with high apparent molecular weight in response to high polysaccharide-like and/or polysaccharide/protein-like mixture (i.e., biopolymer). Halogenated DBPFP derived from IOM and EOM at the exponential phase is similar while IOM mostly contribute THM formation potential followed by HAA from the late-exponential to decline phases. In chlorination, free chlorine preferentially reacts with dissolved organic matter (DOM) before it disrupt or even disintegrate MA cells, especially at increased contact time. Free chlorine reacts with both DOM and MA cells existing at exponential phase, resulting in cell lysis and changes in characteristics of DOM, while it mostly reacts with DOM existing at the decline phase without obvious cell damage. In-situ reaction of free chlorine with AOM (i.e., SMP-, AP- and FA- like substances) existing at exponential and decline phase form the majority of THM followed by HAA. It is concluded that halogenated DBPFP is dependent on MA growth phases with differences in characteristics of AOM origins.

並列關鍵字

algogenic organic matter ； disinfection by-product ； oxidation ； NaOCl

參考文獻

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