高科技污水處理廠生物處理程序溫室氣體排放評估

Abstract

由於人類活動中，直接或間接使用大量能源與資源，導致大量溫室氣體排放到大氣中，加劇溫室效應，導致全球暖化，氣候異常、環境生態的改變，甚至影響了農業與糧食的穩定。我國產業發展以外銷為導向，尤其高科技工業是國內經濟發展的命脈，為避免高科技工業園區內所有高科技產品在國際市場上遭受抵制，其污水處理廠應遵守國際溫室氣體盤查與削減規範。 本研究針對高科技工業園區污水處理廠，進行溫室氣體排放量評估，內容大致分為五個部份：首先透過污泥成分分析後，計算出污泥分子式，接著假設葡萄糖為微生物反應物的基質，以微生物動力學理論及質量平衡原理，推導出微生物呼吸產生能量與合成產生污泥的總反應方程式；第一部分首先依據高科技污水處理廠每日進出流水COD、BOD5、每日廢水量、每日生物性污泥產生量等資料，推算101年高科技污水處理廠溫室氣體直接排放量約1,317,437 ~ 3,108,635 Kg CO2(e)。另依據用電量、鹼液、助凝劑、污泥運輸等資料，推算101年高科技污水處理廠溫室氣體間接排放量6,994,659 Kg CO2(e)，直接加間接之總排放量為8,321,822~10,113,020 Kg CO2(e)。直接排放源中，以基質代謝與污泥生成反應之排放為主，約佔直接排放量之56~64%；間接排放源中，則以用電量之排放為主，約佔間接排放量之69.9%。 第二部分，為因應未來放流水質新增氨氮管制標準，高科技污水處理廠將採用厭氧-缺氧-好氧複合式污水處理系統，推導微生物計量反應式，並計算其溫室氣體直接排放量為24,274,999 Kg CO2(e)；處理過程用電量、中和用鹼、污泥助凝劑及甲醇等化學品之溫室氣體間接排放量為12,212,272 Kg CO2(e) ，總排放量為36,487,271 Kg CO2(e)。 第三部分，依據文獻之排放係數，計算現行好氧與未來厭氧微生物處理系統之放流水溫室氣體排放量分別為9,154,291 Kg CO2(e)與3,791,185 Kg CO2(e) 。 第四部分，比較現行好氧與未來厭氧微生物處理系統之污泥，採掩埋或焚化爐等不同污泥處理方式之溫室氣體排放量，現行污泥掩埋與燒結再利用兩案並行方式，溫室氣體總排放量11,757,681 Kg CO2(e)，厭氧複合處理系統污泥如果採燒結再利用，所產生之溫室氣體排放量9,054,760 Kg CO2(e) ，相較污泥全部採掩埋處理排放量24,651,846 Kg CO2(e)大幅削減63.3%。 第五部分，針對高科技污水處理廠如果新增一套污泥厭氧消化槽後，可處理污泥並收集甲烷發電，相較於污泥掩埋法，101年好氧處理系統減少溫室氣體排放量 -24,124,928 Kg CO2(e) ，削減率為-101.9 %；厭氧複合處理系統其溫室氣體排放削減量為 -33,928,285 Kg CO2(e) ，削減率為 -137.6 %，削減成效卓著。

As a result of energy and materials consumed by diverse human activities, a great deal of green house gases had been discarded and emitted into the global atmosphere. The GHGs (green house gases) make the earth warming, climate abnormality, bio-system changing and even destroy the stability of agriculture product and food. Because of export trading, the high technology industry is the main driving force of economic growth in Taiwan, R.O.C. The wastewater treatment plant of high technology industrial park should obey all GHGs inventory and reduction protocols to avoid the boycotts from international GHGs alliances. There are five main issues about GHGs emission of high technology industry wastewater treatment plant in this research . First of all, the empirical formula of microbial cells was proved by elementary analysis and stoichiometry calculating; accordingly, the overall reactions for biological expiration and biomass growth equations was induced by bacteria kinetics and mass balance with an assumption of glucose acting as a reactive substrate of influent. Then, the GHGs on-site emissions can be evaluated in accordance with the dairy data of aerobic wastewater treatment plant, such as the volumetric flow rate, BOD, COD , SS and sludge output, etc. The GHGs on-site emission of high technology industy wastewater treatment plant in 2012 ranges from 1,317,437 to 3,108,635 Kg CO2(e). The GHGs off-site emissions are 6,994,659 Kg CO2(e) estimated by the inventory of electricity, alkalinity, flocculation reagent and sludge transportation, etc. The overall GHGs emission ranges from 8,321,822 to 10,113,020 Kg CO2(e).. Biological expiration and biomass growth reaction, emitted about 56~64% of all the GHGs on-site emissions, is the major GHGs on-site resource. Otherwise, electricity comsumption, emitted about 69.9% of all the GHGs off-site emissions, is the major GHGs off-site resource. Secondry, high technology industy wastewater treatment plant is going to establish a A2O(Anaerobic-Aerobic/Anoxic ) hybrid bio-reaction system to ensure the quality of effluent meets the new public ammonia criteria. The new biological stoichiometry equations , on-site and off-site GHGs emissions have been demonstrated in this research with an assumption of biomass yield from textbooks. The GHGs on-site emissions of anaerobic hybrid treatment system are 24,274,999 Kg CO2(e). The GHGs off-site emissions are 12,212,272 Kg CO2(e) estimated by the inventory of electricity, alkalinity, flocculation reagent and methane, etc. The overall GHGs emission are 36,487,271 Kg CO2(e).. The third, the residual organisms and ammonia of effluent decomposed and emitted the GHGs in the recevier. The emissions for aerobic and anaerobic hybrid treatment systems are 9,154,291 Kg CO2(e) and 3,791,185 Kg CO2(e) respectively, in accordance with the emission factors from literatures. The fourth, the different sludge treatments, such as landfill or incinerating, may cause significant environmental impact of GHGs and has been evaluated. The GHGs emissions through landfill and incinerating for aerobic treatment systems at present are 11,757,681 Kg CO2(e). Otherwise, the GHGs emissions by incinerating for anaerobic hybrid treatment systems are 9,054,760 Kg CO2(e), reducing 63.3% of landfill emissions. The fifth, the GHGs reduction benefits was also estimated to establish a set of sludge anaerobic digestor and electricity generator for methane reuse in high technology industy wastewater treatment plant. Comparing with the landfill, the GHGs reduction through a sludge anaerobic digestor of the aerobic and anaerobic hybrid treatment systems are -23,240,100 Kg CO2(e) and -33,928,285 Kg CO2(e) respectively. The reduction ratios are -101.9 % and -137.6 % accordingly. The performance of GHGs reduction of the sludge anaerobic digestor is very distinguished.