The study of treatment functions of activated sludge/contact aeration combined system
|Keywords:||活性污泥/接觸曝氣法合併系統;生物相;人工合成生活污水;屠宰場廢水;餐廳廢水;垃圾滲出水;變性梯度膠凝電泳;AS/CA system;biological phase;synthetic domestic wastewater;slaughterhouse wastewater;restaurant wastewater;leachate||Issue Date:||2006||Abstract:||
由AS與AS/CA系統處理人工合成生活污水之結果得知，對COD、BOD及色度之去除，AS/CA系統均較單一AS系統佳，當油脂進流濃度由15 mg/L逐步提升至60 mg/L時，AS系統油脂出流濃度為13 mg/L，已超過國內放流水標準10 mg/L，但AS/CA系統油脂出流濃度為8 mg/L，仍可維持在放流水標準以內；但當油脂進流濃度再提昇至120 mg/L，兩系統的出流濃度均超過放流水標準。
由AS/CA合併系統之小模廠處理高濃度屠宰廢水的研究結果得知，生物曝氣槽之總水力停留時間若為8小時，COD平均值可降低至71 mg/L(去除率為94% )，BOD平均值可降至29 mg/L(去除率為91% )，SS平均值可降至43 mg/L(去除率為86%)，真色色度平均值可降至47 unit(去除率為84%)，油脂平均值則從54 mg/L降低至7 mg/L，去除率達87%。由實廠採樣資料驗證，屠宰場廢水經AS/CA合併系統處理，AS與CA槽的污泥顏色均呈金黃色，放流水水質穩定且均符合放流水標準。
餐廳廢水之小模廠實驗結果顯示，在生物曝氣槽之總水力停留時間8小時情況下，可將水質變異大的餐廳廢水，處理至穩定的出流水質，例如BOD之標準偏差值可由進流水之158.0 mg/L降至出流水的8.8 mg/L。由AS槽及CA槽之反應動力參數分析結果得知，AS槽COD之體積負荷(P值)為625 g/m3•day大於CA槽之233 g/m3•day，AS/CA整體系統的P值為455 g/m3•day，介於兩槽之間；而AS槽之Ks值較CA槽為高，分別為41 mg/L與20 mg/L。
本研究以變性梯度膠凝電泳(Denatural Gradient Gel Electrophoresis, DGGE)方法，分析單獨活性污泥系統、單獨接觸曝氣系統以及AS/CA合併系統中之生物相，結果顯示AS/CA合併系統所含之生物相與生物量均較單一活性污泥法或單一接觸曝氣法為多。
The activated sludge/contact aeration (AS/CA) combined system was created by adding biological contact filters into the rear sector of the activated sludge tank. The system contains both suspended and fixed microorganisms. This combined system presents the advantages of both AS system and CA system. It also improves the disadvantages of these two individual systems. A special feature is that the AS/CA system can enhance the removal ratios of the true color, oil and grease.
Both AS/CA and AS-only systems were tested to treat the synthetic domestic sewage. The BOD, COD and color removal ratios of both treatment systems were compared. The results showed that the pollutant removal ratios of the AS/CA system were higher than those of the AS-only system. When the oil and grease was spiked into the sewage, oil and grease concentrations were gradually increased from 15 mg/L to 60 mg/L. When the influent oil and grease concentration was 60 mg/L, the effluent concentration of the AS system was 13 mg/L, which was higher than 10 mg/L, the effluent standard of oil and grease. However, in the AS/CA system, the effluent oil and grease concentration was 8 mg/L, which was under the regulated standard. When the influent oil and grease concentrations reached 120 mg/L, the effluent concentrations of both systems exceeded the regulated standard.
A pilot treatment plant was constructed and located in a slaughterhouse. The AS/CA system was operated with eight-hour hydraulic retention time (HRT), and the results indicated that average effluent COD = 71 mg/L (94% removal ratio), BOD = 29 mg/L (91% removal ratio), SS = 43 mg/L (86% removal ratio), and true color = 47 unit (84% removal ratio). The AS/CA system can treat the oil and grease concentration from 54 mg/L to 7 mg/L (87% removal ratio). In the case of slaughterhouse wastewater treatment, the sludge presented as golden color in AS and CA tanks. The effluent water quality can meet Taiwan’s regulation, and the AS/CA system was much more stable.
In terms of the removal ratios of SS, BOD and COD of the leachate, these ratios in AS/CA system are 10.3%, 6.4% and 4% higher than those ratios in AS system, respectively. The AS/CA system efficiently decomposes the leachate, resulting in a 35.2% ~ 42.5% removal ratio of COD and a 59.9% ~ 65.4% removal ratio of BOD.
Under eight hours of HRT, the AS/CA system was able to treat restaurant wastewater which had fluctuating quality, and to reduce the standard deviations of COD and BOD from 115.8 and 158 to 40.5 and 8.8, respectively.
The kinetic parameters derived through the linear regression analysis of COD data yielded a volume loading P value of 625 g/m3•day for the AS tank, greater than 233 g/m3•day for the CA tank. The p value of 455 g/m3•day for the complete AS/CA system was between those for AS and CA tanks. The Ks values of 41 mg/L for the AS tank was greater than 20 mg/L for the CA tank.
Denaturing Gradient Gel Electrophoresis (DGGE) analysis was applied to samples taken from activated sludge system, contact aeration system, and AS/CA system. The analytical results suggested that when these three systems were compared, the microbe diversity and quantity of the combined system was relatively high.
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