Fe(II)活化過一硫酸鹽氧化調理剩余活性污泥

劉昌庚,伍 斌,謝四才

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Fe(II)活化過一硫酸鹽氧化調理剩余活性污泥

劉昌庚*,伍 斌,謝四才

(攀枝花學院資源與環境工程學院,四川攀枝花 617000)

采用Fe(II)活化過一硫酸鹽(Fe(II)-PMS)氧化對剩余活性污泥進行調理研究.結果表明,Fe(II)-PMS氧化能有效改善污泥的脫水性能;在優化實驗條件下(pH為6.7,Fe(II)和PMS投量分別為60和120mg/gTSS),標準化毛細吸附時間(SCST=CST0/CST)和毛細吸附時間(CST)減少率分別為11.28和91.13%.Fe(II)-PMS氧化有助于污泥穩定性提高和組分溶出,處理后VSS減少率為15.74%、上清液中TN和TOC的含量較初始值分別增加6.21和9.13倍.此外,研究表明Fe(II)-PMS氧化能有效破解和降解胞外聚合物(EPS)(特別是蛋白質),釋放出EPS結合水,進而顯著改善污泥脫水性能.

過一硫酸鹽；脫水性能；剩余活性污泥；毛細吸附時間

1 材料與方法

1.1 實驗材料

牛血清蛋白為生化試劑,其他試劑均為分析純試劑.供試污泥取自攀枝花市某污水處理廠的污泥濃縮池,取回后自然沉淀12h,去掉上清液后將污泥存放于4℃的冰箱中,其基本性質如表1.

表1 供試剩余活性污泥的基本性質

注:a為污泥上清液中濃度.

1.2 實驗方法

取200mL供試剩余活性污泥于500mL錐形瓶中,然后預熱至室溫(~20℃);隨后考察不同初始pH、Fe(II)及PMS投量對污泥脫水性能的影響.pH采用濃度為2mol/L的硫酸和氫氧化鈉調節,待pH調至設置值后,同時加入Fe(II)及PMS進行氧化調理,并以120r/min的速度攪拌至結束.在處理過程中,按預先設定時間取樣5mL用于測定毛細吸附時間(CST).為保證實驗數據可靠性,每組實驗重復操作3次.

1.3 分析方法

pH值和毛細吸附時間分別利用酸度計(雷磁,PHS-3C)和CST測定儀(304B,英國Triton公司)測定;總懸浮固體(TSS)和揮發性懸浮固體(VSS)采用重量法測定;EPS分層方法詳見文獻[13],多糖和蛋白質濃度分別采用硫酸-蒽酮法和考馬斯亮藍G-250法測定[13,16];上清液中總氮(TN)和總有機碳(TOC)含量利用TOC/TN分析儀測定(TOC-L,日本Shimadzu公司).標準化毛細吸附時間(SCST)用于表征污泥的脫水性能,SCST值越大,污泥脫水性能越好,其計算式如下:

式中:CST0和CST分別表示污泥處理前后的毛細吸附時間.

2 結果與討論

2.1 pH對污泥脫水性能的影響

相比Fenton氧化,Fe(II)-PMS氧化調理污泥受初始pH值影響較小,可在污泥原始pH值條件下取得較好的脫水效率;而Fenton氧化則需在酸性條件才能獲得較好的污泥脫水效率,但是在極酸性條件下,其氧化效率會因[Fe(H2O2)]2+的形成而嚴重受到抑制[20].由圖1可知,在反應20min后,pH值為3、5、6.7、9時的SCST值分別為6.32、8.95、11.18、3.24,對應CST減少率分別為84.18%、88.83%、91.06%、69.14%.因此,可推斷出pH值并非Fe(II)-PMS氧化改善污泥脫水性能的主要影響因素.該研究結果與前期Zhen等[7]報道的結論相似,他們指出Fe(II)活化過硫酸鹽(Fe(II)-PDS)氧化能在較廣pH范圍內(3.0~8.5)顯著改善污泥的脫水性能.由以上研究結果可知,Fe(II)-PMS氧化改善污泥脫水性能在成本控制和處理效率方面均具有優勢.

圖1 pH值對污泥脫水性能的影響

2.2 Fe(II)和PMS投量對污泥脫水性能的影響

2.3 Fe(II)-PMS氧化對污泥組分溶出的影響

本研究還探究了Fe(II)-PMS氧化對污泥穩定性的改善效果.在優化條件下,污泥經Fe(II)- PMS氧化處理后,VSS減少率為15.74%.VSS減少率是污泥穩定性的重要指標,VSS減少率越高,污泥穩定性能越好[26].因此,Fe(II)-PMS氧化有利于提高污泥穩定性.最近,Kim等[25]指出污泥經熱活化PMS和PDS處理后,VSS減少率分別為4.9%~15.4%和4.1%~7.7%.此外,Chen等[14]同樣指出PMS較PDS氧化更能有效的降解有機物.因此,活化PMS氧化較活化PDS氧化可能更有助于提高污泥的穩定性.

圖4 Fe(II)-PMS氧化處理后VSS減少率、上清液中TN和TOC的濃度

2.4 Fe(II)-PMS氧化對EPS的影響

EPS是污泥的重要組成部分,可分為黏液層EPS(S-EPS)、松散結合EPS(LB-EPS)和緊密結合EPS(TB-EPS)[13].EPS主要由蛋白質和多糖組成,這兩者可占其總質量的70%~80%,是影響污泥脫水性能的主要因素[7,27].本研究為考察Fe(II)-PMS氧化對污泥EPS破解的影響,在優化條件下氧化處理前后EPS各層中蛋白質和多糖的變化如圖5所示.由圖可知,原始污泥蛋白質和多糖含量分別為413.34和60.47mg/L,且主要存在于S-EPS和TB-EPS層中.經Fe(II)-PMS氧化后,蛋白質含量迅速下降至91.46mg/L;而多糖含量則輕微增加至65.14mg/L.鑒于蛋白質含量大量減少的同時污泥脫水性能得到顯著改善,因此可推測出EPS中蛋白質含量對污泥的脫水性能的改善具有負面的影響.

圖5 Fe(II)-PMS氧化處理后蛋白質和多糖在EPS各層中的濃度

3 結論

3.1 Fe(II)-PMS氧化能顯著改善污泥的脫水性能.優化實驗條件:pH為6.7,Fe(II)和PMS投量分別為60和120mg/gTSS.此時,SCST值為11.28,CST減少率為91.13%.

3.2 Fe(II)-PMS氧化有助于污泥穩定性提高和組分溶出.在優化條件下,VSS減少率為15.74%、上清液中TN和TOC的含量較初始值分別增加6.21和9.13倍.

3.3 Fe(II)-PMS氧化處理污泥能有效破解和降解EPS(特別是蛋白質),釋放出EPS結合水,進而顯著改善污泥脫水性能.

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Conditioning of excess activate sludge by Fe(II)-activated peroxymonosulfate oxidation.

LIU Chang-geng*, WU Bin, XIE Si-cai

(School of Resources and Environmental Engineering, Panzhihua University, Panzhihua 617000, China)., 2017,37(10)：3794~3799

Fe(II)-activated peroxymonosulfate (Fe(II)-PMS) oxidation applied to condition excess activated sludge was investigated in this work. The results showed that Fe(II)-PMS oxidation could effectively improve sludge dewaterability. The optimal pH and dosages of Fe(II) and PMS were 6.7, 60mg/gTSS, and 120mg/gTSS, respectively, under which the standardized-capillary suction time (SCST=CST0/CST) and CST reduction were 11.28 and 91.13%, respectively.Fe(II)-PMS oxidation was also favor of sludge solubilization and enhanced stabilization. Under the optimum experimental conditions, VSS reduction was 15.74% and the concentrations of TN and TOC in the supernatant increased 6.21 and 9.13-fold compared to their initial values, respectively. In addition, Fe(II)-PMS oxidation was beneficial to destroy and degrade extracellular polymeric substances (EPS) (especially for proteins), which resulted in the release of EPS-bound water and subsequently improved sludge dewaterability significantly.

peroxymonosulfate；dewaterability；excess activated sludge；capillary suction time

X703.1

A

1000-6923(2017)10-3794-06

劉昌庚(1985-),男,四川宜賓人,副教授,博士,主要從事高級氧化技術及大氣環境化學研究.發表論文20余篇.

2017-03-17

國家自然科學基金資助項目(21607088);攀枝花學院博士基金資助項目(0210600022);攀枝花市科技計劃資助項目(2015TX-8);干熱河谷特色生物資源開發四川省高校重點實驗室開放基金資助項目(GR-2017-E-04)

* 責任作者, 副教授, changwyx@163.com