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(huán)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(yōu)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(wěn)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(jié),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(shù)據(jù)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(fā)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(yōu)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(wěn)定性的改善效果.在優(yōu)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(wěn)定性的重要指標,VSS減少率越高,污泥穩(wěn)定性能越好[26].因此,Fe(II)-PMS氧化有利于提高污泥穩(wěn)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(wěn)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(yōu)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(yōu)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(wěn)定性提高和組分溶出.在優(yōu)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(huán)境化學研究.發(fā)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(fā)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