何足道,王電站,顏 成,2,方 迪,鄭冠宇,張衛(wèi)華,周立祥*

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城市污泥生物瀝浸法和化學(xué)法調(diào)理的效果比較——對污泥理化性質(zhì)及其深度脫水性能的影響研究

何足道1,王電站1,顏 成1,2,方 迪1,鄭冠宇1,張衛(wèi)華3,周立祥1*

(1.南京農(nóng)業(yè)大學(xué)資源與環(huán)境科學(xué)學(xué)院,江蘇 南京 210095；2.南京貝克特環(huán)?？萍加邢薰?江蘇 南京 211505；3.北京中科國通環(huán)保工程技術(shù)股份有限公司,北京 100081)

分別用生物瀝浸法(BC)、Fenton法和石灰/三氯化鐵/PAM法(石灰法)對同一批城市污泥進(jìn)行調(diào)理,并以常規(guī)PAM法(CC)為對照,探究不同調(diào)理后污泥的理化性質(zhì)及其脫水性能的變化差異,并用流式細(xì)胞儀測定污泥中細(xì)胞裂解情況,以分析其機(jī)理.結(jié)果表明,BC法、Fenton法和石灰法均能大幅提高城市污泥脫水性能,表現(xiàn)在污泥過濾比阻(SRF)值僅為常規(guī)處理的0.43%~6.12%,尤其以石灰法處理脫水性能最佳.但BC法脫水泥餅中的有機(jī)質(zhì)和養(yǎng)分能得到最大程度的保留,有機(jī)質(zhì)(56.9%)、總氮(4.66%)、速效氮(0.47%)、礦化氮(1.80%)和總磷(1.60%)含量均遠(yuǎn)高于石灰法處理,而且污泥中重金屬能被部分去除(Cr、Mn、Ni、Zn溶出率分別為18.7%、50.0%、48.7%和72.9%),該處理的污泥最具資源化潛力.而石灰法脫水泥餅由于大量脫水劑添加導(dǎo)致有機(jī)質(zhì)(49.5%)、總氮(3.55%)和總磷(1.20%)含量明顯下降,且泥餅呈強(qiáng)堿性(pH值接近11).脫水濾液中的sCOD(645mg/L)和TP(4.62mg/L)也顯著高于其他處理.流式細(xì)胞儀測定結(jié)果顯示,BC法、Fenton法和石灰法均能導(dǎo)致污泥微生物凋亡,活細(xì)胞數(shù)量由原始的86%降至75%左右,特別是石灰法對污泥中細(xì)胞的破解效果最為徹底,從而釋放出更多內(nèi)部水和胞內(nèi)物質(zhì),這可能是引起其有機(jī)質(zhì)和養(yǎng)分大量損失至脫水濾液中的原因之一.與Fenton法和石灰法調(diào)理相比,生物瀝浸法既具有能大幅提高污泥脫水性能,脫水濾液水質(zhì)相對較好的優(yōu)點(diǎn),又具有泥餅有機(jī)質(zhì)和氮磷養(yǎng)分高,重金屬含量低的優(yōu)點(diǎn).

污泥；調(diào)理；脫水性能；生物瀝浸；化學(xué)調(diào)理劑；理化性質(zhì)

常規(guī)脫水污泥含水率(80%~85%)高,后續(xù)處置或資源化(如填埋、焚燒、高溫堆肥等)難度大,因此,污泥深度脫水成為最緊迫的任務(wù)和行業(yè)共識[1].化學(xué)法和生物法調(diào)理均能顯著提高污泥機(jī)械脫水性能,將脫水泥餅含水率降低至60%以下:前者以石灰/三氯化鐵/PAM調(diào)理(以下簡稱石灰法)和Fenton調(diào)理為代表,而后者則以生物瀝浸為代表[2-3].其中,石灰法是現(xiàn)階段國內(nèi)應(yīng)用最多的污泥深度脫水調(diào)理工藝[4],但研究發(fā)現(xiàn)石灰的大量添加會(huì)大幅降低泥餅有機(jī)質(zhì)和熱值而提高pH值,若采用高溫堆肥進(jìn)行資源化處置時(shí)會(huì)因氨氣大量揮發(fā)而引發(fā)惡臭和氮素?fù)p失[5].Fenton法在污水處理方面應(yīng)用較多,也有大量關(guān)于其用于污泥深度脫水調(diào)理的理論研究,但其工程化應(yīng)用起步較晚[6, 7].而生物瀝浸法經(jīng)過多年系統(tǒng)研究[3],其反應(yīng)溫度、反應(yīng)時(shí)間等參數(shù)對城市污泥調(diào)理效果的影響已基本了解.該工藝目前已在北至哈爾濱、南至汕頭的全國各地十余個(gè)大中型污水處理廠投產(chǎn)運(yùn)行,日處理污泥量超過3300t,脫水泥餅含水率低(<60%)、有機(jī)質(zhì)和熱值高、養(yǎng)分損失少,便于后續(xù)資源化處置.

目前,對于上述污泥深度脫水調(diào)理工藝的研究重點(diǎn)多在污泥脫水性能提升效果上[8],缺乏對其脫水濾液、特別是泥餅性質(zhì)的系統(tǒng)研究,導(dǎo)致后續(xù)考慮泥餅資源化處置時(shí)缺少理論依據(jù);與此同時(shí),采用同一批污泥比較不同調(diào)理方法的效果及其差異,包括產(chǎn)生其差異的機(jī)理的報(bào)道較少.為此,本實(shí)驗(yàn)采用污泥深度脫水中最為常見的生物瀝浸法、Fenton法和石灰法對同一批濃縮污泥進(jìn)行調(diào)理,并以常規(guī)調(diào)理(即用PAM調(diào)理)污泥作為對照,比較不同調(diào)理污泥脫水性能、脫水泥餅及濾液性質(zhì)的差異;同時(shí)采用細(xì)胞染色-流式細(xì)胞儀方法對調(diào)理前后污泥中細(xì)胞裂解情況進(jìn)行測定,更好地解釋污泥調(diào)理前后性質(zhì)變化的原因或機(jī)理.該方法能夠快速、準(zhǔn)確地分析成分復(fù)雜樣品中的細(xì)胞活性,已廣泛應(yīng)用于污水污泥體系[9-10].

1 材料與方法

1.1 供試污泥基本性質(zhì)

表1 供試污泥基本理化性質(zhì)Table 1 Preliminary physical-chemical properties of the selected sewage sludge

供試污泥取自江蘇無錫蘆村污水處理廠濃縮池.該廠采用A2O二級處理工藝,承擔(dān)無錫主城區(qū)大部分生活污水處理任務(wù).其中,1、2、3期污水日處理規(guī)模為25萬t,該部分污泥采用生物瀝浸法進(jìn)行深度脫水,每天產(chǎn)生污泥餅約90t.4期污水日處理量為15萬t,污泥采用石灰法化學(xué)調(diào)理后深度脫水,每天產(chǎn)生污泥餅70t[3,5].供試污泥基本性質(zhì)見表1.

1.2 污泥調(diào)理方法

不同調(diào)理方法的工藝參數(shù)均參考無錫蘆村污水處理廠生產(chǎn)實(shí)際,并根據(jù)實(shí)驗(yàn)室實(shí)際情況微調(diào)添加比例,具體如下:

生物瀝浸法調(diào)理:利用本課題組從污泥中分離的嗜酸性氧化亞鐵硫桿菌LX5,按照文獻(xiàn)方法[11]擴(kuò)培并制得生物瀝浸酸化污泥.將酸化污泥:新鮮污泥按照體積比1:1充分混勻,按新鮮污泥干物質(zhì)量20%添加微生物營養(yǎng)劑(含N、P、K、Ca、Fe、S等成分,詳見專利ZL201010221264[12]),振蕩反應(yīng)(28℃,180r/min,下同)24h.反應(yīng)完成的污泥立即測定毛細(xì)吸水時(shí)間(CST)、比阻等指標(biāo),抽濾得到的脫水濾液置于4℃冰箱保存并于24h內(nèi)測定pH值、水溶性有機(jī)碳(WSOC)、總氮(TN)、總磷(TP)等指標(biāo),脫水泥餅冷凍干燥后磨細(xì)過100目篩,用于測定有機(jī)質(zhì)、TN、TP、速效氮(WSN)等指標(biāo),共設(shè)3個(gè)重復(fù).

Fenton法調(diào)理:取一定量新鮮污泥,分別按干物質(zhì)量20%和10%添加FeSO4·7H2O和30% H2O2,充分混勻后振蕩反應(yīng)30min,其余步驟同生物瀝浸法.

石灰法:取一定量新鮮污泥,先按干物質(zhì)量8%加入FeCl3·6H2O并振蕩反應(yīng)20min,再按干物質(zhì)量30%加入石灰并振蕩反應(yīng)20min,最后加入陽離子型聚丙烯酰胺CPAM(使其在污泥中濃度為100mg/L)并振蕩反應(yīng)2min,其余操作同生物瀝浸法.

常規(guī)調(diào)理(CC):取一定量新鮮污泥,加入一定量CPAM(使其在污泥中濃度為150mg/L),先在270r/ min轉(zhuǎn)速下振蕩1min,再在30r/min轉(zhuǎn)速下振蕩9min,其余操作同生物瀝浸法.

1.3 分析方法

污泥pH值采用pH計(jì)(pHS-3C,上海雷磁)測定,比阻SRF采用布氏漏斗-真空抽濾法測定, CST采用CST分析儀(Model 304M,Triton)測定, WSOC)采用TOC儀(TOC-L,Shimadzu)測定,脫水濾液性質(zhì)的測定參考《水和廢水監(jiān)測分析方法》(第四版)[13].脫水泥餅性質(zhì)測定參考《土壤農(nóng)化分析》(第三版)[14]進(jìn)行測定.

細(xì)胞裂解情況測定方法:細(xì)胞膜中的磷脂酰絲氨酸會(huì)在細(xì)胞裂解早期翻轉(zhuǎn)到細(xì)胞膜外,使用Annexin V能夠與其高親和力特異結(jié)合,并在藍(lán)色光激發(fā)下發(fā)出綠色熒光,從而檢測出裂解早期細(xì)胞.碘化丙啶(Propidium iodide,PI)則可以穿透破損的細(xì)胞膜并將細(xì)胞核染紅.基于以上原理,可用Annexin V-FITC/PI對細(xì)胞膜進(jìn)行染色,利用流式細(xì)胞儀測定不同染色情況的細(xì)胞數(shù)量,從而判斷細(xì)胞活性[15].

污泥中細(xì)胞裂解情況根據(jù)參考文獻(xiàn)[16]和試劑盒說明書進(jìn)行測定,步驟如下:稀釋:取適量反應(yīng)完畢的污泥,用超純水稀釋一定倍數(shù),得到細(xì)胞密度為105~106個(gè)/mL;洗滌:吸取一定量稀釋液,分別用冷的磷酸緩沖鹽溶液和上樣緩沖液洗滌,離心棄上清;染色:用1mL上述緩沖液重懸細(xì)胞,分別用Annexin V- FITC和PI進(jìn)行染色,并于1h內(nèi)用流式細(xì)胞儀檢測.

2 結(jié)果與討論

2.1 不同調(diào)理對污泥脫水性能的影響

表2 不同方法調(diào)理后的污泥的SRF和CST Table 2 SRF and CST of sludge conditioned by different methods

SRF、CST是表征污泥脫水性能最常見的兩大指標(biāo)[8,17],由表2可知,CC法僅使SRF和CST較原始污泥分別降低了14.2%和36.1%,在少量程度上提高了其脫水性能,而生物瀝浸法、Fenton法和石灰法卻均能大幅度提升污泥的脫水性.如生物瀝浸法調(diào)理污泥SRF和CST相比調(diào)理前分別降低了95.3%和77.6%,其原因包括生物瀝浸微生物的替代效應(yīng)、生物酸化效應(yīng)和污泥中Fe3+的絮凝作用[3].Fenton法對脫水性能的改善效果與生物瀝浸法相當(dāng),其SRF和CST分別降低了97.9%和87.3%,其原因主要是Fenton反應(yīng)產(chǎn)生的具有強(qiáng)氧化性的·OH能夠有效破解污泥中的EPS和細(xì)胞,同時(shí)改變污泥絮體的表面結(jié)構(gòu)和凝膠狀態(tài)[18-19].而石灰法對污泥脫水性能提升效果最佳,其調(diào)理后污泥的SRF和CST分別下降了99.7%和81.7%,其原因包括:Fe3+水解產(chǎn)生H+能夠酸溶部分EPS,同時(shí)生成的氫氧化鐵絮體能夠包括細(xì)小絮體成團(tuán);石灰的添加顯著提高了體系的pH值,致使大量不耐受強(qiáng)堿環(huán)境的微生物死亡并釋放細(xì)胞內(nèi)的水分,并在顆粒表面形成具有一定剛性的多孔網(wǎng)格狀骨架,在高壓下仍能保持透水通道;最后添加的PAM能夠捕集游離的細(xì)小顆粒并絮凝沉淀,減少細(xì)小顆粒對透水通道的堵塞[20-21].盡管生物瀝浸法,Fenton法和石灰法調(diào)理后污泥脫水性能提高幅度有一定差異,但基本上在相同數(shù)量級上.

2.2 不同調(diào)理對脫水泥餅性質(zhì)的影響

為了解不同調(diào)理工藝產(chǎn)生的脫水泥餅資源化處置的潛質(zhì),對各脫水泥餅的相關(guān)性質(zhì)進(jìn)行了測定,結(jié)果如表3所示.

表3 不同方法調(diào)理后的脫水泥餅的理化性質(zhì) Table 3 Physicochemical properties of dewatered sludge after conditioning by different methods

豐富的有機(jī)質(zhì)和氮磷養(yǎng)分是污泥被視為潛在有機(jī)肥資源的重要原因[22].實(shí)驗(yàn)結(jié)果表明,CC,生物瀝浸法,Fenton法脫水泥餅中有機(jī)質(zhì)、TN和TP含量基本接近,其范圍分別為57.0%~58.6%、42.5~ 46.6mg/g和14.2~16.0mg/g.其中生物瀝浸法脫水泥餅有機(jī)質(zhì)、TN和TP分別達(dá)到了石灰法泥餅的1.15, 1.31和1.33倍.

WSOC和WSN反映了泥餅中能夠被微生物直接利用的有機(jī)質(zhì)和N素的含量[23],而礦化氮?jiǎng)t表征了泥餅的持續(xù)供氮能力[24],以上三者決定了污泥作為原料堆肥啟動(dòng)所需時(shí)間和維持高溫期的能力[5],繼而影響堆肥效率和產(chǎn)品品質(zhì).結(jié)果顯示,CC脫水泥餅中WSOC含量顯著高于其余3種深度脫水泥餅.生物瀝浸法脫水泥餅中WSN和礦化氮含量分別為石灰法的2.96和2.42倍.其他處理的WSN和礦化氮含量也都明顯高于石灰法.由此可以看出,生物瀝浸法脫水泥餅更適于作為堆肥的原料,其堆肥效率和潛在肥力均高于其他處理.

污泥中除含有豐富的有機(jī)質(zhì)和養(yǎng)分外,還含有重金屬等污染物,這些污染物會(huì)在污泥填埋或土地利用時(shí)進(jìn)入環(huán)境,造成二次污染.本實(shí)驗(yàn)中,生物瀝浸法對于Mn、Ni和Zn的浸出效果最好(表4),溶出率分別為50.0%、48.7%和72.9%,而Cr的溶出率則為18.7%.值得一提的是,本實(shí)驗(yàn)以促進(jìn)污泥脫水為目的,反應(yīng)時(shí)間較短,調(diào)理后污泥pH值仍在3.5以上,因此浸出率低于本課題組以往的研究結(jié)果(80%~90%)[25];而對于Cr來說,生物瀝浸法脫水泥餅中的含量是對照的81.3%,這是因?yàn)镃r的浸出需要極低的pH值(<2[26]),而本實(shí)驗(yàn)中生物瀝浸完成時(shí)污泥混合液的pH值仍達(dá)3.74,遠(yuǎn)高于Cr大量浸出的閾值. Fenton法對污泥重金屬浸出的原理與生物瀝浸類似,主要依靠Fe3+的氧化和酸化效應(yīng),但反應(yīng)時(shí)間更短,終點(diǎn)的pH值更高,因此其效果要略差于生物瀝浸法.石灰法對Mn、Ni和Zn的浸出效果明顯遜于上述3種處理,溶出率分別僅為26.6%、19.3%和31.5%,原因是高pH值體系(12.43)不利于重金屬溶出,其相對濃度降低僅是因?yàn)榇罅空{(diào)理劑添加導(dǎo)致的稀釋效應(yīng).CC脫水污泥中的4種重金屬含量均為最高,原因是PAM添加僅起到了一定絮凝作用,對于污泥其他理化性質(zhì)的改變極為有限.在后續(xù)資源化處置的過程中,需要著重注意CC和Fenton法脫水污泥中重金屬的去除和穩(wěn)定.

表4 不同方法調(diào)理后的脫水泥餅pH值和重金屬含量 Table 4 pH and the content of heavy metals in dewatered sludge conditioned by different methods

對脫水泥餅的pH值測定結(jié)果顯示,CC脫水泥餅pH值相比調(diào)理前基本沒有變化;生物瀝浸法和Fenton法脫水泥餅pH值均有大幅下降至5以下.相反的,石灰法脫水污泥則大幅升高至10.84.雖然以上3種深度脫水泥餅pH值均不在適宜微生物繁殖的范圍內(nèi)(一般為6~8.5[27]),但用于堆肥時(shí)可通過添加輔料使其混合物料的pH值趨于中性,且最終堆肥產(chǎn)品的pH值也能達(dá)到中性或弱堿性的合理范圍[5].

2.3 不同調(diào)理對脫水濾液性質(zhì)的影響

不同調(diào)理污泥脫水濾液中的sCOD、TN、NH4+-N、TP測定結(jié)果如表5所示.生物瀝浸法脫水濾液中sCOD和TP最低,分別為CC脫水濾液的90.0%和23.1%,而TN、NH4+-N則達(dá)到了CC脫水濾液的2.58,4.72倍.生物瀝浸微生物對污泥中異養(yǎng)菌具有替代效應(yīng),且其EPS分泌量僅為后者的十分之一[28-29],表現(xiàn)為生物瀝浸法濾液sCOD含量比石灰法脫水濾液更低.而TP降低的原因則歸結(jié)于生物瀝浸過程中微生物對P的利用和液相中大量的Fe3+和磷酸鹽形成沉淀而進(jìn)入到污泥固相中[30].生物瀝浸過程中異養(yǎng)菌的死亡裂解會(huì)釋放蛋白質(zhì)、多糖、DNA等含N有機(jī)物,并部分溶解在液相中,同時(shí)微生物的氨化作用也會(huì)導(dǎo)致濾液中NH4+-N的增加,故而其脫水濾液中的TN和NH4+-N均高于石灰法脫水濾液[31].

表5 不同方法調(diào)理后污泥脫水濾液中sCOD、TN、TP和NH4+-N含量 Table 5 sCOD, total nitrogen, total phosphorus, and NH4+-N of the filtrates from different conditioned sludge through vacuum filtration

Fenton法脫水濾液的TP含量是CC脫水濾液的28.4%,而其sCOD、TN、NH4+-N分別是CC脫水濾液的1.34,1.28,2.26倍.Fenton反應(yīng)產(chǎn)生的HO·能夠有效降解污泥中的大分子有機(jī)物,并將污泥顆粒表面緊密結(jié)合的EPS(TB-EPS)破解為松散結(jié)合的EPS(LB-EPS)和溶解態(tài)的EPS(Slime-EPS),提高了污泥液相中的小分子有機(jī)物種類和濃度[32-33];與此同時(shí),部分污泥微生物也被氧化裂解,釋放出大量含N有機(jī)物,因此其脫水濾液中的sCOD、TN和NH4+-N均高于CC脫水濾液.

值得注意的是,石灰法脫水濾液中sCOD、TN、NH4+-N、TP均高于CC脫水濾液.其中sCOD顯著高于其他處理,為CC脫水濾液的2.14倍,其原因包括:污泥的堿溶效應(yīng);不耐受細(xì)胞死亡釋放出胞內(nèi)物質(zhì);石灰和PAM共同作用破壞了EPS的結(jié)構(gòu),使包裹在EPS內(nèi)的溶解性有機(jī)物(如蛋白質(zhì)、多糖等)釋放到液相中[19-20].后兩者也是造成TN、NH4+-N濃度高于CC濾液的原因.其TP含量亦為所有處理中最高,達(dá)到了4.62mg/L,說明在脫水的過程中會(huì)損失較多的磷元素,導(dǎo)致泥餅中養(yǎng)分減少的同時(shí)也增加了其濾液二次處理的成本.

值得指出的是,雖然石灰法處理對污泥中細(xì)胞的破解效果最為徹底,從而釋放出更多內(nèi)部水和胞內(nèi)物質(zhì)),但脫水濾液中NH4+-N和TN濃度卻明顯低于破解程度相對較低的生物瀝浸法處理.分析其原因在于石灰法處理污泥呈強(qiáng)堿性,pH值極高(10.84),而生物瀝浸法處理污泥呈酸性,pH值最低(4.72),前者有機(jī)物氨化和后續(xù)氨揮發(fā)特別明顯,造成N的損失所致.事實(shí)上,無論是在實(shí)驗(yàn)室還是工程現(xiàn)場,石灰法處理壓濾水周圍空氣中彌漫著濃烈氨味.

2.4 不同調(diào)理對污泥中細(xì)胞裂解的影響

前文討論中提到污泥中的微生物細(xì)胞在調(diào)理過程中會(huì)因不同原因發(fā)生裂解并釋放胞內(nèi)物質(zhì),是導(dǎo)致污泥性質(zhì)發(fā)生變化的重要原因.為此,本研究采用熒光染色-流式細(xì)胞儀檢測的方法對調(diào)理前后污泥中細(xì)胞裂解情況進(jìn)行了分析(圖1).

CC污泥中活細(xì)胞數(shù)量僅下降了0.19個(gè)百分點(diǎn).與之相比,生物瀝浸法,Fenton法和石灰法調(diào)理后污泥中活細(xì)胞數(shù)量明顯下降.其中,生物瀝浸法和Fenton法結(jié)果較為相似,污泥中裂解晚期細(xì)胞和死細(xì)胞總和所占的比例分別增加至原始污泥的1.92和1.95倍.強(qiáng)酸環(huán)境是引起細(xì)胞膜結(jié)構(gòu)破壞的主要原因[34-35],而由此引發(fā)的胞內(nèi)蛋白質(zhì)釋放-水解作用可能是生物瀝浸法、Fenton法脫水濾液中TN和NH4+-N含量較高的原因.對污泥細(xì)胞殺滅效果最強(qiáng)的為石灰法處理,調(diào)理后污泥中裂解晚期細(xì)胞和死細(xì)胞總數(shù)為原始污泥的2.19倍,特別是死細(xì)胞所占比例達(dá)到了16.3%,為原始污泥的3.24倍,說明相比其他處理,石灰法能夠更徹底地破解細(xì)胞,因而能促使更多內(nèi)部水的釋放,更有利于污泥脫水.

3 結(jié)論

3.1 生物瀝浸法,Fenton法和石灰法均能大幅提高城市污泥脫水性能, 表現(xiàn)在污泥過濾比阻(SRF)SRF值僅為常規(guī)處理的0.43%~6.12% ,尤其以石灰法處理脫水性能最佳.

3.2 生物瀝浸法脫水泥餅中的有機(jī)質(zhì)和養(yǎng)分能得到最大程度的保留,有機(jī)質(zhì)(56.9%)、TN(4.66%)、WSN(0.47%)、礦化N(1.80%)和TP(1.60%)均遠(yuǎn)高于石灰法處理,且污泥中重金屬能被部分去除(Cr、Mn、Ni、Zn溶出率分別18.7%、50.0%、48.7%和72.9%),該處理的污泥最具資源化潛力.而石灰法脫水泥餅由于大量脫水劑添加導(dǎo)致有機(jī)質(zhì)、TP和TP含量明顯下降,且泥餅呈強(qiáng)堿性(pH值接近11).且石灰法濾液中sCOD(645mg/L)和TP(4.62mg/L)也顯著高于其他處理.

3.3 生物瀝浸法,Fenton法和石灰法均能導(dǎo)致污泥微生物裂解,活細(xì)胞數(shù)量由原始的86%降至75%左右,特別是石灰法對污泥中細(xì)胞的破解效果最為徹底,從而釋放出更多內(nèi)部水和胞內(nèi)物質(zhì),這可能是引起其有機(jī)質(zhì)和養(yǎng)分大量損失到脫水濾液中的原因之一.

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Effects of bioleaching and chemical conditioning on sludge dewaterability and physicochemical properties.

HE Zu-dao1, WANG Dian-zhan1, YAN Cheng1,2, FANG Di1, ZHENG Guan-yu1, ZHANG Wei-hua3, ZHOU Li-xiang1*

(1.College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China；2.Nanjing BACT Environmental Solutions Co. Ltd, Nanjing 211505, China；3.Beijing Genetre Treatment Co., Ltd, Beijing 100081, China)., 2019,39(3)：1019~1025

Three widely used conditioning methods, including bioleaching (BC), Fenton oxidation (FC), and chemical addition of lime/FeCl3/PAM (LC), were investigated to determine their effects on sludge dewaterability and physicochemical properties. The results showed that the BC, FC, and LC conditioning methods significantly improved sludge dewatering performance, as exhibiting that specific resistance to filtration (SRF) of already-conditioned sludge by BC, FC and LC only were 0.43%~6.12% of that by conventional PAM addition treatment (CC). Furthermore, compared to chemical treatments (FC and LC), relatively high quantities of plant nutrients (56.9% of organic matter, 4.66% of total nitrogen, 0.47% of water soluble nitrogen, 1.80% of mineralized nitrogen, and 1.60% of total phosphorus) were retained in the dewatered sludge of bioleaching treatment. Meanwhile, after bioleaching treatment, 18.7% of Cr, 50.0% of Mn, 48.7% of Ni and 72.9% of Zn were removed from sludge, respectively. Flow cytometry was further used to examine the variation of sludge cell apoptosis before and after the three conditioning methods. It was found that dosing chemical conditioners (FC and LC) lead to the obvious lysis of the sludge cells and accordingly a large amount of internal water and intracellular substances within the sludge flocs were released, which may be responsible for their increased plant nutrients release and improved sludge dewaterability. The results suggested that bioleaching treatment exhibited excellent performance in improving sludge dewatering and heavy metal removal and maintaining sludge nutrients, therefore it’s promising conditioning approach for sludge disposal.

sewage sludge；conditioning；dewaterability；bioleaching；chemical conditioners；physicochemical properties

X703

A

1000-6923(2019)03-1019-07

何足道(1992-),男,浙江溫州人,南京農(nóng)業(yè)大學(xué)碩士研究生,主要從事固體廢物資源化利用.

2018-08-02

國家自然科學(xué)基金資助項(xiàng)目(21477055,21677077,21637003)

* 責(zé)任作者, 教授, lxzhou@njau.edu.cn