Effects of Potassium Ferrate and Low-Temperature Thermal Hydrolysis Co-Pretreatment on the Hydrolysis and Anaerobic Digestion Process of Waste Activated Sludge

This study evaluated the effect of potassium ferrate(PF)and low-temperature thermal hydrolysis co-pretreatment on the promotion of sludge hydrolysis process and the impact on acid production in the subsequent anaerobic digestion process.The analytical investigations showed that co-pretreatment significantly facilitated the hydrolysis process of the sludge and contributed to the accumulation of short-chain fatty acids(SCFAs).The pretreatment conditions under the optimal leaching of organic matter from sludge were hydrothermal temperature of 75℃,hydrothermal treatment time of 12 h,and PF dosage of 0.25 g g^(−1)TSS(total suspended solids),according to the results of orthogonal experiments.By pretreatment under proper conditions,the removal rate of soluble chemical oxygen demand(SCOD)achieved 71.8%at the end of fermentation and the removal rate of total phosphorus(TP)was 69.1%.The maximum yield of SCFAs was 750.3 mg L^(−1),7.45 times greater than that of the blank group.Based on the analysis of the anaerobic digestion mechanism,it was indicated that the co-pretreatment could destroy the floc structure on the sludge surface and improve organic matter dissolving,resulting in more soluble organic substances for the acidification process.Furthermore,microbial community research revealed that the main cause of enhanced SCFAs generation was an increase in acidogenic bacteria and a reduction of methanogenic bacteria.

Preliminary Study on the Treatment Efficiency of Pasteurized Lime Thermal Alkaline Hydrolysis for Excess Activated Sludge and Reduction of Tetracycline Resistance Genes

Thermal alkaline hydrolysis is a common pretreatment method for the utilization of excess activated sludge(EAS).Owing to strict environment laws and need for better energy utilization,new methods were developed in this study to improve the efficiency of pretreatment method.Direct thermal hydrolysis(TH),pasteurized thermal hydrolysis(PTH),and alkaline pasteurized thermal hydrolysis(PTH+CaO and PTH+NaOH)methods were used to treat EAS.Each method was compared and analyzed in terms of dissolution in ammonium nitrogen(NH_(4)^(+)-N)and soluble COD(SCOD)in EAS.Furthermore,the removal of tetracycline resistance genes(TRGs)and class 1 transposon gene intI1 from EAS was investigated.The NH_(4)^(+)-N and SCOD concentrations in EAS treated by PTH were 1.24 and 2.58 times higher than those of TH.However,the removal efficiency of total TRGs and intI1 between the groups was comparable.The SCOD concentration of the PTH+NaOH group was 4.37 times higher than that of the PTH group,and the removal efficiency of total TRGs was increased by 9.52%compared with that by PTH.The NH_(4)^(+)-N and SCOD concentrations of the PTH+CaO group could reach 85.04%and 92.14%of the PTH+NaOH group,but the removal efficiency of total TRGs by PTH+CaO was 19.78%lower than that by PTH+NaOH.Thus,to reduce the financial cost in actual operation,lime(CaO)can be used instead of a strong alkali(NaOH),and pasteurized steam at 70℃ instead of conventional high-temperature heating to treat EAS.This study provides a reference for the development of alkaline hydrolysis under moderate temperatures along with the removal of TRGs in EAS.

Kinetic analysis of waste activated sludge hydrolysis and short-chain fatty acids production at pH 10

The accumulation of short-chain fatty acids （SCFAs）, a preferred carbon source for enhanced biological phosphorus removal microbes, was significantly improved when waste activated sludge （WAS） was fermented at pH 10. The kinetics of WAS hydrolysis and SCFAs production at pH 10 was investigated. It was observed that during WAS anaerobic fermentation the accumulation of SCFAs was limited by the hydrolysis process, and both the hydrolysis of WAS particulate COD and the accumulation of SCFAs followed first-order kinetics. The hydrolysis and SCFAs accumulation rate constants increased with increasing temperature from 10 to 35℃, which could be described by the Arrhenius equation. The kinetic data further indicated that SCFAs production at pH 10 was a biological process. Compared with the experiment of pH uncontrolled （blank test）, both the rate constants of WAS hydrolysis and SCFAs accumulation at 20℃ were improved significantly when WAS was fermented at pH 10.

Hydrolysis and acidification of activated sludge from a petroleum refinery

The cost-effective treatment of activated sludge that is generated by refining petroleum is a challenging industrial problem.In this study, semi-continuous stirred tank reactors(CSTRs) containing petroleum refinery excess activated sludge(PREAS)were used to comparatively investigate hydrolysis and acidification rates, after the addition of heneicosane(C_(21)H_(44))(R1)and 1-phenylnaphthalene(C16 H12)(R2) to different and individual reactors. Operation of the reactors using a sludge retention time(SRT) of 6 days and a pH of 5.0, resulted in the maintenance of stable biological activity as determined by soluble chemical oxygen demand(SCOD), volatile fatty acids(VFAs) production and oil removal efficiency. The optimum conditions for hydrogen production include a SRT of 8 days, at pH 6.5. Under these conditions, hydrogen production rates in the control containing only PREAS were 1567 mL/L(R0), compared with 1365 mL/L in Rl and 1454 mL/L-PREAS in R2.Coprothermobacter, Fervidobacterium, Caldisericum and Tepidiphilus were the dominant bacterial genera that have the potential to degrade petroleum compounds and generate VFAs. This study has shown that high concentrations of heneicosane and 1-phenylnaphthalene did not inhibit the hydrolytic acidification of PREAS.

Extraction of Amino Acids from Excess Activated Sludge by Enzymatic Hydrolysis

A study was undertaken to investigate the production of amino acids from excess activated sludge (EAS) by enzymatic hydrolysis. Firstly, the protein was extracted from EAS. Secondly, the protein solution was further hydrolyzed under free enzyme or immobilized enzyme. The reversed phase high performance liquid chromatography (RP-HPLC) and inductively coupled plasma emission spectrometer (ICP) were applied to determine the contents of amino acids and heavy metals, respectively. The effects of enzyme/substrate(E/S), pH, temperature, and reaction time were investigated in detail. The results indicated that, the optimum conditions for protein hydrolysis were temperature 55℃, pH 10, E/S 9 g/L, and reaction time 8 h, and the highest yield of amino acids was more than 10 g/100 g dry sludge (DS) under free enzyme. Moreover, the security and nutrition were taken into consideration. There were seven kinds of essential amino acids and ten non-essential amino acids in the raw amino acid (RAA) solution, and the contents of heavy metals were lower, living up to Hygienical standard for feeds (China). This technology widens the source of amino acids and makes the extraction of amino acids from EAS more economic and effective.

Enhanced Biohydrogen Production by Accelerating the Hydrolysis of Macromolecular Components of Waste Activated Sludge Using TiO₂Photocatalysis as a Pretreatment

The effects of TiO2 photocatalysis on the hydrolysis of protein of waste activated sludge (WAS) and its biodegradability were investigated in this study. After 12-h UV irradiation, the removal ratio of protein by TiO2 photocatalysis reached 98.1%. The optimal condition for photocatalytic degradation of protein is TiO2 dosage of 5.0 mg·L–1 under 2.4 w·m–2 UV light irradiation. TiO2 photocatalysis in comparison with other pretreatments obviously accelerated the hydrolysis of WAS and improved the conversion of total COD (tCOD) to soluble COD (sCOD). The sCOD/tCOD ratio of WAS pretreated by TiO2 photocatalysis, UV photolysis and TiO2 adsorption and that of the control were 92.8%, 32.5%, 18.0% and 16.6%, respectively. TiO2 photocatalytic pretreatment accelerated the biohydrogen production from 10-fold diluted WAS. The bioreactors containing UV photolysis and TiO2 adsorption pretreated WASs and the control reactor require 0.5-d, 0.9-d and 0.7-d start-up period for biohydrogen production, respectively. While the bioreactor containing TiO2 photocatalysis pretreated WAS obtained a hydrogen yield of 0.5 mL-H2/g-VS merely after 0.5-d mesophilic fermentation. The cumulative biohydrogen production from TiO2 photocatalysis pretreated WAS during 4-d mesophilic fermentation reached 11.7 mL-H2/g-VS, which was 1.2 times higher than that from the control. TiO2 photocatalytic pretreatment enhanced the biohydrogen production from WAS via accelerating the hydrolysis of its macromolecular components to smaller molecule weight hydrolysates.

Evaluation of activated sludge properties’changes in industrial-wastewater pre-treatment:role of residual aluminum hydrolyzed species with different polymerization degree

With the widespread introduction of pre-coagulation prior to the biological unit in various industrial wastewater treatments,it is noteworthy that long-term accumulation of residual coagulants has certains effect on both micro and macro characteristics of activated sludge(AS).In this study,the morphology distributions of residual aluminum salts(RAS)and their effects on the removal efficiency of AS were investigated under different PAC concentrations.The results showed that the dominance of medium polymeric RAS,formed under an appropriate PAC dose of 20 mg/L enhanced the hydrophobicity,flocculation,and sedimentation performances of AS,as well as the enzymatic activity in cells in the sludge system,improving the main pollutants removal efficiency of the treatment system.Comparatively the species composition with monomer and dimer/high polymer RAS as the overwhelming parts under an over-dosed PAC concentration of 55 mg/L resulted in excessive secretion of EPS with loose flocs structure and conspicuous inhibition of cellular activity,leading to the deterioration of physico-chemical and biological properties of AS.Based on these findings,this study can shed light on the role of the RAS hydrolyzed species distributions,closely relevant to Al dosage,in affecting the comprehensive properties of AS and provide a theoretical reference for coagulants dosage precise control in the pretreatment of industrial wastewater.

污泥热碱液对干旱胁迫下小青菜生长的缓解机制

近年来,为实现城市生活污泥的资源化利用,通过碱热水解技术制成的污泥热碱液被广泛关注。干旱是自然界中主要非生物胁迫之一,严重限制了作物的生长发育。为了改善干旱胁迫对蔬菜作物的影响,同时实现污泥资源化利用,本研究以小青菜(Brassica chinensis)为材料,通过盆栽试验设置4个水分梯度模拟不同干旱程度,在不同干旱程度下分别冲施等氮量的热碱液和尿素溶液,探讨热碱液对叶菜抵抗干旱胁迫的作用机制。结果表明:干旱胁迫下,经热碱液处理后,小青菜根长密度、根表面积密度和根体积密度均显著增加,进而促进对水分和氮素营养的吸收,提高叶片相对含水量,维持光合作用;冗余分析表明热碱液的施用主要提高过氧化氢酶活性和叶片相对含水量降低干旱胁迫对小青菜生长的负面影响。综上所述,将污泥热碱液应用到蔬菜生产中可缓解干旱胁迫对叶菜造成的生长抑制,为干旱地区蔬菜生产提供了策略,也为有效无害化、资源化利用城市生活污泥提供了一种新途径。

预处理促进有机固体废弃物厌氧发酵生产挥发性脂肪酸

有机固体废弃物发酵生产挥发性脂肪酸是一种具有应用价值的资源化方式。该研究利用典型的有机固体废弃物,剩余污泥、餐厨垃圾和白酒酒糟生产挥发性脂肪酸,针对厌氧产酸效率和速率低这一限制因素,采用预处理方法实现挥发性脂肪酸的大量积累。结果表明,剩余污泥经过80℃处理后总挥发性脂肪酸浓度达到1.41 g/L,以乙酸为主;餐厨垃圾经过80℃处理后总挥发性脂肪酸浓度达到7.24 g/L,餐厨垃圾产酸的种类与剩余污泥不同,正丁酸、丙酸占比更高。餐厨垃圾与剩余污泥体积比为1∶2混合发酵时,总挥发性脂肪酸浓度为3 g/L,80℃处理后发酵产酸浓度约为18 g/L,比未经过处理的总量提高了6倍,且挥发性脂肪酸种类更加丰富,异丁酸、戊酸、异戊酸均有产生。餐厨垃圾与白酒酒糟1∶5比例混合在底物固体浓度20%时总挥发性脂肪酸浓度约为46.8 g/L。研究结果可为进一步探究有机固体废弃物资源化提供借鉴。

三氯乙烯对厌氧水解酸化菌的抑制作用及去除特性

三氯乙烯(TCE)是石化废水中典型的有机污染物,对微生物具有极强的毒性。通过对挥发性脂肪酸批次试验进行生物测定,探讨TCE对厌氧水解酸化菌的产酸抑制作用,在TCE作用下水解酸化菌的胞外聚合物(EPS)和污泥zeta电位的变化以及TCE的去除特性。结果表明:TCE浓度为75 mg/L(半抑制浓度,EC_(50))时,对水解酸化菌的产酸量有抑制作用;随着TCE浓度升高,水解酸化菌的EPS中蛋白质浓度先增大后减少,其中TCE浓度为_(50) mg/L时EPS中蛋白质浓度达到最大值,为(33.94±0.25)mg/L;zeta电位的结果显示,污泥的凝聚性能随TCE浓度增大(0~100 mg/L)而增大;厌氧水解酸化菌对TCE的脱氯能力随TCE浓度的升高而降低,水解酸化菌转化TCE的脱氯率由TCE浓度为10 mg/L时的77.83%降为200 mg/L时的6.67%。TCE对水解酸化菌具有强烈的抑制作用,TCE主要是通过抑制细胞的蛋白质合成来抑制微生物活性,进而限制水解酸化菌降解TCE的能力。

IFAS工艺处理尼龙66帘子布生产废水

针对尼龙66帘子布生产废水高COD、高氨氮、低C/N、污染因子复杂、难生物降解的特点,在生化系统的水解酸化池、缺氧池和好氧池安装弹性填料,构成固定生物膜-活性污泥耦合(IFAS)工艺对其进行处理。介绍了该工艺的主要构筑物、设备和运行效果,结果表明,IFAS生化系统微生物经驯化成功后,对废水处理效果稳定,COD、氨氮、TN、己二胺去除率分别在95%、97%、89%、99%以上,出水水质优于园区污水处理厂接管标准,达到《城市污水处理厂污染物排放标准》(GB 18918-2002)一级A标准。成本分析表明,本项目总投资1006万元,直接运行成本约4.21元/t,具有较好的经济性。IFAS工艺在对尼龙66帘子布生产废水的处理中表现出较强的耐冲击负荷能力、抗毒性及生物脱氮性能,可为类似废水的处理提供参考。

pH值对剩余污泥水解酸化溶出物的影响

在室温条件下(25℃),采用批量实验,研究了pH值在4.0～12.0变化时污泥水解酸化效率情况以及水解过程中溶出的可溶性有机物(SCOD)、挥发性有机酸(VFAs)和氮、磷的质量浓度变化.实验结果表明,污泥水解酸化效率递减顺序为碱性>酸性>中性.ρSCOD、ρVFAs、ρ(NH4+-N)和ρ(PO34--P)随时间延续而增大,并且都随pH值升高(4.0～11.0)而呈现出先减小后增大的趋势.在pH=11.0时,ρSCOD和ρVFAs值最大,分别为2 599 mg/L和749 mg/L;pH=4.0时,ρ(NH4+-N)和ρ(PO43--P)值最大,分别为208.1 mg/L和193.4 mg/L.通过调整pH值能改变污泥水解酸化效率,并且选择pH值在10.0～11.0时,可以协调水解酸化效率与后续脱氮除磷系统N、P负荷之间的关系,既为脱氮除磷系统提供SCOD和VFAs,又可以实现剩余污泥减量.

剩余污泥水解酸化过程中胞外聚合物的影响因素研究

为了解胞外聚合物(EPS)对污泥水解酸化处理的影响,采用批量试验研究了污泥厌氧水解酸化处理过程中EPS的变化以及温度、pH值、污泥来源、污泥浓度对其的影响.结果表明,pH值和污泥来源对EPS产率、成分有显著的影响.强酸性和强碱性条件下污泥水解过程中溶解性EPS产率是中性条件下的2倍多;强酸性条件下细胞破裂较多,DNA物质占总EPS含量的20%左右;强碱性条件多糖类物质溶出量占总EPS的80%以上.A/O工艺污泥水解酸化EPS产率最大,平均值为41.1mg/gVSS;其次为SBR、氧化沟(OD)和A2/O工艺污泥,其中OD工艺污泥水解酸化产生的EPS中糖类与蛋白质的质量比(φ)值远小于其他工艺污泥.温度由18℃升高至35℃时,溶解性EPS产率增加近50%,多糖所占比例逐渐增大.污泥浓度由2000mg/L升高至6000mg/L,EPS产率增大至38.1mg/gVSS,当污泥浓度达到8000mg/L时,EPS产率明显减少(23.1mg/gVSS).

水解酸化/AAO工艺的同步脱氮除磷及污泥减量研究

针对传统活性污泥法脱氮除磷效率低、污泥产量高的缺点，提出了水解酸化／缺氧-厌氧-好氧（HAAO）污水、污泥一体化处理工艺，研究了该工艺去除COD、氮、磷和污泥减量的效果及其主要影响因素。试验结果表明，在进水COD为286-425mg／L、NH4^＋ -N为36-58mg／L、PO4^3- -P为4-12mg／L、总水力停留时间为11．5h及无外加碳源和碱度的条件下，系统对COD、NH4^＋ -N、TN、PO4^3- -P的去除率分别可达95％、98％、84％、87％。好氧段的DO浓度、固体停留时间（SRT）和剩余污泥回流比对系统的运行效果有重要影响。将污水和剩余污泥同时进行水解酸化，既可有效地改善污水的可生化性，提高系统对碳源的利用效率，又可实现污泥的减量化，试验条件下系统的污泥减量率达56．5％。

剩余污泥碱解上清液作为反硝化碳源的回用量实验研究

考察剩余污泥碱解上清液作为反硝化碳源的反应速率,并据此初步确定上清液的回用量。对剩余污泥进行碱解发酵,选取SRT=9 d的上清液,采用不同的VFA/N比值进行批式试验,考察其反硝化速率,选择出试验条件下的较优比值,并应用于实际生活污水中,与单纯生活污水脱氮对照,考察回用的可行性以及回用量的确定,提出利用阶段反硝化率粗略估计污泥碱解上清液回用量的思路。结果显示,所有比值的反硝化速率曲线均可分为4段,且随着VFA/N比值的增加,反硝化速率明显增加,pH值的变化趋势也与之对应;以VFA/N=2.47为分界点,比值继续增加,反硝化速率的增长并不大;将上清液以一定比例投入生活污水,反硝化速率明显提高,平行组6 h反硝化量分别达到47.0 mg/L和33.9 mg/L。

驯化污泥及生物滤池法处理高含盐石化废水

考察了纯氧曝气活性污泥和生物滤池深度处理石化高盐废水的工艺条件及处理效率。结果表明,在总溶固(TDS)为18000～35000mg/L的范围,通过驯化培养出的耐盐活性污泥能够适应短时间的盐浓度冲击,在纯氧曝气活性污泥工艺中,使废水的化学需氧量(COD)的平均降低率达到85%。进一步采用厌氧生物滤池(AF)和曝气生物滤池(BAF)工艺对生化出水进行深度处理,在共基质质量浓度12mg/L,BAF水力停留时间2.7h、水力负荷1.1m3/(m2.h)条件下,当待处理废水的COD在58.1～114.1mg/L、NH3-N质量浓度在1.2～19.0mg/L范围时,废水的COD平均降低率可达43.7%,NH3-N平均降低率达74.2%,出水的COD和NH3-N的质量浓度平均值分别为42.9和2.2mg/L。

游离氨对热水解联合中温厌氧消化处理剩余污泥的影响

热水解预处理强化了污泥厌氧消化过程,但同时增加了微生物受游离氨抑制的风险.对比传统工艺,在有机容积负荷率1.74-4.27g VS/（L·d）条件下,研究了游离氨（FA）对热水解联合中温厌氧消化工艺性能的影响.结果表明,组合工艺甲烷产量较传统反应器提高89%-121%,有机去除率提高1.21-1.46倍.但同时导致系统中游离氨浓度达89-382mg N/L,显著高于传统工艺中37-84mg N/L的范围.游离氨毒性测试显示,传统工艺中FA浓度从43mg N/L升至84mg N/L,没有抑制解乙酸产甲烷途径,而组合工艺中FA升至264mg N/L时,表现出抑制作用,尽管厌氧菌对高浓度FA表现更强的驯化趋势.结合氮负荷试验,FA浓度与基质利用能力,解乙酸产甲烷途径抑制程度和挥发性有机酸积累的关系表明,高有机负荷条件下组合工艺效率可通过控制氮负荷优化.

正交优化制备污泥水解蛋白质的实验研究

以武汉市污水处理厂剩余活性污泥为原料,在不同加水量、温度和催化条件下水解制备水解蛋白质,并通过正交试验优化了剩余污泥水解的反应条件。结果表明,当时间固定在6h时,以固液比(此为鲜泥与加水量的质量之比)为1∶2,温度1200℃,盐酸催化(pH为1.5)为水解反应的最佳条件。本研究为污泥水解蛋白液的制备及污泥处理的减量化、无害化和资源化提供了理论支持和数值依据。

提高污泥厌氧消化效率的溶胞预处理技术

剩余污泥的厌氧消化既可以解决污泥对环境的污染问题,又可以实现污泥的资源化,是污泥处置的理想途径。为了提高厌氧消化过程的效率,各种溶胞技术被用于厌氧消化的预处理。详尽地介绍了各种化学、物理、生物溶胞技术的效果及研究现状。机械、臭氧、超声波、热处理等方法在国外已经得到了较好的应用,辐射法是新兴的预处理技术,其污泥的预处理机理、效果及经济可行性有待进一步探讨。投加能分泌胞外酶细菌的溶胞技术在经济合理、操作简单、对设备无腐蚀、环保节能等方面显示了较大的优势,为提高厌氧消化效率开辟了新的途径。

温度与污泥浓度对剩余污泥水解及脱水性能的影响

污泥碱性水解产生短链脂肪酸,可应用到污水脱氮除磷中,但会使其脱水性能恶化.为考察温度和污泥浓度对剩余污泥水解及脱水性能的影响,试验研究了20 d内剩余污泥在pH=10、温度25和35℃、不同总悬浮固体(total suspended solids,TSS)下厌氧水解和脱水性能的变化,对溶解性化学需氧量(soluble chemical oxygen demand,SCOD)和毛细管吸收时间(capillary suction time,CST)进行了分析.试验表明:25℃时污泥脱水性随ρ(TSS)升高先恶化后变化不大,各发酵时间SCOD均升高后变缓;35℃时污泥脱水性随ρ(TSS)升高先恶化后略提高,SCOD变化与25℃时一致.SCOD变化情况与CST显著正相关;较高温度SCOD溶出更多,脱水性能稍有恶化;TSS对污泥脱水性能的影响较温度更显著.