二级出水中有机物深度处理工艺的研究进展

随着我国经济发展,城市污水和工业废水排放量不断增加。由于目前污水处理厂多采用生物法,二次出水中仍含有部分难以被生物降解的有机物,如果不经过处理直接排放,会对人体和生态环境造成威胁。污水二级出水有机物(EfOM)是污水经二级生化处理后剩余的有机物,主要来源于天然有机物、可溶性微生物产物和合成有机化合物。文中介绍了EfOM的主要组成并对其进行了量化和表征,综述了各种深度处理工艺(即混凝、高级氧化、吸附、膜分离)在去除EfOM方面的性能和优缺点,并通过组合工艺对污染物去除效果与单一工艺进行对比分析,为EfOM的有效去除提供理论依据。

Effects of effluent organic matters on endocrine disrupting chemical removal by ultrafiltration and ozonation in synthetic secondary effluent

Endocrine disrupting chemicals(EDCs) in the secondary effluent discharged from wastewater treatment plants are of great concern when water reuse is intended. Ozonation and ultrafiltration(UF) are powerful technologies reported to eliminate EDCs. Due to the importance of effluent organic matters(EfOMs) in secondary effluent, the effects of three kinds of EfOM on the treatment of five EDCs using ozonation and UF were investigated. The three kinds of EfOM studied were humic acid sodium salt(NaAH), bovine serum albumin(BSA)and sodium alginate(NaAg); and the five EDCs were estrone, 17β-estradiol, estriol, 17α-ethynyl estradiol and bisphenol A. The results showed that EfOM accelerated the decay rate of ozone and inhibited the degradation efficiency of EDCs by ozonation in the order NaAH > BSA > NaAg.The ultraviolet absorbance at 280 nm(UVA_(280)) has potential for use as a surrogate indicator to assess EDC removal via ozonation without conducting difficult EDC analyses. When the decline in UVA_(280) exceeded 18%, the five EDCs had been completely removed. The UF behavior of NaAH,BSA and NaAg was found to follow the cake filtration law. The fouling potential of EfOM followed the order NaAg > NaAH > BSA; while EfOM on the membrane surface enhanced EDC removal in the order NaAH > BSA > NaAg. The mean retention rate of the membrane was increased by 24%, 10% and 8%, respectively. The properties of EDCs and EfOM cakes both influenced the EDC removal rates due to adsorption, size exclusion and charge attraction.

Molecular characterization of effluent organic matter in secondary effluent and reclaimed water:Comparison to natural organic matter in source water

Municipal wastewater reclamation is becoming of increasing importance in the world to solve the problem of water scarcity. A better understanding of the molecular composition of effluent organic matter（Ef OM） in the treated effluents of municipal wastewater treatment plants（WWTPs） is crucial for ensuring the safety of water reuse. In this study, the molecular composition of Ef OM in the secondary effluent of a WWTP in Beijing and the reclaimed water further treated with a coagulation–sedimentation–ozonation process were characterized using a non-target Fourier transform ion cyclotron resonance mass spectrometry（FT-ICR MS） method and compared to that of natural organic matter（NOM） in the local source water from a reservoir. It was found that the molecular composition of Ef OM in the secondary effluent and reclaimed water was dominated by CHOS formulas, while NOM in the source water was dominated by CHO formulas. The CHO formulas of the three samples had similar origins. Anthropogenic surfactants were responsible for the CHOS formulas in Ef OM of the secondary effluent and were not well removed by the coagulation-sedimentation-ozonation treatment process adopted.

Mechanisms for simultaneous ozonation of sulfamethoxazole and natural organic matters in secondary effluent from sewage treatment plant

Sulfamethoxazole(SMX)is commonly detected in wastewater and cannot be completely decomposed during conventional treatment processes.Ozone(O_(3))is often used in water treatment.This study explored the influence of natural organic matters(NOM)in secondary effluent of a sewage treatment plant on the ozonation pathways of SMX.The changes in NOM components during ozonation were also analyzed.SMX was primarily degraded by hydrolysis,isoxazole-ring opening,and double-bond addition,whereas hydroxylation was not the principal route given the low maximum abundances of the hydroxylated products,with m/z of 269 and 287.The hydroxylation process occurred mainly through indirect oxidation because the maximum abundances of the products reduced by about 70%after the radical quencher was added,whereas isoxazole-ring opening and double-bond addition processes mainly depended on direct oxidation,which was unaffected by the quencher.NOM mainly affected the degradation of micropollutants by consuming•OH rather than O_(3)molecules,resulting in the 63%–85%decrease in indirect oxidation products.The NOM in the effluent were also degraded simultaneously during ozonation,and the components with larger aromaticity were more likely degraded through direct oxidation.The dependences of the three main components of NOM in the effluent on indirect oxidation followed the sequence:humic-like substances>fluvic-like substance-s>protein-like substances.This study reveals the ozonation mechanism of SMX in secondary effluent and provides a theoretical basis for the control of SMX and its degradation products in actual water treatment.

慢滤-低压纳滤对二级出水中有机物和抗生素抗性基因的去除效能研究

抗生素抗性基因(Antibiotic Resistance Genes,ARGs)作为新型环境污染物,在污水处理厂二级出水中被频繁检出,成为人类健康和生态安全的潜在威胁。本文采用慢滤-低压纳滤(Nanofiltration,NF)组合工艺去除二级出水中ARGs和溶解性有机物(Dissolved Organic Carbon,DOC),探讨该工艺对ARGs和DOC的去除机制及效能。结果表明,生物膜慢滤-NF组合工艺对二级出水中ARGs和DOC的去除效果最好,对DOC的去除率为82.5%,质量浓度降为2.0 mg/L;对富里酸类有机物和腐殖酸类有机物的去除率分别达到87.2%、85.8%,对不同分子质量区间有机物的去除率均在90%以上,其中,对>100 kDa、50~100 kDa以及10~<50 kDa区间有机物的去除率均在95%以上,出水中几乎不含有这类物质;组合工艺对4种ARGs(tet A、tet W、sulⅠ、sulⅡ)的去除量为10^(4.83)~10^(5.67)copies/mL;生物膜慢滤对水中细胞态和游离态ARGs的去除效果优于慢滤,其对细胞态和游离态ARG的削减量分别为10^(1.06)~10^(3.52)copies/mL和10^(1.73)~10^(3.07)copies/mL;水中DOC与不同类型ARGs均具有显著正相关性;生物膜表面生长的变形菌门、放线菌门、假单胞菌属及蛭弧菌属等微生物可以加强对水中ARGs和DOC的去除。综上,慢滤-NF组合工艺可以有效去除二级出水中的ARGs和DOC,可以作为二级出水深度处理的有效方式。

Tracking the reactivity of ozonation towards effluent organic matters from WWTP using two-dimensional correlation spectra

The characteristics of effluent organic matter(EfOM) from a wastewater treatment plant(WWTP) during ozonation were investigated using excitation and emission matrix(EEM)spectra, Fourier transform infrared spectroscopy(FT-IR) and high-performance size exclusion chromatography(HPSEC) at different ozone dosages. The selectivity of ozonation towards different constituents and functional groups was analysed using two-dimensional correlation spectra(2D-COS) probed by FT-IR, synchronous fluorescence spectra and HPSEC.The results indicated that ozonation can destroy aromatic structures of EfOM and change its molecular weight distribution(MWD). According to 2D-COS analysis, microbial humiclike substances were preferentially removed, and then the protein-like fractions. Terrestrial humic-like components exhibited inactivity towards ozonation compared with the above two fractions. Protein-like substances with small molecular weight were preferentially reacted during ozonation based on 2D-COS probed by HPSEC. In addition, the selectivity of ozone towards different functional groups of EfOM exhibited the following sequence:phenolic and alcoholic C\O groups > aromatic structures containing C_C double bonds >aliphatic C\H. X-ray photoelectron spectroscopy(XPS) further elucidated the preferential reaction of aromatic structures in EfOM during ozonation.

紫外光高级氧化法处理二级出水中难降解有机物的研究

紫外光高级氧化法是处理二级出水中难降解有机物的有效方法。在紫外光作用下,以过一硫酸钾(PMS)、过氧化氢(H2O2)和次氯酸钠(NaClO)为氧化剂,研究了氧化剂类型、浓度和紫外光强度对二级出水中2,4-二硝基苯酚(DNP)和亚硝基二甲胺(NDMA)去除效率的影响。结果表明,NaClO的降解效果最好,当NaClO浓度为1 mmol·L^(-1)、处理时间为60 min时,DNP和DNMA的去除率分别为25%和20%,这是由于在紫外光的照射下,NaClO分解产生HOCl·和OCl·自由基的量子产率高于PMS和H_(2)O_(2)所致;当NaClO初始浓度为2.5 mmol·L^(-1)、处理时间为60 min时,二级出水中DNP和DNMA的去除效率分别达到了50%和35%,DNP去除效率高是由于NaClO分解产生的自由基对芳香族化合物降解活性更高所致。当紫外光强度为6×10^(-11)E·s^(-1)时,DNP和DNMA的去除效率较好,再增加光强度,去除效率增加不明显。

煤气化废水二级生化处理出水的有机物特征研究

为了明确煤气化废水二级生化处理出水的水质特征,试验应用超滤对废水进行分子量分级,采用XAD-8树脂进行分离,并进行光谱分析。结果表明,在不同分子量的各组分中,疏水性物质占比大于亲水性物质,其中疏水性中性有机物(HoN)占比最高。三维荧光光谱分析发现,疏水性有机酸(HoA)和HoN腐殖化程度较高,疏水性有机碱(HoB)中芳香族化合物和富里酸类有机物比较多,而亲水性有机物(HI)中富里酸类有机物和溶解性微生物代谢产物较多。

生化出水中各类有机污染物的特性及在混凝处理过程中的行为

以城市生活污水厂二级生化出水为研究对象,考察了生化出水中有机污染物中各组分含量、分子量分布特点等特性,以及各类有机物在三氯化铁混凝处理过程中的行为。实验结果表明:当生化出水中有机物浓度以DOC表征时,水中疏水性物质与亲水性物质各占50%,其中疏水酸浓度最高,约为42%,其次为亲水酸和非酸亲水物质,分别占26%和24%,非酸疏水物质仅为8%。其中疏水酸中的不饱和双键或芳香环有机物的含量较高。二级生化出水中的DOC主要集中在分子量大于10 000 D的有机物,占48.8%。在三氯化铁混凝过程中,能去除几乎所有的大分子量有机物以及大部分芳香族有机物(61%的UV254),对小分子、亲水性有机物基本没有去除效果。因此,混凝法需与其他能去除亲水性、小分子量有机物(<3 000 D)的处理工艺结合,以进一步提高有机物的去除效率。

二级出水中溶解性有机物的分级表征特性

以城市污水厂二级出水为研究对象,利用大孔吸附树脂将污水中溶解性有机物(Dissolved organic matter,DOM)分离成疏水酸性、中性、碱性物质和亲水性物质等4个组分,同时分析了各组分的有机物特性.结果表明,二级出水溶解性有机物中疏水酸性物质是二级出水溶解性有机物的主要组成部分.4种组分中均含有腐殖质类物质,疏水酸性物质(Hydrophobic acids,HOA)和疏水中性物质(Hydrophobic neutrals,HON)中腐殖酸类峰的荧光强度较大,亲水性物质(Hydrophilic fraction,HI)中的蛋白峰荧光强度较大.腐殖质类物质分子量分布较为单一,主要分布在0.9 k Da左右,而疏水性组分蛋白类物质分子量分布较为广泛,在200 k Da左右及小于9 k Da时均有一定分布,亲水性组分蛋白类物质主要由分子量小于9 k Da的物质组成.X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)分析结果表明,HOA、HON中含有较多的芳香族化合物,而疏水碱性物质(Hydrophobic bases,HOB)、HI中则含有较多的羰基和羧基类官能团.

水中残留有机物分子量分布特征和对膜性能的影响

本试验分析了城市二级处理水的残留有机物分子量分布特征及对超滤膜过滤透水性能的影响,并利用混凝法,活性炭吸附,臭氧-活性炭吸附进行了处理。研究结果表明:(1)城市污水厂二级出水中溶解态有机物主要集中在<2k分子量区间上;(2)混凝处理后,高分子量有机物低分子化效果明显;PAC吸附能有效去除小分子量有机物;臭氧-PAC联用,大分子量有机物和小分子量有机物所占比例均有所下降,表明臭氧氧化与PAC吸附联用在去除有机物方面具有很好的互补性;(3)分子量分布对原水的透水通量影响较大;选择混凝、PAC或臭氧-PAC等作为膜法处理的预处理单元,对城市污水再生处理具有重要价值。

典型城市污水二级处理水中DOM性状特征

以西安市典型城市污水二级出水为对象，分别测定了溶解性有机物的分子质量分布、亲疏水性组分以及荧光性质等。结果表明，无论以TOC或UV254计，二级出水中溶解性有机物分子质量分布趋势基本相同，大部分为小分子有机物，〈10 ku的有机物分别占60%~75%和71%~79%，〉50 ku的大分子有机物分别占14%~28%和13%~16%，其他区间所占比例较小，整个区间成“双峰”状。二级出水中亲水性组分较疏水性组分多，出水中难降解物质包括腐殖酸、富里酸和蛋白质类物质。含腐殖质较多的水样SUVA较高，而含蛋白质类物质较多的水样SUVA较低，且腐殖质等大部分存在于疏水性有机物中。

城市污水二级出水溶解性有机物(DOM)与Cu^(2+)作用的聚集和光谱特性

利用三维荧光光谱法、紫外分光光度法和动态光散射技术,研究城市污水二级出水中溶解性有机物(DOM)与Cu^(2+)作用的粒径变化、光谱特性和络合能力.结果表明,利用修正型Stern-Volmer方程得到二级出水DOM与Cu^(2+)作用的条件稳定常数(lg K)和配位荧光官能团比例分别为1.74—2.59和8.77%—39.44%.在一定实验范围内,随投加Cu^(2+)浓度和pH增大,二级出水DOM和Cu^(2+)作用后的UV253/UV203值增大.pH值为7—9时,随pH增大,荧光强度基本增强而荧光指数降低;相同pH下,随投加Cu^(2+)浓度增加,荧光强度降低而荧光指数增大.表明二级出水DOM络合Cu^(2+),改变两者在水中的存在状态和迁移.pH 7时,DOM与Cu^(2+)有较高的络合稳定性和络合能力.

二级出水水质对中试臭氧-微滤工艺运行的影响

在以膜微滤为主的组合工艺对二级出水的处理过程中,二级出水水质可能对于微滤过程中膜污染的发展有较强影响.为此考察了2座污水处理厂及1个中试处理设施的二级出水水质,包括常规水质指标、水中颗粒物粒径分布及树脂吸附分离后不同有机物部分的荧光光谱所表征的有机物组分等对于死端微滤中TMP发展变化的影响.研究结果表明:①颗粒物浓度和颗粒物粒径分布对于微滤过程中的可逆污染有较大贡献;②二级出水中的有机物,尤其是其中的腐殖质部分,对于微滤过程中的不可逆污染有较大贡献.

pH值对SBR生物反应器出水溶解态有机质含量与构成的影响

为探讨污水二级生化出水中有机物(EfOM)的构成特点和变化规律,采用配置生活污水,对不同pH值运行条件下,SBR生物反应器出水中的溶解态有机质(DOM)含量和构成进行了比较研究.结果表明,运行期间pH值的调节对SBR反应器出水DOM含量与构成的影响均较大.初始pH为6.5的SBR反应器,pH值降低为6.0后,出水DOC由原来的4.0 mg.L-1不断升高,进一步提高pH值,能够起到一定的缓解作用;初始pH为8.0的SBR反应器,出水DOC从4.0 mg.L-1快速降低并保持在2mg.L-1左右,pH值降低为6.5后,DOC变化不大.单宁酸和蛋白质、碳水化合物、DNA等微生物代谢产物(SMPs)是出水DOM的主要组成部分,pH值对SMPs生成的影响是一个长期的过程,运行过程中降低pH值,造成出水SMPs含量不断升高.pH值对整个循环过程中溶解态有机物降解情况的影响,在厌氧阶段发挥了主要作用,较高pH值有利于厌氧阶段有机物的降解,而好氧阶段的有机物降解受pH值影响不大.

生物活性炭过滤对污水二级出水的深度处理效能研究

采用生物活性炭(BAC)过滤技术深度处理污水二级出水,分析了该技术对二级出水有机物(EfOM)的去除效果及对EfOM分子量分布、荧光特性的影响。通过分层取样,考察了EfOM在BAC柱中的沿程变化,并在此基础上探讨了空床停留时间(EBCT)对BAC柱去除EfOM效果的影响。结果表明,当EBCT为30min时,BAC柱运行稳定后对污水二级出水中溶解性有机碳(DOC)、有机污染物(以水样在254nm紫外光下的吸光度(UV254)表征)和TN的平均去除率分别为25%、25%、11%。BAC柱对分子量<1ku的小分子有机物去除效果最显著。分层取样结果表明,EBCT为30min时,EfOM的高效去除主要发生在BAC柱顶层10cm,EBCT延长至60min时,EfOM的去除主要发生在BAC柱顶层20cm内,延长EBCT能够加强BAC柱对EfOM的去除效果。

不同预处理方式缓解超滤膜污染的效能研究

以二级出水为处理对象,研究了活性炭(Activated Carbon,AC)吸附,生物活性炭(Biological Activated Carbon,BAC)过滤,臭氧(Ozone,O3)氧化对超滤膜污染的缓解作用及其对水中有机物的去除效果。具体考察了AC投加量和吸附时间,BAC的空床停留时间(Empty Bed Contact Time,EBCT),以及臭氧投加量等因素产生的影响。结果表明,这三种预处理方式可有效去除有机物,使水中DOC与UV254值明显降低。AC投加量由0.5 g/L增加至5 g/L,吸附时间由5min延长至8h,膜污染未得到缓解。BAC预处理随EBCT由30min延长至60min,增加了超滤膜的不可逆污染(Irreversible Fouling,IF)。臭氧投加量由0.2mg O3/mg DOC增加至0.94mg O3/mg DOC,臭氧预氧化缓解膜污染的效果越明显。臭氧投加量较低(0.48mg O3/mg DOC)时,IF随臭氧投加量的增大略有上升,而臭氧投加量增至0.94mg O3/mg DOC时,IF出现明显下降。

粉末活性炭-超滤组合工艺对二级出水中污染物的去除及膜污染机制研究

采用粉末活性炭(PAC)-超滤(UF)组合工艺处理污水处理厂二级出水,探讨不同PAC投加量下PAC-UF组合工艺对溶解性有机物(DOC)及抗生素抗性基因(ARGs)的去除效果,分析PAC对UF膜污染的缓解机制。结果表明,与直接UF相比,PAC-UF组合工艺可有效降低出水DOC和ARGs含量;水中4种ARGs与微生物含量、整合子intI1、DOC浓度间呈显著相关关系,说明去除上述指标有助于削减不同类型ARGs;PAC可吸附水中小分子量有机物,提高膜比通量,改善UF膜的反冲洗效果,PAC投加量为20mg/L时效果最好;PAC投加量增加可使滤饼层变得致密,使UF膜的不可逆污染阻力下降,但总污染阻力增加;直接UF与PAC-UF组合工艺的膜污染主导机制均为滤饼层污染,其中PAC-UF组合工艺受滤饼层污染机制影响更大。综合考虑污染物去除及膜污染缓解效果,采用低投加量(20mg/L)的PAC-UF组合工艺处理二级出水最为适宜。