Fate of volatile organic compounds in constructed wastewater treatment wetlands

The fate of volatile organic compounds was evaluated in a wastewater-dependent constructed wetland near Phoenix, AZ, using field measurements and solute transport modeling. Numerically based volatilization rates were determined using inverse modeling techniques and hydraulic parameters established by sodium bromide tracer experiments. Theoretical volatilization rates were calculated from the two-film method incorporating physicochemical properties and environmental conditions. Additional analyses were conducted using graphically determined volatilization rates based on field measurements. Transport (with first-order removal) simulations were performed using a range of volatilization rates and were evaluated with respect to field concentrations. The inverse and two-film reactive transport simulations demonstrated excellent agreement with measured concentrations for 1,4-dichlorobenzene, tetrachloroethene, dichloromethane, and trichloromethane and fair agreement for dibromochloromethane, bromodichloromethane, and toluene. Wetland removal efficiencies from inlet to outlet ranged from 63% to 87% for target compounds.     

Fate of endocrine-active compounds during municipal biosolids treatment: a review

For two decades, the fates of endocrine-disrupting compounds (EDCs) across various wastewater treatment processes have been studied using chemical and in vitro bioassay measurements. In comparison, little work has been conducted to track the fates of EDCs during municipal biosolids stabilization, particularly using bioassay approaches. This leads to knowledge gaps with respect to understanding which single or combined biosolid treatments facilitate EDC removal, and what the total endocrine-active potency of treated biosolids might be. These unknowns in turn heighten public opposition and distrust of biosolids reuse applications. This review aims to summarize what is currently known regarding EDC removal during commonly used full-scale biosolids treatment processes and highlights analytical challenges that are relevant when in vitro bioassays and chemical analyses are applied to biosolids samples.     

Fate of surfactants in membrane bioreactors and conventional activated sludge plants

Two membrane bioreactors (MBRs) were operated at high sludge retention time (SRT) (between 30 and 75 d) in parallel to a conventional activated sludge plant (CASP) conducted at SRT = 10 d. The fate of linear alkylbenzene sulfonate (LAS), nonylphenol ethoxylates (NP(n)EO, n = 1-15), nonylphenoxy carboxylates (NP(n)EC, n = 1-2), and nonylphenol (NP) in these systems was investigated. All systems were very efficient in the removal of LAS (around 99%). The analysis of variance showed that the difference in the removal efficiency of LAS in the CASP and the MBR operated at SRT = 65-75 d (respectively 99.0 ± 0.43 and 99.8 ± 0.11) were significant (p < 0.05), confirming the importance of SRT in the removal of LAS. Comparison between the CASP and the MBRs in the removal efficiency of nonylphenolic compounds were conducted considering NP(3-15)EO, the sum of NP(1-15)EO, NP(1-2)EC, and nonylphenol (NP). In all cases MBRs were more efficient than the CASP. In the case of NP the removal was about 76 ± 7.5% for the CASP and 90% ± 12.1 and 82 ± 8.7% for the MBRs. Better performance of MBRs in the removal of nonylphenolic compounds can be attributed to a better degradation. For example, if the sum of NP(1-15)EO and NP(1-2)EC is considered, estimated biodegradation was about 48% for the CASP and 72% for MBRs.     

啤酒废水处理系统中活性污泥微型生物群落结构分析

为了分析啤酒厂废水处理系统活性污泥运行状态,选取了啤酒厂污水处理系统中不同阶段的微型生物群落结构作为研究对象。本文利用16S rDNA及18S rDNA特异性引物作为分子标记,通过PCR扩增污水处理系统中的环境生物群落DNA,以变性梯度凝胶电泳(DGGE)技术分离检测PCR产物获得微生物群落的DNA指纹图谱。研究结果显示,经过活性污泥处理的啤酒厂废水中细菌群落和真核生物群落结构发生了明显的改变。其中在细菌群落DGGE图谱中检测到21条特异性条带,而在真核生物DGGE图谱检测到10条。UPGMA聚类分析显示,进水与活性污泥中的细菌及真核群落结构十分相似(相似性>0.67),而与出水的差异较大(相似性<0.41),这表明了进水对活性污泥生物群落结构的重要影响。     

A model to predict the adsorber thermal behavior during treatment of volatile organic compounds onto wet activated carbon

A model for adsorption of volatile organic compounds (VOCs) onto a wet activated carbon bed was proposed in this study. This model accounts for temperature changes induced by the reversed and coupled mass-transfer processes of both organic species adsorption and water desorption. Indeed, it was experimentally pointed out that temperature rises, which result from the exothermal nature of the energetic interactions between the organic molecule and the activated carbon surface, are notably reduced when the adsorbent contains an initial moisture of approximately 10% in weight. Moreover, it was shown that water rate desorption was enhanced in the presence of organic vapor. This phenomenon may be explained by the displacement of sorbed water bythe organic molecules, owing to more intensive interactions with the activated carbon surface. The model proposed was elaborated from a previous comprehensive analysis of the diffusion mechanisms governing VOC adsorption at high concentrations onto a dry activated carbon bed. In a similar way, a theoretical approach was developed to model water desorption during drying of a wet activated carbon bed under pure flowing air. At last, a theoretical depiction of both competitive and reverse processes was outlined. The final model fits reasonably with experimental data relative to both breakthrough curves and thermal wave shape along the bed, even if local temperature change calculation may require some further improvement.     

中段水处理中活性污泥的培养

华远造纸集团有限公司以麦草为主要原料,采用碱法蒸煮工艺生产漂白浆,在造纸和纸加工过程中产生的麦草浆中段水与铜版纸废水,溶解性有机物浓度高、悬浮物多、色度深,对环境危害严重.我公司于1998年初动工兴建了日处理2万m3的中段水处理站,采用化学絮凝处理一级沉淀,二级活性污泥生化处理的工艺路线.在试车中,我们采用同步培驯与接种培驯相结合的方法,在15天内成功地培养出了良好的活性污泥,保证了处理系统按计划正常运行,并顺利通过国家环保总局的达标验收.……     

Research Watch: Fate of PAH compounds

Contaminants.     

Investigation of sorption behavior between pyrene and colloidal organic carbon from activated sludge processes

The sorption behavior of pyrene for different size fractions of colloidal organic carbon (COC) originating from two biological wastewater treatment facilities (a full-scale activated sludge system (FSAS) and a membrane bioreactor (MBR)) was investigated by fluorescence quenching. Fluorescence lifetime measurements demonstrated a dynamic quenching component in all samples, including the colloidal-free filtrates. COC sorption coefficients (Kcoc) for pyrene ranged from <1 x 10(3) L/kgcoc to 80 x 10(3) L/kgcoc and were comparable to values obtained in the literature for natural organic matter. Both linear and nonlinear behaviors were observed in the Freundlich-described converted isotherms (n = 0.89-2.1). The aromatic content of COC was quantified by the molar extinction coefficient at 280 nm (e280). Good correlations were observed between COC-pyrene sorption coefficients and e280 coefficients, suggesting that e280 may be a useful tool for predicting colloidal transport of hydrophobic organic compounds (HOCs) from activated sludge systems. The removal of COC from treated effluents may appreciably reduce the concentrations of HOCs discharged to receiving streams.     

Fate of deoxynivalenol and nivalenol during storage of organic whole-grain wheat flour

This study was carried out to determine the level of retention of the mycotoxins deoxynivalenol (DON) and nivalenol (NIV) during 120 days of storage (aging) of flours produced from organic wheat grain naturally infected with Fusarium fungi. Three types of flour (standard white flour prepared by a roller-grinder mill - IRG, whole-grain flour produced by a hammer-crusher mill - IHC and whole-grain flour prepared by a millstone - OMS) were packaged in food-grade paper or polypropylene plastic bags and stored at two different storage temperatures (constant 10 °C or 25 °C). The concentrations of DON and NIV were measured prior to and after storage by means of HPLC-UV detection methods. After 120 days of storage, the concentrations of DON and NIV decreased between 0% and 29% compared to the initial measurements, depending on the combination of experimental factors. The greatest decrease in mycotoxin concentration was observed in the IHC and OMS flours packaged in paper bags and stored at 25 °C. The smallest decrease in mycotoxin concentration was observed in the IRG flours packaged in sealed plastic bags and stored at 10 °C. Statistical analysis showed that the level of retention of DON and NIV depended significantly on the type of packaging material, but did not depend on the type of flour or the storage temperature.     

运用活性污泥法进行污水处理工艺的研究

通过介绍活性污泥的培养驯化原理,指出了污泥系统出现问题的原因及对策,为生产实践提供了技术指导。     

Characterization of organic compounds collected during southeastern aerosol and visibility study: water-soluble organic species

As part of the Southeastern Aerosol and Visibility Study (SEAVS), water-soluble organic species (WSOS) in fine aerosols collected from July 15 to August 25, 1995, at the Great Smoky Mountain National Park, Tennessee (USA), were chemically classified into seven groups, with concentrations ranging from around 1 to >200 ng/m3. Dicarboxylic acids represented the dominant identified compound class, and succinic acid was the most abundant dicarboxylic acid. The trends in data suggest that most WSOS collected in the SEAVS samples were mainly generated from secondary photochemical reactions, especially during the first (cleaner) half of the sampling campaign. High relative humidity at the sampling site resulted in substantial water uptake by the aerosols, which may have enhanced the levels of succinic acid by reducing its rate of photooxidation. Concurrent trends in malic and malonic acid concentrations suggest these were generated from the oxidation of succinic acid. Consistent with the conversion of 3-hydroxypropanoic acid to malonic acid, it appears that 4-hydroxybutanoic acid served as a major precursor contributing to high levels of succinic acid in the daytime. Nocturnal WSOS generally followed the trend of diurnal WSOS, but they exhibited different chemical compositions and lower concentrations, unlike what has been reported for an urban site. A nocturnal-to-diurnal ratio of succinic acid larger than 0.25 may indicate an atmosphere dominated by photochemical reactions, rather than by primary emissions.     

Modeling effective diffusivity of volatile organic compounds in activated carbon fiber

Volatile organic compounds (VOCs) comprise 67% of total hazardous air pollutants (HAPs) that are emitted by major industrial point sources into the U.S. atmosphere (1). Adsorption by activated carbon fiber (ACF) has been recognized as one of the feasible regenerative control processes to separate and recover VOCs for reuse. Characteristics of VOCs transport in ACFs are required to efficiently design ACF sorption systems. However, extensive resources are spent experimentally obtaining transient sorption data to design adsorption systems. As an alternative, this work develops a new model that predicts effective diffusivities of VOCs into ACFs. The diffusion process is modeled as Knudsen transport into the ACF open pore spaces coupled with activated surface diffusion on the ACF's internal surface area. Temperature and Darken's factors are included in the surface diffusion model to provide corrections for thermodynamic state and deviation from Fick's Law, respectively. Depth of the adsorption potential well is considered as the product of the heat of adsorption of a reference VOC, an adsorption similarity factor, and a surface diffusion energy factor. Introduction of the adsorption similarity factor in the effective diffusivity model is a new concept providing a means to predict effective diffusivity of similar adsorption systems from a reference system. Experimental data from a short length column are used to determine effective diffusivity of acetone in ACF. Results from this diffusivity model are compared to experimental values for the acetone/ACF system to describe the degree of closure between modeled and experimental results.     

Effect of dissolved oxygen changes on activated sludge fungal bulking during lab-scale treatment of acidic industrial wastewater

The cloning and sequencing of fungal 18S rRNA genes followed by the identification of filamentous fungal species by fluorescent in situ hybridization (FISH) and the enumeration of filamentous fungal cells by flow cytometry-FISH (FC-FISH) were used to investigate the effect of dissolved oxygen (DO) changes on activated sludge (AS) fungal bulking during a lab-scale treatment of acidic industrial wastewater. By increasing DO levels from < .5 to > 2 mg L?1, bulking started to occur due to the outbreak of fungal filaments, whereas the chemical oxygen demand (COD) removals sharply increased from < 40 to > 70%. Clone library analyses revealed that all clonal fungal sequences were of yeast origin, and that only one and four yeast species were individually detected in AS at two DO levels. Subsequent FISH identification of filamentous yeast species within bulking sludge using self-designed oligonucleotide probes suggested that all probe-reactive cells of Trichosporon asahii had a filamentous morphology and were the dominating filamentous microorganism in the AS. The FC-FISH analyses of bacteria and two main yeast species showed that the DO shift resulted in a sharp increase of T. asahii, by a factor of 48-60, which caused filamentous yeast bulking. Subsequently, the restoration of DO levels to <0.5 mg L?1 effectively restored the sludge settlement and yeast community, as well as unacceptable COD removals.     

Biotransformation of the antiviral drugs acyclovir and penciclovir in activated sludge treatment

The biotransformation of the two antiviral drugs, acyclovir (ACV) and penciclovir (PCV), was investigated in contact with activated sludge. Biodegradation kinetics were determined, and transformation products (TPs) were identified using Hybrid Linear Ion Trap- FT Mass Spectrometry (LTQ Orbitrap Velos) and 1D (1H NMR, 13C NMR) and 2D (1H,1H-COSY, 1H-(13)C-HSQC) NMR Spectroscopy. ACV and PCV rapidly dissipated in the activated sludge batch systems with half-lives of 5.3 and 3.4 h and first-order rate constants in relation to the amount of suspended solids (SS) of 4.9±0.1 L gss(-1) d(-1) and 7.6±0.3 L gss(-1) d(-1), respectively. For ACV only a single TP was found, whereas eight TPs were identified for PCV. Structural elucidation of TPs exhibited that transformation only took place at the side chain leaving the guanine moiety unaltered. The oxidation of the primary hydroxyl group in ACV resulted in the formation of carboxy-acyclovir (Carboxy-ACV). For PCV, transformation was more diverse with several enzymatic reactions taking place such as the oxidation of terminal hydroxyl groups and β-oxidation followed by acetate cleavage. Analysis of different environmental samples revealed the presence of Carboxy-ACV in surface and drinking water with concentrations up to 3200 ng L(-1) and 40 ng L(-1), respectively.     

Fate, partitioning, and mass loading of polybrominated diphenyl ethers (PBDEs) during the treatment processing of municipal sewage

Sewage treatment plant (STP) effluents are likely a major source of contamination for PBDEs, especially in the receiving water bodies of local aquatic environments surrounding the location of these discharges. Congeners of the pentaBDE mixture, 2,2,',4,4'-tetrabromodiphenyl ether (BDE47), 2,2,',4,4',5-pentabromodiphenyl ether (BDE99), 2,2,',4,4',6-pentabromodiphenyl ether (BDE100), 2,2,',4,4',5,5'-hexabromodiphenyl ether (BDE153), and 2,2,',4,4',5,6'-hexabromodiphenyl ether (BDE154), are of great environmental concern in North America due to their persistence, potential for bioaccumulation, and >97% use of the global production of the mixture in the region. Detailed characterization of the distribution of eight PBDE congeners (2,4,4'-tribromoDE (BDE28) and BDE47, 99, 100, 138, 153, 154, and 183) was carried out at five sites along the treatment process at an activated sludge-type secondary treatment municipal STP facility. PentaBDE mixture congeners, sigma5PBDE (sum of BDE47, 99, 100, 153, and 154) accounted for >98% of the total (sigma 8) PBDE concentration at all sites, with over 80% of the composition being BDE47 and BDE99. Presence of dissolved organic matter affected the mobility of PBDEs during the initial stages of the treatment process. About 9% of the influent mass of sigma5PBDE to the facility is estimated to be discharged into the Little River (leading to the Detroit River) with the final effluent, resulting in an estimated mass loading of approximately 0.7 kg/year. The total mass loading of sigma5PBDE to the Detroit River is expected to be much larger as effluent from this facility accounts for <10% of the total STP discharges to the river.     

Fate of pharmaceutical and trace organic compounds in three septic system plumes, Ontario, Canada

Three high volume septic systems in Ontario, Canada, were examined to assess the potential for onsite wastewatertreatment systems to release pharmaceutical compounds to the environment and to evaluate the mobility of these compounds in receiving aquifers. Wastewater samples were collected from the septic tanks, and groundwater samples were collected below and down gradient of the infiltration beds and analyzed for a suite of commonly used pharmaceutical and trace organic compounds. The septic tank samples contained elevated concentrations of several pharmaceutical compounds. Ten of the 12 compounds analyzed were detected in groundwater at one or more sites at concentrations in the low ng L(-1) to low microg L(-1) range. Large differences among the sites were observed in both the number of detections and the concentrations of the pharmaceutical compounds. Of the compounds analyzed, ibuprofen, gemfibrozil, and naproxen were observed to be transported atthe highest concentrations and greatest distances from the infiltration source areas, particularly in anoxic zones of the plumes.