Acute ecotoxicity and genotoxicity assessment of two wastewater treatment units

Environmental Science and Pollution Research - Water contamination by discharge of untreated or poorly treated wastewater into water bodies is a current issue that may cause harm to humans. Water...     

Treatment of Arctic wastewater by chemical coagulation,UV and peracetic acid disinfection

Conventional wastewater treatment is challenging in the Arctic region due to the cold climate and scattered population. Thus, no wastewater treatment plant exists in Greenland, and raw wastewater is discharged directly to nearby waterbodies without treatment. We investigated the efficiency of physicochemical wastewater treatment, in Kangerlussuaq, Greenland. Raw wastewater from Kangerlussuaq was treated by chemical coagulation and UV disinfection. By applying 7.5 mg Al/L polyaluminium chloride (PAX XL100), 73% of turbidity and 28% phosphate was removed from raw wastewater. E. coli and Enterococcus were removed by 4 and 2.5 log, respectively, when UV irradiation of 0.70 kWh/m³ was applied to coagulated wastewater. Furthermore, coagulated raw wastewater in Denmark, which has a chemical quality similar to Greenlandic wastewater, was disinfected by peracetic acid or UV irradiation. Removal of heterotrophic bacteria by applying 6 and 12 mg/L peracetic acid was 2.8 and 3.1 log, respectively. Similarly, removal of heterotrophic bacteria by applying 0.21 and 2.10 kWh/m³ for UV irradiation was 2.1 and greater than 4 log, respectively. Physicochemical treatment of raw wastewater followed by UV irradiation and/or peracetic acid disinfection showed the potential for treatment of arctic wastewater.     

Removal and formation of chlorinated triclosan derivatives in wastewater treatment plants using chlorine and UV disinfection

Triclosan, a common antimicrobial agent, may react during the disinfection of wastewater with free chlorine to form three chlorinated triclosan derivatives (CTDs). This is of concern because the CTDs may be photochemically transformed to tri- and tetra-chlorinated dibenzo-p-dioxins when discharged into natural waters. In this study, wastewater influent, secondary (pre-disinfection) effluent, and final (post-disinfection) effluent samples were collected on two occasions each from two activated sludge wastewater treatment plants, one using chlorine disinfection and one using UV disinfection. Concentrations of triclosan and three CTDs were determined using ultra performance liquid chromatography-triple quadrupole mass spectrometry with isotope dilution methodology. Triclosan and the CTDs were detected in every influent sample at levels ranging from 453 to 4530 and 2 to 98 ng L⁻¹, respectively, though both were efficiently removed from the liquid phase during activated sludge treatment. Triclosan concentrations in the pre-disinfection effluent ranged from 36 to 212 ng L⁻¹, while CTD concentrations were below the limit of quantification (1 ng L⁻¹) for most samples. In the treatment plant that used chlorine disinfection, triclosan concentrations decreased while CTDs were formed during chlorination, as evidenced by CTD levels as high as 22 ng L⁻¹ in the final effluent. No CTDs were detected in the final effluent of the treatment plant that used UV disinfection. The total CTD concentration in the final effluent of the chlorinating treatment plant reached nearly one third of the triclosan concentration, demonstrating that the chlorine disinfection step played a substantial role in the fate of triclosan in this system.     

Soil ecotoxicity assessment using cadmium sensitive plants

Four crop plant species (sweet corn, Zea may; wheat, Triticum aestivum; cucumber, Cucumis sativus; and sorghum, Sorghum bicolor) were tested to assess an ecotoxicity in cadmium-amended soils. The measurement endpoints used were seed germination and seedling growth (shoot and root). The presence of cadmium decreased the seedling growth. The medium effective concentration values (EC50) for shoot or root growth were calculated by the Trimmed Spearman-Karber method. Due to the greater accumulation of Cd to the roots, root growth was a more sensitive endpoint than shoot growth. Bioavailability and transport of Cd within plant were related to concentration and species. The ratio of bioaccumulation factor (BAF) in the shoots to the roots indicated high immobilization of Cd in the roots. Seed germination was insensitive to Cd toxicity, and is not recommended for a suitable assay. Among the test plants and test endpoints, root growth of sorghum and cucumber appears to be a good protocol to assess ecotoxicity of soils contaminated by Cd.     

Biological assessment of bisphenol A degradation in water following direct photolysis and UV advanced oxidation

Endocrine disrupting compounds (EDCs) are exogenous environmental chemicals that can interfere with normal hormone function and present a potential threat to both environmental and human health. The fate, distribution and degradation of EDCs is a subject of considerable investigation. To date, several studies have demonstrated that conventional water treatment processes are ineffective for removal of most EDCs and in some instances produce multiple unknown transformation products. In this study we have investigated the use of direct photolysis with low-pressure (LP) Hg UV lamps and UV+hydrogen peroxide (H(2)O(2)) advanced oxidation process (AOP) for the degradation of a prototypic endocrine disrupter, bisphenol A (BPA), in laboratory water. Removal rates of BPA and formation of degradation products were determined by high performance liquid chromatography (HPLC) analysis. Changes in estrogenic activity were evaluated using both in vitro yeast estrogen screen (YES) and in vivo vitellogenin (VTG) assays with Japanese medaka fish (Oryzias latipes). Our results demonstrate that UV alone did not effectively degrade BPA. However, UV in combination with H(2)O(2) significantly removed BPA parent compound and aqueous estrogenic activity in vitro and in vivo. Removal rates of in vivo estrogenic activity were significantly lower than those observed in vitro, demonstrating differential sensitivities of these bioassays and that certain UV/AOP metabolites may retain estrogenic activity. Furthermore, the UV/H(2)O(2) AOP was effective for reducing larval lethality in treated BPA solutions, suggesting BPA degradation occurred and that the degradation process did not result in the production of acutely toxic intermediates.     

Wastewater disinfection alternatives: chlorine, ozone, peracetic acid, and UV light.

Disinfection tests were carried out at pilot scale to compare the disinfection efficiency of ozone, sodium hypochlorite (NaOCl), peracetic acid (PAA), and UV irradiation. Total coliforms, fecal coliforms, and Escherichia coli were monitored as reference microorganisms. Total heterotrophic bacteria (THB) were also enumerated by cytometry. At similar doses, NaOCl was more effective than PAA, and its action was less affected by contact time. The results obtained by ozonation were comparable for total coliforms, fecal coliforms, and E. coli. On the contrary, some differences among the three indicators were observed for NaOCl, PAA, and UV. Differences increased with increasing values of the disinfectant concentration times contact time (C x t) and were probably the result of different initial counts, as total coliforms include fecal coliforms, which include E. coli. The UV irradiation lead to complete E. coli removals, even at low doses (10 to 20 mJ/cm2). Total heterotrophic bacteria appeared to be too wide a group to be a good disinfection indicator; no correlation was found among THB inactivation, dose, and contact time.     

Characterization of permanent fouling on the surfaces of UV lamps used for wastewater disinfection.

A significant problem with UV disinfection of wastewater is the accumulation of fouling materials at sleeve-water interfaces. It has been shown that automated chemical and/or mechanical cleaning can remove most fouling materials satisfactorily. However, permanent foulants, which cannot be removed completely by typical cleaning operations, always remain on the quartz sleeves. These permanent foulants reduce UV transmittance, in turn reducing disinfecting effectiveness. This research investigated the origins, formation, and composition of permanent fouling. Four instrumental analyses were used: atomic force microscope (AFM), X-ray fluorescence (XRF), scanning electron microscope combined with energy dispersive X-ray microanalysis (SEM/EDX), and sleeve UV transmittance (SUVT). It appeared that permanent foulants were trapped initially by microscale holes and peaks on fresh sleeve surfaces. Based on the topography and roughness measurements from the AFM, after long-term regular chemical and mechanical cleaning, the wipers of cleaning systems damage sleeve surfaces, creating scratches or holes with larger surface areas. Foulants are trapped more easily, and are attached tightly to the surfaces of these scratches or to each other. The results from XRF and SEM/EDX showed that the main fouling components were aluminum, iron, magnesium, calcium, and phosphorus. These could not be related to wastewater quality. For the specific cases studied, chemical plus mechanical cleaning is more effective in removing foulants and avoiding the accumulation of permanent foulants than mechanical cleaning alone; in most cases, SUVT was higher than 90% after chemical plus mechanical cleaning, whereas mechanical cleaning alone achieved only approximately 30% SUVT after long-term usage.     

Point-of-use water disinfection using UV light-emitting diodes to reduce bacterial contamination

The treatment process described in this research explores the impact of exposing water samples containing fecal coliforms to the radiation produced by single ultraviolet (UV) light-emitting diodes (LEDs) operating at 265 nm. UV LEDs are long lasting, compact in size and produce more efficient light output than traditional mercury-vapour bulbs, making them ideal for application in point-of-use disinfection systems, such as in remote areas. In this study, contaminated water samples containing either a pure culture of Escherichia coli or tertiary effluent from the City of Regina Wastewater Treatment Plant were used to study the application and efficiency of using UV LEDs for water disinfection. The results indicate that bacterial inactivation was achieved in a time-dependent manner, with 1- and 2.5-log E. coli reductions in water following 20 and 50 min of UV LED exposure, respectively. Ultraviolet radiation was less effective in reducing coliform bacteria in wastewater samples due to the elevated turbidity levels. Further work remains to be completed to optimize the application of UV LEDs for point-of-use disinfection systems; however, the results from this study support that bacterial inactivation using UV LEDs is possible, meriting further future technological development of the LEDs.     

Degradation of benzimidazoles by photoperoxidation: metabolites detection and ecotoxicity assessment using Raphidocelis subcapitata microalgae and Vibrio fischeri

Environmental Science and Pollution Research - Benzimidazoles (BZ) are among the most used drugs to treat parasitic diseases in both human and veterinary medicine. In this study, solutions...     

Ecotoxicity and genotoxicity assessment of losartan after UV/H2O2 and UVC/photolysis treatments

Environmental Science and Pollution Research - Losartan potassium (LOS) is one of the most antihypertensives used in the world, and its presence in environmental matrices can cause impacts to...     

紫外消毒器辐射剂量模拟与设备设计

基于拉格朗日方法建立了耦合流体流动、紫外光强辐射与粒子辐射剂量的数值计算模型.利用该模型对工业尺寸的紫外消毒设备进行了模拟计算,获得了消毒设备内的场量信息;展示了利用CFD模拟优化设计紫外消毒反应器的方法;讨论了设置挡板和改变灯管布置2种方式对粒子辐射剂量的影响,计算结果表明,调整辐射场对紫外消毒设备性能的改善程度明显高于改变流动状态.     

Ionic liquids as lubricants or lubrication additives: An ecotoxicity and biodegradability assessment

This paper reports on the (eco)toxicity and biodegradability of ionic liquids considered for application as lubricants or lubrication additives. Ammonium- and pyrrolidinium-based cations combined with methylsulphate, methylsulphonate and/or (CF₃SO₂)₂N⁻ anions were investigated in tests to determine their aquatic toxicity using water fleas Daphnia magna, green algae Selenastrum capricornutum and marine bacteria (Vibrio fischeri). Additional test systems with an isolated enzyme (acetylcholinesterase) and isolated leukaemia cells from rats (IPC-81) were used to assess the biological activity of the ionic liquids. These compounds generally exhibit low acute toxicity and biological activity. Their biodegradability was screened according to OECD test procedures 301 B and 301 F. For choline and methoxy-choline ionic liquids ready biodegradability was observed within 5 or 10 d, respectively. Some of the compounds selected have a considerable potential to contribute to the development of more sustainable products and processes.     

O3／UV预处理磺酰脲类除草剂生产废水的研究

采用O3／UV工艺预处理磺酰脲类除草剂生产废水,考察了初始pH值、臭氧投量、叔丁醇投加等因素对废水处理效果的影响,并初步探讨了该工艺处理废水的反应机理。实验结果表明,在废水初始pH为13．59和臭氧投量为65．08mg／min的条件下,预处理80min后废水COD去除率达63．47％,BOD5／COD由0．03提高至0．56,EC50从11％提高至55％。随着叔丁醇浓度的增加,废水COD去除率明显降低,证明该反应体系有·OH存在;体系中加入MnO2后废水COD去除率下降了16％,氧化效率明显下降,证明该反应体系内中间产物HO2O在O3／UV降解有机废水过程中起到了重要的作用。     

Decolorizing of lignin wastewater using the photochemical UV/TiO2 process

Studies on applying the photochemical UV/TiO2 oxidation process to treat the lignin-containing wastewater for dissolved organic carbon (DOC), color and reducing A254 (the absorption at the wavelength of 254 nm) have been carried out. The data obtained in this study demonstrate that the UV/TiO2 process is effective in oxidizing the lignin thus reducing the color and DOC of the wastewater treated. The combined UV/TiO2 treatment can achieve better removal of DOC and color than the UV treatment alone. Color removal, based on American Dye Manufacture Index (ADMI) measurement, is greater than 99% if the pH is maintained at 3.0 with the addition of 1 g l(-1) TiO2. When 10 g l(-1) TiO2 is applied, the oxidation reduction potential (ORP) value is reached to result in an 88% removal of both DOC and color. A model was developed based on the variation of ORP during the photochemical reaction to simulate the decoloring process. The proposed model can be used to predict the color removal efficiency of the UV/TiO2 process.     

Impact assessment of cadmium contamination on rice (Oryza sativa L.) seedlings at molecular and population levels using multiple biomarkers

Assessment of environmental contamination on ecology (plant) at molecular and population levels is important in risk quantification and remediation study. Random amplified polymorphic DNA (RAPD) assay and related other fingerprinting techniques have been employed to detect the genotoxin-induced DNA damage and mutations. This research compared the effects occurring at molecular and population levels in rice seedlings exposed to cadmium (Cd) concentrations of 15-60 mg l(-1) for 8 days with quartz sand culture. Inhibition of root growth and increase of total soluble protein content in root tips of rice seedlings were observed with the increase of Cd concentration. For the RAPD analyses, 12 RAPD primers of 50-70% GC content were found to produce unique polymorphic band patterns and subsequently were used to produce a total of 180 bands of 179-3056 bp in molecular size in the control root tips of rice seedlings. Results produced by these RAPD primers indicate that changes in RAPD profiles of root tips after Cd treatment include modifications in band intensity and gain or loss of bands by comparison with control. The effect of changes was dose-dependent. Genomic template stability compares favourably with the traditional indices such as root growth and soluble protein content. The DNA polymorphisms detected by RAPD analysis can be applied as a suitable biomarker assay for the detection of genotoxic effects of Cd contamination on plants.     

Effects of activated sludge and UV disinfection processes on the bacterial community and antibiotic resistance profile in a municipal wastewater treatment plant

Environmental Science and Pollution Research - Wastewater tertiary treatment has been pointed out as an effective alternative for reducing the concentration of antibiotic resistant bacteria and...     

Peracetic acid disinfection: a feasible alternative to wastewater chlorination.

The paper summarizes the results of a bench-scale study to evaluate the feasibility of using peracetic acid (PAA) as a substitute for sodium hypochlorite both for discharge into surface water and for agricultural reuse. Trials were carried out with increasing doses (1, 2, 3, 5, 10, and 15 mg/L) and contact times (6, 12, 18, 36, 42, and 54 minutes) to study disinfectant decay and bacterial removal and regrowth, using fecal coliform and Escherichia coli (E. coli) as process efficiency indicators. Peracetic acid decay kinetics was evaluated in tap water and wastewater; in both cases, PAA decays according to first-order kinetics with respect to time, and a correlation was found between PAA oxidative initial consumption and wastewater characteristics. The PAA disinfection efficiency was correlated with operating parameters (active concentration and contact time), testing different kinetic models. Two data groups displaying a different behavior on the basis of initial active concentration ranges (1 to 2 mg/L and 5 to 15 mg/L, respectively) can be outlined. Both groups had a "tailing-off" inactivation curve with respect to time, but the second one showed a greater inactivation rate. Moreover, the effect of contact time was greater at the lower doses. Hom's model, used separately for the two data groups, was found to best fit experimental data, and the disinfectant active concentration appears to be the main factor affecting log-survival ratios. Moreover, the S-model better explains the initial resistance of E. coli, especially at low active concentrations (< 2 mg/L) and short contact times (< 12 minutes). Microbial counts, performed by both traditional methods and flow cytometry, immediately and 5 hours after sample collection (both with or without residual PAA inactivation), showed that no appreciable regrowth took place after 5 hours, neither for coliform group bacteria, nor for total heterotrophic bacteria.     

Post-treatment of bio-treated acrylonitrile wastewater using UV/Fenton process: degradation kinetics of target compounds

In this study, post-treatment of bio-treated acrylonitrile wastewater was performed using the UV/Fenton process. Five target compounds (furmaronitrile, 3-pyridinecarbonitrile, 1,3-dicyanobenzene, 5-methyl-1H-benzotriazole, and 7-azaindole) were selected as target compounds and their degradation kinetics were examined. Under optimal reaction conditions (H₂O₂ dosage 3.0 mM, Fe²⁺ dosage 0.3 mM, and initial pH 3.0), more than 85% of total organic carbon (TOC) was eliminated in 30 min when a 10-W UV lamp was employed, and the electrical energy per order of magnitude for TOC removal was as low as 2.96 kWh m^?3. Furthermore, the target compounds and the toxicity were largely removed from the bio-treated effluent. Size exclusion chromatography with organic carbon detector analysis revealed that organic components with a wide range of molecular weights were greatly reduced after the UV/Fenton process. A simplified pseudo steady-state (SPSS) model was applied to predict the degradation of target compounds during the UV/Fenton process. The concentrations of generated hydroxyl radicals were estimated to be 3.06 × 10^?12 M, 6.37 × 10^?12 M, and 10.9 × 10^?12 M under 5-, 10-, and 15-W UV lamps, respectively. These results demonstrate that the proposed SPSS model fitted well with experimental data on the post-treatment of real wastewater, and consequently indicate that this model can be a useful tool in the prediction of degradation of target compounds during the UV/Fenton process.

     

Ultraviolet and chlorine disinfection of mycobacterium in wastewater: effect of aggregation.

Mycobacteria naturally aggregate in water, a characteristic that may serve to protect them against disinfection in wastewater. Secondary effluent was spiked with Mycobacterium terrae (M. terrae), sequentially filtered through 100-, 41-, and 20-microm nylon filters to partition aggregate sizes, confirmed using particle-size analysis and microscopy. Each sample was exposed to doses of UV light (10 to 60 mJ/cm2 at 254 nm) and free chlorine (27 to 150 mg-min/L at 4 degrees C). Inactivation of M. terrae in wastewater was initially rapid, with 2.5 log reduction at 14 mJ/cm2 and 56 mg-min/L for UV and free chlorine, respectively. However, in effluent and 100-microm filtered wastewater, spiked M. terrae was present to the highest doses evaluated. Interestingly, M. terrae passed through 41- and 20-microm filters were inactivated rapidly, with no survivors after moderate disinfection doses. Inactivation of Mycobacteria in wastewater may be compromised by aggregates larger than 41 microns.