Reduction Of Genotoxicity Research Articles

Alkaline chlorination of drinking water: A trade-off between genotoxicity control and trihalomethane formation

The pH of chlorination is an important factor affecting the formation of disinfection byproducts (DBPs). In this study, we discovered that the genotoxicity induced by chlorination can be effectively reduced under alkaline conditions. As the pH of chlorination increased from 6.5 to 8.5, the genotoxicity of investigated waters reduced by ∼30–90 %. By assessing the genotoxicity of the mixture of measured DBPs, it was found that the contribution of measured DBPs to the overall genotoxicity was lower than 5 %, and the significant reduction of genotoxicity was largely associated with unknown DBPs. The result of Pearson's correlation analysis indicated that humified organics and soluble microbial byproducts were likely responsible for the genotoxicity, and their derived genotoxic compounds (i.e., unknown DBPs) tended to decompose during alkaline chlorination. However, the control of genotoxicity by alkaline chlorination was achieved at the expense of promoting trihalomethane (THM) formation. The highest genotoxicity reduction (93 %) was observed for chlorinated granular activated carbon-treated waters, but the formation of THMs was promoted to a level approaching that in untreated waters. The inconsistent trend of overall genotoxicity and THM concentration during alkaline chlorination suggested the inadequacy of THMs as metric for DBP exposure, and considerations should also be given to the toxicity of bulk water in addition to regulated DBPs.

Reduction of Genotoxicity of Carbamazepine to Human Lymphocytes by Pre-treatment with Vitamin B12.

Carbamazepine (CBZ) is widely used as an anti-epileptic drug. Vitamin B12 has been shown to protect against DNA damage caused by several mutagenic agents. This study aimed to investigate the effect of vitamin B12 on CBZ-induced genotoxicity in cultured human lymphocytes. Sister chromatid exchanges (SCEs) and chromosomal aberrations (CAs) genotoxic assays were utilized to achieve the study objective. The results showed significantly higher frequencies of CAs and SCEs in the CBZ-treated cultures (12 μg/mL) compared to the control group (P<0.01). The genotoxic effects of CBZ were reduced by pre-treatment of cultures with vitamin B12 (13.5μg/ml, P<0.05). Neither CBZ nor vitamin B-12 showed any effects on mitotic and proliferative indices. CBZ is genotoxic to lymphocyte cells, and this genotoxicity can be reduced by vitamin B12.

The impact of natural sunlight irradiation on the biotoxicities of different molecular sizes EfOM/SRNOM and its relationship with spectral and molecular level parameters

Natural sunlight irradiation is regarded as an efficient and low-carbon method for controlling the biotoxicity of effluents from domestic wastewater treatment plants (WWTPs). Dissolved organic matter in WWTPs effluent (EfOM) is responsible for the non-specific biotoxicity of effluent. In the present study, the variation in spectral characteristics, molecular composition, luminescent bacteria toxicity, and genotoxicity of EfOM of different molecular sizes (MOSs) during natural sunlight irradiation were investigated from a systematic perspective, and the standard natural organic matter from the Suwannee River (SRNOM) was synchronously assessed for comparative purposes. To further explore the cause of the biotoxicity changes, the relationships between the spectral or molecular level parameters (obtained from FT-ICR MS analysis) and biotoxicity were assessed using correlation analysis. The molecules in <1 kDa EfOM with lower molecular weight, higher unsaturation degree, and higher humification and fluorescence had higher luminescent bacteria toxicity under sunlight irradiation. However, in the <1 kDa SRNOM, the molecules which were characterized by higher humification and fluorescence had higher luminescent bacteria toxicity. The notable genotoxicity reduction of EfOM under sunlight irradiation was attributed to the photochemical degradation of components with a high unsaturation degree. Such findings could enable ecological safety improvement of aquatic environments using natural sunlight.

Optimization of process variables for reduction of genotoxicity from paper mill effluent

In recent years, microbial techniques for wastewater degradation process optimization under laboratory circumstances have piqued the interest of many academics acress the word, prompting them to investigate practical, cost- effective and long-term wastewater treatment technologies. Some workers claim that certain metabolic compounds have mutagenic nature and endocrine disrupting properties. To confirm the degradation and identification of a variety of metabolic products that may have EDC properties, control and bacterial treated samples were analyzed with the help of HPLC and GC-MS.In this study, toxicity assessment (genotoxicity) were performed to confirm the load of various EDCs present in the RGP effluent.Glucose was the most abundant among the carbon sources used as it showed the greatest reduction in colour (61.93%) and COD (57.86%) at 96 hours of the incubation period. However, galactose and sucrose were also found to be very good, allowing 56% color and 48.4% COD reduction. Sodium nitrate, which is an inorganic nitrogen source, played an important role in pulp paper mill effluent decolorization as well as COD reduction. On the other hand, a negative contribution to the color reduction was shown by the inorganic nitrogen source ammonium nitrate.

TOXICITY ASSESSMENT OF BIOREMEDIATED CONTAMINATED DOMESTIC WATER SOURCES IN WESTERN NIGER-DELTA BY A PHYTOGENOTOXICTY TEST

In this study, fungal mycelium was employed for the bioremoval of heavy metals in drinking water samples obtained from boreholes, streams and a pond in six rural communities in Warri North Local Government Area in Delta State. The efficacy of the fungal-based bioremediation technology for toxicity reduction in the contaminated water samples was evaluated using Allium cepa cyto-genotoxicity bioassay in vitro approach before and after treatment with the fungal biofilters. Data obtained from physicochemical analysis after a 24 h myco-filtration treatment of the water samples revealed significant (p &lt; 0.05) reduction/total elimination of heavy metals and microbial load in the samples. Results obtained from the 96 hour macroscopic evaluation of A. cepa showed that, compared to onions grown in untreated samples, there was significant (p &lt; 0.05) reduction in root growth inhibition in onion bulbs cultivated in mycofiltrated samples. Similarly, results obtained from cytological studies by the aceto-orcein squash technique in root tips of A. cepa grown in the contaminated water samples for 48 hours showed significant (p &lt; 0.05) reduction in chromosomal aberrations. These findings indicate that the reduction in genotoxicity established by the Allium bioassay is highly correlated with myco-filtration bioremediation of the contaminated drinking water sources.

Assessment of the in vitro effect of intra and extracellular extracts of Lactobacillus against genotoxicity and oxidative stress caused by acrylamide

Introduction: acrylamide is formed by the Maillard reaction and is found in many food products subjected to thermal processes, generating genotoxicity and DNA damage. Studies have reported that lactobacilli have the ability to generate compounds with antioxidant, antigenotoxic and antimutagenic activity, which is why the present work aims to evaluate the effect of Lactobacillus strains and their intra and extracellular extracts against genotoxicity and oxidative stress as caused by acrylamide. Methods: a strain of Lactobacillus casei Shirota and a strain of Lactobacillus reuteri NRRL B-14171 were used, both were cultured in MRS broth and subjected to mechanical and enzymatic treatments to obtain extra and intracellular extracts. Lymphocytes were cultured in RPMI medium. Lipid peroxidation was evaluated by TBARS and the antioxidant capacity was measured in the extra and intracellular extracts with the ABTS technique, also using a strain of Saccharomyces cerevisiae RC 212 as a model. The reduction of lipid peroxidation in lymphocytes was measured by TBARS and the reduction of genotoxicity by reducing the formation of micronuclei in lymphocytes. Results: both strains evaluated, as well as their intra and extracellular extracts, showed the ability to counteract oxidative stress and genotoxicity caused by acrylamide. Conclusion: the results found suggest that the use of intra and extracellular extracts of both strains could be an alternative to reduce the effects of genotoxicity and oxidative stress caused by acrylamide without the need for a viable structure.

Oxidative degradation and mineralization of the endocrine disrupting chemical bisphenol-A by an eco-friendly system based on UV-solar/H2O2 with reduction of genotoxicity and cytotoxicity levels

A solar-driven advanced oxidation process at a lab scale was studied for the degradation and mineralization of the known endocrine disrupting chemical (EDC), bisphenol A (BPA). Preliminary tests were performed varying the irradiation source, BPA/H2O2 ratio, temperature, initial H2O2 concentration, initial solution pH, and initial BPA concentration, then, the operational conditions of the UV-solar/H2O2 were optimized by a response surface methodology (RSM), providing the following responses: UV-solar/H2O2 process at pH 3.0, [BPA]0 = 25 mg L−1, [H2O2] = 350 mg L−1, T = 50 °C, achieving BPA degradation of 77.4% and BPA mineralization of 38.2%, H2O2 consumption of 230 mg L−1. From the optimized condition, different pH ranges were tested (3.0; 5.0; 7.0; 9.0; and 11.0), where, at solution pH 5.0 the best removal rates were achieved (89.2% BPA degradation and 49.0% BPA mineralization). The BPA amount in solution was monitored by High Performance Liquid Chromatography (HPLC) and a study of the intermediate reaction by-products was performed by Gas Chromatography–Mass Spectrometry (GC–MS) analyses, highlighting the lower amount of by-products identified when the solution pH 5.0 was employed, rather than the solution pH 3.0. Genotoxicity tests with Zebrafish (Danio rerio) and cytotoxicity tests with Allium cepa were performed aiming to evaluate errors in the cells and nuclear abnormalities of the tested organisms induced by BPA raw samples, as well as by the BPA samples treated by the UV-solar/H2O2 process. Therefore, the bio-toxicity levels for an animal and a vegetal bio-indicator were reduced by applying a renewable source of energy as the irradiation source for the UV/H2O2 process, representing an efficient and eco-friendly alternative for BPA treatment in aqueous solutions.

Protective roles of grape seed (Vitis vinifera L.) extract against cobalt(II) nitrate stress in Allium cepa L. root tip cells.

Excessive doses of toxic metals such as cobalt may cause detrimental hazards to exposed organisms. Six groups of onion bulbs were formed to investigate the therapeutic effects of grape seed extract (GSE) against cobalt(II) nitrate (Co(NO3)2) exposure in Allium cepa L. root tips. Control group was irrigated with tap water, while the latter groups were exposed to 150mg/L GSE, 300mg/L GSE, 5.5ppm Co(NO3)2, 5.5ppm Co(NO3)2 + 150mg/L GSE and 5.5ppm Co(NO3)2 + 300mg/L GSE, respectively. Co(NO3)2 treatment seriously inhibited the root growth, germination and weight gain of the bulbs. Mitotic index was significantly decreased, whereas the chromosomal aberrations and micronuclei incidence exhibited a remarkable increase. In addition, Co(NO3)2 induced a variety of anatomical disorders in onion roots. Lipid peroxidation levels of the cellular membranes were assessed measuring the malondialdehyde content (MDA). MDA amount in Co(NO3)2-treated group reached the highest level among all groups. Co(NO3)2 treatment enhanced the activity of superoxide dismutase and catalase. The addition of GSE to Co(NO3)2 solution substantially suppressed the negative effects of Co(NO3)2 in a dose-dependent manner by strengthening the antioxidant defence system and reducing the cytotoxicity. Moreover, there was a significant recovery in growth parameters following the grape seed addition to Co(NO3)2. GSE had a remarkable reduction in genotoxicity when treated as a mixture with Co(NO3)2. Overall data obtained from this investigation proved that GSE, as a promising functional by-product, had a protective effect on Allium cepa L. against the toxic effects of Co(NO3)2.

Prolonged exposure to particulate Cr(VI) is cytotoxic and genotoxic to fin whale cells

BackgroundHexavalent chromium [Cr(VI)] is a human lung carcinogen and global marine pollutant. High Cr concentrations, resembling the ones observed in occupationally exposed workers, have been observed in fin whales (Balaenoptera physalus) in the Gulf of Maine. This outcome suggests Cr might be disrupting the health of fin whale populations. Indeed, Cr in acute (24 h) exposure does cause toxicity in fin whale cells. However, human cell culture data indicate prolonged exposures (120 h) induce a higher amount of toxicity compared to 24 h exposure due to an inhibition of homologous recombination repair. However, whether prolonged exposure causes similar outcomes in fin whale cells is unknown. ObjectiveDue to the importance of assessing prolonged exposure toxicity, this study focuses on characterizing acute and prolonged exposure of Cr(VI) in male and female fin whale cells. MethodsCytotoxicity was measured by the clonogenic assay, also known as colony forming assay, which measures the ability of cells to proliferate and form colonies after the treatment. DNA double strand breaks were analyzed by neutral comet assay. Clastogenicity was measured using the chromosome aberration assay. Intracellular Cr levels were measured with Graphite Furnace Atomic Absorption Spectrometry (GFAAS) with Syngistix Software. ResultsIn this study, we demonstrate that particulate Cr(VI) induces cytotoxicity and genotoxicity in a treatment-dependent manner after 24 h and 120 h exposures. Cytotoxicity levels were generally low with relative survival above 64 %. DNA double strand break data and chromosome aberration data were elevated after a 24 h exposure, but decreased after a 120 h exposure. While cytotoxicity was similar after 24 h and 120 h exposures, less DNA double strand breaks and chromosomal instability occurred with prolonged exposure. ConclusionParticulate Cr(VI) is cytotoxic and genotoxic to fin whale cells after acute and prolonged exposures. The reduction of genotoxicity we have observed after 120 h exposure may be partly explained by lower intracellular Cr levels after 120 h. However, the decrease in intracellular levels is not reflected by a similar decrease in chromosome aberrations suggesting other mechanisms may be at play. Male fin whale cells appear to be more susceptible to the genotoxic effects of particulate Cr(VI) while female cells are less susceptible possibly due to increased cell death of damaged cells, but more work is needed to clarify if this outcome reflects a sex difference or interindividual variability. Overall, the study shows particulate Cr(VI) does induce toxicity at both acute and prolonged exposures in fin whales cells indicating Cr(VI) exposure is a health risk for this species.

Evaluation of enhanced coagulation combined with densadeg-ultrafiltration process in treating secondary effluent: Organic micro-pollutants removal, genotoxicity reduction, and membrane fouling alleviation

Conventional coagulation is widely used as an ultrafiltration membrane pretreatment process in wastewater reclamation, however it shows little ability to reduce organic micro-pollutants (OMPs) and genotoxicity. In this research, powdered activated carbon (PAC) and potassium ferrate were used respectively with polyaluminum chloride (PACl) to enhance coagulation. Filtration experiments of coagulation (CUF), coagulation-adsorption (CAUF) and coagulation-oxidation (COUF) pretreatment combined with densadeg-ultrafiltration processes were conducted under their optimum doses. The effluent water quality of CAUF and COUF could meet the water reuse quality standard for scenic environment use, while total phosphorus in the conventional CUF discharge was higher than the standard. The average removal efficiency of the selected fourteen OMPs was significantly improved by 1.8 times through the CAUF process compared to the CUF process (31.2%), whereas the COUF process (38.4%) showed limited improvement. Prominent reduction of genotoxicity was observed in the CAUF and COUF processes, and the effluent of the CAUF process had the least genotoxicity of 1.0 ± 0.3 μg 4-Nitroquinoline-N-oxide (4-NQO)/L. Moreover, the average transmembrane pressure increasing rate followed the order of CUF (1.5 kPa/d) > COUF (1.1 kPa/d) > CAUF (0.6 kPa/d), indicated that the enhanced coagulation process could relieve membrane fouling effectively.

Surrogates for the removal by ozonation of the cytotoxicity and DNA double-strand break effects of wastewater on mammalian cells

Effluents from wastewater treatment plants (WWTPs) may contain various pollutants with potential toxic effects. Ozonation is widely applied to purify wastewater, which may influence the toxicity and water quality indices simultaneously. The main goal of this study was to reveal influence of ozonation on toxicity of WWTP effluents and to find the surrogates for toxicity changes. Cytotoxicity and DNA double-strand break (DSB) effect of WWTP effluents were measured based on Chinese hamster ovary (CHO) cells. Changes of water quality parameters and molecular weight distribution of WWTP effluents were also measured. The organic extracts in WWTP effluents were shown to decrease the cell viability. Besides, an increased level of DNA DSBs was found in cells when exposed to the organic extracts. Ozonation significantly eliminated cytotoxicity and DNA DSB-based genotoxicity of WWTP effluents, with removal rates of 53–66% and 51–76% for cytotoxicity and genotoxicity, respectively, with 10 mg/L ozone dose. Although the DOC contents in WWTP effluents were hardly removed by ozonation, the chromophores and fluorophores were significantly eliminated. Organic matter in WWTP effluents mainly consists of fractions with molecular weight (MW) < 500 Da. Ozonation generally decreased the fluorescence intensity and UV254 values of all the MW fractions, but increased the DOC contents of the 100–500 Da fraction. During ozonation, the removal rates of UV254 and SUVA254 were significantly correlated to the removal rates of both cytotoxicity and genotoxicity. UV254 might be an ideal surrogate for cytotoxicity and genotoxicity reduction during wastewater ozonation.

The treatability of trace organic pollutants in WWTP effluent and associated biotoxicity reduction by advanced treatment processes for effluent quality improvement

As increasing attention is paid to surface water protection, there has been demand for improvements of domestic wastewater treatment plant (WWTP) effluent. This has led to the application of many different advanced treatment processes (ATPs). In this study, the treatability of trace organic pollutants in secondary effluent (SE) and associated biotoxicity reduction by four types of ATPs, including coagulation, granular activated carbon (GAC) adsorption, ultraviolet (UV) photolysis and photocatalysis, and ozonation, were investigated at the bench-scale. The ATPs showed different removal capacity for the 48 chemicals, which were classified into seven categories. EDCs, herbicides, bactericides and pharmaceuticals were readily degraded, and insecticides, flame retardants, and UV filters were relatively resistant to removal. During these processes, the efficiency of the ATPs in reducing four biological effects were investigated. Of the four biological effects, the estrogenic activity from SE was not detected using the yeast estrogen screen. In contrast with genotoxicity and photosynthesis inhibition, bacterial cytotoxicity posed by SE was the most difficult biological effect to reduce with these ATPs. GAC adsorption and ozonation were the most robust treatment processes for reducing the three detected biotoxicities. UV photolysis and photocatalysis showed comparable efficiencies for the reduction of genotoxicity and photosynthesis inhibition. However, coagulation only performed well in genotoxicity reduction. The effect-based trigger values for the four bioassays, that were derived from the existing environmental quality standards and from HC5 (hazardous concentration for 5% of aquatic organisms), were all used to select and optimize these ATPs for ecological safety. Conducting ATPs in more appropriate ways could eliminate the negative effects of WWTP effluent on receiving water bodies.

Phytotoxicity and genotoxicity evaluation of 2,4,6-tribromophenol solution treated by UV-based oxidation processes

The environmental detriment due to the presence of emerging contaminants has encouraged the development of advanced oxidation processes. Such methods deal with non-selective chemical reactions. Therefore, toxic byproducts can be generated and distinct post treatment toxicity levels can be expected. The present study investigates the phytotoxicity of 2,4,6-tribromophenol (TBP) to L. sativa seeds and A. cepa bulbs, as well as the TBP phytotoxicity and genotoxicity to A. cepa root. L. sativa seeds and A. cepa bulbs were germinated by being exposed to solutions containing TBP before and after treatment by UV-based processes: direct photolysis (DP), heterogeneous photocatalysis (HP) and photoelectrolysis (PEC). Subsequent analysis of the root length, to determine phytotoxicity, as well as evaluation of chromosomal abnormalities, revealed that the samples treated by DP presented higher phytotoxicity than the untreated ones. On the other hand, samples treated by HP and PEC did not present phytotoxicity. In fact, for the A. cepa assays, phytotoxicity was not observed, including the initial sample. However, genotoxicity assays showed a high frequency of chromosomal aberrations in the initial sample, before the UV-based process treatment. After 140 min of treatment by HP, there was a reduction in genotoxicity, while PEC treatment resulted in a sample with no genotoxicity. In contrast, DP presented high levels of phytotoxicity and genotoxicity. Additionally, DP shows similar degradation and debromination values, when compared to the HP and PEC processes, but less mineralization. Therefore, considering that the DP process did not deals with the HO• radical, the oxidation pathway can generate byproducts with higher toxicity, which lead to higher levels of phytotoxicity and genotoxicity. These results show that different UV-based oxidation processes are associated to distinct byproducts and toxicity levels. In addition, a toxicity assessment with different organisms should be performed to ensure a safe outcome.

Sorption technique as a tool for reduction of genotoxicity.

In the present study, the Allium cepa root chromosomal aberration assay was used to determine the genotoxic effects of copper and cadmium ions solutions before and after sorption processes. The sorption process was carried out using unmodified Dendrocalamus strictus charcoal powder, nitrilotriacetic acid (NTA)-modified D. strictus charcoal powder, and Saccharomyces cerevisiae. The frequency of total chromosomal aberrations was observed to be 24.30-45.13% for copper and 13.16-45.14% for cadmium at different concentrations (1-500 mg/l) before the sorption process. Both metal ions solutions resulted in significant reduction of chromosomal aberrations after all the modes of the sorption processes. However, the order of reduction of percentage chromosomal aberrations for copper and cadmium solutions was found to be 45.29-70.04% and 47.80-84.57%, respectively (NTA-modified D. strictus charcoal powder); >44.53-54.32% and 37.10-79.40%, respectively (unmodified D. strictus charcoal powder); >15.59-48.51% and 13.63-21.50%, respectively (S. cerevisiae).

Reduction of Wastewater Organic Micro-pollutants and Genotoxicity in a Hybrid Process Involving Anaerobic-anoxic-oxic and Ozonation Treatments

In recent years, researchers have drawn greater attention to the occurrence, fate, and risk of organic micro-pollutants (OMPs) in the environment. Effluent from municipal wastewater treatment plants (WWTPs) are an important source for the release of OMPs into aquatic environment and should be monitored and controlled. The migration and transformation of 14 selected OMPs and their reduction of genotoxicity after treatment by a hybrid process of anaerobic-anoxic-oxic (AAO) and ozonation were investigated. Results showed that the activated sludge process was poor in removing most OMPs, with removal rates of less than 50%. However, ozonation improved OMPs removal, and the hybrid process could reduce most of the OMPs by more than 90%-with OMPs containing phenolic, aniline, and anisole groups in their aromatic structures showing particular vulnerability to attack by ozone. The results of genotoxicity analyses showed that the wastewater influent and secondary effluent exhibited genotoxicity to an extent, and ozonation reduced the genotoxicity of secondary effluent by 98%, thus largely reducing the environmental risk posed by OMPs in WWTP effluent.

Optimization of nimesulide oxidation via a UV-ABC/H2O2 treatment process: Degradation products, ecotoxicological effects, and their dependence on the water matrix

Nimesulide (Nim) degradation in ultrapure water (UW) and municipal sewage (MS) via UV-ABC/H2O2 was investigated. The variables included in the experimental design were time, initial Nim, and initial H2O2 concentrations. Resulting decreases in Nim concentration (monitored by high performance liquid chromatography (HPLC) using a photodiode array detector operating at a maximum UV absorbance of 300 nm), mineralization (from total organic carbon (TOC) measurements), and ecotoxicity (assays employing the bioindicators Daphnia similis, Artemia salina, and Allium cepa) were also studied. Degradation rates of 90% or higher were found for 15–20 min reaction times, employing combinations of [H2O2] = 50–150 mg L−1 and [Nim] = 8.5–15 mg L−1 prepared with MS. Mineralization rates of 70% and higher were attained within 60 min of reaction for [Nim] = 15 mg L−1 prepared in MS with [H2O2] = 100 mg L−1. Nim by-products were detected and possible degradation pathways proposed. Ecotoxicity evaluation using A. salina, D. similis, and A. cepa revealed that the treated samples had significantly lower toxicity. Exposure to treated samples resulted in survival rates of 79% for A. salina and over 90% for D. similis. No root growth inhibition was observed in A. cepa exposed to treated samples, whereas exposure to untreated samples inhibited root growth by 60%. Statistical analysis revealed elimination of cytotoxicity and reduction of genotoxicity against A. cepa. The results showed that the UV-ABC/H2O2 process can be employed as a pre- or post-treatment method to remove Nim from contaminated wastewater.

Aflatoxin B1 detoxification by cell-freeextracts of Rhodococcus strains.

Aflatoxin B1 (AFB1) produced by Aspergillus molds is a genotoxic and carcinogenic mycotoxin. For the elimination of mycotoxins from food and feed, biodetoxification can be a successful tool. The aim of this study was to reveal biodetoxification with the cell-free extracts of Rhodococcus erythropolis NI1 and Rhodococcus rhodochrous NI2, which have been already proved to detoxify AFB1. Extracellular matrices of cultures and also intracellular extracts were applied for detoxification. In both cases, media containing constitutively produced and AFB1-induced enzymes were tested, respectively. The pH tolerance of enzymes in the detoxification was examined at pH 7, 7.5, and 8. The remained genotoxicity was detected by SOS-Chromotest and the AFB1 concentration was measured by high performance liquid chromatography with fluorescence detection. In the extracellular matrix, no reduction of genotoxicity was observed. However, detoxification was completed by intracellular enzymes. In intracellular extracts of both strains, genotoxicity was ceased by the constitutive enzymes within 6h but induced and constitutive enzymes collectively achieved this result within minutes. Moreover, total biodetoxification was observed at every pH adjustment. Analytical results confirmed >84% degradation potential in each sample. Our results indicate a uniquely fast way for the detoxification of AFB1 with intracellular enzymes of R. erythropolis NI1 and R. rhodochrous NI2.

Evaluation of acute toxicity, cytotoxicity and genotoxicity of landfill leachate treated by biological lagoon and advanced oxidation processes

The production of domestic waste is increasing so much that waste disposal has become a serious problem in terms concern for the hazard to the human and environment. In Brazil, landfill is the most common method of municipal solid waste disposal. The present study aims to evaluate the efficiency of different advanced oxidation processes (ozonization (alkaline pH), electrochemical oxidation+ozonation (alkaline pH) and photo-electrochemical oxidation) and biological system as a treatment of leachate to remove acute-cyto-genotoxicity of municipal landfills. Toxicity assays were performed on Allium cepa, assessing root growth (acute toxicity), cell division (cytotoxicity), and chromosomal aberrations (genotoxicity). Results indicate high acute toxicity, cytotoxicity and genotoxicity of the raw leachate at nearly all collection times. The biological treatment proved to be inefficient in the improvement of physicochemical properties and in the reduction of genotoxicity. In general, all the advanced oxidation processes presented greater removal for physicochemical parameters as well as a reduction of the genotoxic potential. However, only the treatment with electrochemical oxidation+ozonation provided an effluent with physicochemical properties that are in line with the Brazilian legislation, being suitable for disposal in water bodies. On the other hand, electrochemical oxidation+ozonation and photo-electrochemical oxidation treatments were able in removing the genotoxicity though none managed to totally reduce the acute toxicity.

A comparison of genotoxicity change in reclaimed wastewater from different disinfection processes

Effluents before disinfection from four wastewater reclamation plants were treated with chlorine (Cl2), ozone (O3), chlorine dioxide (ClO2), medium-pressure ultraviolet (MPUV) and four different combinations of the above, to evaluate the effect of disinfection processes on the genotoxicity removal by the SOS/umu test. Results showed that the genotoxicity increased after MPUV irradiation (10–100 mJ/cm2), but declined when adopting other disinfection processes. The effectiveness of genotoxicity reduction by five chemical disinfectants was identified as: O3 > pre-ozonation with Cl2 ≈ ClO2 > combination of ClO2 and Cl2 > Cl2. The sequential combination of MPUV, Cl2 and O3 reduced the genotoxicity to a level similar to the source water. The influence of differential disinfection process varied on iodinated wastewater, which is closely related to the competitive reactions between disinfectants, iodine and dissolved organic matters. The removal of genotoxic pollutants and the formation of genotoxic disinfection by-products are the two major factors that lead to the change in genotoxicity during disinfection.

Comprehensive evaluation of three sets of advanced wastewater treatment trains for treating secondary effluent: Organic micro-pollutants and bio-toxicity

The environmental presence of organic micro-pollutants (OMPs) has posed increasing risks on aquatic organism and human health. The performance of three commonly used advanced wastewater treatment trains, coagulation-sand filter, coagulation-biological aerated filter (BAF) and ozonation-biological activated carbon (BAC), in removing fifteen residual contaminants and bio-toxicity of the effluent from a local municipal wastewater treatment plant (WWTP) were investigated. Relatively high level of OMPs (0.69–14.71 μg/L), genotoxicity (22.64 μg 4-NQO/L) and estrogenic activity (1.4 μg E2/L) were observed from the secondary effluent (SE). Limited OMPs and bio-toxicity reduction was achieved during coagulation with 20 mg/L of polymeric aluminium and sand filter. Ozonation exhibited high advantage in OMPs, genotoxicity and estrogenic activity reduction. More than 80% of removal was achieved for most OMPs after ozonation with normalized dose of 1.25 mg O3/mg DOC, and the removal of OMPs was consistent well with the second reaction kinetics constants of OMPs with ozone. Based on Pearson correlation analysis, spectroscopy indicators such as UV254 and total fluorescence (TF) exhibited a high positive correlation with genotoxicity reduction, while estrogenic activity was related well with OMPs variation. To sum up, spectroscopic indicators showed a high potential to indicate the OMPs and bio-toxicity of SE.