Based on the fact that recycling of combined filter backwash water(CFBW)directly to drinking water treatment plants(WTP)is considered to be a feasible method to enhance pollutant removal efficiency,we were motivated to evaluate the genotoxicity of water samples from two pilot-scale drinking water treatment systems,one with recycling of combined backwash water,the other one with a conventional process.An integrated approach of the comet and micronucleus(MN)assays was used with zebrafish(Danio rerio)to investigate the water genotoxicity in this study.The total organic carbon(TOC),dissolved organic carbon(DOC),and trihalomethane formation potential(THMFP),of the recycling process were lower than that of the conventional process.All the results showed that there was no statistically significant difference(P>0.05)between the conventional and recycling processes,and indicated that the genotoxicity of water samples from the recycling process did not accumulate in 15 day continuous recycling trial.It was worth noting that there was correlation between the concentrations of TOC,DOC,UV254,and THMFPs in water and the DNA damage score,with corresponding R2 values of 0.68,0.63,0.28,and 0.64.Nevertheless,both DNA strand breaks and MN frequency of all water samples after disinfection were higher than that of water samples from the two treatment units,which meant that the disinfection by-products(DBPs)formed by disinfection could increase the DNA damage.Both the comet and MN tests suggest that the recycling process did not increase the genotoxicity risk,compared to the traditional process. 相似文献
Various geographical duckweed isolates have been developed for phytoremediation of lead. The Pb2+ removal efficiency of Lemna aequinoctialis, Landoltia punctata, and Spirodela polyrhiza was investigated in monoculture and polyculture at different levels of pH and initial Pb2+ concentrations. L. aequinoctialis was not sensitive to the tested pH but significantly affected by initial Pb2+ concentration, whereas synergistic effect of pH and initial Pb2+ concentration on removal efficiency of L. punctata and S. polyrhiza was found. Although the majority of polycultures showed median removal efficiency as compared to respective monocultures, some of the polycultures achieved higher Pb2+ removal efficiencies and can promote population to remove Pb2+. Besides, the three duckweed strains could be potential candidates for Pb2+ remediation as compared to previous reports. Conclusively, this study provides useful references for future large-scale duckweed phytoremediation.
Accurate forecasting of municipal solid waste (MSW) generation is crucial and fundamental for the planning, operation and optimization of any MSW management system. Comprehensive information on waste generation for month-scale, medium-term and long-term time scales is especially needed, considering the necessity of MSW management upgrade facing many developing countries. Several existing models are available but of little use in forecasting MSW generation at multiple time scales. The goal of this study is to propose a hybrid model that combines the seasonal autoregressive integrated moving average (SARIMA) model and grey system theory to forecast MSW generation at multiple time scales without needing to consider other variables such as demographics and socioeconomic factors. To demonstrate its applicability, a case study of Xiamen City, China was performed. Results show that the model is robust enough to fit and forecast seasonal and annual dynamics of MSW generation at month-scale, medium- and long-term time scales with the desired accuracy. In the month-scale, MSW generation in Xiamen City will peak at 132.2 thousand tonnes in July 2015 – 1.5 times the volume in July 2010. In the medium term, annual MSW generation will increase to 1518.1 thousand tonnes by 2015 at an average growth rate of 10%. In the long term, a large volume of MSW will be output annually and will increase to 2486.3 thousand tonnes by 2020 – 2.5 times the value for 2010. The hybrid model proposed in this paper can enable decision makers to develop integrated policies and measures for waste management over the long term. 相似文献
Cyber security often depends on decisions made by human operators, who are commonly considered a major cause of security failures. We conducted 2 behavioral experiments to explore whether and how cyber security decision-making responses depend on gain–loss framing and salience of a primed recall prior experience. In Experiment I, we employed a 2 × 2 factorial design, manipulating the frame (gain vs. loss) and the presence versus absence of a prior near-miss experience. Results suggest that the experience of a near-miss significantly increased respondents’ endorsement of safer response options under a gain frame. Overall, female respondents were more likely to select a risk averse (safe) response compared with males. Experiment II followed the same general paradigm, framing all consequences in a loss frame and manipulating recall to include one of three possible prior experiences: false alarm, near-miss, or a hit involving a loss of data. Results indicate that the manipulated prior hit experience significantly increased the likelihood of respondents’ endorsement of a safer response relative to the manipulated prior near-miss experience. Conversely, the manipulated prior false-alarm experience significantly decreased respondents’ likelihood of endorsing a safer response relative to the manipulated prior near-miss experience. These results also showed a main effect for age and were moderated by respondent’s income level. 相似文献
Serious problems are faced in several parts of the world due to the presence of high concentration of fluoride in drinking water which causes dental and skeletal fluorosis to humans. Nalgonda district in Andhra Pradesh, India is one such region where high concentration of fluoride is present in groundwater. Since there are no major studies in the recent past, the present study was carried out to understand the present status of groundwater quality in Nalgonda and also to assess the possible causes for high concentration of fluoride in groundwater. Samples from 45 wells were collected once every 2 months and analyzed for fluoride concentration using an ion chromatograph. The fluoride concentration in groundwater of this region ranged from 0.1 to 8.8 mg/l with a mean of 1.3 mg/l. About 52% of the samples collected were suitable for human consumption. However, 18% of the samples were having less than the required limit of 0.6 mg/l, and 30% of the samples possessed high concentration of fluoride, i.e., above 1.5 mg/l. Weathering of rocks and evaporation of groundwater are responsible for high fluoride concentration in groundwater of this area apart from anthropogenic activities including irrigation which accelerates weathering of rocks. 相似文献