bluuebunny/crossref_metadata_2025 huggingface dataset:
Trained meta-models and evolutionary algorithm based multi-objective management of coastal aquifers under parameter uncertainty
Authors: Roy Dilip Kumar , Datta Bithin
Published: October 2018

Meta-model based coupled simulation-optimization methodology is an effective tool in developing sustainable saltwater intrusion management strategies for coastal aquifers. Such management strategies largely depend on the accuracy, reliability, and computational feasibility of meta-models and the numerical simulation model. However, groundwater models are associated with a certain amount of uncertainties, e.g. parameter uncertainty and uncertainty in prediction. This study addresses uncertainties related to input parameters of the groundwater flow and transport system by using a set of randomized input parameters. Three meta-models are compared to characterize responses of water quality in coastal aquifers due to groundwater extraction patterns under parameter uncertainty. The ensemble of the best meta-model is then coupled with a multi-objective optimization algorithm to develop a saltwater intrusion management model. Uncertainties in hydraulic conductivity, compressibility, bulk density, and aquifer recharge are incorporated in the proposed approach. These uncertainties in the physical system are captured by the meta-models whereas the prediction uncertainties of meta-models are further addressed by the ensemble approach. An illustrative multi-layered coastal aquifer system is used to demonstrate the feasibility of the proposed approach. Evaluation results indicate the capability of the proposed approach to develop accurate and reliable management strategies for groundwater extraction to control saltwater intrusion.
Groundwater productivity potential mapping using frequency ratio and evidential belief function and artificial neural network models: focus on topographic factors
Authors: Kim Jeong-Cheol , Jung Hyung-Sup , Lee Saro
Published: October 2018

This study analysed groundwater productivity potential (GPP) using three different models in a geographic information system (GIS) for Okcheon city, Korea. Specifically, we have used variety topography factors in this study. The models were based on relationships between groundwater productivity (for specific capacity (SPC) and transmissivity (T)) and hydrogeological factors. Topography, geology, lineament, land-use and soil data were first collected, processed and entered into the spatial database. T and SPC data were collected from 86 well locations. The resulting GPP map has been validated in under the curve analysis area using well data not used for model training. The GPP maps using artificial neural network (ANN), frequency ratio (FR) and evidential belief function (EBF) models for T had accuracies of 82.19%, 81.15% and 80.40%, respectively. Similarly, the ANN, FR and EBF models for SPC had accuracies of 81.67%, 81.36% and 79.89%, respectively. The results illustrate that ANN models can be useful for the development of groundwater resources.
A reduced-order model for the regeneration of surface currents in Gorgan Bay, Iran
Authors: Kheirabadi Hassan , Noori Roohollah , Samani Jamal M. V. , Adamowski Jan Franklin , Ranjbar Mohammad Hassan , Zaker Naser Hajizadeh
Published: October 2018

This study developed a hydrodynamic reduced-order model (ROM) to regenerate surface currents in Gorgan Bay, Iran. The developed ROM was based on linking a three-dimensional hydrodynamic model, MIKE3-FM, with a data reduction technique, proper orthogonal decomposition (POD). The MIKE3-FM model was first run to simulate surface currents in the bay under a real wind scenario for two years starting July 1, 2010. Thereafter, time and space steps of 6 hours and 500 m, respectively, were chosen to capture 2,920 snapshots of the simulated surface currents using the MIKE3-FM model on 1,937 grids in the bay. The snapshots were then used as input for the POD model to develop the ROM. By applying the POD on the snapshots, necessary spatial and temporal components of surface currents used to develop the ROM were calculated. Having spatial and temporal terms, two ROMs for regeneration of surface currents U and V in two directions x and y, respectively, were developed. Analysis of ROM results revealed they accurately regenerated surface currents using only the first ten modes (among 2,920 modes). Comparison of MIKE3-FM and ROMs developed by the first ten modes revealed there were only negligible differences between their results when they simulated and regenerated, respectively, U and V, in the bay.
Selection of optimal escape routes in a flood-prone area based on 2D hydrodynamic modelling
Authors: Guo Peng , Xia Junqiang , Zhou Meirong , Falconer Roger A. , Chen Qian , Zhang Xiaolei
Published: October 2018

Optimizing escape routes during an extreme flood event is an effective way to mitigate casualties. In this study, a model for selecting optimal escape routes in a flood-prone area has been proposed, which includes a module for predicting the two-dimensional (2D) hydrodynamics and modules for assessing the hazard degree for evacuees, calculation of evacuation times and determination of different escape routes. In the module for determining escape routes, two evacuation schemes were used: scheme A to find optimal escape routes based on established road networks and scheme B to design a new optimal evacuation route. Extreme overbank floods occurred in the Lower Yellow River (LYR) in July 1958 (‘58.7’) and August 1982 (‘82.8’) and the proposed model was applied to select the optimal escape routes on a typical floodplain area of the LYR for these two floods. Model predictions indicated that: (i) the optimal escape routes for these two floods were the same for all three starting locations, and the optimized routes provided 3 h more time for evacuees to escape; and (ii) the time of evacuation would need to be earlier for the ‘58.7’ flood because of its larger amount of water volume and higher peak discharge.
Variability of spatial patterns of autocorrelation and heterogeneity embedded in precipitation
Authors: Liu Dedi , Zhao Qin , Guo Shenglian , Liu Pan , Xiong Lihua , Yu Xixuan , Zou Hui , Zeng Yujie , Wang Zhaoli
Published: October 2018

Spatial interpolation of precipitation data is an essential input for hydrological modelling. At present, the most frequently used spatial interpolation methods for precipitation are based on the assumption of stationary in spatial autocorrelation and spatial heterogeneity. As climate change is altering the precipitation, stationary in spatial autocorrelation and spatial heterogeneity should be first analysed before spatial interpolation methods are applied. This study aims to propose a framework to understand the spatial patterns of autocorrelation and heterogeneity embedded in precipitation using Moran's I, Getis–Ord test, and semivariogram. Variations in autocorrelation and heterogeneity are analysed by the Mann–Kendall test. The indexes and test methods are applied to the 7-day precipitation series which are corresponding to the annual maximum 7-day flood volume (P-AM7FV) upstream of the Changjiang river basin. The spatial autocorrelation of the P-AM7FV showed a statistically significant increasing trend over the whole study area. Spatial interpolation schemes for precipitation may lead to better estimation and lower error for the spatial distribution of the areal precipitation. However, owing to the changing summer monsoons, random variation in the spatial heterogeneity analysis shows a significant increasing trend, which reduces the reliability of the distributed hydrological model with the input of local or microscales.
Estimation of suspended sediment and dissolved solid load in a Mediterranean semiarid karst stream using log-linear models
Authors: Martínez-Salvador Alberto , Conesa-García Carmelo
Published: October 2018

Many models have been developed to predict the sediment transport in watercourses. This paper attempts to test the effectiveness of log-linear models (LLM) to estimate the suspended (S-LMM), dissolved (D-LLM), and total suspended (T-LLM) load into a Mediterranean semiarid karst stream (the Argos River basin, in southeast Spain). An assessment of the supposed validity of each model and a leave-one-out cross-validation were carried out to determine their degree of statistical robustness. The T-LLM model showed higher prediction accuracy (R2 = 0.98, RMSE = 0.15, and PE = ±5.4–6.6%) than the D-LLM model (R2 = 0.97, RMSE = 0.16, and PE = ±5.5–6.8%) or the D-LLM model (R2 = 0.77, RMSE = 0.71, and PE = ±101–493%). In addition, different model variants, according to two flow patterns (FP1 = base flow and FP2 = rising water level), were developed. The FP2-SLLM model provided a very good fit (R2 = 0.94, RMSE = 0.34, and PE = ±25.3–61.5%), substantially improving the results of the S-LLM model.
Inter-comparison between retrospective ensemble streamflow forecasts using meteorological inputs from ECMWF and NOAA/ESRL in the Hudson River sub-basins during Hurricane Irene (2011)
Authors: Saleh F. , Ramaswamy V. , Georgas N. , Blumberg A. F. , Pullen J.
Published: October 2018

The objective of this work was to evaluate the benefits of using multi-model meteorological ensembles in representing the uncertainty of hydrologic forecasts. An inter-comparison experiment was performed using meteorological inputs from different models corresponding to Hurricane Irene (2011), over three sub-basins of the Hudson River basin. The ensemble-based precipitation inputs were used as forcing in a hydrological model to retrospectively forecast hourly streamflow, with a 96-hour lead time. The inputs consisted of 73 ensemble members, namely one high-resolution ECMWF deterministic member, 51 ECMWF members and 21 NOAA/ESRL (GEFS Reforecasts v2) members. The precipitation inputs were resampled to a common grid using the bilinear resampling method that was selected upon analysing different resampling methods. The results show the advantages of forcing hydrologic forecasting systems with multi-model ensemble forecasts over using deterministic and single model ensemble forecasts. The work showed that using the median of all 73 ensemble streamflow forecasts relatively improved the Nash–Sutcliffe Efficiency and lowered the biases across the examined sub-basins, compared with using the ensemble median from an individual model. This research contributes to the growing literature that demonstrates the promising capabilities of multi-model systems to better describe the uncertainty in streamflow predictions.
Sanitation for all: a Panglossian perspective?
Authors: Das Priyam , Crowley Julia
Published: October 2018

At the deadline for meeting the Millennium Development Goals (MDGs), 2.1 billion (109) people had gained access to improved sanitation and 95 countries were able to meet the MDG sanitation target. However, 2.4 billion still lacked improved sanitation facilities. India is among those countries where open defecation stubbornly persists. Despite decades of government spending on the construction of toilets, and the recent Swachh Bharat Mission (SBM) to eradicate open defecation, toilet use remains a challenge. To draw attention to the deep deficits in sanitation services in smaller Indian cities, we explore what motivates sanitation uptake by the urban poor. Household survey data from 13 low-income settlements combined with interviews, focus-group discussions, and transect walks in three cities in central India allowed us to examine factors that influenced resource-constrained households' toilet ownership and toilet use versus open defecation. Our findings indicate that in urban settings, toilet ownership could, in fact, deter open defecation given the presence of other key conditions. Programs to build toilets under the SBM could, therefore, see favorable outcomes in cities provided there is a broadening of access to sanitation to include fecal sludge management. Our findings also underscore the importance of coproducing basic services.
Pretreatment of evaporated condensate generated during metal cutting process by Fe-C micro-electrolysis
Authors: Lin Weiteng , Li Ji , Zhang Xiaolei , Dong Wenyi
Published: October 2018

Fe-C micro-electrolysis was employed to the pretreatment of evaporated condensate generated during metal cutting process. The effect of the reaction conditions on the contaminant removal and degradation mechanism were studied. Through single-factor experiments, the effects of solid–liquid ratio, gas–liquid ratio and reaction time on the treatment of wastewater were preliminarily determined. The optimal reaction condition obtained was: 500 g/L solid–liquid ratio, 30:1 gas–liquid ratio with 4 h reaction time. Under the optimal condition, the chemical oxygen demand (COD) removal efficiency of micro-electrolysis could reach around 25%, and the biodegradability of wastewater increased from 0.12 to 0.32. According to the analysis results of gas chromatography-mass spectrometry (GC-MS) qualitative analysis, it was observed that the most organic contaminants in the influent were degraded or converted into simple structures under Fe-C micro-electrolysis, indicates that Fe-C micro-electrolysis pretreatment could improve the biodegradability of the evaporated condensate generated during metal cutting process and achieve certain degree removal of COD.
Decomplexation of electroplating wastewater by ozone-based advanced oxidation process
Authors: Wang Zhuoyue , Li Ji , Song Wei , Zhang Xiaolei , Song Jiangyu
Published: October 2018

Heavy metal contamination from electroplating wastewater is a serious risk to terrestrial life and public health. The complexed metal cannot be effectively removed by traditional precipitation without decomplexing. In this work, four ozone-based advanced oxidation processes, O3, O3/H2O2, O3/UV and O3/H2O2/UV to decomplex electroplating wastewater were investigated and their performance compared. Ethylenediaminetetraacetic acid (EDTA) and citric acid are the most common components of electroplating wastewater. They were used as representatives to study the decomplexation and mineralization of complexes in the ozone-based advanced oxidation processes. Among all, the highest degradation and mineralization efficiency of EDTA occurred in O3/UV and was 65% and 53% in 60 min, respectively. For citric acid, the highest degradation (77%) and mineralization (56%) efficiency was observed in the O3/H2O2/UV process. This indicates that selection of the advanced oxidation process is determined by the target contaminant.
Laboratory study on response of underwater cohesive sediment to columnar vibration source
Authors: Zhao Peng , Chen Feier , Yu Guoliang
Published: October 2018

This paper investigates the responses of cohesive sediment to mechanical vibration by experimental observation, containing: (1) the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration to the vibration source; (2) the soil pressure distribution in the near field centered in an artificial columnar vibration source. Under the mechanical vibration with a frequency of 200 Hz and an amplitude of 1.15 mm, the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration of underwater viscous sediment were measured in the sediment of four different depositing conditions. Results of the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration of underwater viscous sediment in the near field responding to artificial vibration source are exhibited and discussed. It is found that, excited by the sinusoidal vibrator, the soil pressure presents a response of statistical sinusoidal fluctuation with the same frequency to the vibration source. In the sediment of lower initial yield stresses, the soil pressure distribution distinctly tends to firstly increase and then decrease with distance. The amplitude of the soil pressure is attenuated exponentially with distance.
Assessment of atmospheric conditions over the Hong Thai Binh river watershed by means of dynamically downscaled ERA-20C reanalysis data
Authors: Ho C. , Nguyen A. , Ercan A. , Kavvas M. L. , Nguyen V. , Nguyen T.
Published: October 2018

Long-term, high spatial and temporal resolution of atmospheric data is crucial for the purpose of reducing the effects of hydro-meteorological risks on human society in an economically and environmentally sustainable manner. However, such information usually is limited in transboundary regions due to different governmental policies, and to conflicts in the sharing of data. In this study, high spatial and temporal resolution atmospheric data were reconstructed by means of the Weather Research and Forecasting Model-WRF with input provided from the global atmospheric reanalysis of the 20th century (ERA-20C) over the Hong-Thai Binh River watershed (H-TBRW). The WRF model was implemented over the physical boundaries of the study region based on ERA-20C reanalysis data and was configured based on existing ground observation data in Vietnam's territories, and the global Aphrodite precipitation data. With the validated WRF model for H-TBRW, the reconstructed atmospheric data were first reconstructed for 1950–2010, and then were evaluated by time series and spatial analysis methods. The results of this study suggest no significant trend in the annual accumulated precipitation depth, while there were upward trends in annual temperature at both the point and watershed scale. Furthermore, the results confirm that topographic conditions have significant effects on the climatic system such as on precipitation and temperature.
Enterococci as a key parameter for water quality index: Purires River, Costa Rica
Authors: Chacón Luz , Arias Víctor , Barrantes Kenia , Beita-Sandí Wilson , Reyes Liliana , Achí Rosario
Published: October 2018

This study used the Canadian Water Quality Index (CWI) to characterize water sampled at three points within the Purires River micro basin, Costa Rica. The first sampling point is located in a high zone with domestic agricultural activities, the second point around the mid-point of the flow of the river, and the third point at the lowest zone with extensive agricultural activities mainly centered on the production of fresh vegetables. Eleven physicochemical parameters (As, Cd, Cr, biochemical oxygen demand (BOD), chemical oxygen demand (COD), NH4+, NO3−, Pb, pH, percent saturation of dissolved oxygen (PSO), and total suspended solids (TSS)) and two microbiological parameters (fecal coliforms and enterococci) were evaluated. We evaluated three different Canadian Water Quality Indexes (CWIs): CWI-1 included only physicochemical parameters, CWI-2 included CWI-1 parameters plus fecal coliforms, and CWI-3 included CWI-2 in addition to enterococci. Statistical analysis of individual parameters showed significant differences between sampling sites. CWI-1 was unable to discriminate between the three sampling points, and characterized the water quality as ‘fair’. CWI-2 was only able to discriminate when the water contained high levels of chemical and microbiological contaminants, while CWI-3 adequately discriminated water quality at each of the sampling points. The evaluation of enterococci together with more traditional water quality parameters enabled better categorization of surface water quality.
Interaction between typical sulfonamides and bacterial diversity in drinking water
Authors: Wu Qing , Li Shuqun , Zhao Xiaofei , Zhao Xinhua
Published: October 2018

The abuse of antibiotics is becoming more serious as antibiotic use has increased. The sulfa antibiotics, sulfamerazine (SM1) and sulfamethoxazole (SMZ), are frequently detected in a wide range of environments. The interaction between SM1/SMZ and bacterial diversity in drinking water was investigated in this study. The results showed that after treatment with SM1 or SMZ at four different concentrations, the microbial community structure of the drinking water changed statistically significantly compared to the blank sample. At the genus level, the proportions of the different bacteria in drinking water may affect the degradation of the SM1/SMZ. The growth of bacteria in drinking water can be inhibited after the addition of SM1/SMZ, and bacterial community diversity in drinking water declined in this study. Furthermore, the resistance gene sul2 was induced by SM1 in the drinking water.
Chlorine inactivation of coxsackievirus B5 in recycled water destined for non-potable reuse
Authors: Wati Satiya , Robinson Bret S. , Mieog John , Blackbeard Judy , Keegan Alexandra R.
Published: October 2018

Currently guidelines for disinfection of water with free chlorine, while primarily developed for potable water, are often used for virus disinfection of nitrified recycled water of >1 NTU (Nephelometric Turbidity Unit). More information is needed on the disinfection efficacy of free chlorine for viruses in waters of varying turbidity and pH due to significant reuse of treated wastewater of varying quality. In this study, disinfection efficacy in nitrified/denitrified activated sludge treated wastewater was investigated for coxsackievirus B5 (CB5), an enterovirus known to be highly resistant to free chlorine. The required chlorine contact times (CT) values (mg.min/L) for inactivation of CB5 were established in treated wastewater at 10 °C and of varying turbidity (0.2, 2, 5 and 20 NTU) and pH (7, 8 and 9). CTs were calculated to achieve 1 to 4 log10 inactivation. Robust data is presented in support of the chlorine CT values required to inactivate a chlorine-resistant virus in a range of turbidities and pHs in treated wastewaters. The testing method used a conservative approach and the data presented have been used to develop the free chlorine virus inactivation guildelines for recycled water in Victoria and South Australia, Australia.
Group multicriteria model for allocating resources to combat drought in the Brazilian semi-arid region
Authors: Gonçalo Thomas Edson Espíndola , Morais Danielle Costa
Published: October 2018

The world is facing a growing water scarcity problem in the most diverse regions. The Rio Grande do Norte (RN), a Brazilian semi-arid region, is facing its severest drought in the last 100 years. Given this context, managing water resources and combating the effects of the drought have become even more important. Decisions made in this context may involve multiple criteria established by more than one decision-maker. To tackle this issue, a multicriteria model for group decisions is proposed in order to rank the municipalities of the region and thus guide the public administration's efforts in tackling the drought and mitigating its effects. The applicability of the model is exemplified by studying the Apodi-Mossoró river basin, for which the PROMETHEE GDSS method was selected and the preferences of three decision-makers were calculated.
Urban groundwater use in Tropical Africa – a key factor in enhancing water security?
Authors: Foster Stephen , Bousquet Anne , Furey Sean
Published: October 2018

A regional scoping study has reviewed the limited data on groundwater use for 10 cities in Tropical Africa. In those cities where the water utility has been able to develop groundwater rationally, the public water-supply usually offers a better service at lower cost by enabling phased investment and avoiding advanced treatment, and offers greater water-source security in drought and from pollution. Urban dwellers obtain water from multiple sources, according to availability and affordability. Among the more affluent, private water-supply boreholes are increasingly used to improve security and reduce cost but in the absence of international charity finance groundwater access is beyond the financial reach of the urban poor, except where the water table is shallow allowing the use of low-cost dugwells. The way forward must be to integrate more effectively utility and private investments, and piped and non-piped solutions, for urban water-supply provision, and for water utilities to establish low-income (‘pro-poor’) policy and technical units to pursue ways of supporting alternative water-supply provision, including advisory services and regulatory functions (where appropriate) for private borehole and dugwell use. To facilitate this, water utilities will need to partner with resource regulators and knowledge centres, which may require modifications to their mandate.
Flood maps and their potential role in local spatial planning: a case study from Slovakia
Authors: Vojtek Matej , Vojteková Jana
Published: October 2018

The article is focused on the creation of flood maps for ungauged basins (i.e. local spatial scale areas), using a hydrologic-hydraulic approach, geographic information systems (GIS) and remote sensing techniques, and their role in local spatial planning. The case study is represented by the Turniansky potok catchment which was not mapped in the preliminary flood risk assessment (EU Floods Directive) as an area with existing potential risk. The design discharges were estimated by applying the regional formula. The design discharge with 100-year return period was chosen for hydraulic modeling using the one-dimensional HEC-RAS model. The basis for creating the flood vulnerability map for the selected hydraulic domain was the current land use. Each land use category was assigned a category of acceptable risk (low, medium, high). Furthermore, the vulnerability was defined by digitizing buildings within the hydraulic domain. The role of the created flood maps, as regulatory tools in local spatial planning (i.e. local development plan of municipality), was highlighted and discussed. The importance of flood maps is primarily seen in limiting the irresponsible expansion and densification of construction in the areas near the watercourse which were assigned the low acceptable risk.
Quality standards and monitoring as water management tools: the case of nitrogen in rivers in France and Brittany
Authors: Carré Catherine , Boccarossa Alexandra , Hellier Emmanuelle , Dupont Nadia
Published: October 2018

Water quality standards (QS) and river monitoring are widely accepted as preventive management strategies for the preservation of watercourses and at the same time they are criticized for imposing universal threshold values, leading to regulatory rather than voluntary action. Based on the example of nitrate, the article explains how QS applications are the result of national or regional negotiations, with no direct link to the scientific foundations underlying the development of these tools. These conflicting perceptions and how these tools are actually used are illustrated by the situation in Brittany. Here, the monitoring network and actions to prevent increasing nitrate concentrations in rivers form part of regional programs set up jointly by all the main stakeholders. However, while QS can act as an alarm signal, their effectiveness depends on local political support, which depends on the extent to which river quality is recognized as a key factor in regional development.
Supporting capacity and structural optimization of water resources in the oasis city of Urumqi, China
Authors: Yin Qi , Tang Hong , Ran Ruiping , Sun Zhanli
Published: October 2018

Water scarcity has been the main restraint factor for the development of oasis cities around the world. Urumqi, a typical oasis city in arid northwestern China, is facing an increasing water shortage with rapid development over the past decades. In this paper, we use a system dynamics method and multi-scenario simulation to predict the water-resource demand and the supporting capacity of water resources for the urban development of Urumqi under different scenarios. The results show that existing water resources can hardly meet the needs of urban development. Even if water transfer and saving projects are adopted, in the medium and high-speed development scenarios, there will still be a large water deficit in Urumqi in 2030. Also, to relieve the constraint of water resources on urban development, both water-use structure and industrial structure should be optimized. It is suggested that the demands of ecological water and domestic water are given a primary guarantee; that the proportion of industrial water should significantly increase while drastically decreasing the proportion of agricultural water; that the development of secondary industry should be strengthened while reducing the proportion of primary industry; and, finally, restriction placed on high-water-consuming industry while encouraging low- and medium-water-consuming industries.
River rehabilitation in urban areas – restrictions, possibilities and positive results
Authors: Weyand Michael , Rullich Ludgerus
Published: October 2018

Reaching the goal of good ecological status stipulated by the European Water Framework Directive (WFD) is generally difficult in German rivers. Appropriate habitat conditions for multiple and abundant incidence of flora and fauna are still missing. Existing water bodies, particularly in urban areas, are extremely affected by anthropogenic-induced pressures, resulting in reinforced river bottoms and river banks. In such regions, river rehabilitation is a challenging task and often requires a step by step approach to alter the given conditions. Nevertheless, work must be done and may create successful results as in the case of the Sprockhoevel creek. Over recent years this 11-km-long river in the western and industrialised part of the Ruhr River basin has partly been changed in shape to better resemble nature. Such change implies the widening of the river bed, the improvement of the river bottom by inserting natural gravel substrate, the removal of drop structures and the construction of a new river bed. Presently, this part of the river has again become a valuable habitat for aquatic life. Moreover, the area surrounding the rehabilitated Sprockhoevel creek is now also attractive for the neighbourhood community. Rehabilitation projects have the additional effects of reconnecting people to nature, encouraging public interest in near-natural aquatic systems, and catalysing further investments in similar projects.
Efficient removal of arsenic from water by dielectrophoresis-assisted adsorption
Authors: Jin Q. H. , Cui C. Y. , Chen H. Y. , Wang Y. , Geng J. F. , Wu Y. H.
Published: October 2018

Adsorption (ADS) and dielectrophoresis (DEP) techniques were combined (ADS/DEP) to efficiently remove As(V) in industrial wastewater. Fly ash, activated carbon, corncob and plant ash were tested to determine the best adsorbent by their adsorption capacity. Plant ash showed the highest adsorption capacity compared with the others. Different parameters such as solution pH and adsorbent dose were explored. The maximum As(V) removal efficiency was 91.4% at the optimized conditions (pH 9.0, adsorbent dose 5 g/L) when the initial concentration of As(V) was 15 mg/L. With the ADS/DEP technique, the plant ash particles with adsorbed As(V) were trapped on the electrodes in a DEP device. The ADS/DEP process could increase the removal efficiency of As(V) to 94.7% at 14 V even when the initial concentration of As(V) was 15 mg/L. And the residual concentration of As(V) decreased to 0.34 mg/L after two series of the ADS/DEP process. The adsorbents before and after DEP were examined by scanning electron microscope (SEM) and energy dispersive X-ray (EDX) analysis. After the DEP process, the weight percentage of As(V) on the adsorbent surface increased to 0.96% from 0.5%. The ADS/DEP process could be a new efficient way to remove arsenic pollutant at high concentrations.
Nitrate removal from water using complex of activated carbon with Fe3+
Authors: Azhdarpoor Abooalfazl , Khosrozadeh Leila , Shirdarreh Mohammadreza
Published: October 2018

Pollution of surface and ground waters with nitrate is a serious issue in many regions of the world. Therefore, this study attempts to investigate the extent of nitrate removal from aqueous solutions using a new complex of activated carbon. The effects of operating parameters such as pH of solution (3 to 9), adsorbent dosage (0.4 to 5 g in 50 mL), contact time (5 to 300 min) and initial concentration of nitrate (50 to 300 mg L−1) were studied. The highest efficiency of nitrate removal (95.4%) was related to application of modified activated carbon to a solution with pH of 7 and 100 mg L−1 nitrate concentration. Increasing the amount of modified activated carbon from 0.5 to 1 g in 50 mL promoted removal of nitrate from 82.6% to 94.1%. Furthermore, increasing contact time from 5 to 30 min improved removal efficiency from 76.6% to 92.3%. The obtained experimental data were compatible with the Langmuir isotherm model. In general, the results demonstrated that employing Fe3+-modified activated carbon can be considered as a new method of nitrate removal from aqueous solutions due its convenience, safety and high efficiency.
Upflow packed bed Anammox reactor used in two-stage deammonification of sludge digester effluent
Authors: Çelen-Erdem İ. , Kurt E. S. , Bozçelik B. , Çallı B.
Published: October 2018

The sludge digester effluent taken from a full scale municipal wastewater treatment plant (WWTP) in Istanbul, Turkey, was successfully deammonified using a laboratory scale two-stage partial nitritation (PN)/Anammox (A) process and a maximum nitrogen removal rate of 1.02 kg N/m3/d was achieved. In the PN reactor, 56.8 ± 4% of the influent NH4-N was oxidized to NO2-N and the effluent nitrate concentration was kept below 1 mg/L with 0.5–0.7 mg/L of dissolved oxygen and pH of 7.12 ± 12 at 24 ± 4°C. The effluent of the PN reactor was fed to an upflow packed bed Anammox reactor where high removal efficiency was achieved with NO2-N:NH4-N and NO3-N:NH4-N ratios of 1.32 ± 0.19:1 and 0.22 ± 0.10:1, respectively. The results show that NH4-N removal efficiency up to 98.7 ± 2.4% and total nitrogen removal of 87.7 ± 6.5% were achieved.
Fault signatures and bias progression in dissolved oxygen sensors
Authors: Samuelsson Oscar , Björk Anders , Zambrano Jesús , Carlsson Bengt
Published: October 2018

Biofilm fouling is known to impact the data quality of sensors, but little is known about the exact effects. We studied the effects of artificial and real biofilm fouling on dissolved oxygen (DO) sensors in full-scale water resource recovery facilities, and how this can automatically be detected. Biofilm fouling resulted in different drift direction and bias magnitudes for optical (OPT) and electrochemical (MEC) DO sensors. The OPT-sensor was more affected by biofilm fouling compared to the MEC-sensor, especially during summer conditions. A bias of 1 mg/L was detected by analysing the impulse response (IR) of the automatic air cleaning system in the DO sensor. The IR is an effect of a temporal increase in DO concentration during the automatic air cleaning. The IRs received distinct pattern changes that were matched with faults including: biofilm fouling, disturbances in the air supply to the cleaning system, and damaged sensor membrane, which can be used for fault diagnosis. The results highlight the importance of a condition-based sensor maintenance schedule in contrast to fixed cleaning intervals. Further, the results stress the importance of understanding and detecting bias due to biofilm fouling, in order to maintain a robust and resource-efficient process control.
Controlled experiment contradicts the apparent benefits of the Fenton reaction during anaerobic digestion at a municipal wastewater treatment plant
Authors: Uman Ahmet E. , Usack Joseph G. , Lozano José L. , Angenent Largus T.
Published: October 2018

A previous study had reported that the Fenton reaction at full scale increased the digestibility of thickened sludge in a digester. The authors of the study had observed a positive effect on biogas productivity, but without a control. Here, we evaluated this result by investigating the anaerobic treatment characteristics of fresh, thickened sludge in an experimental design with a control. To accomplish this, two identical continuously stirred anaerobic digesters (CSADs) were operated in parallel at mesophilic conditions. We also included anaerobic settlers to mimic the full-scale plant and to accomplish sludge recycling. We fed fresh, thickened sludge to both setups once every other day, but performed the Fenton reaction with only the experimental system by adding H2O2 to the recycled biosolids from the anaerobic settler. We observed very large fluctuations in biogas production due to ever-changing characteristics of the thickened sludge both on a daily and seasonal basis. Regardless, the two setups performed almost identically with: 1) chemical oxygen demand removal efficiencies of 63.8 ± 2.9% and 62.1 ± 3.2%; and 2) biogas productivities of 0.280 and 0.279 L CH4·g−1 volatile solids for the experimental (with Fenton) and control (without Fenton) CSADs, respectively. These results indicate that the use of a Fenton reaction did not affect biogas productivities.
Comparison of the photocatalytic performance of TiO2/AC and TiO2/CNT nanocomposites for methyl orange photodegradation
Authors: Wang Liping , Guo Jingru , Dang Jingjing , Huang Xiaojun , Chen Si , Guan Weisheng
Published: October 2018

To enhance the photocatalytic degradation efficiency of TiO2 on methyl orange (MO) removal, TiO2/AC (activated carbon) and TiO2/CNT (carbon nanotube) composites were synthesized. The prepared catalysts were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The photocatalytic performance of the obtained composites were investigated by the degradation of MO under UV irradiation (254 nm, 365 nm). The results revealed that the prepared nanocomposite showed higher MO degradation efficiency than pure nano-TiO2. Additionally, batch experiments of influencing factors, including H2O2 dosage, metal dopants, inorganic anions, chloride ion concentration and ultraviolet wavelength on the MO removal efficiency were also conducted. The results demonstrated that metal dopant and the presence of H2O2 significantly enhanced MO removal efficiency.
Utilizing modern experimental methodology to quantify jet-breaker dimension effects on drop manhole performance
Authors: Hasheminejad Seyedreza , Khanjani Mohammad-Javad , Barani Gholam-Abbas
Published: October 2018

Drop structures and especially drop manholes are extensively employed in supercritical routes of sewer and drainage systems. Drop manholes remarkably affect hydraulic features of their downstream system, while their operation is dominated by the flow regime inside them. Poor hydraulic performance of these structures under Regime R2 was improved with the jet-breaker, yet its proper dimensions were needed to be precisely determined. In this paper, effects of the jet-breaker length, width, sagitta, and angle on drop manhole energy dissipation and air demand (as responses), under the inlet pipe 80% filling ration, were experimentally studied. The modern statistical design of experiment (DoE) methodology and dimensional analysis were utilized to design the experiments in accordance with the 24-1IV fractional factorial design. Ten specific jet-breakers were examined and more than 135 tests were performed. The statistical analysis of the results revealed that both responses were significantly improved when the jet-breaker length and width were 2 and 1.4 times the inlet pipe diameter, respectively; its sagitta was equal to 0, and its angle was at 70°. The use of DoE resulted in 21% reduction in experimental runs, straightforward data analysis, and unbiased concluding.
Variations of sludge characteristics during the advanced anaerobic digestion process and the dewaterability of the treated sludge conditioning with PFS, PDMDAAC and synthesized PFS-PDMDAAC
Authors: Zhang Jinghui , Yang Hong , Li Wei , Wen Yang , Fu Xingmin , Chang Jing
Published: October 2018

Anaerobic digestion with thermal hydrolysis pretreatment (THP), also called advanced anaerobic digestion (AAD), is a mainstream technology for sludge treatment. AAD changes sludge, it can degrade extracellular polymeric substances (EPS), release EPS from the sludge, and alter the particle size distribution. We synthesized PFS–PDMDAAC from the inorganic coagulant polyferric sulfate (PFS) and the organic coagulant polymer polydimethyldiallylammonium chloride (PDMDAAC) in various PFS:PDMDAAC weight ratios. We investigated the effects of PFS–PDMDAAC pretreatment on AAD sludge dewaterability, and developed an explanation for them. Capillary suction time (CST) was used as a measure of sludge dewaterability. Dissolved organic matter, the three-dimensional excitation emission matrix, particle size (d0.5), zeta potential, and sludge microstructure were observed in order to explain changes in sludge dewaterability that resulted from different compositions and dosages of coagulants. Treatment with PFS alone gave no significant improvement in sludge dewaterability. PDMDAAC used alone greatly improved sludge dewaterability. Synthesized PFS–PDMDAAC which had a relatively high proportion of PDMDAAC by weight performed similarly to PDMDAAC. PFS–PDMDAAC synthesized in the ratio (PDF:PDMDAAC) 1:5 by weight provided good dewaterability. The dosage can be reduced by 16.7% of the dosage for conditioning by PDMDAAC alone.
Highly efficient Cd(II) adsorption using mercapto-modified bentonite as a novel adsorbent: an experimental design application based on response surface methodology for optimization
Authors: Ecer Ümit , Yılmaz Şakir , Şahan Tekin
Published: October 2018

We report the optimization with response surface methodology (RSM) for adsorption conditions required for removal of Cd(II) from an aqueous environment with 3-mercaptopropyl trimethoxysilane-modified bentonite (MMB). Central composite design (CCD) in RSM was used to optimize the most significant adsorption variables of initial pH, temperature (°C), initial Cd(II) concentration (Co, mg L−1) and adsorbent dosage (g). With the quadratic model equation obtained from CCD, the optimum values were determined as initial pH 6.40, temperature 20 °C, Co 49.55 mg L−1 and adsorbent dosage 0.17 g. Under optimum conditions, the optimum adsorption amount of Cd(II) was 27.55 mg Cd(II)/g adsorbent and adsorption yield was 94.52%. The obtained results showed that the Langmuir and Dubinin Radushkevich (D-R) adsorption isotherms were more suitable for adsorption equilibrium data. The kinetic studies indicated that the pseudo-second-order kinetic model was fitted to the adsorption kinetic data. Additionally, thermodynamic studies indicated that the adsorption process was spontaneous and exothermic. As a result, MMB can be chosen as an effective adsorbent for treating heavy metals such as Cd(II) in wastewater and removing them from aqueous solutions. Furthermore, it is thought that it will positively contribute to the literature since the adsorbent-adsorbate combination (MMB-Cd(II)) is used for the first time.
Performance comparison of uninsulated and insulated hybrid anaerobic baffled reactor (HABR) operating at warm temperature
Authors: Khalekuzzaman Md , Alamgir Muhammed , Hasan Mehedi , Hasan Md Nahid
Published: October 2018

In this research, a hybrid anaerobic baffled reactor (HABR) configuration was proposed consisting of a front sedimentation chamber and four regular baffled chambers followed by two floated filter media chambers for the treatment of domestic wastewater. Performance comparison of uninsulated and insulated HABRs was carried out operating at warm temperature (18.6–37.6 °C) under variable HRTs (30 h and 20 h). The study suggests that almost similar chemical oxygen demand (91% vs 88%), total suspended solids (90% vs 95%), turbidity (98% vs 97%), and volatile suspended solids (90% vs 93%) removal efficiencies were obtained for uninsulated and insulated HABRs. Higher removal of total nitrogen (TN) of 41%, NH4+-N of 44%, and NO3−-N of 91% were achieved by the insulated HABR compared to TN of 37%, NH4+-N of 36%, and NO3−-N of 84% by the uninsulated HABR, whereas lower PO43− removal efficiency of 17% was found in the insulated HABR compared to 24% in the uninsulated HABR. This indicated insulation increased nitrogen removal efficiencies by 4% for TN, 8% for NH4+-N and 7% for NO3−-N, but decreased PO43−removal efficiency by 7%.
Flocculation performance of anionic starch in oil sand tailings
Authors: Zhao Nana , Al Bitar Hani , Zhu Yunyin , Xu Yuming , Shi Zhiqing
Published: October 2018

A series of carboxymethyl starches (CMSs), with various degrees of substitution from 0.1 to 0.79, were synthesized and selected as a model to study the feasibility of using natural polymers as flocculants for oil sand tailings treatment. The flocculation performance of modified CMS in kaolin clay suspensions and oil sand tailings was evaluated in terms of settling rate, solids content, capillary suction time, and specific resistance to filtration of the sediment phase. It was found that the synthesized CMS effectively accelerates settling of kaolin suspensions and oil sand fine tailings, thus demonstrating the feasibility of this application.
Gliding arc plasma pre-treatment of kaolin in spatial post-discharge mode for removal of Reactive Red 2 dye from aqueous solution
Authors: Sop-Tamo B. , Acayanka E. , Boyom-Tatchemo W. F. , Nzali S. , Kamgang-Youbi G. , Laminsi S.
Published: October 2018

This study investigates the ability of spatial post-discharge mode functionalized kaolin to remove textile dye Reactive Red 2 from aqueous solution compared to that of the raw kaolinite. To fulfill the aim, the removal conditions, including plasma exposure time, processed mode (direct and post-discharge), pH of the aqueous dye solution, initial dye concentration and adsorbent dosage, were investigated. The changes that occur on clay surfaces before and after gliding arc plasma treatment were followed by Fourier transform infrared spectroscopy, scanning electron microscopy and nitrogen physisorption. The point of zero charge and the changes of the textural properties after gliding arc plasma treatment were also examined. The experimental data were analyzed using pseudo-first-order, pseudo-second-order and empirical Elovich models. The diffusion phenomenon was also studied. The results obtained indicate that spatial post-discharge pre-treatment of kaolin deeply influences the functional groups of some of its minerals as well as the morphology and texture of its particles. Consequently, at room temperature (∼30 °C), the maximum adsorption capacities of natural raw kaolin clay were tripled after treatment with gliding arc plasma in spatial post-discharge mode and were almost doubled after the direct treatment mode.
Effects of inorganic anions on the photolysis of triclosan under UV irradiation
Authors: Chen Lei , Wang Zhipeng , Qian Cheng , He Yuchen
Published: October 2018

Triclosan is a widely used antimicrobial agent and may pose health risks to many aquatic organisms. Photodegradation is an important transformation pathway for triclosan, but studies on the effects of inorganic anions on photodegradation of triclosan are limited. In the present study, the single and combined effects of NO3−, Cl− and HCO3− on the photolysis of triclosan in aqueous solutions under UV irradiation was evaluated. The results showed that photodegradation of triclosan was inhibited by NO3− and promoted by HCO3−, while no significant effect was observed with Cl−. When Cl− was added to NO3−, no effect was observed, but the addition of Cl− hindered the promotion effect of HCO3−. The coexistence of NO3−, Cl− and HCO3− inhibited the photolysis of triclosan. These results showed the complex effects of inorganic anions in the photolysis of triclosan and provide useful information for an accurate ecological risk assessment of triclosan in natural waters. It will also help to develop appropriate treatment ways of triclosan.