Showing papers in "Water and Environment Journal in 2019"

The current state of the use of large wood in river restoration and management

Abstract: Trees fall naturally into rivers generating flow heterogeneity, inducing geomorphological features, and creating habitats for biota. Wood is increasingly used in restoration projects and the potential of wood acting as leaky barriers to deliver natural flood management by ‘slowing the flow’ is recognised. However, wood in rivers can pose a risk to infrastructure and locally increase flood hazards. The aim of this paper is to provide an up‐to‐date summary of the benefits and risks associated with using wood to promote geomorphological processes to restore and manage rivers. This summary was developed through a workshop that brought together academics, river managers, restoration practitioners and consultants in the UK to share science and best practice on wood in rivers. A consensus was developed on four key issues: (i) hydrogeomorphological effects, (ii) current use in restoration and management, (iii) uncertainties and risks and (iv) tools and guidance required to inform process‐based restoration and management.

Evaluating Algibon adsorbent and adsorption kinetics for launderette water treatment : towards sustainable water management

Abstract: Grey water from commercial laundry facility was used for treatment to substitute the conventional water sources. Algibon, A800 derived from mesoporous alginic acid and Starbon S300, carbonaceous mesoporous polysaccharide-derived materials, silica gel (SG) and activated carbon (AC) were used for the treatment of wastewater. The optimum adsorbent dosing and pH value for each adsorption system are defined. The adsorption efficiency are in the order of A800 > SG > AC > S300 and the removal rate reached to 91% when A800 was used. Furthermore, the reaction followed the second-order kinetic model and the rate constant is high when A800 adsorbent is applied.

Microbiota in anaerobic digestion of sewage sludge with and without co‐substrates

Abstract: In this study, seven full‐scale anaerobic digesters, with or without co‐substrate regime, were analysed by physicochemical and molecular biological methods A combination of robust community fingerprinting and Illumina MiSeq sequencing revealed a core bacterial community dominated by Chloroflexi, Firmicutes, Bacteroidetes and Proteobacteria, with variations in the profiles because of differences in the co‐substrate feeding regime Despite these differences, physicochemical properties revealed a stable performance of all reactors, indicating a resilient bacterial microbiota in all full‐scale reactors A rich bacterial core community ensured reactor functionality, whilst feeding regime and reactor type impacted the overall and the core bacterial diversity Within the Archaea, Methanosaeta dominated in all reactors Results indicated no relationship between archaeal community structure and the type of co‐substrate digested Methanogens rely on the metabolic end products of bacterial activity and are thus less dependent on differences in the initial co‐substrate regime

Impact of climate change on meteorological, hydrological and agricultural droughts in the Lower Mekong River Basin: a case study of the Srepok Basin, Vietnam

Abstract: The objective of this study is to assess future changes in meteorological, hydrology and agricultural droughts under the impact of changing climate in the Srepok River Basin, a subbasin of LMB, using three drought indices; standardized precipitation index (SPI), standardized runoff index (SRI) and standardized soil moisture index (SSWI). The well‐calibrated Soil and Water Assessment Tool (SWAT) is used as a simulation tool to estimate the features of meteorological, hydrological and agricultural droughts. The climate data for the 2016–2040 period is obtained from four different regional climate models; HadGEM3‐RA, SNU‐MM5, RegCM4 and YSU‐RSM, which are downscaled from the HadGEM2‐AO GCM. The results show that the severity, duration and frequency of droughts are predicted to increase in the near future for this region. Moreover, the meteorological drought is less sensitive to climate change than the hydrological and agricultural droughts; however, it has a stronger correlation with the hydrological and agricultural droughts as the accumulation period is increased. These findings may be useful for water resources management and future planning for mitigation and adaptation to the climate change impact in the Srepok River Basin.

Degradation of azo dye by an UV/H2O2 advanced oxidation process using an amalgam lamp

Abstract: The discharge of dyes into water is an ecological problem that can be alleviated by advanced oxidation processes (AOPs), such as UV/H₂O₂ treatments. Searching for more efficient light sources is a way to improve AOPs’ efficiency. This work tested the efficiency of an amalgam lamp on the degradation of an azo dye, studying the effect of dye and H₂O₂ concentrations and pH, and the influence of some salts on the decolouration rate of methyl orange. Actinometry showed that the amalgam lamp system was able to provide a high incident photon irradiance (6.30·10⁻⁵ mol/cm² s). The amalgam lamp‐driven AOP was able to decolourize the dye at pseudo‐first‐order rates of 0.654–4.008 1/min, with increasing rates at low dye concentration and low pH and at high H₂O₂ concentrations until a maximum value is reached. The results show that the amalgam lamp can be an alternative light source for fast dye degradation by AOPs.

A mixing‐length‐scale‐based analytical model for predicting velocity profiles of open‐channel flows with submerged rigid vegetation

Abstract: In open‐channel flows with submerged vegetation, the vertical velocity profile can often be described by two layers: the vegetation layer in the lower region and the surface layer in the upper non‐vegetated region. In this paper, a new mixing‐length scale of eddy is proposed for predicting the vertical velocity profile of flow in an open‐channel with submerged rigid vegetation. The analytical model of velocity profile is based on the momentum equation of flow where the turbulent eddy viscosity is assumed to have a linear relationship with the local velocity. The proposed model was tested against different datasets from the literature. The 22 datasets used cover a range of submergence [flow depth (H)/vegetation height (h) = 1.25 ~ 3.38], different vegetation densities of ah = 0.11 ~ 1.85 (a defined as the frontal area of the vegetation per unit volume) and bed slopes (Sₒ = 1.8 × 10⁻⁶ ~4.0 × 10⁻³). This study showed that the proposed model can predict the velocity profiles well against all datasets, and that the mixing length scale of eddies (λ) is well related with both vegetation height (h) and flow depth of surface layer (i.e. the height of non‐vegetation layer, H–h). Close examination of λ in the proposed model showed that when λ = 0.03h(H-h), the model predicts vertical velocity profiles well for all datasets used except for very shallow submergence (i.e. H/h < 1.5).

Trees and wood: working with natural river processes

Abstract: A history of land clearance and riparian tree and wood management has resulted in limited riparian woodland and wood along British rivers. However, river management approaches are now being promoted that ‘work with natural processes’ to reduce flood risk through measures intended to restore, protect and emulate the natural function of catchments, rivers, estuaries and coasts. Wood has started to be reintroduced into river channels during river restoration and natural flood management activities, but this needs to be undertaken using appropriate quantities, locations and designs that mimic natural tree‐wood features. This paper reviews the knowledge that is needed to support wood reintroduction activities including (i) the characteristics of the riparian tree species and wood that are present; (ii) the importance of river size relative to that of trees and wood pieces; and (iii) the way trees, wood and geomorphic processes interact across rivers and floodplains of different energy and style.

Study of mathematical models for the removal of Ni2+ from aqueous solutions using Citrullus lanatus rind, an agro‐based waste

Abstract: The defilement of water bodies is going on increasing due to the use of noxious chemicals. In the present study, to alleviate the deadly effects of the heavy metal, the agricultural solid waste Citrullus lanatus rind was used as the precursor for the Nickel ion removal. To remove Nickel from synthetic solution, adsorption studies were conducted. Characterization was done using TGA, SEM and FT‐IR analysis. Various parameters on the adsorption capacity of the adsorbent, isotherm and kinetic studies were carried out. The maximum loading capacity of Ni²⁺ was found to be 38.98 mg/g from Langmuir model. Error analyses were also studied to validate the best fit of the curve for isotherm models. The kinetic models were studied to understand the adsorption mechanism. The dynamic behaviour of the fixed column and the modelling of the breakthrough curves were carried out. Desorption studies were performed to consider the reusability of the rind.

A conceptual model of riparian forest restoration for natural flood management

Abstract: There is an increasing emphasis on using natural processes, including riparian forest restoration, to enhance the ecological, hydrological and geomorphological functioning of watercourses. However, we have insufficient knowledge on how the supply and retention of in-channel wood from riparian forest stands changes with age, with inferences typically based on data from terrestrial forests. This presents a challenge in estimating the efficacy and functional lifespan of restoration projects. In this paper, we use a riparian forest growth model to show there is a lag of up to 40–50 years between the start of forest growth and trees delivering wood to the channel that is large enough to resist fluvial transport, anchor logjams and so increase channel complexity and hydraulic resistance. Resource managers need to account for realistic timescales over which changes promoted by riparian woodland restoration will occur and may need to consider using interim engineered logjams as the forest develops.

Remediation of suspended solids and turbidity by improved settling tank design in a small-scale, free-standing toilet system using recycled blackwater.

Abstract: Our research is focused on the development of decentralized waste water treatment technologies enabling onsite water reuse Accumulation of solids with recycling of treated blackwater increases the energy required for disinfection with an electrochemical process We hypothesized that improving the preprocess settling of blackwater by increasing the tortuosity of the liquid flow path would reduce this energy demand by reducing particle-associated chemical oxygen demand (COD) This approach successfully reduced the total suspended solids and turbidity in the process liquid accumulated per user-day equivalent A modest reduction in the apparent steady-state accumulation of COD was also observed, likely because of the retention of COD associated with larger particles in the settling tanks Interestingly, these improvements did not improve the energy efficiency of the electrochemical disinfection process, as predicted These observations suggest that improving the energy efficiency of electrochemical disinfection will require remediation of dissolved COD

Optimization of phenol removal from wastewater by activation of persulfate and ultrasonic waves in the presence of biochar catalyst modified by lanthanum chloride

Abstract: In this paper, the effects of phenol concentration, pH, catalyst dose, persulfate concentration, temperature and contact time on the phenol removal from wastewater by activation of persulfate (S₂O₈⁻²) in the presence of biochar modified by lanthanum chloride and ultrasonic waves (US) are optimized. Experimental design and optimization were carried out by response surface methodology. The optimum conditions for the maximum phenol removal were obtained pH of 4, phenol concentration of 86 mg/L, catalyst dose of 43 mg/L, persulfate concentration of 86 mg/L, temperature of 41 °C and contact time of 63 min. The optimum phenol removal from synthetic wastewater was attained 97.68%. Phenol removal by the mentioned system was fitted with the first‐order kinetic model. The combination of the ingredients of ‘S₂O₈⁻²/US/Biochar‐LaCl₃’ system had a synergistic effect on the phenol removal.

Trends in the use of large wood in UK river restoration projects: insights from the National River Restoration Inventory

Abstract: Large Wood (LW) is increasingly employed in river restoration to promote physical habitat heterogeneity and ecological diversity. To explore how LW has been used in restoration schemes across the United Kingdom in recent decades, we analysed data on 912 LW projects archived in the UK’s National River Restoration Inventory (NRRI). The number of LW schemes has continued to increase following the earliest records in the 1990s, largely tracking overall trends in river restorations. LW projects have been predominantly located in lowland, rural streams, although there has been a notable cluster in and around London. LW projects have mainly revolved around the desire to deliver hydromorphological improvements and specifically the creation of fish habitat. Most schemes used LW in simple deflector forms despite the growing scientific evidence of the benefits of using structurally complex LW. Post project monitoring has been limited and mostly restricted to photographic records. This type of database analysis can provide important insights and help guide future restoration practice.

Comparative analysis of the novel infiltration model with other infiltration models

Abstract: Variability in infiltration characteristics of soils creates need for selection of appropriate infiltration model. Recently, a novel infiltration model was proposed and reported to perform excellently in estimating infiltration rate of soils of Kurukshetra, India, however, this model need to be tested for its reliability at global level. In this regard, the present study analyses the reliability of the novel model based on infiltration database comprising of 16 data sets from different parts of the world to arrive at some generalized results on the reliability of novel model as compared to commonly used infiltration models. Comparative analysis reveals that out of the 16 data sets for 9 sites (57%). Horton model was found to be best model while novel model was found as best‐fit model in five cases (31%). Based on the present study and earlier investigations, it may be inferred that novel model could be a useful model to estimate infiltration rate in loams.

Validating a rapid assessment framework for screening surface water flood risk

Abstract: This research evaluates performance of a rapid assessment framework for screening surface water flood risk in urban catchments. Recent advances in modelling have developed fast and computationally efficient cellular automata frameworks which demonstrate promising utility for increasing available evidence to support surface water management, however, questions remain regarding trade‐offs between accuracy and speed for practical application. This study evaluates performance of a rapid assessment framework by comparing results with outputs from an industry standard hydrodynamic model using a case study of St Neots in Cambridgeshire, UK. Results from the case study show that the rapid assessment framework is able to identify and prioritise areas of flood risk and outputs flood depths which correlate above 97% with the industry standard approach. In theory, this finding supports a simplified representation of catchments using cellular automata, and in practice presents an opportunity to apply the framework to develop evidence to support detailed modelling.

A fast and automated hydrologic calibration tool for SWAT

Abstract: In order to apply hydrological models in the water resources investigation successfully, careful calibration and uncertainty analysis are required. Although many automatic calibration methods were developed, the time consumed for running the hydrologic model is still a problem for hydrologic modelers. To reduce the computational complexity and increase performance of the calibration procedure, a software package (Fast Automated Calibration Tool, FACT) that works on Soil and Water Assessment Tool (SWAT) was developed. Sequential Uncertainty Fitting Algorithm (SUFI‐2) was chosen to build the software package on, because SUFI‐2 combines optimization with uncertainty analysis and can handle a large number of parameters. SUFI‐2 implemented in SWAT‐CUP (a software program that was developed for SWAT) is very useful in an interactive manner, however; it has some drawbacks which are the time consumed, user interaction requirement and update problems of SWAT model files. In this study, the calibration procedure was implemented in a MATLAB script, which completes the full calibration in one single run. The developed tool was applied on Sarisu‐Eylikler Basin SWAT model that had r² = 0.41, NSE = 0.11 between 1992 and 2010 without calibration. When the model was calibrated using SUFI‐2 in SWAT‐CUP, the model was improved to r² = 0.57, NSE = 0.44, P‐factor = 0.69 and R‐factor = 1.00 at the end of 42 iterations using 100 simulation counts in each iteration. However; when the developed calibration tool was applied with 250 simulation counts without any user interaction for each iteration, the model was improved to r² = 0.59, NSE = 0.57, P‐factor = 0.72, and R‐factor = 1.32 at the end of three iterations. Thus, the developed calibration procedure took a shorter time (unlike SUFI2 in SWAT‐CUP, FACT takes several hours) compared to SWAT‐CUP with minimum user involvement.

A comparative study on treatment of wastewaters with various biodegradability and various pH values using single‐chamber microbial fuel cells

Abstract: This work assessed the performance of a single‐chamber microbial fuel cell (MFC) with various substrates. Primary settled domestic wastewaters were used to simulate wastewaters of high biodegradability; while phenol‐based wastewaters and benzene‐based wastewaters were used to simulate wastewaters of low biodegradability. Experiments were performed at initial pH values of 6, 7 and 8. The maximum voltage production, power density and removal of substrate were obtained using primary settled domestic wastewater, whereas the lowest values were obtained using phenol‐based wastewater. The maximum chemical oxygen demand removal efficiency, phenol removal efficiency and benzene removal efficiency were 80.8, 63.3 and 77.8%, respectively. The performance of the MFC was enhanced by increasing the influent pH. The lowest coulombic efficiencies were obtained from phenol‐based wastewater and benzene‐based wastewater, which indicated that electrogenic bacteria were not the primary microorganisms responsible for the biodegradation of low biodegradable wastewater.

Water footprint assessment considering intermediate products: model and a 2016 case study of China

Abstract: Analysing intermediate products within a water footprint (WF) across different economic sectors can show the root causes of water usage and is helpful for water resource management and policy making. However, conventional methods and data for a WF rarely assess the input and output of intermediate products directly and comprehensively. Therefore, this study proposes an approach to access the WF of intermediate products as well as final products in each sector of an economy’s water sustainability profile. An Economic Input‐output‐based Life‐Cycle Assessment (EIO‐LCA) framework is designed for the accounting, which describes the intermediate WF products of each sector in a material‐product network. This method is implemented into a 2016 case study for a comprehensive Chinese WF. The results showed that the total WF of Chinese inhabitants (consumers) in 2016 was 5.76 × 10¹¹ m³, and the top three sectors with the largest WF were agriculture (1.78 × 10¹¹ m³), food (1.05 × 10¹¹ m³) and machinery manufacturing (5.68 × 10¹⁰ m³); agriculture provided the largest quantity of virtual water contained in its intermediate product for the other sectors. From the perspective of producers, the total WF of the Chinese economic sectors in 2016 was 5.84 × 10¹¹ m³. The sectors with the largest direct water use were agriculture (2.20 × 10¹¹ m³), electricity (7.64 × 10¹⁰ m³) and chemical Industry (2.35 × 10¹⁰ m³); and large parts of their direct water usage were consumed to prepare intermediate products for other sectors. The results of this study show that a more inclusive approach provides an enhanced qualitative and resource‐ethical view for water accounting and management.