Inflow Load Research Articles

Assessing flood-depth effects on water quality, nutrient uptake, carbon sequestration, and rice yield cultivated on Histosols

In the Everglades Agricultural Area (EAA), Florida, cultivating rice in flooded paddies is becoming increasingly popular to conserve water and soil health. Flood depth is a critical factor affecting the discharged water quality, soil carbon, and yield production. However, few studies have comprehensively investigated the optimal flood depth in EAA, considering multi-functional indices. To address this gap, we investigated drainage water quality, water quantity, nutrient uptake, soil carbon, and rice yield in rice paddies in histosol soils over a two-year period at four flood depths (5, 10, 15, and 20 ​cm). For each flood depth, averaged over two years, total outflow loadings of suspended solids, nitrogen, phosphorus, and potassium were significantly reduced by 40 ​%, 38 ​%, 36 ​%, and 32 ​%, respectively, compared to inflow water loadings (p ​< ​0.001). Soil organic carbon (SOC) in 5, 10, 15, and 20 ​cm flood treatments increased annually at a rate of 3.85 ​%, 5.64 ​%, 6.86 ​%, and 6.86 ​%, respectively; for these same treatments, soil active organic carbon (AOC) decreased annually at rates of 11.75 ​%, 8.63 ​%, 20.07 ​%, and 8.48 ​%, and rice grain yield was 4488, 5103, 5450, and 5386 ​kg ​ha−1, respectively. Overall, considering the water quality, SOC, AOC, and rice yield production, irrigating rice paddies at a flood depth of 15 ​cm most effectively improves water quality, increases carbon sequestration, reduces active carbon, and yields more rice than other flood depths. By evaluating the effects of flood depth on the soil–water–plant nexus in a holistic manner, we propose a more sustainable and environmentally friendly mode of rice cultivation within the EAA.

Energy efficiency evaluation and optimization for wastewater treatment plant

Wastewater treatment plants (WWTPs) are considered as energy-intensive industries. A comprehensive assessment of energy efficiency in sewage treatment reveals issues of energy waste, offers insights into the energy consumption structure, fosters optimization of energy management, and enhances overall energy utilization. However, the mathematical modeling for energy efficiency evaluation becomes challenging due to the ambiguity and uncertainty of the parameters regarding energy consumption and various indicators. In this paper, the newly constructed evaluation method was used to quantify the energy efficiency. This method employs dimensional reduction, projecting the numerical values of unit energy consumption for various pollutants onto a lower-dimensional space, and then computing the projected eigenvalues. Larger eigenvalues indicate higher energy efficiency. Based on the evaluation results, the back propagation (BP) neural network is used to simulate the sewage treatment process. The results demonstrated that when the inflow load is small and the concentration of pollutants is high, the energy efficiency of sewage treatment plants performs well. When the inflow load is high and the concentration of pollutants is low, the energy efficiency of sewage treatment plants is poor. Meanwhile, the energy consumption could be decreased by 11.61 %, 14 %, and 15.26 % respectively in different scenarios.

A blind test on wind turbine wake modelling based on wind tunnel experiments: Phase I – The benchmark case

Wind turbine wake and modelling is crucial to optimizing future wind farm layouts and hence reducing the cost of energy. This paper presents the first phase of a blind test on modelling controlled and uncontrolled wind turbine wakes. The blind test is based on wind tunnel experiments of two model scale wind turbines (D = 1.1 m) one downstream of the other. The exercise is split into two phases and the first one is presented here, where participants are invited to simulate the baseline case, in which both turbines are aligned with the flow and there is no control on the either turbine. The objective of this phase is to ensure all participants can benchmark their numerical approach against a baseline open data set, where no wake control is applied. Experimental measurements include inflow velocity, turbine power and loads for a range of tip speed ratios. In the second phase, not presented here, the wake of the upstream turbine will be controlled and the performance of the downstream one will be recorded. This will be a blind test with the data not released prior to submissions. The present paper gives an overview of the initial, open benchmark case, including its objectives, methodology and experimental results.

Evaluation of Phosphate and E. coli Attenuation in a Natural Wetland Receiving Drainage from an Urbanized Catchment

A natural wetland receiving drainage from a 24-ha urbanized catchment in the Falls Lake Watershed of North Carolina was evaluated to determine if it was providing ecosystem services with regards to phosphate and Escherichia coli (E. coli) attenuation. Inflow and outflow characteristics including nutrient and bacteria concentrations along with physicochemical properties (discharge, pH, oxidation reduction potential, temperature, and specific conductance) were assessed approximately monthly for over 2 years. The median exports of phosphate (0.03 mg/s) and E. coli (5807 MPN/s) leaving the wetland were 85% and 57% lower, respectively, relative to inflow loadings, and the differences were statistically significant (p &lt; 0.05). Hydraulic head readings from three piezometers installed at different depths revealed the wetland was a recharge area. Phosphate and E. coli concentrations were significantly greater in the shallowest piezometer relative to the deepest one, suggesting treatment occurred during infiltration. However, severe erosion of the outlets is threatening the stability of the wetland. Upstream drainageway modifications were implemented to slow runoff, and septic system repairs and maintenance activities were implemented to improve water quality reaching the wetland and Lick Creek. However, more work will be needed to conserve the ecosystem services provided by the wetland.

Developing a digital twin framework for wind tunnel testing: validation of turbulent inflow and airfoil load applications

Abstract. Wind energy systems, such as horizontal-axis wind turbines and vertical-axis wind turbines, operate within the turbulent atmospheric boundary layer, where turbulence significantly impacts their efficiency. Therefore, it is crucial to investigate the impact of turbulent inflow on the aerodynamic performance at the rotor blade scale. As field investigations are challenging, in this work, we present a framework where we combine wind tunnel measurements in turbulent flow with a digital twin of the experimental set-up. For this, first, the decay of the turbulent inflow needs to be described and simulated correctly. Here, we use Reynolds-averaged Navier–Stokes (RANS) simulations with k−ω turbulence models, where a suitable turbulence length scale is required as an inlet boundary condition. While the integral length scale is often chosen without a theoretical basis, this study derives that the Taylor micro-scale is the correct choice for simulating turbulence generated by a regular grid: the temporal decay of turbulent kinetic energy (TKE) is shown to depend on the initial value of the Taylor micro-scale by solving the differential equations given by Speziale and Bernard (1992). Further, the spatial decay of TKE and its dependence on the Taylor micro-scale at the inlet boundary are derived. With this theoretical understanding, RANS simulations with k−ω turbulence models are conducted using the Taylor micro-scale and the TKE obtained from grid experiments as the inlet boundary condition. Second, the results are validated with excellent agreement with the TKE evolution downstream of a grid obtained through hot-wire measurements in the wind tunnel. Third, the study further introduces an airfoil in both the experimental and the numerical setting where 3D simulations are performed. A very good match between force coefficients obtained from experiments and the digital twin is found. In conclusion, this study demonstrates that the Taylor micro-scale is the appropriate turbulence length scale to be used as the boundary condition and initial condition to simulate the evolution of TKE for regular-grid-generated turbulent flows. Additionally, the digital twin of the wind tunnel can accurately replicate the force coefficients obtained in the physical wind tunnel.

A Comprehensive Study on the Aerodynamic Characteristics of Electrically Controlled Rotor Using Lattice Boltzmann Method

An electrically controlled rotor (ECR) is a kind of swashplateless rotor that implements the primary control via the trailing-edge flap system instead of a swashplate and demonstrates great potential in vibration reduction and noise alleviation. In this paper, the mesoscopic numerical simulation method known as the lattice Boltzmann method (LBM) is employed to investigate the aerodynamic characteristics of an ECR. In the LBM, the discretized Boltzmann transport equation is solved to simulate the macroscopic motion of the fluid, and the D3Q27 model is applied for this study. The effects of the flap deflection on the ECR aerodynamic characteristics can be accurately included with the appropriate refined wall lattice resolution. On this basis, the adaptive wake-refinement strategy is applied to track the evolution of the wake and adequately capture details of the wake structure in the wake flow field. Based on this method, an aerodynamic analysis model for the ECR can be established on the XFlow simulation platform. The aerodynamic analysis model is validated, and the results indicate that the LBM can accurately capture the details of the rotor flow field and calculate blade aerodynamic load, as well as predict the downwash of the rotor. Therefore, based on this model, the ECR aerodynamic characteristics under hovering and forward flight conditions are analyzed, and the effects of the flap deflection on the wake structure, induced inflow, and disc load can be captured. The results indicate that a relatively large flap deflection required to trim the rotor will cause the additional intense flap wake vortex in the ECR wake flow field, apart from the concentrated vorticity at the blade tip and root demonstrated in the conventional rotor wake flow field, and thus significantly change the distributions of the disc-induced inflow and aerodynamic load.

Linking watershed nutrient loading to estuary water quality with generalized additive models.

Evaluating estuary water quality responses to reductions (or increases) in nutrient loading attributed to on the ground management actions can be challenging due to the strong influence of environmental drivers on nutrient loads and non-linear relationships. This study applied generalized additive models to calculate watershed nutrient loads and assess responses in estuary water quality to seasonally-adjusted freshwater inflow and flow-adjusted nutrient loads in Lavaca Bay, Texas. Lavaca Bay is a secondary embayment on the Texas coast displaying early potential for eutrophication and water quality degradation. Use of flow-adjusted nutrient loads allowed the study to evaluate the response in water quality to changes in nutrient loads driven by anthropogenic sources. Cross-validation indicated that, despite data constraints, semiparametric models performed well at nutrient load prediction. Based on these models, delivered annual nutrient loads varied substantially from year to year. In contrast, minimal changes in flow-normalized loads indicate that nutrient loadings were driven by natural variation in precipitation and runoff as opposed to changes in management of nonpoint sources. Models indicated no evidence of long-term changes in dissolved oxygen or chlorophyll-a within Lavaca Bay. However, site specific long-term increases in both organic and inorganic nitrogen are concerning for their potential to fuel eutrophication. Further analysis found freshwater inflow had strong influences on nutrient and chlorophyll-a concentrations but there was no evidence that changes in watershed nutrient loading explained additional variation in dissolved oxygen and limited evidence that watershed nutrient loadings explained chlorophyll-a concentrations. In addition to providing a baseline assessment of watershed nutrient loading and water quality responses in the Lavaca Bay watershed, this study provides methodological support for the use of semiparametric models in load regression models and estuary assessments.

Climate Change Impact on Inflow and Nutrient Loads to a Warm Monomictic Lake

This study analyses the impact of climate change on the inflows, sediment loads, and nutrient inputs to the Sabalan dam reservoir, a warm monomictic lake located northwest of Iran. For this purpose, the Soil and Water Assessment Tool (SWAT) was calibrated (2005–2018) and validated (2001–2004). Future climate-based data under the AR5 emission scenarios were obtained from the HadGEM2–ES general circulation model and then downscaled using the LARSWG 6.0. The tuned SWAT model was used to investigate the climate change impact on the hydrological processes and pollution loads to the Sabalan dam reservoir. Our findings based on the Nash–Sutcliffe efficiency coefficient and the coefficient of determination indicated an acceptable performance of the SWAT model in the simulation of inflows, sediment loads, and nutrient inputs to the reservoir. Inflow and sediment load to the reservoir will increase during the period of 2030–2070 compared to the base period (1998–2018). The annual total nitrogen (phosphorus) load to the reservoir will increase by 8.5% (9.4%), 7.3% (8.2%), and 5% (3.4%) under the emission scenarios of RCP2.6, RCP4.5, and RCP8.5, respectively. An increase in sediment loads and nutrient inputs to the Sabalan dam reservoir will significantly exacerbate the reservoir eutrophic condition, leading to water quality deterioration with acute consequences for the positive functions of the dam.

Removal of pollutants and accumulation of high-value cell inclusions in a batch reactor containing Rhodopseudomonas for treating real heavy oil refinery wastewater

Treating wastewater using purple non-sulfur bacteria (PNSB) is an environmentally friendly technique that can simultaneously remove pollutants and lead to the accumulation of high-value cell inclusions. However, no PNSB system for treating heavy oil refinery wastewater (HORW) and recovering high-value cell inclusions has yet been developed. In this study, five batch PNSB systems dominated by Rhodopseudomonas were used to treat real HORW for 186 d. The effects of using different hydraulic retention times (HRT), sludge retention times (SRT), trace element solutions, phosphate loads, and influent loads were investigated, and the bacteriochlorophyll, carotenoid, and coenzyme Q10 concentrations were determined. The community structure and quantity of Rhodopseudomonas in the systems were determined using a high-sequencing technique and quantitative polymerase chain reaction technique. The long-term results indicated that phosphate was the limiting factor for treating HORW in the PNSB reactor. The soluble chemical oxygen demand (SCOD) removal rates were 67.03% and 85.26% without and with phosphate added, respectively, and the NH4+-N removal rates were 32.18% and 89.22%, respectively. The NO3−-N concentration in the effluent was stable at 0–3 mg/L with or without phosphate added. Adding phosphate increased the Rhodopseudomonas relative abundance and number by 13.21% and 41.61%, respectively, to 57.35% and 8.52 × 106 gene copies/μL, respectively. The SRT was the limiting factor for SCOD removal, and the bacteria concentration was the limiting factor for nitrogen removal. Once the inflow load had been increased, the total nitrogen (TN) removal rate increased as the HRT increased. Maximum TN removal rates of 64.46%, 68.06%, 73.89%, 82.15%, and 89.73% were found at HRT of 7, 10, 13, 16, and 19 d, respectively. The highest bacteriochlorophyll, carotenoid, and coenzyme Q10 concentrations were 2.92, 4.99, and 4.53 mg/L, respectively. This study provided a simple and efficient method for treating HORW and reutilizing resources, providing theoretical support and parameter guidance for the application of Rhodopseudomonas in treating HORW.

Constructed wetlands as neglected fixed source of microplastics and antibiotic resistance genes in natural water bodies?

The pollution status and the harm caused by microplastics and antibiotic resistance genes (ARGs) in aquatic ecosystems have been a growing concern. The presence of microplastics could accelerate the transfer and spread of ARGs. Before sewage reaches natural water bodies, microplastics and ARGs need to be eliminated through specific processes. Constructed wetlands are currently an effective and environmentally friendly wastewater treatment process. Research has shown significant effectiveness in removing microplastics and ARGs. Microplastics and ARGs can be removed through processes such as adsorption, capture, adhesion, and biodegradation. However, long-term continuous operation could lead to constructed wetlands becoming significant reservoirs of microplastics and ARGs. Inflow loads and seasonal variations in constructed wetlands may result in the reintroduction of persistent microplastics and ARGs into the receiving water body, establishing the constructed wetland as a continuous source of these pollutants in the receiving water body. The key to the widespread application of constructed wetlands lies in solving this challenging problem. Therefore, although constructed wetlands serve as a green strategy for removing microplastics and ARGs, there are still many gaps in our knowledge. Based on the current accumulation of microplastics and ARGs in constructed wetlands, this paper summarizes the removal of microplastics and ARGs in existing constructed wetlands and explores the interaction between them. Additionally, it proposes suggestions for optimizing the process and improving the reliability of monitoring microplastics and ARGs in sewage.

Formulation of a Computational Aeroelastic Model to Predict Trim and Response of a Helicopter Rotor System

Comparison of theoretical and experimental data (flight test data) reveals that still there is a gap between theory and experiment. Some of the observed phenomenon in flight test may be due to the nonlinearities associated with the aeroelastic problems and this paper attempts to develop a theoretical formulation including the geometrical nonlinearities associated with structural modeling and the aerodynamic nonlinearities associated with dynamic stall. In this paper, the consolidated set of equations representing blade dynamics, rotor inflow and sectional aerodynamics are presented. The iterative computational solution technique developed for trim and response analysis is described and a systematic study is undertaken to analyse the influence of various aerodynamic models, representing rotor inflow and sectional loads, on the helicopter trim and aeroelastic response of the rotor blades. It is also shown that the structural coupling due to blade pretwist significantly influences the rotor blade response and loads compared to an untwisted rotor blade.

The retention of nitrogen and phosphorus in aboveground biomass of plants growing in constructed wetlands treating agricultural drainage

Three horizontal subsurface flow constructed wetlands (CW1, CW2 and CW3) for treatment of agricultural tile drainage water were built in 2018. Two wetlands were filled with a mixture of washed gravel and birch woodchips (10:1 volume ratio), in the third one the layer of woodchips was on top of a gravel layer. All wetlands were planted with Gyceria maxima and Phalaris arundinacea in parallel bands and parallel to water flow. Four-year study (2019–2022) was aimed at the amount of nutrients retained in aboveground plant biomass. The results revealed that the biomass of both species was lower as compared to biomass of these species growing in constructed wetlands for municipal sewage. Due to low aboveground macrophyte biomass, the nitrogen and phosphorus standing stocks were low (maximum 1.3 g P m−2 and 11.1 g N m−2). When comparing the nitrogen standing stocks with the inflow annual loadings and removed load, it represented on average only 2.38% of the removed load and 0.85% of the inflow load because of very high inflow loading (1298, 866 and 842 g N m−2 yr−1 in CW1, CW2 and CW3, respectively). On the other hand, the respective values for phosphorus amounted to 43.9% and 21.6% due to very low inflow loading (8.8, 6.6 and 6.0 g P m−2 yr−1 in CW1, CW2 and CW3, respectively). The study confirmed that plant contribution to nutrient removal in constructed wetlands expressed as removal percentage is strongly affected by inflow loading. The study also revealed that under low load conditions the plant uptake may substantially contribute to nutrient removal.

TP Concentration Inversion and Pollution Sources in Nanyi Lake Based on Landsat 8 Data and InVEST Model

Phosphorus is a limiting nutrient in freshwater ecosystems. Therefore, it is of great significance to use remote sensing technology to estimate the Total phosphorus (TP) concentration in the lake body and identify the contribution of TP inflow load in the surrounding area of the lake body. In this study, two main frameworks (empirical method and machine learning algorithm) for TP estimation are proposed and applied to the development of the Nanyi Lake algorithm. Based on the remote sensing data and ground monitoring data, the results obtained by the two main algorithms are compared to explore whether the machine learning algorithm has better performance than the empirical method in the TP inversion prediction of Nanyi Lake. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model was used to simulate the TP inflow load in the Nanyi Lake Basin and determine the key pollution source areas. The results show that the accuracy of the machine learning algorithm is higher than that of the empirical method and has better performance. Among the four machine learning algorithms—support vector machines (SVR), artificial neural network (BP), extreme gradient boosting algorithm (XGBoost) and random forest regression (RF)—the TP concentration inversion model established by the XGBoost algorithm is more accurate and has strong spatiotemporal heterogeneity. The simulation results in the southern and northeastern parts of the Nanyi Lake Basin contribute the most to the pollution load of the lake area, and the simulation results can provide direction for the effective prevention and control of Nanyi Lake, help to further effectively identify the key source areas of TP pollution in the water body of Nanyi Lake, and provide a meaningful scientific reference for water quality monitoring and management, to comprehensively improve the water quality of Nanyi Lake.

Quantifying the Nitrogen-Removal Performance of a Constructed Wetland Dominated by Diffuse Agricultural Groundwater Inflows Using a Linked Catchment–Wetland Model

Nitrogen loading from diffuse agricultural sources is a major water-quality problem worldwide. Constructed wetlands have been increasingly used to treat runoff and drainage from agricultural lands. However, the diffuse nature of nitrogen loading from farmlands often makes it challenging to trace flow pathways and measure the direct input loading to wetlands, and assess their nutrient-reduction performance. The Owl Farm wetland, Cambridge, New Zealand, receives inputs mainly from a subsurface drain and groundwater seepage. As it was not possible to directly measure wetland inflows, we used the Soil and Water Assessment Tool (SWAT) to estimate and partition the wetland inflow and nitrogen loading from the drain and seepage. A dynamic first-order tanks-in-series wetland model was linked with SWAT to evaluate the wetland capacity for nitrogen removal over a four-year period. The linked catchment–wetland model could simulate flow and nitrate load at the wetland outlet reasonably well with a Nash–Sutcliffe efficiency (NSE) of 0.7 and 0.76, respectively, suggesting that it provides a good representation of the hydrological and nitrogen processes in the upland catchment and the constructed wetland. We used two approaches, a mixed measurement-and-modelling-based approach and a process-based modelling approach to estimate the wetland efficiency of nitrogen removal. In both approaches, we found that the percentage load removal for nitrate-N and total N was related exponentially to the wetland outflow rate. Based on the process-based model estimates, the Owl Farm constructed wetland is very effective in removing nitrate-N with annual estimates of 55–80% (average 61%) removal. However, this capacity is very dynamic depending on the inflow from the catchment. The removal efficiency is very high at low flow and reduces when flow increases but is still maintained at around 20–40% during higher-flow periods. However, actual nitrogen-load removal in the wetland is greatest during high-flow periods when input loads are elevated. This study illustrates how a linked catchment–wetland modelling approach can be used to partition and quantify diffuse nitrogen input loads into wetlands from different types of runoff and to evaluate their subsequent reduction rates. The tool is particularly useful for situations where diffuse groundwater inflows, which are difficult to measure, are important nutrient sources.

Degradation of Dimethylacetamide from Membrane Production through Constructed Wetlands—Pathways, Ecotoxicological Effects and Consequences for Chemical Analysis

Wastewater from factories producing polysulfone-based membranes mainly contains the used organic solvent, i.e., dimethylacetamide (DMAc). Due to the environmental impact of DMAc, wastewater treatment is mandatory. Several biological treatment options based on the activated sludge process are described in the literature. Due to artificial aeration, these techniques have high energy requirements. Near-nature processes such as vertical flow constructed wetlands (VF wetlands) have a low energy demand, high tolerance to load fluctuations, and low maintenance requirements. Therefore, high-loaded, two-stage VF wetlands are an efficient option for treating wastewater. However, constructed wetlands have so far only been used to a limited extent for the treatment of industrial wastewater. In the present study, the ability of laboratory-scale, high-load, two-stage VF wetlands to treat DMAc was investigated. This included their DMAc degradation efficiency and corresponding pathways, removal of the total organic carbon (TOC), nitrification and denitrification of the nitrogen, as well as the ecotoxicological effects (mutagenicity, genotoxicity, reactive oxygen species) of untreated and treated wastewater. The focus was to determine the effect of different grain size distributions on removal rates, the maximum inflow loading, and the effect of high inflow concentrations on effluent concentrations. In general, DMAc was completely degraded using VF wetlands, with dimethylamine (DMA) identified as the main intermediate. TOC removal rates reached more than 99%. The nitrogen bound to DMAc was completely nitrified. However, the start-up of the VF wetlands without seeded filter material temporarily leads to high nitrite accumulation. This may affect the mutagenicity of the treated wastewater. The results show that high-loaded, two-stage VF wetlands are an effective option for treating wastewater containing DMAc with higher efficiency than comparable biological processes.

Modeling multi-year phosphorus dynamics in a bioretention cell: Phosphorus partitioning, accumulation, and export

Phosphorus (P) export from urban areas via stormwater runoff contributes to eutrophication of downstream aquatic ecosystems. Bioretention cells are a Low Impact Development (LID) technology promoted as a green solution to attenuate urban peak flow discharge, as well as the export of excess nutrients and other contaminants. Despite their rapidly growing implementation worldwide, a predictive understanding of the efficiency of bioretention cells in reducing urban P loadings remains limited. Here, we present a reaction-transport model to simulate the fate and transport of P in a bioretention cell facility in the greater Toronto metropolitan area. The model incorporates a representation of the biogeochemical reaction network that controls P cycling within the cell. We used the model as a diagnostic tool to determine the relative importance of processes immobilizing P in the bioretention cell. The model predictions were compared to multi-year observational data on 1) the outflow loads of total P (TP) and soluble reactive P (SRP) during the 2012–2017 period, 2) TP depth profiles collected at 4 time points during the 2012–2019 period, and 3) sequential chemical P extractions performed on core samples from the filter media layer obtained in 2019. Results indicate that exfiltration to underlying native soil was principally responsible for decreasing the surface water discharge from the bioretention cell (63 % runoff reduction). From 2012 to 2017, the cumulative outflow export loads of TP and SRP only accounted for 1 % and 2 % of the corresponding inflow loads, respectively, hence demonstrating the extremely high P reduction efficiency of this bioretention cell. Accumulation in the filter media layer was the predominant mechanism responsible for the reduction in P outflow loading (57 % retention of TP inflow load) followed by plant uptake (21 % TP retention). Of the P retained within the filter media layer, 48 % occurred in stable, 41 % in potentially mobilizable, and 11 % in easily mobilizable forms. There were no signs that the P retention capacity of the bioretention cell was approaching saturation after 7 years of operation. The reactive transport modeling approach developed here can in principle be transferred and adapted to fit other bioretention cell designs and hydrological regimes to estimate P surface loading reductions at a range of temporal scales, from a single precipitation event to long-term (i.e., multi-year) operation.

The effect of aboveground biomass harvesting on nutrients removal in a constructed wetland treating municipal sewage

The study was performed at the constructed wetland treating municipal sewage from 200 population equivalent. The aim of the study was to evaluate the role of Phalaris arundinacea and Phragmites australis harvesting on nutrient removal. The highest phosphorus concentrations in leaves were found in the re-grown P. arundinacea in October (3.12 m g−1), followed by those in June (2.68 mg g−1) and July (2.67 mg g−1). Phosphorus concentrations in P. australis leaves were higher in July (2.14 mg g−1) than in September (1.79 m g−1). Phosphorus concentrations in stems were lower and varied between 1.07 mg g−1 in P. australis in September and 2.21 mg g−1 in P. arundinacea regrowth in October. Nitrogen leaf concentrations varied between 21.0 mg g−1 in P. arundinacea in June and 33.7 mg g−1 in P. arundinacea regrowth in October. In stems, the highest concentration was observed in P. australis in July (18.6 mg g−1) while the lowest N concentration was measured in July in P. arundinacea (3.8 mg g−1). The results showed that there was no difference between nutrients standing stock in a single harvested of P. arundinacea as compared to double harvested biomass. There was a significant higher biomass and consequently higher standing stock in P. arundinacea in the inflow zone as compared to outflow zone. Biomass and nutrients standing stocks in P. australis were significantly higher than that in P. arundinacea. The phosphorus sequestered in the aboveground biomass represented 6.3% of the inflow P load and phosphorus in the harvested biomass represented 44% of removed P load. For nitrogen, the respective values represented 14% and 41.6%. The data indicate that to remove 20% of the inflow annual load via biomass cutting, the inflow load should not exceed 20 g P m−2 yr−1 and 300 g N m−2 yr−1.

Evaluation of the Feasibility of Foam Glass as Filter Media in Rain Garden

Objectives:In order to recycle and resource waste glass, the feasibility of foam glass as filter media was evaluated, and column experiments using foam glass media were conducted to confirm the applicability as filter media in rain garden. Through this experiment, various design factors to be considered can be derived in application of foam glass media in the rain garden.Methods:Sieve analysis and SEM/EDS analysis were conducted to confirm the physicochemical properties of the foam glass. Column experiments filled with only foam glass and mixtures of sand and foam glass were conducted to simulate rain garden to evaluate the removal efficiency of suspended solids and turbidity using the foam glass media, head difference (&lt;i&gt;Δh&lt;/i&gt;) and hydraulic conductivity (&lt;i&gt;K&lt;/i&gt;) changes, and calculation of filtered suspended solids loading using both discrete and cumulative mass approach. Finally, comparison of filtration performance with various filter media used in LID facilities was performed to evaluate the feasibility of foam glass media in rain garden.Results and Discussion:Since foam glass media has a lower density than water, homogeneous particle size, and smooth surface with pores of various sizes, foam glass media effectively induces internal capture and external adsorption of suspended solids. Foam glass media has been applied to high suspended solids and turbidity removal efficiency. As the suspended solids inflow load increased, clogging occurred in the pores and the removal efficiency gradually decreased, but the foam glass media with lower density than water was continuously disturbed and rearranged due to the head difference energy, and some clogging were alleviated by rearrangement of pores and channels. The load of suspended solids in precipitated, adsorbed, and retained on the foam glass was calculated using the effluent sample (discrete) collected at regular time intervals and the continuously accumulated sample (cumulative) from the output. The filtered suspended solids load calculated using the cumulative mass approach was higher due to the estimation of the amounts of suspended solids remaining in the filtration column is lower because the samples (discrete) collected at regular time intervals from the output do not reflect the amount of suspended solids that change over time. Thus, the amounts of suspended solids removed through the filtration process can be much more accurately estimated using the cumulative samples. Finally, when comparing the removal efficiency with other filter media, foam glass can be used as excellent filter media with higher removal efficiency and greater lifespan.Conclusion:Foam glass media with smooth surface, pores of various sizes, and lower density than water can rearrange and regenerate pores to alleviate some clogging, resulting in high suspended solids and turbidity removal efficiency for a long period of time. Considering that the amount of suspended solids filtered is determined by various factors such as particle size and distribution, porosity, depth, linear velocity, and inflow load of the suspended solids, the feasibility test using foam glass media through long-term field experiments is warranted. The amounts of suspended solids removed through the filtration process can be much more accurately estimated using the cumulative samples.

Optimization of a sequencing batch reactor with the application of the Internet of Things

Internet of Things (IoT) technology was applied to the operation of the sequencing batch reactor (SBR) process to increase nitrogen removal and tackle the disturbances caused by the inflow fluctuations. To cope flexibly with the fluctuations in the inflow load, the time required for settling and discharging (TRSD) was reduced by inventing an automatic mechanical decanter, operated by monitoring the height of the sludge blanket layer and the concentration of suspended solid (SS) in the supernatant. The average TRSD of the automatic mechanical decanter was 1 hr, which was reduced by 27–59% compared to the conventional SBR processes treating domestic wastewater. Increasing the bio-reaction time with reduced TRSD allows improved performance while maintaining the overall cycle time of the SBR processes. Nitrogen removal was enhanced by feeding the influent in two steps in an 8:2 ratio while monitoring nitrogen ions in the bioreactor. The total nitrogen (T-N) removal of the step-feed modes was 92–93%, while that of the single-feed modes was 82–88%. Although the average time required for the bio-reaction steps increased by 51 min in the step-feed mode under the same temperature condition (13–16 °C), the total cycle time of the SBR process did not exceed 6 hr/cycle due to the reduced TRSD. By applying IoT technology, reliable operation of the SBR and improved T-N removal were achieved.

Nitrification potential of daily-watered biofiltration designs for high ammonium wastewater treatment

The vegetated biofiltration systems (VBS), also known as bioretentions or rain gardens, are well-established technology for treatment of urban stormwater and recently greywater, offering multiple benefits to urban environments. However, the impact of high ammonium strength wastewater (60 mg/L) on the nitrification process in these systems is not well understood. Hence, a laboratory-based column study was conducted to uncover dominant nitrification mechanisms, based on the learnings from similar onsite wastewater treatment systems. The experimental columns tested the effect of contact time (filter media depth, 150 mm, 300 mm and 700 mm), media oxygenation (active and passive) and alkalinity/pH (marble chips 5 % weight), as well as optimal operational conditions (inflow loading, concentrations, and dissolved oxygen (DO)). All nitrogen species (NH4+, NO3−, NO2−), chemical oxygen demand (COD) and physical parameters (DO, pH, electrical conductivity) were monitored across seven events over thirteen weeks. The results show that dosing with 30 and 60 mg/L of NH4+ resulted in 700 mm sand column depth to perform almost complete nitrification of NH4+ to NO3− (< 90 %), while 300 mm designs achieved partial nitrification of NH4+ to NO2−, likely due to limited contact time and inefficient nitrite oxidizing bacteria activity. Nitrification potential of all designs further supported that appropriate aerobic contact time is necessary for effective nitrification. Inflow concentration of NH4+ and DO did not significantly impact nitrification performance, while reducing daily volume loading reduced NO3− and NO2− leaching. Active and passive aeration and alkalinity buffering did not positively affect ammonium removal. While there is a potential to apply both nitrification-denitrification and anammox processes to future VBS design, further understanding of aeration and alkalinity on microbially driven nitrification processes is needed.