Total Phosphorus Reduction Research Articles

Mechanisms of total phosphorus removal and reduction of β-lactam antibiotic resistance genes by exogenous fungal combination activated sludge

This study utilized Trichoderma and activated sludge to construct combined activated sludge (TAS). The metagenomic approach was employed to examine the shifts in microbial community structure and function of TAS under amoxicillin stress and investigate the mechanism underlying the reduction of β-lactam antibiotic resistance genes (β-ARGs). The findings demonstrated that the elevated aundance of glpa, glpd, ugpq, glpq, and glpb were primarily responsible for the reduction in total phosphorus (TP) removal by TAS. The increased abundance of Proteobacteria and Verrucomicrobia led to enhanced expression of ugpb, phnd, and phne, thereby improving the TP removal of TAS. Furthermore, antibiotic inactivation has gradually become the primary antibiotic resistance mechanism in TAS. Specifically, an increase in the abundance of OXA-309 in TAS will decrease the probability of amoxicillin accumulation in TAS. A decrease in β-ARGs diversity confirmed this. This study presents a novel approach to reducing antibiotic and ARG accumulation in sludge.

Response of streamflow and nutrient loads in a small temperate catchment subject to land use change

The aim of this study was to quantify the effect of land use change (LUC) implemented to meet nutrient load targets for a freshwater lake in New Zealand. We used the Soil and Water Assessment Tool (SWAT) model in combination with a non-parametric statistical test to determine whether afforestation of 15% of a subcatchment area was adequate to meet assigned nutrient load targets. A regional management authority set nutrient load targets of reduction in total nitrogen (TN) by 0.9 t yr−1 and reduction in total phosphorus (TP) by 0.05 t yr−1 to avoid eutrophication in the receiving waters of a freshwater lake. The load reduction was designed to be achieved through 200 ha of LUC from pasture to trees. Analysis of nutrient loads before, during, and following LUC shows that a 15% increase in forest cover decreased the annual flow (7.2%), TP load (33.3%), and TN load (13.1%). As flow and water quality observations were discrete and at irregular intervals, we used a parametric test and the SWAT model as different lines of evidence to demonstrate the effect of afforestation on flow and water quality. Policymakers concerned with decisions about LUC to improve the quality of receiving waters can benefit from applying our findings and using a statistical and numerical modelling framework to evaluate the adequacy of land use change to support improvements in water quality.

Phytoremediation for Nutrient Removal in an Environmentally Friendly Floating Cage System: A Field Experiment

Aquaculture is one of the efforts to optimize the utilization of water bodies. Aquaculture using floating net cages is detrimental to water, namely causing pollution from uneaten feed and fish excretion. Water quality would be degraded due to eutrophication, oxygen depletion, and uncontrolled growth of algae and aquatic plants. High concentrations of nitrogen and phosphorus mainly trigger water quality degradation and eutrophication. To reduce the negative impact of aquaculture activities in floating net cages in reservoir/lake waters, an environmentally friendly cage technology that is low waste is needed. The technology offered is a loop bio-phytoremediation system equipped with floating net cages, a water management system with recirculation, and plants. The floating net cage used is a double net where the upper net consists of two nets and a bottom net. The upper net is used for rearing carp fish, and the bottom net for tilapia. The plants used as phytoremediation agents were water spinach and vetiver grass. Moreover, the physical filter used for processed water before recirculating to the waterbody in the FNC consists of sand, palm fiber, and limestone layers. The results showed that the effectiveness of nutrient removal on water spinach hydroponic (HRT=15 h), vetiver grass wetland (HRT=36 h), and physical filters (HRT=2,4 h) in reducing nitrate was 83%, 86%, and 67%, respectively; maximal reduction of the organic matter reached 94%, 96%, and 96%, respectively; as well as the highest reduction in total phosphorus was 78%, 89%, and 82%, respectively.

Assessment of a diel phosphorus pattern's potential to benefit phosphorus retention in the stormwater treatment areas

The Stormwater Treatment Areas (STAs) are constructed wetlands used to reduce the total phosphorus (TP) level in water discharged to the environmentally sensitive areas of the Everglades Protection Area. Analysis of high temporal frequency TP data reveals that TP concentrations discharged from selected STA flow-ways exhibit diel and seasonal cyclic patterns and are most affected by discharge rate and water depth. The objective of this paper is to describe the diel TP pattern and evaluate the possibility of using it to reduce TP in STA discharge. The amplitude of diel TP pattern ranged from 0.7 to 1.5 μg L−1 (3–6% deviation from daily mean) at three flow-ways, peaking in the early afternoon and reaching lowest concentrations between midnight and 4 am. To assess the possibility of further reducing TP concentration discharged from the STAs by increasing the proportion of daily flow discharged at night when diel TP is at a minimum, a General Additive Model (GAM) was created with discharge rate, water depth, year, location, day-of-year, and time-of-day as covariates. While time-of-day was a statistically significant factor in the model (p < 0.001), its average marginal effect was smaller than all other significant model covariates: discharge rate, season, and water depth. Modeling suggests that within specific ranges of discharge rate and water depth, the opportunity exists to provide additional TP reduction in STA outflow by discharging a greater proportion of the daily flow at night when TP concentrations are lower. Further research is needed to quantify the effect of increasing nighttime flow on annual flow weighted mean TP. Additionally, an evaluation of the practicality and logistical cost required to redistribute flow is needed before attempting to take advantage of this natural cyclic pattern to improve STA TP retention.

Optimization of the Coagulation-flocculation Process Using Ferric Chloride and Phosphate for the Reduction of Contaminants in the Slaughterhouses Wastewater

In this work, the coagulation-flocculation process was optimized using ferric chloride and phosphate for the reduction of pollutants in the wastewater from the Conchucos S.A., Lima. Parameters were measured in percentage reduction of chemical oxygen demand (COD), turbidity (NTU) and total phosphorus (PT mg/L), adding ferric chloride as coagulant and potassium dihydrogen phosphate as flocculant. The effects of four independent variables were investigated: ferric chloride dose (500-700 ppm), phosphate dose (700-900 mg/L), fast agitation speed (250-320 rpm) and slow agitation speed (90-100 rpm). The experimental data were optimized by the response surface method using a central composite design. The results show that the statistical models obtained F-values of 3.33, 4.27 and 4.16 for the percent reduction of COD, turbidity and total phosphorus, respectively. Furthermore, the statistical models developed to predict the responses were confirmed by significant probability values (p&lt;0.05). On the fit of the models, an R2 of 0.61, 0.66 and 0.67 are shown for COD, turbidity and total phosphorus percentage, respectively. The optimum conditions were found experimentally at 700 ppm of ferric chloride dose, 900 ppm of phosphate, 320 rpm fast speed and 100 rpm for a reduction of 75.46% of COD, 83.47% of turbidity and 44.08% of total phosphorus presenting a desirability of 0.7.

Monitoring, Modeling and Planning Best Management Practices (BMPs) in the Atwood and Tappan Lake Watersheds with Stakeholders Engagements

This study was conducted in the Atwood and Tappan Lakes watersheds of the Tuscarawas basin of Ohio. The flow, total nitrogen (TN), and total phosphorus (TP) loadings were monitored with the help of local stakeholders for a few years at various locations of the watershed to develop the Soil and Water Assessment Tool (SWAT). The multi-site SWAT model calibration and validation were accomplished with a reasonable model performance. In the next step, the scenario analysis was conducted in the SWAT model using various BMPs, including vegetative filter strips, grass waterways, fertilizer reduction, crop rotation, and cover crops to evaluate their performance in reducing TN and TP from the watershed. While BMPS in many studies are decided based on researchers’ intuition, these BMPs were selected based on active consultation with the local stakeholders, who were engaged in the reduction of TN and TP loadings from the watersheds. Since the SWAT model calibration for TN and TP was not as good as the hydrologic model calibration, various scenarios of TN and TP reduction using BMPs were investigated for several years using both calibrated and uncalibrated SWAT models. We examined all the BMPs in 12 sub-watersheds of the Atwood and 10 sub-watersheds of the Tappan Lake watershed. The analysis indicated that the management practices of cover crops (rye) in combination with grass waterways with a 10% fertilizer reduction could minimize the TN and TP loading by as much as 88%, without significantly compromising the agricultural yield. However, a 10% fertilizer reduction without any BMPs could reduce TN and TP by just 9%. The cover crop (rye) including 10% fertilizer reduction with grass waterways seemed to be the most effective in reducing TN and TP, whereas the implementation of a filter strip led to a 70% reduction and was the next effective BMPs in reducing TN and TP loadings. In general, TN losses were reduced by 8% to 53%, while TP losses were reduced by 7% to 88%, depending on the BMPs used. By and large, the TN and TP reduction achieved through the calibrated model was not significantly different from the uncalibrated model, even though the reduction using the calibrated model was slightly higher for all scenarios than that of the uncalibrated model. The TN and TP loadings were highly sensitive to cattle grazing. When just 50% of the cattle were permitted to graze, the model predicted that there would be a 40% increase in total nitrogen and a 70% increase in total phosphorus in both watersheds. Our investigation revealed that monitoring the watershed at a small sub-watershed scale and calibrating the SWAT model for nitrogen and phosphorus is delicate.

The Effects of Long-Term Application of Stabilized and Coated Urea on Soil Chemical Properties, Microbial Community Structure, and Functional Genes in Paddy Fields

The addition of fertilizers is indispensable in agricultural production, and currently, there is a wide variety of new types of fertilizers available. For example, commonly used are stabilized fertilizers with inhibitors and coated slow-release fertilizers, among others. However, the long-term effects of these fertilizers, when applied continuously are still uncertain. This study will provide scientific and theoretical support for the development and promotion of these fertilizers. A 16-year paddy field with brown soil treated with different urease and nitrification inhibitors, sulfur-coated urea (SCU), and resin-coated urea (PCU) was studied. The study showed that long-term use of conventional urea nitrogen fertilizer resulted in a significant reduction in soil total phosphorus (TP). Long-term application of NBPT and conventional urea significantly increased soil organic matter (SOM). Moreover, except for HQ and NBPT+DMPP, the prolonged application of new urea fertilizers also significantly enhanced soil total potassium (TK). Application of SCU fertilizer in brown soil type paddy fields resulted in a significant decrease in soil pH over time. However, changes in pH had no effect on the abundance of ammonia-oxidizing bacteria (AOB), as AOB was mainly affected by soil-available N. DMPP, HQ+DCD, NBPT+DMPP, SCU, and PCU significantly reduced the 16S rRNA gene copy number of soil bacteria, with the greatest effect of coated urea fertilizer (SCU and PCU). Long-term application of stable urea fertilizer with HQ significantly reduced the bacterial community in paddy soil. Conversely, HQ+DCD-stabilizede urea fertilizer significantly increased the population structure and abundance of Basidiomycota fungi while decreasing the population structure and abundance of Rozellomycota fungi. DMPP-stabilized urea fertilizer notably increased the population structure and abundance of Ascomycota fungi while decreasing the population structure and abundance of Rozellomycota and Chytridiomycota fungi. Furthermore, HQ-stabilized urea fertilizer significantly reduced the population structure and abundance of Chytridiomycota fungi.

Stand age alters fungal community composition and functional guilds in subalpine Picea asperata plantations

Soil fungi participate in a variety of forest ecological processes and drive the succession of degraded forests. However, how the soil fungal community and functional taxa change with stand age remains unclear in subalpine plantations. We established five vegetation survey plots in four planted Picea asperata forests aged 25, 40, 50 and 75 years and one natural P. asperata forest aged approximately 200 years in a subalpine region and randomly collected rhizosphere and bulk soils of two representative P. asperata individuals in each plot for high-throughput sequencing of fungal communities and determination of soil properties. The fungal community composition in both rhizosphere and bulk soils varied significantly among different stand ages. Fungal operational taxonomic unit (OTU) richness and Shannon diversity in bulk but not rhizosphere soil changed significantly with stand age. Except for the 75-year-old plantation, there was no difference in the fungal community composition between rhizosphere soil and bulk soil. Soil properties, plant production (P. asperata growth indicators) and plant richness jointly determined the fungal community composition, and soil total phosphorous (TP) accounted for the most variation in the fungal community. P. asperata regulated the community composition of fungal functional guilds (i.e., plant pathogens, saprophytes, ectomycorrhizal fungi and endophytes) mainly by changing soil properties rather than plant richness. Interestingly, the community composition of fungi and functional guilds in plantations became increasingly similar to that in the natural forest over time, and the fungal restoration rate (represented by the Bray–Curtis distance between plantations and natural forest) in bulk soil was faster than that in rhizosphere soil. In addition, with increasing stand age, the relative abundance of ectomycorrhizal fungi increased, and the diversity of plant pathogens decreased, both of which were significantly associated with the reduction in soil total phosphorus. These results suggest that stand age is a major factor affecting soil fungal community variation in subalpine P. asperata plantations, which is largely dependent on soil property changes. In particular, soil TP may play a key role in the regulation of different ecological functional fungi.

Integrating ACPF and SWAT to Assess Potential Phosphorus Loading Reductions to Lake Erie: A Case Study.

Lake Erie is threatened by eutrophication and harmful algal blooms due to excess nutrient loading from agricultural sources. To reduce nutrient loading to Lake Erie, widespread adoption of agricultural conservation practices (ACPs) has been proposed. However, identifying appropriate and effective locations for ACP placement has been challenging. Another challenge is understanding how effective the ACPs are in reducing nutrient loading and achieving water quality goals. Therefore, identifying the most effective ACPs, as well as spatially optimal placement of ACPs to achieve the maximum environmental benefit, is of paramount importance. The main objective of this study was to integrate the Agricultural Conservation Planning Framework (ACPF) with the Soil and Water Assessment Tool (SWAT) to assess the potential effectiveness of ACPs developed by ACPF in reducing phosphorous losses from an agriculturally dominated small watershed within the Western Lake Erie Basin. ACPF was used to develop a series of ACP opportunity plans, which were then integrated into a calibrated SWAT model. SWAT simulation of ACPF developed ACP opportunity plans for grassed waterways (GWs), contour buffer strips (CBSs), water and sediment control basins (WASCOBs), nutrient removal wetlands (NRWs), and farm ponds (FPs) revealed various reductions in sediment, soluble reactive phosphorus (SRP), and total phosphorus (TP) at the watershed-scale. The simulation of individual ACP opportunity plans revealed that GW resulted in the greatest annual average SRP and TP reductions (19% and 30%, respectively), followed by CBS (16% and 22%), and WASCOB (13% and 16%); NRWs were the most effective at reducing sediment (56%) but increased SRP (27%). Combined GW, CBS, and WASCOB opportunity plans resulted in the greatest reduction of SRP (34%), while the combination of all ACP opportunity plans resulted in the greatest reduction of TP (49%) and sediment (78%).

Effects of Livestock Exclusion on Pollutant Export From a North Carolina Beef Cow Pasture

Highlights Exclusion of beef cattle from two streams resulted in significant reductions in nitrogen, phosphorus, and sediment exports. Reductions in nutrient and sediment export improved following four or more years of exclusion. Nitrogen and phosphorus concentrations in storm samples decreased more than those in baseflow samples. Abstract. Fences were installed to exclude cattle from two adjacent small streams on a beef and swine farm located in central North Carolina. The two streams, referred to as UTA and North, originated in a pasture used for beef cow production and the application of swine waste. Rainfall and discharge were continuously monitored for 1.34 years prior to and 1.8 years after the fencing was installed in order to quantify the effect of the livestock exclusion on pollutant export/loads in the two streams originating in the pasture. Monitoring results documented reductions in total nitrogen (TN), phosphorus (TP), and total suspended solids (TSS) exports via the North stream of 15%, 54%, and 67%, respectively. Monitoring on the UTA stream was restarted 3.7 years after the initial 1.8 years and continued for about 1 year to assess the effect of natural vegetation growth and stream channel soil recovery. The combined reductions for the two periods were 39%, 64%, and 74% for TN, TP, and TSS, respectively. Exports of TN, TP, and TSS during the later monitoring period decreased by 13%, 60%, and 22%, respectively, compared to the initial 1.8-year monitoring period. These results indicated that exclusion fencing was effective at reducing pollutant exports during the first 1.8 years and that its effectiveness increased after about four years. Consequently, studies that report effectiveness during the first 2 to 4 years after exclusion likely underestimate the long-term effectiveness of the exclusion fencing. Keywords: Best management practices, Discharge monitoring, Livestock exclusion.

Multivariate methods in modelling the removal of nitrogen and phosphorus in deep-bed two-media down-flow sand filters

Abstract Multiple linear regression (MLR) was applied to study the operation and efficiency of simultaneous denitrification with sodium acetate (NaAc) as a carbon and energy source and the chemical precipitation of phosphate with iron salts in a pilot sand filter. Different loads were simulated with the addition of primary settled wastewater (PW) containing suspended solids (SS) and biological SS from the aeration tank. SS from PW partly passed the filter. Biological SS was caught by the filter. The validation of the model showed that phosphorus concentration and chemical oxygen demand reduction were easier to predict correctly than the time of operation of the filter. The reduction of total phosphorus differed between 0.01 and 0.31 mg P/L, and the nitrate concentration in the filtrate differed between 0 and 5.2 mg N/L when comparing the experimental values with the model. Experiments showed filtrate concentrations of 0–0.12 mg PO4-P/L, 3.0–8.8 mg NO3-N/L, and 1.9–34 mg SS/L. The addition of NaAc gave a small increase in the reduction of PO4-P probably because of the assimilation of PO4-P into the denitrifying sludge. The dosage of Fe gave a small decrease in the reduction of NO3-N probably because of PO4-P limitation for denitrifying bacteria, as Fe acts as a precipitation agent upon PO4-P.

Identification of pollutant sources and evaluation of water quality improvement alternatives of a large river.

While pollutants are the most important factors for the deterioration of surface water quality, the identification of major pollutant sources for rivers is challenging, especially in areas with diverse land covers and multiple pollutant inputs. This study aims to identify the significant pollutant sources from the tributaries that are affecting the water quality and identify the limiting nutrient for algal growth in the Geum river to provide a management alternative for an improvement of the water quality. The positive matrix factorization (PMF) was applied for pollutant source identification and apportionment of the two major tributaries, Gab-cheon and Miho-cheon. Positive matrix factorization identifies three and two major pollutant sources for Gab-cheon and Miho-cheon, respectively. For Gab-cheon, wastewater treatment plants, urban, and agricultural pollution are identified as major pollutant sources. Furthermore, for Miho-cheon, agricultural and urban pollution were identified as major pollutant sources. Total phosphorus (TP) is also identified as a limiting nutrient for algal growth in the Geum river. Water quality control scenarios were formulated and improvement of water quality in the river locations was simulated and analyzed with the Environmental Fluid Dynamic Code (EFDC). Scenario results were evaluated using a water quality index. The reduction of total phosphorus (TP) from the tributaries has greatly improved the water quality, especially algal bloom in the downstream stations.

Phytoremediation of nitrogen and phosphorus pollutants from glass industry effluent by using water hyacinth (Eichhornia crassipes (Mart.) Solms): Application of RSM and ANN techniques for experimental optimization.

The present study aimed to assess the efficiency of the water hyacinth (Eichhornia crassipes (Mart.) Solms) plant for the reduction of nitrogen and phosphorus pollutants from glass industry effluent (GIE) as batch mode phytoremediation experiments. For this, response surface methodology (RSM) and artificial neural networks (ANN) methods were adopted to evidence the optimization and prediction performances of E. crassipes for total Kjeldahl's nitrogen (TKN) and total phosphorus (TP) removal. The control parameters, i.e., GIE concentration (0, 50, and 100%) and plant density (1, 3, and 5 numbers) were used to optimize the best reduction conditions of TKN and TP. A quadratic model of RSM and feed-forward backpropagation algorithm-based logistic model (input layer: 2 neurons, hidden layer: 10 neurons, and output layer: 1 neuron) of ANN showed good fitness results for experimental optimization. Optimization results showed that maximum reduction of TKN (93.86%) and TP (87.43%) was achieved by using 60% of GIE concentration and nearly five plants. However, coefficient of determination (R2) values showed that ANN models (TKN: 0.9980; TP: 0.9899) were superior in terms of prediction performance as compared to RSM (TKN: 0.9888; TP: 0.9868). Therefore, the findings of this study concluded that E. crassipes can be effectively used to remediate nitrogen and phosphorus loads of GIE and minimize environmental hazards caused by its unsafe disposal.

Hydrologic and water quality performance of a subsurface gravel wetland treating stormwater runoff

Subsurface gravel wetlands are an emerging type of green infrastructure that can be used to manage stormwater through the capture and slow release of runoff. They are unique to other types of green infrastructure in that they have a distinct fully saturated gravel layer below an occasionally saturated soil layer that influences pollutant removal processes. While they have been widely applied to treat wastewater, our understanding of their efficiency in treating stormwater with variable pollutant inputs is limited. To fill this gap, this study monitored the flow and water quality (total suspended solids, total nitrogen, total phosphorus, and chloride) in a subsurface gravel wetland in Oshkosh, Wisconsin at the influent, effluent, and in an observation well. Results from nine storm events indicated that the wetland had a median volume reduction of 74% and a median peak flow reduction of 89%. The reduction in pollutant concentrations where highly dependent upon the influent concentration. Average reductions of total suspended solids, total nitrogen, and total phosphorus were 49%, −21% and −0.2%, respectively, indicating an increase in nutrients; however, where influent concentrations were above irreducible levels, total phosphorus was reduced by 45% (influent ≥0.25 mg/L) and total nitrogen was reduced by 38% (influent ≥2.5 mg/L). Overall, this study shows that the subsurface gravel wetland performed similar to other types of green infrastructure and could be a good management practice to mitigate the harmful effects of stormwater runoff.

Removal of nutrients from pulp and paper biorefinery effluent: Operation, kinetic modelling and optimization by response surface methodology

This study investigated the effectiveness of extended aeration system (EAS) and rice straw activated carbon-extended aeration system (RAC-EAS) in the treatment of pulp and paper biorefinery effluent (PPBE). RAC-EAS focused on the efficient utilization of lignocellulosic biomass waste (rice straw) as a biosorbent in the treatment process. The experiment was designed by response surface methodology (RSM) and conducted using a bioreactor that operated at 1–3 days hydraulic retention times (HRT) with PPBE concentrations at 20, 60 and 100%. The bioreactor was fed with real PPBE having initial ammonia-N and total phosphorus (TP) concentrations that varied between 11.74 and 59.02 mg/L and 31–161 mg/L, respectively. Findings from the optimized approach by RSM indicated 84.51% and 91.71% ammonia-N and 77.62% and 84.64% total phosphorus reduction in concentration for EAS and RAC-EAS, respectively, with high nitrification rate observed in both bioreactors. Kinetic model optimization indicated that modified stover models was the best suited and were statistically significant (R2 ≥ 0.98) in the analysis of substrate removal rates for ammonia-N and total phosphorus. Maximum nutrients elimination was attained at 60% PPBE and 48 h HRT. Therefore, the model can be utilized in the design and optimization of EAS and RAC-EAS systems and consequently in the prediction of bioreactor behavior.

Hydrological and water quality simulation and future runoff prediction under CMIP6 scenario in the upstream basin of Miyun Reservoir

AbstractWater resources are a key factor restricting human survival and social and economic development. The Miyun Reservoir, which is the only surface drinking water source in Beijing and the water storage reservoir of the South-to-North Water Diversion Project, plays a decisive role in ensuring water-use sustainability of the capital. This study focused on the Baihe River Basin, which is one of the important inflows of the Miyun Reservoir. The mathematical data on the climate and hydrological changes of the Baihe River Basin over the past 30 years were obtained, and the evolution law of the Baihe River runoff and its influencing factors was analyzed. Our analysis used the data obtained via multi-source meteorology to establish the Soil and Water Assessment Tool (SWAT) model of the Baihe River Basin. Sequential Uncertainty Fitting version 2 (SUFI-2) and Generalized Likelihood Uncertainty Estimation (GLUE) were used to simulate runoff from 1990 to 2017 on a monthly scale, along with sediment, total nitrogen (TN), and total phosphorus (TP) contents from 1990 to 2010. Then, the parameter uncertainty of the SWAT model and the applicability of the SWAT model in the Baihe River Basin were determined. The land-use transfer matrix showed that land-use changes are complex and the transformation forms are diverse. The simulation results showed that the transformation of land-use patterns in 1990 and 2010 had slight impacts on the hydrologic and water quality of the basin. By identifying the key source areas of non-point source pollution in the basin, the impacts of three management measures on the hydrological and water quality of the basin were simulated. The results showed that the reductions in flow rates, sediment content, TN, and TP (4.37, 31.93, 23.13, and 35.30%, respectively) obtained through terrace engineering were significantly better than those acquired via stubble mulch and contour planting. Additionally, this study uses the Sixth International Coupling Mode Comparison Program (CMIP6) climate change scenario and the BCC-CSM2-MR climate model coupled with the corrected SWAT model to predict future runoff, thereby providing references and suggestions for managing the Baihe River Basin and the Miyun Reservoir.

Floating Wetlands for Sustainable Drainage Wastewater Treatment

The preservation of water resources in modern urbanized society is a major concern. In this study, a floating constructed wetland (FWT) pilot plant was designed and constructed for the treatment of a polluted wastewater drain. A series of experiments were run continuously for a year in pilot-scale FWTs in a semi-arid area located in Egypt’s Delta. Four aquatic plant species (Eichhornia, Ceratophyllum, Pistia stratiotes, and Nymphaea lotus) were used to assess the performance of FWTs for pollutant removals, such as biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), electrical conductivity (EC), and total dissolved solids (TDS), from drainage wastewater to reuse the treated effluent in irrigation practices. The FWT systems were fed drainage tainted water on a weekly basis, and the concentrations and removal efficiency were assessed in the experiments. The average reduction in BOD, COD, TSS, TDS, TN, EC, and TP were 76–86%, 61–80%, 87–95%, 36.6–44.1%, 70–97%, 37–44%, and 83–96%, respectively. ANOVA with Post-HOC t-tests show that the Eichhornia, Pistia stratiotes, and Nymphaea lotus have the highest BOD and COD removal performance, whereas Pistia stratiotes and Nymphaea lotus have the highest TN and TP removal performance. In all cases, the Nymphaea lotus performed well in terms of pollutant removal. In addition, a design procedure for a FWT systems is presented. For wastewater treatment, FWT systems have proven to be a low-cost, long-term option.

Reduction of Phosphorus Using Electric Arc Furnace Slag Filters in the Macatawa Watershed (Michigan)

Eutrophication is a major problem in lakes and rivers throughout the world. One such system is Lake Macatawa, located in West Michigan, which hydrologically connects to Lake Michigan. Lake Macatawa and its watershed suffer from excess phosphorus and sediment loads. The total maximum daily load for the lake calls for a total phosphorus (TP) reduction of 75%, which would reduce the water column total phosphorus concentration from 125 μg/L to 50 μg/L. Understanding how P moves through this landscape, into Lake Macatawa, and ultimately to Lake Michigan and the St. Lawrence Seaway, is critical to managing and controlling P runoff. A potentially significant source of P to Lake Macatawa occurs through agricultural tile drainage. Various best management practices (BMPs) have been implemented in the Macatawa watershed to reduce P loading, especially surface runoff, but their overall effectiveness has been limited. Electric arc furnace (EAF) slag, a waste product from the steel industry, can chemically bind P and has been used previously in agricultural settings. Three iron slag filters were installed at the end of agricultural tile lines in the Macatawa watershed and evaluated to assess their effectiveness in removing P, while also monitoring for the presence of potentially toxic chemicals leaching from the slag. After 1 year of slag filter performance, both SRP (soluble reactive phosphorus) and TP decreased in the tile drain effluent: percent reductions of soluble reactive phosphorus and TP ranged from 7.4% to 57.3% and 59.5–76.5%, respectively. Absolute concentrations of TP were reduced to between 100 and 329 μg/L, which still exceeds the 50 μg/L goal for Lake Macatawa. Concentrations of toxic metals, polycyclic aromatic hydrocarbons compounds, and cyanide all were at levels below drinking water standards. Our preliminary conclusions are that the installation of these filters should be targeted to areas where tile drain effluent P levels are very high (SRP &amp;gt; 250 μg/L) to obtain an optimal cost/benefit ratio. While they are not a panacea, when installed in combination with other BMPs (Best Management Practices), EAF slag filters may play an important localized role in reducing P to Lake Macatawa and farther downstream.

Use of the cyanobacterium Spirulina platensis in cattle wastewater bioremediation

In the present study, the microalga Spirulina platensis (Arthrospira) was grown in two horizontal photobioreactors (HPBR) under two different irradiances (150 and 270 μmol m-2 s-2). Anaerobically digested cattle wastewater (ACWW) was used as substrate. The experiment was carried out in batches for a period of 8 days. The maximum specific growth rate of 0.347 day-1 and the doubling time of 2.08 days were obtained under the highest illumination of the culture. Dry biomass production reached maximum values between 2.17 g L-1 and 6.52 g L-1, with volumetric biomass productivities between 0.0812 and 0.5578 g L-1 day-1. Productivity per area was equal to 47.97 g m-2 d-1, which is the highest value recorded compared to those found in the literature consulted. As for CO2 biofixation, relevant values for reducing this gas in the atmosphere were obtained, ranging from 128.52 to 882.36 mg L-1 day-1. In terms of organic matter, 16.3-77% of BOD5 and 12.6-61.6% of COD were reduced. In the reduction of TS, TSS and VSS, values of 71.3-78.5%, 79.5-84.4% and 87.0-88.3%, respectively, were reached. NH4+ reduction was 32.5-98.3%, organic nitrogen reduction was 20.3-95.9% and total phosphorus reduction was 33.5-89.9%. The reductions of thermotolerant coliforms were between 71.7% and 99.9%. In view of the results found, it can be considered that the bioremediation of the effluent reached promising efficiencies, with the advantage of producing biomass with potential to obtain bioproducts of relevant economic value

Seasonal Dynamics of Algal Net Primary Production in Response to Phosphorus Input in a Mesotrophic Subtropical Plateau Lake, Southwestern China

A comprehensive 3-dimensional hydrodynamic and eutrophication model, the environmental fluid dynamics code model (EFDC) with three functional phytoplankton groups, was applied to simulate the algal dynamics in a mesotrophic P-limited subtropical plateau lake, Lake Erhai, Southwestern China. Field investigations revealed the seasonal patterns in external total phosphorus (TP) input and TP concentration, as well as the composition of the phytoplankton community. The model was calibrated to reproduce qualitative features and the succession of phytoplankton communities, and the net primary production was calculated. The modeled daily net primary production (NPP) ranged between −16.89 and 15.12 mg C/m2/d and exhibited significant seasonal variation. The competition for phosphorus and temperature was identified as the primary governing factor of NPP by analyzing the parameter sensitivity and limitation factors of the lake. The simulation of four nutrient loading reduction scenarios suggested high phytoplankton biomass and NPP sensitivity to the external TP reduction. A significant positive correlation was found among NPP, total phytoplankton biomass and TP concentration. Overall, this work offers an alternative approach to estimating lake NPP, which has the potential to improve sustainable lake management.