Phosphorus Mass Balance Research Articles

A bioenergetic approach to manage production and control phosphorus discharges from a salmonid hatchery

The environmental effects of fish culture operations are important issues in Michigan as well as many other parts of the world. The State of Michigan Department of Natural Resources operates the Platte River State Fish Hatchery (PRSFH) located near Honor, Michigan (USA). This facility has a restrictive discharge permit that limits the input of phosphorus into the Platte River that subsequently drains into a downstream oligotrophic lake (Platte Lake). The permit has been violated on occasion in recent years. Hatchery managers and operators need to understand the cause of these violations and prevent them in the future; and at the same time meet production goals to satisfy fishery management objectives. This paper describes the development and application of models designed to quantitatively analyze these issues. First, a bioenergetic growth and consumption model is developed for juvenile coho (Oncorhynchus kisutch) and Chinook (Oncorhynchus tshawytscha) salmon to quantify the relationship between fish production and by-product phosphorus loads. Next, phosphorus mass balance equations are used to calculate the phosphorus discharge from the facility as a function of the by-product phosphorus load and the efficiency of various phosphorus removal equipment and processes. The accuracy and consistency of the energy and mass balance equations are verified using extensive measurements. The ability of the model to successfully match various aspects of system performance supports the contention that the bioenergetic modeling approach developed here can provide reliable estimates of salmonid growth and feed requirements for a variety of food compositions, rations, and temperatures. This capability, along with knowledge of the effectiveness of phosphorus removal equipment, forms the basis of a practical operational and management tool. An example of model utility is presented that analyzes the PRSFH phosphorus discharge and provides insights into why permit violations occurred in 2009 but not in 2010. The model demonstrates how to avoid food waste caused by over feeding, lower the food conversion ratio, and evaluate the effectiveness of phosphorus removal treatment processes. A steady-state version of the model can be used by managers to establish production goals that avoid future violations of the phosphorus discharge limits. Statement of relevanceThe environmental effects of fish culture operations are important issues in many parts of the world. This paper describes the development and application of models designed to quantitatively analyze the relationships among fish production, by-product phosphorus loads, and the phosphorus concentration of the discharge following treatment. The ability of the model to successfully match various aspects of system performance supports the contention that the bioenergetic modeling approach developed here can provide reliable estimates of salmonid growth and feed requirements for a variety of food compositions, rations, and temperatures. This capability, along with knowledge of the effectiveness of phosphorus removal equipment, forms the basis of a practical operational and management tool. The model demonstrates how to avoid food waste caused by over feeding, lower the food conversion ratio, and evaluate the effectiveness of phosphorus removal treatment processes. A steady-state version of the model can be used by managers to establish production goals that avoid future violations of the phosphorus discharge limits.

Daily mass balance of phosphorus and nitrogen in effluents of production sectors of trout farming system

Abstract Aim: The mass balance has recently been applied in Brazilian aquaculture. In relation to trout farming, few studies have used this methodology as environmental indicator, especially when considering each development stage of fish. The daily mass balance allows an estimate of nutrients discharge, because the sampling effort over 24 hours enables to monitor the variations throughout the day. This study aimed to identify the breeding sector (fingerlings, juveniles and adults) in trout farming contributes with the great discharge of phosphorus and nitrogen in the effluent. Methods The concentrations of total phosphorus (TP), orthophosphate (PO4-P), total nitrogen (TN) and ammonium (NH4-N) were determined in affluent and effluents of the production system. The environmental indicators were calculated based on the values of nutrients loads and by quantifying the daily discharge of nutrients from the mass balance method. Results Over the 24 hours, the trout farming exported an average of 0.26 kg TP, 0.11 kg PO4-P, 3.11 kg TN and 0.18 kg NH4-N. The discharge of phosphorus and nitrogen in the effluent was higher at night associated to feeding management (hours and feeding frequency) and the nocturnal habits of trout. The juvenile and adult sectors accounted for the greatest contribution of these nutrients, related the largest fish biomass and metabolism, supported by the feed conversion ratio of 1.95:1 and 2.01:1, respectively. Conclusion In order to reduce exports of phosphorus and nitrogen there is a need to adequate the feeding management (feeding frequency from two to four times per day according to the trout development stage; carry out feeding in times close at twilight due to the nocturnal habits of this specie; reduce excess of ration offered and use good quality ration considering the distinct nutritional requirements of each trout stage of development). Besides the mass balance, the feed conversion ratio is also an efficient tool to detect the efficiency of feed utilization; therefore, it is proposed its use as environmental indicator, aiming the aquaculture environmental sustainability.

Long-term trends of nitrogen and phosphorus mass balances on New York State dairy farms

The whole-farm nutrient mass balance (NMB) is an adaptive management tool that can be used to identify areas for improvement in nutrient management and to monitor progress over time. The objectives of this study were to (1) evaluate the trends of nitrogen and phosphorus mass balances of 27 New York State dairy farms over 6 to 10 yr, (2) identify specific management changes made by 4 case study farms that improved NMB over time by shifting NMB up or down depending on the initial NMB, and (3) evaluate the potential of key indicators to identify opportunities for improvement in NMB. During the study period, milk price fluctuated whereas costs associated with feed and fertilizer increased substantially. Of the 27 farms, 67 to 74% (depending on the nutrient) decreased NMB per hectare over time, whereas 63 to 67% decreased NMB per megagram of milk over time. In general, changes in NMB were directionally correct, with 43 to 56% of farms operating in the optimum operational zone (with both NMB per hectare and per megagram of milk below the feasible levels suggested for New York) toward the end of the study versus 22 to 26% in the first 2 yr of the assessments. The 4 case study farms improved their NMB, whole-farm nutrient use efficiencies, and feed nutrient use efficiencies while maintaining or increasing milk production per cow. The case study farmers made the largest changes in precision feed management, reducing protein and P in purchased feed by replacing concentrates with blends with lower nutrient concentrations. Total nutrient imports, feed imports, the percentage of homegrown feed and nutrients, the concentration of nutrients in the purchased feed, fertilizer imports, and overall crop yields were useful in identifying potential areas for improvement in NMB.

Phosphorus retention and mass balance in an integrated constructed wetland treating domestic wastewater

This study quantified the contributions of different P removal pathways in an integrated constructed wetland (ICW) treating domestic wastewater. Findings over the study period (February 2008 to March 2012) showed average P retention rates of 31 ± 2 mg/m2/day for molybdate reactive phosphate (MRP) and 40 ± 3 mg/m2/day for total P. Near complete P removal was achieved during the first 2 years of operation. Thereafter, effluent concentrations increased slightly. According to the mass balance estimation, assimilation by plants accounted for approximately 16% of the total P retained, while sediment storage contributed nearly 60%. Sediment storage was the major P removal pathway in the ICW. Thus, high effluent concentrations recorded during high effluent flow volumes was due to remobilisation of P from the sediment. Management of ICW systems may therefore require implementing sediment removal schemes. The combination of plants with high biomass production can be beneficial for improving ICW performance.

A nitrogen source in spring in the surface mixed-layer of the Baltic Sea: Evidence from total nitrogen and total phosphorus data

The combined mass balance for total nitrogen (TN: concentrations of organic+inorganic nitrogen compounds) and total phosphorus (TP: concentrations of organic+inorganic phosphorus compounds) at 12 stations in the Baltic Sea for the period 1995–2013 clearly indicated the existence of a significant nitrogen source in the surface mixed layer in May of up to 86mmolm−2month−1 at the Baltic Proper stations. The analysis is based on monthly changes in TN with reference to the concentrations in April, and taking into account the atmospheric deposition of inorganic nitrogen compounds and the sedimentation of particulate organic nitrogen. The nitrogen source is closely linked to the consumption of excess phosphate and thus to the production of organic matter in the surface mixed-layer. Processes such as early nitrogen fixation and nitrogen transport by migrating plankton organisms are discussed as possible causes for the nitrogen input into the surface mixed layer in May. The long-term mean of the nitrogen source amounted to 55mmolm−2 in the Baltic Proper corresponding to a regional nitrogen input of 83kt. We also obtained data for the mid-summer nitrogen fixation of 141mmolm−2 which corresponds to an input of 202kt.

Optimization de la producción de lodos en un sistema de lodos activados a través de la calibración del modelo ASM1

Recently several protocols have been proposed for the calibration the ASM1 model and each one of them emphasizes obtaining a good adjustment in the production of sludge. Precisely here is where the discrepancies are evaluated and adjustments made to data, through a mass balance. The objective of this work was to conduct first a balance of flows in the wastewater treatment plant “Dulces Nombres” in Monterrey, Nuevo Leon, Mexico, and then adjust them until closing properly the mass balance for the total phosphorus, total suspended solids, and inorganic suspended solids (ISS). On might say that to calibrate the biological model was important to determine reliably the flow of sludge (QWAS) since on it depends the cell retention mean time (θC) in the reactor; this was accomplished successfully through the balance of the ISS and using of GPS-X software for the simulation of scenarios of optimization.

A novel scheme for denitrifying biological phosphorus removal via nitrite from nutrient‐rich anaerobic effluents in a short‐cut sequencing batch reactor

AbstractBACKGROUNDIn this work a novel scheme was developed for nitrifying and denitrifying biological phosphorus removal via nitrite, the anaerobic co‐digestate of waste activated sludge, and the organic fraction of municipal solid waste (OFMSW) in a sequencing batch reactor (SBR).RESULTSThe on‐site available fermentation liquid of OFMSW was used to promote the biological via nitrite nutrient removal. The specific phosphorus uptake rate under anoxic conditions was, on average, 10.7 and 9.2 and mg P VSS−1 h−1 and occurred at nitrite concentrations exceeding 10 mg L−1 and up to 140 mg L−1. Biomass was able to acclimatise and cope with such nitrite concentrations and denitrifying phosphorus‐accumulating organisms steadily developed. From the phosphorus mass balances, the phosphorus removal was mainly attributed to phosphorus‐accumulating organisms (68–71%) and partly to heterotrophic biomass growth (19–22%).CONCLUSIONSThe denitrifying biological phosphorus removal via nitrite can be successfully integrated into existing municipal plants of anaerobic co‐digestion for short‐cut nitrogen removal and enhanced biological phosphorus accumulation. © 2014 Society of Chemical Industry

Characterization of nitrogen, phosphorus, and potassium mass balances of dairy farms in New York State

A whole-farm nutrient mass balance (NMB) is a useful measure of the nutrient status of a dairy farm. Research is needed to define and determine a feasible NMB range for dairy farm systems in New York State (NY). The objectives of this study were to (1) document the distribution of N, P, and K mass balances of 102 NY dairy farms (including 75 small, 15 medium, and 12 large farms); (2) establish initial NMB benchmarks based on what 75% of the farms achieved; (3) determine the maximum animal density that allows an example NY dairy farm to balance cow P excretions and crop P removal without exporting crops or manure; and (4) identify opportunities to improve NMB over time. Nutrient mass balances of the 102 farms ranged from −39 to 237kg of N/ha for N without including N2 fixation (N1), from −14 to 259kg of N/ha when N2 fixation was included (N2), from −7 to 51kg of P/ha, and from −46 to 148kg of K/ha. Seventy-five percent of the farms were operating at NMB less than 118kg of N/ha for N1, 146kg of N/ha for N2, 13kg of P/ha, and 41kg of K/ha (75% benchmarks). Farms with the highest nutrient use efficiencies (lowest NMB per unit of milk produced) operated with less than 8.8kg of N/Mg of milk for N1, 11.8kg of N/Mg of milk for N2, 1.1kg of P/Mg of milk, and 3.0kg of K/Mg of milk. The biggest contributor to the NMB was the amount of imported nutrients, primarily feed purchases. The example farm assessment (assuming no export of crops or manure) suggested that, when 70% of the feed is produced on the farm and P in feed rations does not exceed 4g of P/kg of DM, cow P excretion and crop P removal were balanced at a maximum animal density of 2.4 animal units (AU)/ha (~0.97 AU/acre). Dairy farms operating with animal densities <2.4 AU/ha typically had NMB below the 75% benchmark, whereas most dairies with more than 2.4 AU/ha needed to export manure or crops to meet the 75% benchmark. Opportunities to reduce NMB on many farms, independent of size and without changes in animal density, are possible by more tightly managing fertilizer and feed imports, increasing the percentage of farm-produced nutrients, implementing precision feeding, and exporting crops or manure.

Effluent of a Polyculture System (Tilapias and Shrimps): Assessment by Mass Balance of Nitrogen and Phosphorus

From the estimation of the mass balance model, which can also be classified as “black box” model, it is possible to infer the impact of management on the system considered. This study aimed to evaluate water pollution generated by wastewater from a polyculture system of tilapia and shrimp and discuss the management employee and their relation to the quality of the effluent released. It used a pond measuring 1500 m2, average depth 1.6 meters, where 12 cages of 1 m3 populated with tilapia juveniles were installed 33 days after the shrimps’ population. The tilapia juveniles were distributed in densities from 200 to 400 fish per cubic meter, reaching the density of 2.4 fish per square meter within the total pond area. Shrimp post-larvae were released outside the cages within the pond area in a density of 3.3 organisms per square meter. Total density considering fish and shrimps was of 5.7 organisms per square meter in the pond area. Water samples were taken weekly in affluent and effluent of the pond (January-August/2009). The mass balance model was calculated from the difference between the estimated load for the output and input of the pond. The average flow rate was 4.46 L/s. The average loads nitrogen was 0.072 Kg/day (affluent) and 0.179 Kg/day (effluent) and phosphorus 0.0136 Kg/day (affluent) and 0.031 Kg/day (effluent). The mass balance resulted in mean values of 0.11 ± 0.06 Kg/day for total nitrogen and 0.017 ± 0.010 Kg/day for total phosphorus indicating that the system exported nutrients. The use of Best Management Practices (BMP) likes better feed and water management as a way to minimize nutrient export.

Mass balances of nitrogen and phosphorus in an integrated culture of shrimp (Litopenaeus vannamei) and tomato (Lycopersicon esculentum Mill) with low salinity groundwater: A short communication

This study re-examines the performance of an integrated shrimp-tomato system using the nutrients mass balance approach. A budget was calculated based on nutrients analysis, water management, feeding, fertilization, stocking, harvest and sludge removal. Nitrogen and P content in the input water (groundwater) were low, contributing 33.5% and 0.5%, of the total inputs, respectively. Most of the N (43.6%) and P (98.8%) entered to the system as shrimp food. Likewise, 15.2% and 2.5% of the input N, and 8.9% and 4.3% of the input P, were converted to harvested shrimp and tomato plants, respectively; 4.1% N and 24.6% P remained in the organic sludge, while the environmental losses expressed per unit of production were relatively low, 57kgNton−1 and 7.1kgPton−1 of product harvested. About 13.4% of input N was unaccounted for, and was assumed to be lost to the atmosphere via denitrification and volatilization. Comparison between these results and previous studies indicate that the shrimp-tomato system produces a relatively low recovery of N and P as harvested products, however, the main progress reached with this system is the reduction of the environmental losses of N and P in terms of kg of each nutrient per ton of the product harvested.

Determinants of phosphorus mobilization during hemodialysis

Our recent work proposed a pseudo one-compartment model for describing intradialysis and postdialysis rebound kinetics of phosphorus. In this model, phosphorus is removed directly from a central distribution volume with the rate of phosphorus mobilization from a second, very large compartment proportional to the phosphorus mobilization clearance. Here, we evaluated factors of phosphorus mobilization clearance and postdialysis central distribution volume from 774 patients in the HEMO Study. Phosphorus mobilization clearance and postdialysis central distribution volume were 87 (65, 116) ml/min, median (interquartile range), and 9.4 (7.2, 12.0) liter, respectively. The phosphorus mobilization clearance was significantly higher for male patients than for female patients. Both the phosphorus mobilization clearance and the postdialysis central distribution volume were significantly associated with postdialysis body weight but negatively with the predialysis serum phosphorus concentration. The postdialysis central distribution volume was also significantly associated with age. Overall, the postdialysis central distribution volume was 13.6% of the postdialysis body weight. Thus, the phosphorus mobilization clearance during hemodialysis is higher when predialysis serum phosphorus concentration is low and higher in male patients than in female patients. The central distribution volume of phosphorus is a space approximating the extracellular fluid volume.

Environmental, Social, and Management Drivers of Soil Nutrient Mass Balances in an Extensive Andean Cropping System

Sustainable nutrient cycling in agroecosystems combining grazing and crops has global ramifications for protecting these ecosystems and for the livelihoods they support. We sought to understand environmental, management, and social drivers of nutrient management and sustainability in Andean grazing/crop systems. We assessed the impact of farmer wealth, fields’ proximity to villages, topography, and rangeland net primary productivity (NPP) on mass balances for nitrogen (N), phosphorus (P), and potassium (K) of 43 fields. Wealthier farmers applied greater total amounts (kg) of manure nutrients. However, higher manure application rates (kg ha−1) were associated with field proximity and NPP rather than wealth. Manure P inputs in far fields (> 500-m distant) were half those in near fields. Harvest exports increased with manure inputs (P < 0.001) so that balances varied less than either of these flows. Erosion nutrient losses in steeper far fields matched crop exports, and yields declined with increasing field slope (P < 0.001), suggesting that erosion reduces productivity. Balances for P were slightly positive in near and far fields (+2.2 kg P ha−1 y−1, combined mean) when calculated without erosion, but zero in near fields and negative in far fields with erosion included (−6.1 kg P ha−1 y−1 in far fields). Near/far differences in both inputs and erosion thus drove P limitation. Crop K exports dominated K balances, which were negative even without accounting for erosion. Modeled intensification scenarios showed that remediating far field deficits would require P addition and erosion reduction. Management nested within environmental constraints (NPP, erosion) rather than socioeconomic status drives soil nutrient sustainability in these agroecosystems. Time-lags between management and long-term degradation are a principal sustainability challenge to farming in these montane grazing/crop agroecosystems.

Can simple phosphorus mass balance models guide management decisions? A case study in the Bay of Quinte, Ontario, Canada

We test the capacity of an existing simple mass-balance total phosphorus (TP) model to evaluate nutrient loading scenarios in the Bay of Quinte, Ontario, Canada. Our study examines whether model parameters and loading inputs are well characterized and relevant to the current conditions in the Bay of Quinte and its drainage areas. We also identify critical data gaps and influential assumptions in regard to the uncertainty of model outputs and the credibility of predictive statements about the achievability of delisting objectives of the system. Our analysis shows that the model closely reproduced the observed variability of the TP seasonal averages during the calibration period 1972–2001, but its performance was significantly reduced when the actual predictive capacity was assessed in the 2002–2009 validation period. The most troublesome result is the inability of the model to reproduce the observed TP variability at temporal scales that are more meaningful from an environmental management point of view (i.e., monthly averages or daily snapshots from the system). Sensitivity analysis shows that several parameters associated with the role of the sediments were significant drivers of the model outputs, suggesting that considerable uncertainty exists in regard to the characterization of the sediments. The loadings from Trent River and the TP levels of the inflowing water masses from Lake Ontario predominantly shape the variability in the upper and lower segments of the Bay of Quinte, respectively. We also present a critical review of the suitability of the existing water quality criteria to depict the trophic status throughout the system. Our study contends that the summer average TP concentrations do not adequately reflect the prevailing conditions and that the development of proper water quality criteria should place more emphasis on inshore sites, where the eutrophication problems are more frequently manifested. Finally, we pinpoint factors unaccounted for by the original model that are likely to modulate the response of the system in its present state. We also discuss important directions of model structure augmentation and ways to optimize the spatial segmentation.

Improving the representation of internal nutrient recycling with phosphorus mass balance models: A case study in the Bay of Quinte, Ontario, Canada

We evaluate the relative importance of the causal connection between exogenous total phosphorus (TP) loading and internal nutrient recycling with the water quality conditions in the Bay of Quinte, Ontario, Canada. First, we examine the temporal trends of all the major point and non-point loading sources over the last four decades. We then enhance the mechanistic foundation of an existing simple mass-balance total phosphorus (TP) model, originally developed to guide the eutrophication management in the system. The structural improvements include the incorporation of macrophyte dynamics, the explicit representation of the role of dreissenids in the system, and the improved portrayal of the interplay between water column and sediments. The upgraded model was in good agreement with the observed TP variability in the system during the study period (2002–2009) and successfully reproduced the TP accumulation patterns toward the end of the summer-early fall. We provide evidence that phosphorus dynamics in the upper Bay are predominantly driven by the inflows from Trent River, while the middle and lower segments likely receive substantial internal subsidies from the sediment diagenesis mechanisms and/or the activity of macrophytes and dreissenids (e.g., pseudofeces production, nutrient pump effect). We also forced the model with scenarios of reduced nutrient loading and examine the likelihood of the system to meet its water quality delisting targets, although we caution that our complex overparameterized modeling construct is primarily intended for heuristic purposes. The present study together with the companion paper by Zhang et al. (2013) illustrate how phosphorus mass balance models can offer useful tools for improving our understanding of freshwater ecosystems.

Fundamental Research on a Rational Steelmaking Slag Recycling System by Phosphorus Separation and Collection

Recently, reduction of the steelmaking slag stock in Japan has been required, but utilization of steelmaking slag is restricted due to its chemical properties. On the other hand, the price of phosphorus ore is increasing rapidly due to the very tight supply/demand balance worldwide. In this work, (FetO) and (P2O5) reduction in steelmaking slag and recovery as a phosphorus source were investigated in feasibility studies and laboratory-scale experiments in order to develop a rational recycling process for steelmaking slag. The results are summarized as follows: (a) Steelmaking slag was reduced by carbon under high temperature conditions (1373–1873 K), and high-P hot metal was recovered. The phosphorus content of the reduced slag was <0.3 mass%. (b) Higher temperatures were required for slag reduction with carbon, corresponding to increasing slag basicity. (c) The oxygen partial pressure calculated from the FeO content ranged from 10−13 to 10−17 atm. More than 50 mass% of phosphorus in the slag can be removed under the condition that FeO activity is less than 0.01. (d) From the mass balance of phosphorus, 0–30 mass% of undefined phosphorus was observed, which was estimated by thermodynamic calculations and SEM-EPMA analysis to be caused by gaseous dephosphorization. (e) The gaseous dephosphorization ratio becomes more than 10% at the condition of log LP ≤ 0. (f) Phosphorus was enriched in slag to higher than 30 mass% P2O5 by dephosphorization of high-P (1.05 mass%) hot metal.

Phosphorus Mass Balance of the Illinois River Watershed in Arkansas and Oklahoma

Water quality degradation in the Illinois River Watershed (IRW) has been linked to excess nutrients, primarily phosphorus (P). A mass balance study was performed on the IRW in Oklahoma and Arkansas to quantify the magnitude of P entering the watershed between the closure of Lake Tenkiller’s dam in 1954 to 2006. Results showed that a substantial mass of P was, and is, being imported into the watershed relative to the mass of P leaving the watershed. The study demonstrated that poultry production has been the major contributor of P imported to the watershed since 1964, and is currently responsible for more than 76% of the net annual P additions to the IRW. Between 1949 and 2002, more than 200,000 tonnes of P was added to the IRW. A P delivery ratio for the IRW was computed from the mass balance results and observed loads indicating that 4% of annual P applied to the IRW landscape reached Lake Tenkiller between 1999 and 2006. Allocation of P loads from 1949 to 2002 to Lake Tenkiller computed with the delivery ratio showed that wastewater treatment plant (WWTP) discharges were responsible for more than 50% of P reaching Lake Tenkiller in 1949, followed by dairy cattle (32% of loads). Poultry contribution to P reaching Lake Tenkiller was 5% in 1949 but increased rapidly to become the largest source in 1969 at approximately 49%, and in 2002 at 54%. Both dairy and WWTP portions of the loads declined from 1949 levels with less than 4% attributable to dairy and less than 34% assigned to WWTP in 2002.

The application of a phosphorus mass balance model for estimating the carrying capacity of Lake Kariba

The aim of this study was to use an empirical mass balance equation to estimate the carrying capacity of Lake Kariba, where cage culture for Nile tilapia Oreochromis niloticus has been practiced since 1996. The carrying capacity for the lake was estimated at 33.2 × 103 t per year using the Dillon-Rigler phosphorus budget model.

Steady State Phosphorus Mass Balance Model during Hemodialysis Based on a Pseudo One-Compartment Kinetic Model

Purpose Mathematical models of phosphorus kinetics and mass balance during hemodialysis are in early development. We describe a theoretical phosphorus steady state mass balance model during hemodialysis based on a novel pseudo one-compartment kinetic model. Methods The steady state mass balance model accounted for net intestinal absorption of phosphorus and phosphorus removal by both dialysis and residual kidney function. Analytical mathematical solutions were derived to describe time-dependent intradialytic and interdialytic serum phosphorus concentrations assuming hemodialysis treatments were performed symmetrically throughout a week. Results Results from the steady state phosphorus mass balance model are described for thrice weekly hemodialysis treatment prescriptions only. The analysis predicts 1) a minimal impact of dialyzer phosphorus clearance on predialysis serum phosphorus concentration using modern, conventional hemodialysis technology, 2) variability in the postdialysis-to-predialysis phosphorus concentration ratio due to differences in patient-specific phosphorus mobilization, and 3) the importance of treatment time in determining the predialysis serum phosphorus concentration. Conclusions We conclude that a steady state phosphorus mass balance model can be developed based on a pseudo one-compartment kinetic model and that predictions from this model are consistent with previous clinical observations. The predictions from this mass balance model are theoretical and hypothesis-generating only; additional prospective clinical studies will be required for model confirmation.

Phosphorus mass balance in a surface flow constructed wetland receiving piggery wastewater effluent

This research was conducted to investigate the phosphorus forms present in water, soil and sediment and to estimate the phosphorus mass balance in a surface flow constructed wetland (CW). Water quality and sediment samples were collected from each cell along the hydrologic path in the CW from October 2008 to December 2010. At the same time, three dominant plant species (e.g. common reed and cattails) were observed through the measurement of the weight, height and phosphorus content. Based on the results, the orthophosphate constituted 24-34% of total phosphorus in water for each cell. The overall average phosphorus removal efficiency of the CW was approximately 38%. The average inflow and outflow phosphorus loads during the monitoring period were 1,167 kg/yr and 408 kg/yr, respectively. The average phosphorus retention rate was 65%, was mainly contributed by the settling of TP into the bottom sediments (30%). The phosphorus uptake of plants was less than 1%. The estimated phosphorus mass balance was effective in predicting the phosphorus retention and release in the CW treating wastewater. Continuous monitoring is underway to support further assessment of the CW system and design.

Steady state phosphorus mass balance model during hemodialysis based on a pseudo one-compartment kinetic model

Mathematical models of phosphorus kinetics and mass balance during hemodialysis are in early development. We describe a theoretical phosphorus steady state mass balance model during hemodialysis based on a novel pseudo one-compartment kinetic model. The steady state mass balance model accounted for net intestinal absorption of phosphorus and phosphorus removal by both dialysis and residual kidney function. Analytical mathematical solutions were derived to describe time-dependent intradialytic and interdialytic serum phosphorus concentrations assuming hemodialysis treatments were performed symmetrically throughout a week. Results from the steady state phosphorus mass balance model are described for thrice weekly hemodialysis treatment prescriptions only. The analysis predicts 1) a minimal impact of dialyzer phosphorus clearance on predialysis serum phosphorus concentration using modern, conventional hemodialysis technology, 2) variability in the postdialysis-to-predialysis phosphorus concentration ratio due to differences in patient-specific phosphorus mobilization, and 3) the importance of treatment time in determining the predialysis serum phosphorus concentration. We conclude that a steady state phosphorus mass balance model can be developed based on a pseudo one-compartment kinetic model and that predictions from this model are consistent with previous clinical observations. The predictions from this mass balance model are theoretical and hypothesis-generating only; additional prospective clinical studies will be required for model confirmation.