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Given the importance of the watershed protection plans, direct determination of phosphorus (P) mineralization rates in advanced wastewater treatment facility effluents is crucial for developing the most protective strategies minimiz eutrophication in receiving surface waters. In this study, algal bioassays were used to determine the uptake rate of dissolved P in effluents from a broad range of advanced nutrient removal technologies (e.g., membrane biological reactor, traditional biological, tertiary membrane, Blue PRO™, etc.). Dissolved P uptake kinetics were fit to a gamma model and three first-order decay models. A traditional one-pool model correlated poorly with the experimental data (i.e., r 2 = 0.73 ± 0.09), whereas two-pool model and three-pool models performed much better (i.e., r 2 > 0.9). These models also provided strong evidence for the existence of recalcitrant P in the effluents from these tertiary facilities. The Gamma model showed the mineralization of organic P followed a reactive continuum and further suggested the partitioning of P loads with different bioavailability levels should be accounted for the future modeling practices. From a modeling perspective, the Gamma model should be considered to be the theoretically best model as it gave the most parsimonious fit to the data using the fewest terms. Our study suggested that the current Total Maximum Daily Load (TMDL) model could be easily modified with the updated mineralization kinetics, which should lead to both ecological and economic benefits. [ABSTRACT FROM AUTHOR]

Abstract: Because eutrophication is a widespread consequence of wastewater discharges, there is a strong impetus to develop new approaches to remove phosphorus (P) from wastewater treatment plant (WWTP) effluents. We examined the effluents from a pilot plant that is testing various alum based processes for achieving>99% P removal, however, it is not known how these advanced P removal technologies affect the bioavailability of P (BAP). We tested how the percent BAP (%BAP) varied with different P removal levels using an algal growth bioassay methodology. This facility reduced total P concentrations from ≈ 500μgL−1 in the pilot plant influent to 19±4 (±SD)μgL−1 in the final effluent, and our results showed that as the level of P removal increased, the %BAP of the product declined sharply, r 2 =0.98. Prior to alum treatment, the influent had an average %BAP of 79±13%, and after three steps of alum-based removal the %BAP averaged 7±4%. Thus, this alum based P removal process was very effective at sequestering the P forms that most readily stimulate algal growth. Further, our results show the final BAP of the effluent was only ≈ 50% of the “reactive” P concentration. These results have important implications for nutrient management and trading schemes. [Copyright &y& Elsevier]

1. We conducted a statistical reassessment of data previously reported in the lake total phosphorus (TP) input/output literature ( n = 305) to determine which lake characteristics are most strongly associated with lake phosphorus concentration and retention. We tested five different hypotheses for predicting lake TP concentrations and phosphorus retention. 2. The Vollenweider phosphorus mass loading model can be expressed as: TPout = TPin/(1 + σ τw), where TPin is the flow-weighted input TP concentration, τw is the lake hydraulic retention time and σ is a first-order rate constant for phosphorus loss. 3. The inflow-weighted TP input concentration is a moderately strong predictor ( r2 = 0.71) of lake phosphorus concentrations when using log–log transformed data. Lake TP retention is negatively correlated with lake hydraulic retention time ( r2 = 0.35). 4. Of the approaches tested, the best fit to observed data was obtained by estimating σ as an inverse function of the lake's hydraulic retention time. Although this mass balance approach explained 84% of the variability in log–log transformed data, the prediction error for individual lakes was quite high. 5. Estimating σ as the ratio of a putative particle settling velocity to the mean lake depth yielded poorer predictions of lake TP ( r2 = 0.77) than the approach described above, and in fact did not improve model performance compared with simply assuming that σ is a constant for all lakes. 6. Our results also demonstrate that changing the flow-weighted input concentration should always have a directly proportionate impact on lake phosphorus concentrations, provided the type of phosphorus loaded (e.g. dissolved or particulate) does not vary. [ABSTRACT FROM AUTHOR]

Abstract: Using total phosphorus concentrations to estimate eutrophication risk is problematic for management purposes, as only some forms of phosphorus are biologically available for phytoplankton growth. This study estimated the bioavailability of particulate phosphorus, in forested, urban, agricultural (i.e. dairy farm) and mixed land cover streams. Sixteen stream sites were sampled during base and storm flow conditions and the following parameters were determined: total suspended solids, total phosphorus, total dissolved phosphorus, particulate phosphorus, percent bioavailable particulate phosphorus (%BAPP), total bioavailable phosphorus and sediment particle size distribution. Algal assays with Pseudokirchneriella subcapitata were used to measure %BAPP. Percent BAPP averaged 17%, 26% and 24% for streams draining catchments with forested, mixed use and agricultural land cover, respectively, and %BAPP did not vary significantly between base and storm flow conditions in these stream types. In contrast, %BAPP averaged 73% in the urban streams during baseflows but declined to an average of only 19% during storms. Particle size distributions did not correlate with %BAPP in these samples. During storm events, particulate phosphorus concentrations increased in all streams by an average of 614% and total phosphorus increased by 200%, whereas total BAP (i.e. total dissolved phosphorus+%BAPP×particulate phosphorus) only increased by 72% because on average only 20% of the particulate phosphorus transported during these events was biologically available. [Copyright &y& Elsevier]

1. A series of experiments examined growth of Daphnia magna on three algal diets ( Rhodomonas minuta , Scenedesmus acutus and Synechococcus sp.) at varying physiological states [nitrogen and phosphorus (P) limitations] to test whether variation in algal fatty acid and/or elemental composition can predict Daphnia growth. 2. These algae differed widely in their essential fatty acid (EFA) composition while phosphorus (P) or nitrogen limitation had only a small influence on their ω3-polyunsaturated fatty acid (PUFA) content. 3. Individually, algal ω3-PUFA content explained 69% of the variation in the normalised growth of D. magna, while algal phosphorus content explained 11% of the variation. Quantitative models for D. magna growth used both algal ω3-PUFA content and algal C : P ratio as food quality indices. Together, algal ω3-PUFA content and C : P ratio explained 70% of the variation in the normalised growth rate of D. magna . 4. Our results indicate that EFA influenced algal food quality much more strongly than P. The EFA and mineral P impacts appear to be independent. [ABSTRACT FROM AUTHOR]

We performed 12 experiments where the herbivorous zooplankter Daphnia pulex was fed three different phytoplankton food types (cyanophytes, chlorophytes, or cryptophytes) at two phosphorus (P) deficiency levels (C : P ∼ 400 or 600) and with two different fatty acid (FA) supplements. Phosphatidylcholine liposome amendments were used to manipulate P availability and/or deliver FA in order to simultaneously test the relative importance of phytoplankton P and FA limitation as constraints on Daphnia somatic growth rate and reproduction. We used multiple regression analyses to test the data set for six main effects and three interaction terms. The six main effects tested were phytoplankton taxa, FA supplementation, FA type (EPA or FA-mix), direct (P-D) and indirect (P-ID) phosphorus limitation, and P deficiency level. Food quality was most strongly affected by phytoplankton taxa followed by P-ID, FA supplementation, the interaction between phytoplankton taxa and P-ID, and P-D. Daphnia fed cryptophytes grew 0.18 day-1 faster and had an additional 2.6 eggs individual-1 than Daphnia fed cyanophytes. Indirect P limitation reduced Daphnia somatic growth rates by 0.16 day-1 and egg production by 2.6 eggs individual-1. Direct P limitation reduced Daphnia growth rates by 0.04 day-1 and egg production by 1.2 eggs individual-1. FA supplementation improved growth by 0.09 day-1 and egg production by 2.2 eggs individual-1. These results suggest that FA supplementation exerted stronger effects on Daphnia somatic growth rate and reproduction than did direct P limitation. Furthermore, these results suggest that phytoplankton taxa and indirect P limitation had the greatest effects on Daphnia growth and reproduction. [ABSTRACT FROM AUTHOR]

We revisit the phosphorus-retention and nutrient-loading models in limnology using a Bayesian hierarchical framework. This methodological tool relaxes a basic assumption of regression models fitted to data sets consisting of observations from multiple systems, i.e., the systems are assumed to be identical in behavior, and therefore the models have a single common set of parameters for all systems. Under the hierarchical structure, the models are dissected into levels (hierarchies) that explicitly account for the role of significant sources of variability (e.g., morphometry, mixing regime, geographical location, land-use patterns, trophic status), thereby allowing for intersystem parameter differences. Thus, the proposed approach is a compromise between site-specific (where limited local data is a problem) and globally common (where heterogeneous systems in wide geographical areas are assumed to be identical) parameter estimates. In this study, we used critical values of the mean lake depth $$ \left( {\bar{z} = 10.3\,{\text{m}}} \right) $$ and the hydraulic residence time ( τw = 2.6 years) to specify the hierarchical levels of the models. Our analysis demonstrates that the hierarchical configuration led to an improvement of the performance of six out of the seven hypothesized relationships used to predict lake-phosphorus concentrations. We also highlight the differences in the posterior moments of the group-specific parameter distributions, although the inference regarding the importance of different predictors (e.g., inflow-weighted total phosphorus input concentration, and hydraulic retention time) of lake phosphorus or the relative predictability of the models examined are not markedly different from an earlier study by Brett and Benjamin. The best fit to the observed data was obtained by the model that considers the first-order rate coefficient for total phosphorus loss from the lake as an inverse function of the lake hydraulic retention time. Finally, our analysis also demonstrates how the Bayesian hierarchical framework can be used for assessing the exceedance frequency and confidence of compliance of water-quality standards. We conclude that the proposed methodological framework will be very useful in the policy-making process and can optimize environmental management actions in space and time. [ABSTRACT FROM AUTHOR]