Freshwater Phosphorus Research Articles

Nitrogen and Phosphorus Removal from Wastewater Using Calcareous Waste Shells—A Systematic Literature Review

Nitrogen and phosphorus in freshwaters are a global environmental challenge. Concurrently, the shellfish industry’s calcareous waste shells (CWSs) amount to ~10 million tonnes annually. CWSs can effectively adsorb dissolved pollutants, including nutrients, from water, which has motivated a growing number of experimental studies on recycling CWSs in wastewater treatment. This comprehensive literature review summarises and critically assesses the effectiveness of using different CWSs for removing nutrients from water. The effects of CWS type, initial pollutant concentration, adsorbent dosage, particle size, and contact time (CT) are investigated. The results show that phosphorus removal has been examined more than nitrogen. Most studies have been conducted using synthetic wastewater under laboratory conditions only. There is a large variability in experimental conditions, such as CWS adsorbent dosages (0.1–100 g/L) and CT (0.083–360 h). The calcination of CWSs is frequently used to enhance adsorption capacity. The Langmuir isotherm model has been found to fit adsorption data best when raw oyster shells are used, while the Freundlich isotherm is best when the adsorbent is calcinated mussel shells. The pseudo-second-order (PSO) kinetics model tends to describe adsorption data better than the pseudo-first-order (PFO) model in all shell types. There is significant potential for using calcareous waste shells to remove nutrients from wastewater in line with circular economy aspirations.

Spectrophotometric Determination of Total Phosphorus in Fresh Water Using Ammonium Molybdate

Spectrophotometric Determination of Total Phosphorus in Fresh Water Using Ammonium Molybdate

Allocation and stoichiometric regulation of phosphorus in a freshwater zooplankton under limited conditions: Implication for nutrient cycling

Because zooplankton is potentially limited by phosphorus (P) in freshwater, they may modify their body P distributions in different biochemical and anatomic components depending on the environmental P levels. In the present study, we quantified the distribution and regulation of P in a freshwater zooplankton Daphnia magna under P-limited conditions by using 33P as a radiotracer. We demonstrated that the P allocation patterns in D. magna were independent of the ontogenic development. Carapace accounted for 35–54% of total body P, followed by small molecules and nucleic acids (11–30%), whereas phospholipids represented only a minor P pool. The proportion of body P allocated into carapace decreased from 51.8% in +P adults to 16.5% in the −P adults, and a lower proportion of body P was also allocated to eggs in the −P adults than in the +P adults (3.8 vs. 16.5%). Meanwhile, no difference in allocation pattern was detected in the juveniles under +P and −P conditions, demonstrating an interaction between effects of P condition and ontogeny. Furthermore, the P turnover rates of nucleic acids and phospholipids in the −P juveniles were only half of those found in the +P individuals, suggesting a reduced metabolic rate under P-deficient conditions. However, the P turnover rate of small molecules, nucleic acids and phospholipids did not vary with the P condition in adults. It appeared that the adults could maintain their basic P metabolism by down-regulating the P allocation to carapace and eggs. Our results provide an insight into the tolerance of zooplankton to P-deficiency and bear implications on involvement of Daphnia in regulation of P cycling and availability in the epilimnion.

Phosphorus nutrition in farmed Atlantic salmon (Salmo salar): Life stage and temperature effects on bone pathologies

Bone health is important for a viable and ethically sound Atlantic salmon aquaculture industry. Two important risk factors for vertebral deformities are dietary phosphorus and water temperature. Here, we explore the interplay between these two factors during a full production of Atlantic salmon. Salmon were fed one of three diets (low 4.4–5.0 g kg−1, medium 7.1–7.6 g kg−1, or high 9.0–9.7 g kg−1 soluble phosphorus) from 3 to 500 g body weight, followed by a common diet of 7.3 g kg−1 soluble phosphorus until harvest size at 4 kg. Additional groups were included to investigate the effects of water temperatures of 10 vs 16 °C (low and high diets only) and the switching of dietary phosphorus levels (from low to medium or high, from medium to low or high, from high to low or medium), starting at seawater transfer (~100 g body weight) and lasting for 4 months (~500 g body weight). During the experimental feeding period, the low phosphorus diet caused reduced bone mineralization and stiffness and a greater prevalence of vertebral deformities, compared to the medium and high phosphorus diets. However, the prevalence of severely deformed fish at harvest was reduced by switching from the low to either the medium or high phosphorus diets for 4 months after seawater transfer, followed by rearing on the standard commercial feed. Concurrently, switching from either the medium or high to a low phosphorus diet for the same period following seawater transfer had no effect on vertebral deformities at harvest. The higher water temperature for 4 months following seawater transfer increased the severity of deformities at harvest, irrespective of dietary phosphorus. Finally, low dietary phosphorus was associated with increased fillet damage, due to ectopic connective tissue around the spine, at harvest. In conclusion, dietary phosphorus levels of 5 g kg−1 for the initial 4 months in seawater are more of a risk factor for vertebral pathologies if preceded by low, but not medium or high, dietary phosphorus in freshwater. However, dietary phosphorus levels may not play a role in temperature induced radiologically detectable vertebral pathologies. Under the reported growing conditions and diet compositions, a combination of 7.5–7.6 g kg−1 soluble phosphorus during freshwater and 5.0 g kg−1 for the first 4 months in seawater, was sufficient for normal bone health and growth in Atlantic salmon.

Harmful Algal Blooms Get “Hotter” in 2018

Harmful Algal Blooms Get “Hotter” in 2018

Prevention of Harmful Algal Blooms by Control of Growth Parameters

Harmful Algal Blooms (HAB) were investigated to prevent the outbreak of HAB in both freshwater and seawater. Parameters inducing HAB were volcanic eruption, sunlight, aeolian dust, environmental factors (current, pH, dissolved oxygen, food web, turbulence, growth phase), enzyme, iron, nutrients (carbon, nitrogen, phosphorus, sulfur, silicon, minerals) while the critical growth parameter for the outbreak of HAB was iron (Fe). HAB development was halted in freshwater and seawater due to the sulfur compounds (H2S, sulfates) inducing the deficiency of the dissolved Fe in the water. The atomic ratio of N/P is commonly known to be 16/1 in freshwater and 176/1 in seawater for HAB. Therefore, nitrogen can be a relatively limiting factor in seawater while phosphorus in freshwater. HAB could be prevented by control of growth parameters such as pH, temperature, sunlight, turbulence, nitrogen, phosphorus, iron, and sulfur compounds prior to reaching the early exponential phase of algal growth.

A modified DGT technique for the simultaneous measurement of dissolved inorganic nitrogen and phosphorus in freshwaters

A modified diffusive gradients in thin films (DGT) technique uses both a mixed binding layer (PrCH and A520E resins for NH4-N and NO3-N, respectively) and multiple binding layers (Metsorb binding layer for PO4-P overlying the mixed binding layer) for the simultaneous measurement of dissolved inorganic nitrogen (nitrate and ammonium) and phosphate in freshwater (INP-DGT). High uptake and elution efficiencies were determined for a mixed (PrCH/A520E) binding gel for dissolved inorganic nitrogen and an agarose-based Metsorb binding layer for PO4-P. Diffusion coefficients (D) obtained from DGT time-series experiments (conductivity 180 μS cm−1) for NH4-N, NO3-N and PO4-P agreed well with those measured using individual DGT techniques in previous studies, but were characterised over a wider range of ionic strengths here. D for NO3-N and PO4-P were constant over a range of ionic strengths (between 100 and 800 μS cm−1) while the diffusion coefficient for NH4-N decreased with increasing ionic strength, as reported previously. The measurement of NH4-N, NO3-N and PO4-P using the INP-DGT was independent of pH (3.5–8.5) and quantitative over varying ionic strength ranges (up to 0.004 mol L−1 NaCl for NH4-N, up to 0.014 mol L−1 NaCl for NO3-N and over 0.1 mol L−1 NaCl for PO4-P) for a 24 h deployment time. Performance of INP-DGT in synthetic freshwaters with differing conductivity indicated the three nutrients were affected differently, with NH4-N measurements being most sensitive. Representative performance was determined for NO3-N (90–330 μS cm−1) and PO4-P (all tested conductivities) over a 72 h deployment period and for NH4-N (<330 μS cm−1) over a 24 h deployment period. Field validations showed that the ratios of INP-DGT concentrations to the average concentrations from grab samples were generally between 0.80 and 1.13 over 24 and 48 h deployment periods. To ensure the representative performance of INP-DGT for all three nutrients, the conductivity should not exceed 400 μS cm−1 and deployment times should be no longer than 24 h. The results of this study have demonstrated that INP-DGT could provide a cost-effective monitoring technique for measuring time-weighted average concentrations of dissolved inorganic nutrients in many freshwaters.

Effect of nitrogen and phosphorus on growth of toxic and nontoxic Microcystis strains and on intracellular microcystin concentrations.

The growth and intracellular microcystin concentration of two hepatotoxic and two nontoxic axenic Microcystis strains were measured in batch cultures with variable nitrogen (0.84-84 mg L(-1)) and phosphorus (0.05-5.5 mg L(-1)) concentrations. Growth was estimated by measuring dry weight, optical density, chlorophyll a, and cellular protein concentration. Microcystin concentrations in cells and in culture medium were measured by HPLC analysis. Both nontoxic strains needed less nutrients for their growth at low nutrient concentrations. With high nutrient concentrations the toxic strains grew better than the nontoxic strains. Growth and intracellular microcystin concentration did not correlate in the hepatotoxic strains. Multivariate regression analysis together with mathematical modeling revealed a significant interactive effect of nitrogen and phosphorus, which partly explains the controversial results obtained in previous studies. In this study we have shown that variation of nitrogen and phosphorus concentrations influence the growth and the microcystin production of Microcystis strains and that the strains differ in their response to nutrients. High levels of nitrogen and phosphorus in freshwaters may favor the growth of toxic Microcystis strains over nontoxic ones.

UV‐induced changes in phytoplankton cells and its effects on grazers

1. This review addresses the effects of UV‐radiation on the morphology and biochemistry of phytoplankton and the potential effects on grazers.2. UVA and UVB radiation inhibit the uptake of inorganic nutrients in phytoplankton. Reduced rates of ammonium and nitrate uptake in marine diatoms, and reduced uptake of phosphorus in freshwater flagellates are reported. The effects on cell stoichiometry are not settled.3. UVA and UVB radiation promote increased cell volumes owing to a decoupling between the photosynthetic processes and cell division. Loss or inactivation of flagellae and loss of motility are also reported for a number of phytoplankton species.4. UVA and UVB radiation may affect major biochemical constituents. Accumulation of intracellular, photosynthetic products (lipids or carbohydrates) is a common, although not unique, property of UV‐stressed algae. Fatty acid (FA) profiles seem susceptible to UV radiation. A relative increase of short‐chained, and a decrease in polyunsaturated FA (PUFA) are reported. The important membrane FA like eicosapentaenoic acid (EPA, 20 : 5ω3) and docosahexaenoic acid (DHA, 22 : 6ω3) seem particularly susceptible, owing to lipid peroxidation or reduced biosynthesis.5. UV‐related responses are highly dependent on taxonomy, cell‐cycle stage, nutrient‐limitation and the UV : PAR (photosynthetic active radiation)‐ratio.6. Nutrient deficiency, cell size, cell wall properties and FA can all have significant impacts on grazers. Thus the reported effects on cell morphology and biochemical constituents could have profound effects on grazers and energy transfer in aquatic foodwebs.

Semi-Micro Determination of Total Phosphorus in Fresh Waters with Perchloric Acid Digestion

Abstract A simple test-tube semi-micro method for the determination of total phosphorus in water is described. Samples are evaporated with perchloric acid at 115 °C overnight, digested at 170 °C for 40 minutes, diluted, hydrolyzed at 100 °C for 1 hour in order to decompose pyrophosphate and the liberated orthophosphate is determined without further neutralization and transfer steps by the phosphomolybdate blue method of Murphy and Riley (1962). The method can be applied directly to samples with phosphorus concentrations ranging from 4 to 1000 μg.1−1. Comparability with the classic perchloric acid and sulphuric acid—persulphate digestion methods has been demonstrated using a wide range of fresh waters.

Reverse osmosis as a concentration technique for soluble organic phosphorus in fresh water

The chemical nature and availability of soluble organic phosphorus for algal growth is largely unknown. A commercially available reverse osmosis water purification system was adapted for concentrating the soluble organic phosphorus fraction form 100-l volumes of drainage water collected from tile drains underlying an intensively managed grassland area in the Lough Neagh catchment. After membrane filtration the drainage water was recirculated through the reverse osmosis module while the permeate was removed from the system. During a single passage across the reverse osmosis membrane, 20% of the sample was discarded as pure water while the remaining 80% of the sample was pumped back to the reverse osmosis cartridge. Recirculation was continued, with the addition of an intermediate sodium ion-exchange step to prevent the precipitation of insoluble (largely calcium and magnesium) salts, until the volume was reduced to 2.5 l. The recovery of soluble organic phosphorus based on the original sample concentration was almost 93%. A further tenfold increase in concentration was achieved without salt precipitation or loss of soluble organic phosphorus by vacuum-assisted rotary evaporation. The mild, efficient concentration process developed a soluble organic phosphorus concentrate suitable for chemical fractionation and algal availability studies.

Nutrient dynamics and pelagic food web interactions in oligotrophic and eutrophic environments: an overview

The concept of limiting nutrients is a cornerstone of theories concerning the control of production, structure and dynamics of freshwater and marine plankton. The current dogma is that nitrogen is limiting in most marine environments while freshwater ecosystems are mostly phosphorus-limited, although evidence of phytoplankton limitation by either N or P has been found in both environments. However, the same considerations apply to the availability of phosphorus in freshwater as to nitrogen in oceans. In resource-limited environments the plankton dynamics depend mostly on the internal mechanisms which act to recycle the limiting nutrient many times over within the surface waters. As the overall productivity increases, this dependence on nutrient regeneration decreases. The relationship between the stock of limiting nutrient, rates of supply and plankton dynamics must therefore be seen in the light of the processes operating within the entire food chain over quite different time scales. There is strong evidence that process-rates are mostly size-dependent and that food web interactions at the microbial level (picophytoplankton, bacteria, microheterotrophs) strongly effect the production of carbon and the regeneration of nutrients in the pelagic zone.

Nutrient Limitation of Phytoplankton Growth in Brackish Coastal Ponds

In general, the nutrient most limiting to phytoplankton growth is phosphorus in freshwaters and nitrogen in the sea. We investigated the effect of N and P enrichment to waters from seven brackish, coastal ponds ranging in salinity from 0 to 31 ppt and to nearby coastal seawater (32 ppt). Phytoplankton from the least saline ponds (0–6.5 ppt) responded to P additions, and biomass increased 2–6 times over unenriched controls. Nitrogen additions stimulated phytoplankton growth only in waters from the most saline coastal pond (31 ppt) and seawater. Phytoplankton from ponds of intermediate salinity did not respond when either N or P was added alone but, as in all ponds, increased greatly in biomass when N and P were added in combination. The high salinity at which a switch from P to N limitation occurred could be due to the high N:P loading ratios to these ponds.

Is proteolysis dependent on phosphorus in fresh water?

HPA proteolytic assay was used to study the dependence of proteolysis on phosphorus in fresh water. Inorganic phosphate (Pi) stimulated the growth of bacteria producing proteases in water when P was limiting factor, but did not affect the biochemical activity of enzymes which were P-in-dependent. In proteolytic assays, bacteria utilised nitrogen and carbon from HPA. Therefore, during long incubations, significant increases in microbial biomass were observed. The original HPA procedure [12] gives artificial and non-realistic values of proteolytic rates in aquatic habitats due to accelerated and uncontrolled bacterial growth and enzyme production during the assay. The use of toluene to prevent microbial growth in HPA assays is recommended [10].

Is proteolysis dependent on phosphorus in fresh water?

Is proteolysis dependent on phosphorus in fresh water?

Different forms of phosphorus in freshwater

The first page of this article is displayed as the abstract.

Evaluation of the Procedure for Determining Low Levels of Phosphorus in Fresh Water

Abstract Low levels of phosphorus in fresh water were determined by a variant of the heteropolyblue method using extraction with isobutanol to bring the detection limit to 0.001 mg phosphorus/litre. The estimation was accurate and reliable under controlled conditions and a number of internal errors were eliminated. Although filtration of the sample at the site was desirable it was sometimes impracticable, so satisfactory alternative ways of maintaining the total phosphorus/dissolved phosphorus ratio were found. Samples could be stored for no longer than three days at 5°C or at ambient room temperature. A modification of the method excluded the additive effect of arsenic.

Phosphorus in fresh water and the marine environment

Phosphorus in fresh water and the marine environment

International association on water pollution research regional conference on phosphorus in fresh water and the marine environment

International association on water pollution research regional conference on phosphorus in fresh water and the marine environment

Determination of Total Phosphorus in Fresh Waters

Determination of Total Phosphorus in Fresh Waters