PO4-P Uptake Research Articles

Innovative receiving phase for Chemcatcher® passive sampler for phosphorus in the water environment: Calibration of sampling rate by water temperature and pH

Passive sampling is a technique for monitoring orthophosphate (PO4-P) in the water environment. Compared with traditional grab sampling followed by PO4-P quantification, kinetic-type passive samplers such as Chemcatcher® express representative concentrations of PO4-P as time-weighted average concentrations (CTWA). They can also potentially evaluate much lower PO4-P concentrations, but the available receiving phases of Chemcatcher® used for PO4-P were extremely limited. We developed a new receiving phase, the PSfZS sheet, comprising a zirconium sulfate–surfactant micelle mesostructure and polysulfone matrix. We examined its performance in terms of PO4-P sorption characteristics, PO4-P selectivity, and PO4-P sampling rate (Rs). Its capacity was adequate (12.0 μg-P/cm2) and selectivity for PO4-P uptake was good. The Rs for PO4-P increased with increasing water temperature (8.1–29.1 °C) and decreasing pH (4.1–9.7) in a laboratory calibration, and ranged from 5.27 × 10−2 L/d to 1.66 × 10−1 L/d. We placed the samplers in a municipal wastewater treatment plant, a shallow eutrophic lake, and an oligotrophic caldera lake. The Rs in the deployment sites was calibrated by monitored water temperature and pH. The estimated CTWA of PO4-P in the municipal wastewater treatment plant was similar to the averaged concentration of soluble reactive phosphorus determined by multiple grab samplings. In the lake deployments, we found that the new sampler can quantify CTWA values of PO4-P below 10 μg/L, and thus it provides more technical monitoring options and contributes to the conservation and management of the water environment.

Enhancement of anoxic phosphorus uptake of denitrifying phosphorus removal process by biomass adaption

Economical and efficient phosphorus (PO4-P) removal technologies with low oxygen and organic carbon demand are needed to avoid eutrophication and reduce wastewater treatment costs. A sequencing batch reactor (SBR) treating synthetic wastewater with similar characteristics to real domestic wastewater using peptone and meat extract as carbon sources and nitrate as terminal electron acceptor was set up to enhance anoxic PO4-P uptake of denitrifying phosphorus removal process. In the anaerobic/anoxic/oxic SBR, activated sludge inoculum was gradually adapted to prolonged anoxic and shortened aerobic phase durations of 3.5 h and 1 h, respectively. During biomass adaption, anoxic PO4-P uptake fraction from total PO4-P (anoxic + aerobic) uptake was enhanced from 70.5 to 90.4%. SBR long-term operation results showed that dosed nitrate loading and aeration phase duration affected PO4-P and total nitrogen (TN) removal. The highest PO4-P removal of 22.4 mg PO4-P g−1 mixed liquor suspended solids (MLSS) and average TN removal efficiency of 74.2% were achieved with 1-h aeration duration. The best dosed nitrate loading ranges for effective PO4-P and TN removal were 11.3–13.7 and 11.1–19.4 mg N g−1 MLSS d−1, respectively. Chemical oxygen demand and dissolved organic carbon removal efficiencies remained unaffected by changes in operating conditions with average values up to 96.3% and 98.0%, respectively. Pyrosequencing results demonstrated that during biomass adaption microbial community changed and adapted sludge probably contained some novel denitrifying phosphorus accumulating organisms. Therefore, this research shows that biomass adaption enabled to achieve efficient denitrifying phosphorus removal without acetate/propionate addition in the conditions similar to real domestic wastewater.

The metabolic activity of denitrifying microorganisms accumulating polyphosphate in response to addition of fusel oil

The effect of distillery waste product (fusel oil) as an alternative external organic carbon source (EOCS) was investigated in terms of the metabolic properties of denitrifying polyphosphate accumulating organisms (DPAOs). Samples of the non-acclimated biomass were collected from a local full-scale wastewater treatment plant employing A2/O type bioreactors. The acclimated biomass was obtained after cultivation (with fusel oil added) in a bench-scale reactor with a process configuration similar to the full-scale bioreactor. Changes in the functional properties of the biomass were investigated by measuring the phosphate release/uptake rates (PRRs and PURs), and nitrate utilization rates (NURs) with fusel oil in anaerobic-anoxic batch tests. Furthermore, a validated extended Activated Sludge Model no 2d (ASM2d) was used as a supporting tool to analyze the experimental results and estimate the contribution of DPAOs to the overall denitrification. In the non-acclimated biomass with fusel oil, the PRRs, PURs and NURs were low and close to the rates obtained in a reference test without adding EOCS. With the acclimated biomass, the PUR and NUR increased significantly, i.e., 3.5 and 2.7 times, respectively. In the non-acclimated biomass, approximately 60.0 ± 3.6% and 20.0 ± 2.2% of the total NUR was attributed to the utilization of endogenous carbon and examined EOCS, respectively. The remaining portion (20% of the total NUR) was attributed to PHA utilization (linked to PO4-P uptake) by DPAOs. With the acclimated biomass, the contribution of the EOCS to the NUR increased to approximately 60%, while the contribution of the endogenous carbon source decreased accordingly. Very accurate predictions of PURs and NURs (R2 = 0.97–1.00) were obtained with the extended ASM2d. Based on model simulations, it was estimated that the activity of DPAOs and denitrifying ordinary heterotrophic organisms corresponded to approximately 20% and 80% of the total NUR, respectively.

Colimitation and the coupling of N and P uptake kinetics in oligotrophic mountain streams

Ecosystem element cycles can be tightly linked by both abiotic and biotic processes. Evidence for multi-element limitation (i.e., colimitation) of a variety of ecosystem processes is growing rapidly, yet our ability to quantify patterns of coupled nutrient dynamics at the ecosystem level has been hindered by logistical and methodological constraints. Here we quantify coupled nitrogen and phosphorus uptake kinetics in three oligotrophic mountain streams by using novel experimental techniques that quantify colimitation dynamics across a range of nutrient concentrations and stoichiometries. We show that relative demand for NO3-N and PO4-P varied across streams, but that short term availability of one nutrient consistently resulted in elevated, but variable, uptake of the other nutrient at all sites. We used temporally offset, pulsed nutrient additions to parameterize dual-nutrient Michaelis–Menten uptake surface models that represent NO3-N and PO4-P uptake at any given concentration or dissolved NO3-N:PO4-P stoichiometry. Our results indicated that the uptake of N and P were strongly enhanced in the presence of the other nutrient. Surface models quantitatively reflect patterns of colimitation and multi-element demand in streams, and should allow for parameterization of more realistic stream network models that explicitly account for interactions among element cycles.

Hypereutrophication events in the Ca’Pisani lagoons associated with intensive aquaculture

Parameters of ecosystem structure and functioning were analyzed in three hypereutrophic lagoons of Ca’Pisani during the season of 2001. Lagoons are situated at wetlands of the NW Adriatic in the vicinity of the Porto Viro, Po River delta. They are associated with intensive fish culture enterprise and accept its wastewater. In June, the lagoons were found overloaded with the biomass of nitrophylic algae. At the end of July, a bloom of potentially toxic dinoflagellate Alexandrium tamarense occurred. Soon, it was supplanted by the picocyanobacterial assemblage, which arrived into the lagoons from the coastal Adriatic via the Marine channel. Wet biomass of this new picocyanobacterial bloom arrived in September attained 30–60 g m−3. Decrease of white disk water transparency down to 30–40 cm resulted in a gross mortality of macrophytes accompanied by spreading of floating saprobic alga Enteromorpha. Phytoplankton was dominated in June to July by small mixotrophic phytoflagellates with a wet biomass of 200–1300 mg m−3. Number of bacterioplankton ranged between 4 and 7 × 106 ml−1 and its wet biomass between 1.4 and 2.1 g m−1. Its maximum of 18 × 106 ml−1 was observed in late August, when the mortality of macrophytes had occurred. Zooplankton and zoobenthos were found depleted in the lagoons especially during the blooms. Diel fluctuations of dissolved oxygen in the lagoons in June to July reached 150–200% of saturation. Photosynthetic oxygen production ranged between 15 and 30 g O2 m−2 d−1. Water column deoxygenation rate was 1–1.5 mg O2 l−1 h−1. Total photosynthesis production reached 3–8 g C m−2 d−1 by the share of phytoplankton 5–15%. Hyper-accumulation of total phosphorus in the water column and of toxic labile sulfides in the bottom sediments was documented. Content of inorganic phosphorus in water remained unusually high even by its intensive uptake by microplankton. The PO4P uptake rate measured with 32P-label ranged during the bloom of picocyanobacteria between 10 and 50 nM l−1 min−1, and the residence time of PO4P between 15 and 50 min. The data were generalized via the calculation of energy balance and the deduction of the energy flow scheme in the ecosystem. Their analysis demonstrates the invalidation of ecosystems in hypereutrophic lagoons due to their overload with organic matter, with nutrients and with labile sulfides. After having depleted their animal food web, they are unable to decompose local plus external organic loading.

Influence of Nitrate and COD on Phosphorus and Nitrogen Removals under Batch Methanogenic and Denitrifying Conditions

In this study the effects of chemical oxygen demand (COD)-to-NO3-N ratio on phosphorus and nitrogen removals were investigated through denitrification and methanogenesis in batch reactors seeded with granulated anaerobic sludge. For the COD-to-NO3-N ratios varying between 2 and 3.7 maximum denitrification was observed. The volatile fatty acid (VFA) production decreased to 120 from 2,000 mg/L for the COD-to-NO3-N ratios varying between 2 and 3.7 through methanogenesis. The methane percentages were between 45 and 60% for the reactors exhibiting COD-to-NO3-N ratios of 2 and 3.7 on days 4–6. After days 10–12, the methane gas production ceased while the daily N2 gas production reached a maximum level of 42 mL for the COD to NO3-N ratios of 2 and 3.75. NO3-N was used as the electron acceptor after methanogenesis had been completed. High and low COD concentrations such as 10,000 and 200 mg/L decreased the PO4-P uptake, resulting in 10% PO4-P removal efficiency. COD concentrations of 2,000 and 4,000 mg/L increased the PO4-P uptake, resulting in PO4-P removal efficiencies of 89 and 95, respectively, in anoxic batch reactors. The NO3-N concentrations decreased to 500 from 1,500 mg/L at COD concentrations varying between 2,000 and 4,000 mg/L through PO4-P uptake under anoxic conditions. Suitable COD-to-NO3-N ratios provide effective NO3-N, PO4-P removals and minimize the external carbon requirement through anaerobic/anoxic treatment of nutrient containing wastewaters.

Effects of riparian vegetation removal on nutrient retention in a Mediterranean stream

We examined the effects of riparian vegetation removal on algal dynamics and stream nutrient retention efficiency by comparing NH4-N and PO4-P uptake lengths from a logged and an unlogged reach in Riera Major, a forested Mediterranean stream in northeastern Spain. From June to September 1995, we executed 6 short-term additions of N (as NH4Cl) and P (as Na2HPO4) in a 200-m section to measure nutrient uptake lengths. The study site included 2 clearly differentiated reaches in terms of canopy cover by riparian trees: the first 100 m were completely logged (i.e., the logged reach) and the remaining 100 m were left intact (i.e., the shaded reach). Trees were removed from the banks of the logged reach in the winter previous to our sampling. In the shaded reach, riparian vegetation was dominated by alders (Alnus glutinosa). The study was conducted during summer and fall months when differences in light availability between the 2 reaches were greatest because of forest canopy conditions. Algal biomass and % of stream surface covered by algae were higher in the logged than in the shaded reach, indicating that logging had a stimulatory effect on algae in the stream. Overall, nutrient retention efficiency was higher (i.e., shorter uptake lengths) in the logged than in the shaded reach, especially for PO4-P. Despite a greater increase in PO4-P retention efficiency relative to that of NH4-N following logging, retention efficiency for NH4-N was higher than for PO4-P in both study reaches. The PO4-P mass-transfer coefficient was correlated with primary production in both study reaches, indicating that algal activity plays an important role in controlling PO4-P dynamics in this stream. In contrast, the NH4-N mass-transfer coefficient showed a positive relationship only with % of algal coverage in the logged reach, and was not correlated with any algal-related parameter in the shaded reach. The lack of correlation with algal production suggests that mechanisms other than algal activity (i.e., microbial heterotrophic processes or abiotic mechanisms) may also influence NH4-N retention in this stream. Overall, this study shows that logging disturbances in small shaded streams may alter in-stream ecological features that lead to changes in stream nutrient retention efficiency. Moreover, it emphasizes that alteration of the tight linkage between the stream channel and the adjacent riparian zone may directly and indirectly impact biogeochemical processes with implications for stream ecosystem functioning.

Phosphorus and nitrogen relationships of Cladophora glomerata in two lake basins of different trophic status

SUMMARY Cladophora has increased in abundance and cover in the South Basin of Windermere, English Lake District, in recent years. During the growing seasons of 1992 and 1993, the maximum biomass of Cladophora in the South Basin, at nearly 200 g dry weight m‐2, was nearly six times greater and the percentage cover, at 95%, was nearly ten times greater than in the North Basin. Nutrient analysis showed that Cladophora from the South Basin had significantly higher average contents of N than that from the North Basin. The suggested rate‐limiting tissue N content, 1.3% of dry weight, was never reached in the South Basin but was reached in 20% of samples from the North Basin. In contrast, the average P content was not significantly different, at about 0.24% in both basins. The suggested rate‐limiting P content, 0.16% of dry weight, was reached in 31% of the samples from the South Basin and 37% from the North Basin. On average, the standing stock of P in the South Basin was 0.12 g m‐2, twelvefold that in the North Basin at 0.01 g m‐2 and the standing stock of N in the South Basin was 1.81 g m‐2, elevenfold that in the North Basin at 0.16 g m‐2. Maximum standing stocks of P were 0.38 g m‐2 in the South and 0.05 g m‐2 in the North Basin. Maximum standing stocks of N were 5.02 g m‐2 in the South and 0.60 g m‐2 in the North Basin. The maximal rate of PO4–P uptake ranged between 298 and 2949 μg P g‐1 DW h‐1 and the specific affinity varied between 2.9 and 24.3 μg P g‐1 DW h‐1 (mg PO4–P m‐3)‐1. The higher values of both characteristics are within the range which is believed to indicate severe P limitation. Using the nutrient uptake characteristics, rates of uptake at pelagic and littoral concentrations of PO4–P were calculated to be between 0.1 and 1.7% of the maximal rates apart from one site where rates were up to 5.6% of Vmaxi and 40% of Vmaxi based on pelagic and littoral concentrations of PO4–P, respectively. Despite these generally low rates of uptake, calculations suggest they were just sufficient to account for the measured rate of increase of P standing stock, assuming no biomass loss. Similar calculations suggested that pelagic concentrations of NO3–N could support between 21 and 30% of maximal rates and these were between four and six times (North Basin) and twenty‐five times (South Basin) the observed rates of increase in N standing stock. Littoral concentrations of NO3–N were similar and so would have allowed similar rates. Evidence from nutrient tissue contents, standing stocks and rates of uptake suggests that the growth of Cladophora, in both basins of Windermere, is controlled primarily by the availability of P.

The Effect of Lime, Irrigation-water Source, and Water-soluble Fertilizer on Root-zone pH, Electrical Conductivity, and Macronutrient Management of Container Root Media with Impatiens

Hybrid impatiens (Impatiens Wallerana Hook. F.) were planted in a peat-based medium containing two dolomitic liming materials (1.8 kg Ca(OH)2·Mg(OH)2/m3 or 8.4 kg CaCO3·MgCO3/m3) and subirrigated for 17 weeks using four irrigation-water sources (IWSs) with varied bicarbonate alkalinity, Ca2+, Mg2+, and SO4-S content and three water-soluble fertilizers (WSFs) that contained (in mg) 200N-20P-200K/liter but a variable NH4: NO3 ratio, Ca2+, Mg2+, and SO4-S content. The factorial arrangement of the IWS and WSF resulted in a range of Ca2+, Mg2+, and SO4-S concentrations varying by a factor of 10. After 8 weeks, medium pH ranged from 4.5 to 8.5. The maximum critical medium pH for PO4-P uptake was 7.4 to 7.7, which probably was due to a change in most of the water-soluble P to the less-available HPO42- form. Lime type did not affect the long-term increase in medium pH, Ca2+, and Mg2+ concentrations with nutrient solutions containing low NH4+-N and high Ca2+ and Mg2+. The carbonate lime buffered the medium pH and Ca2+ and Mg2+ concentrations with nutrient solutions containing high NH4+-N and low Ca2+ and Mg2+ compared to that measured with the hydrated lime. With both lime types, there was a linear increase in tissue Ca and Mg as the applied concentrations of the various nutrient solutions increased from 18 to 210 mg Ca2+/liter and 7 to 90 mg Mg2+/liter. The relationship was similar for both lime types up to week 8, after which tissue Ca and Mg decreased more rapidly with the hydrated lime and low solution Ca2+ and Mg2+ compared to that of the same carbonate lime treatments. The minimum critical SO4-S concentration in the applied nutrient solution for plant uptake was 30 to 40 mg S/liter. Below this concentration, tissue S decreased rapidly; above, there was little effect on tissue S.

Phosphorus metabolism in coral reef communities: exchange between the water column and bottom biotopes

Exchange of phosphate between components of the reef bottom and the water column were studied on reefs around Heron Island (Great Barrier Reef), both in aquaria and in in situ enclosures, using radioactive phosphorus (32P) as a tracer. Living corals, dead corals, coral rubble overgrown with periphyton, and soft sediments of coral sand were used in experiments. In all of these components of bottom reef biotopes, two opposite flows of inorganic phosphate were recorded and measured, i.e. the rate of PO4-P uptake from water (Ac), and its release (Ae). At ambient PO4-P concentrations in water of 0.1– 0.3 µmoll−1, both flows varied in living corals and coral rubble between 10 and 70 µg P kg−1 h−1, 3–10 mg P m–2 day–1, and in coral sand between 10 and 30 µg P kg−1 h−1, or 2–7 mg P m−2 day−1. Under the latter concentration range (which is typical for coral reef areas), the reciprocal PO4-P flows almost balanced each other, so that net uptake (At) was very low. Often it approached zero or was positive, showing that a net PO4-P release had taken place. The uptake flow (Ac) in living coral was much more dependent on the PO4-P content in overlying water than was the release flow (Ae). The influence of conditions of illumination upon the values of Ac and Ae was comparatively low. The data obtained are used to discuss problems of phosphorus balance and dynamics in coral reef ecosystems.

Phosphorus metabolism in Coral Reef Communities: Dynamics in the Water Column

Phosphorus dynamics were studied in the coral reef waters of Heron and Wistari Reefs in the Capricornia group, Great Barrier Reef, Australia, using radioisotopic techniques. All studies were made during August-October 1986. Labelled phosphate (PO4 -33P) was used to measure total uptake as well as uptake by bacterioplankton alone. Rates of total PO4-P uptake by microplankton varied between 20 and 120 ng P L-1 h-1 at water temperatures of 20-24� C. The daily (24 h) uptake rate of PO4-P was 0.5-3.0 �g L-1. The ambient PO4-P content of water over the reefs was low (0.03- 0.3 �mol L-1, or 1-10 �g P L-1). Turnover time of PO4-P in the water column of these reef areas is therefore very short, being in the range of 2-8 days, even when its possible net consumption by bottom biota is ignored. Bacterioplankton, not phytoplankton, was found to be the major consumer of inorganic phosphorus in these waters. The percentage of total PO4-P uptake by bacteria varied from 50 to 90%. The results of these estimations are discussed in terms of the importance of active phosphorus dynamics in the water column to the nutrient budget of the coral reef ecosystem.