Phosphorus Co-precipitation Research Articles

Factors influencing K-struvite purity via phosphorus coprecipitation in synthetic urine: Verification, Quantification, and Modelling

Due to its plethora of nitrogen (N), phosphorus (P), potassium (K) in urine, it is bound to trigger phosphorus coprecipitation, thereby adversely affecting K-struvite purity in the coprecipitates. To obtain high pure K-struvite, the present study was to innovatively explore the effect of residual NH4+ concentration, pH and initial Mg2+ concentration on phosphorus coprecipitation in synthetic urine. Importantly, a Back-Propagation Artificial Neural Network (BPANN) model was innovatively proposed to simulate and predict crystal purities in the coprecipitates. It was revealed that K-struvite, struvite, hydroxyapatite and cattiite dominated the coprecipitates. Comparatively, the content of calcium in synthetic urine is far lower than that of phosphorus and potassium, resulting in low hydroxyapatite purity in the coprecipitates. Notably, cattiite purity is highly dependent of Mg2+ concentration, because it was low at the Mg2+ concentration of <10 mmol/L, but increased up to above 50% at the Mg2+ concentration of 50 mmol/L.At 10 mmol/L Mg2+ and pH 10, K-struvite purity in the coprecipitates decreased from 64.6% to 43.3% following the increase of NH4+ concentration from 0 to 300 mg/L. The BPANN model well simulated and predicted the purities of the crystals in the coprecipitates from synthetic urine. At 10 mmol/L Mg2+ and 100 mg/L NH4+, an increase in pH from 8.5 to 10 can facilitate K-struvite crystallization in synthetic urine. The adjustment of pH and initial Mg2+ concentration can significantly mitigate the inhibitory effect of residual NH4+ on K-struvite crystallization. The BPANN model herein can effectively obtain optimized operational parameters for the full-scale implementation of slow-release NPK fertilizers from urine, which can also provide an effective reference for nutrient recovery from various waste streams.

Interspecific Differences in the Effects of Calcium and Phosphorus Coprecipitation Induced by Submerged Plants on the Water-to-Phosphorus Cycle

The effects of submerged plant-induced calcium and phosphorus coprecipitation on the phosphorus cycle in aquatic environments and interspecific differences are still unclear. Herein, we selected Ceratophyllum demersum L. and Potamogeton crispus L. to construct a sediment–water-submerged plant system. We examined how phosphorus concentrations in the water, sediment, and plant ash changed over time with different phosphorus and calcium treatments and explored the effects of photosynthesis-induced calcium and phosphorus coprecipitation on water’s phosphorus cycle and variations between different submerged plant species. The main results were as follows: (1) The phosphorus reduction in the P. crispus system was less than that in the C. demersum system. (2) P. crispus had higher total ash phosphorus (TAP) values than C. demersum. (3) The sediment total phosphorus (STP) and its fractions with P. crispus were most affected by phosphorus concentration while those with C. demersum were most affected by time. Overall, the two submerged species exhibited different calcium and phosphorus coprecipitation levels and had distinct effects on the water-to-phosphorus cycle. When submerged plants are introduced to reduce and stabilize the phosphorus levels, plant interspecific differences in their induced calcium and phosphorus coprecipitation on water and phosphorus cycling must be fully assessed.

Iron and phosphorus geochemistry in the core sediments of an urbanized mangrove ecosystem, Southwest coast of India

This study has been carried out to understand the geochemistry of elements namely, iron (Fe) and phosphorus (P) in the core sediments of an urbanized tropical mangrove ecosystem along the Southwest coast of India. The study revealed the coupling of iron and phosphorus in which the reductive conditions induced reductive dissolution and upward transport of Fe, causing surface coprecipitation of phosphorus incorporated Fe oxyhydroxides. The accumulation and transformation of phosphorus were significantly influenced by processes viz., phosphorus regeneration due to organic matter mineralization and adsorption to inorganic iron oxides/Ca bound minerals in the surface sediments, and phosphorus retention in the sedimentary column by transformation into refractory organic phosphates. Bioavailable phosphorus (BAP) accounted for more than 50% of TP, so that the mangrove sediments act as an important internal nutrient source of iron and phosphorus for coastal eutrophication.

Effect of calcium addition on phosphorus removal of the submerged plant for ecological environment protection

Submerged plants can create a suitable microenvironment for calcium and phosphorus co-precipitation (CaCO3-P) to further enhance the removal of phosphorus from the water column. To investigate the effect of calcium addition on the phosphorus removal in water bodies of submerged plants, this paper used Elodea nuttallii as a research object and monitord the phosphorus content in water column, sediment, plants and water environmental factors. The results showed that the addition of calcium was more effective in removing phosphorus than the group without calcium, and the final phosphorus content was controlled at a lower level; the effect of the calcium group on the phosphorus content of sediment was greater, and the addition of calcium promoted the increase of calcium-phosphorus content in the sediment. Moreover, the phosphorus content in the plant of the calcium group was higher than the plant group. It is clear that the addition of calcium ions contributed to both the removal of phosphorus from the water column and the enrichment of phosphorus by the plants.

Plant distribution, stature, rarity, and diversity in a patterned calcareous fen: tests of geochemical and leaf-height models.

In patterned fens, patches of short, sparse, species-rich vegetation often occur on substrates rich in precipitated carbonates near calcareous springheads, with taller, denser vegetation farther away. Boyer and Wheeler (1989) hypothesized that phosphorus co-precipitation near springheads limits plant productivity and coverage, and Givnish (1982) proposed that aggregations of rare, short-statured plant species might reflect their competitive restriction to sparsely covered microsites. We tested these hypotheses by quantifying species distributions, leaf heights, plant coverage, community composition, and substrate and leaf chemistry of Eupatorium perfoliatum along a gradient of hydrology and geochemistry in a wetland complex in southeastern Wisconsin, USA, ranging from marl flats and fens on peat mounds near springheads to surrounding sedge meadows. Community composition was strongly correlated with a one-dimensional environmental gradient along which coverage and height increased moving downslope from marl flats, while soil carbonate, phosphorus immobilization capacity, and local species richness decreased, consistent with theory. Regionally rare species were short and restricted to sparsely covered microsites; within and among species, leaf height increased with local coverage. NPK tissue stoichiometry did not entirely support the Boyer-Wheeler hypothesis, although nitrogen limitation appeared strongest in sedge meadows. Shifts in stature and tissue chemistry of E. perfoliatum along the marl flat-sedge meadow gradient suggested that zinc toxicity may help limit coverage near springheads despite no significant change in soil zinc content. We propose a modified Boyer-Wheeler hypothesis to account for cascading effects of phosphorus co-precipitation near springheads on nitrogen fixation, nitrogen+phosphorus co-limitation, and zinc mobility.

Phosphorus Fluxes from Three Coastal Watersheds under Varied Agriculture Intensities to the Northern Gulf of Mexico

This study aims to evaluate recent total phosphorus (TP) and dissolved inorganic phosphorus (DIP) transport from three coastal rivers—the Calcasieu, Mermentau, and Vermilion Rivers—that drain watersheds with varied agriculture intensities (21%, 67%, and 61%, respectively) into the northern Gulf of Mexico, one of the world’s largest summer hypoxic zones. The study also examined the spatial trends of TP and DIP from freshwater to saltwater along an 88-km estuarine reach with salinity increasing from 0.02 to 29.50. The results showed that from 1990–2009 to 2010–2017, the TP fluxes for one of the agriculture-intensive rivers increased while no significant change was found for the other two rivers. Change in river discharge was the main reason for this TP flux trend. The two more agriculture-intensive river basins showed consistently higher TP and DIP concentrations and fluxes, as well as higher DIP:TP ratios than the river draining less agriculture-intensive land, confirming the strong effect of land uses on phosphorus input and speciation. Longitudinal profiles of DIP along the salinity gradient of the estuarine reach displayed characteristic input behavior. Desorption of DIP from suspended solids and river bed sediments, urban inputs, as well as stronger calcium carbonate and phosphorus co-precipitation at the marine endmember could be the reasons for such mixing dynamics.

Effects of natural organic matter on calcium and phosphorus co-precipitation

Phosphorus (P), calcium (Ca) and natural organic matter (NOM) naturally occur in all aquatic ecosystems. However, excessive P loads can cause eutrophic or hyper-eutrophic conditions in these waters. As a result, P regulation is important for these impaired aquatic systems, and Ca–P co-precipitation is a vital mechanism of natural P removal in many alkaline systems, such as the Florida Everglades. The interaction of P, Ca, and NOM is also an important factor in lime softening and corrosion control, both critical processes of drinking water treatment. Determining the role of NOM in Ca–P co-precipitation is important for identifying mechanisms that may limit P removal in both natural and engineered systems. The main goal of this research is to assess the role of NOM in inhibiting Ca and P co-precipitation by: (1) measuring how Ca, NOM, and P concentrations affect NOM’s potential inhibition of co-precipitation; (2) determining the effect of pH; and (3) evaluating the precipitated solids. Results showed that Ca–P co-precipitation occurs at pH 9.5 in the presence of high natural organic matter (NOM) (≈30mgL−1). The supersaturation of calcite overcomes the inhibitory effect of NOM seen at lower pH values. Higher initial P concentrations lead to both higher P precipitation rates and densities of P on the calcite surface. The maximum surface density of co-precipitated P on the precipitated calcite surface increases with increasing NOM levels, suggesting that NOM does prevent the co-precipitation of Ca and P.

Factors controlling phosphorus speciation in a Mediterranean basin (River Guadalfeo, Spain)

Summary There is a lot of interest nowadays in the role of riverbed sediments in phosphorus cycling and particularly, in the processes that lead the exchange of phosphorus between the sediment and the water column. This study presents results on phosphorus forms and other properties from surface riverbed sediments of the River Guadalfeo and its main tributaries. Results show a wide range of spatial variability within the basin with differences of phosphorus concentration higher than an order of magnitude among different sites. The most abundant form is the apatite inorganic phosphorus (AIP) which accounts for 68% of total phosphorus followed by total organic phosphorus (OP) that represents 29%. The high oversaturation of calcite reached during the summer and early autumn in most studied rivers shows as calcite–phosphorus co-precipitation is the most important self-cleansing mechanism that removes phosphorus from the water column, controlling the phosphorus content in the sediment and the dominance of AIP. Hydroxyapatite formation is only important in a few sampling points, in spite of the vastly oversaturation obtained. External factors such as the lithology of drainage area and sewage inputs are less important in the concentration of sediment phosphorus than physico-chemical and biological processes that take place in the rivers. Taking into account the low biodegradable characteristics of dominant phosphorus forms, it could be concluded that the surface sediment in the Guadalfeo basin acts as a phosphorus sink.

Phosphorus Co-Precipitation in the Biological Treatment of Slaughterhouse Wastewater in a Sequencing Batch Reactor

The effect of phosphorus co-precipitation with ferric chloride ( FeCl3 ) dosing on biological phosphorus (P) along with carbon (C) and nitrogen (N) removal was investigated in a sequencing batch reactor (SBR) for slaughterhouse wastewater treatment. Additional phosphorus removal due to chemical co-precipitation was evaluated as the difference in System P removal between Phase 1 (control—without FeCl3 dosing) and Phase 3 (with FeCl3 dosing). Phase 2 was mainly studied to improve nitrification/denitrification process with acetate addition by Filali-Meknassi et al. in 2004. Both systems (Phases 1 and 3) exhibited high P removal but a co-precipitation with FeCl3 dosing only allowed us to have an orthophosphates (o- PO4 ) concentration below 1 mg P∕L in the effluent. Without FeCl3 addition, the total P concentration was reduced from 85±12 to 14±2 mg P∕L (84% removal), whereas with the addition of FeCl3 an additional 11 mg P∕L was removed bringing the effluent P concentration to 3 mg P∕L (as total P). Although,...

Calcite saturation in the River Dee, NE Scotland.

The spatial and temporal variations in calcite (calcium carbonate) solubility within the Dee basin of NE Scotland were assessed using water chemistry data gathered from a network of 59 sites monitored for water quality from June 1996 to May 1997. Calcite solubility, expressed in terms of a saturation index (SIcalcite), was determined from measured streamwater pH, Gran alkalinity and calcium concentrations and water temperature. In general, the waters of the Dee system are undersaturated with respect to calcite, though the saturation index is higher during the summer months indicating a dependency on flow conditions and biological activity. Under low-flow conditions, the streamwaters are dominated by water derived from the lower soil horizons and deeper groundwater stores and therefore, ions such as Gran alkalinity and calcium are at their highest concentrations as they are derived mainly from bedrock weathering. The influence of biological activity on the carbonate system is also evident as the observed pH and estimated EpCO2 values indicate strong seasonal patterns, with the highest pH and lowest EpCO2 values occurring during the summer low-flow periods. Only at three sites in the lowland region of the catchment, during the summer low-flow period, are the waters oversaturated. As such, the Dee system represents an extreme 'end-member' case when compared to many UK rivers that span both under- and oversaturated conditions during the year. Regression analysis highlights a systematic change in the SIcalcite-pH relationship in a broad east-west direction across the Dee system. At sites draining the relatively impermeable upland areas, the regression of SIcalcite against pH gives a straight line with a gradient in the range 1.6-2.4. Correspondingly, under the most extreme alkaline conditions found at sites draining lowland agricultural areas, a straight-line relationship exists but with a gradient of unity. It is concluded that these changes in the SIcalcite-pH relationship are due to variations in the bicarbonate system induced by the flow conditions and biological activity. Given the waters are undersaturated, then calcite precipitation and hence phosphorus co-precipitation cannot occur within the water column.

Restoration of a Stratified Lake (Feldberger Haussee, Germany) by a Combination of Nutrient Load Reduction and Long-Term Biomanipulation

A long-term biomanipulation has been performed in the stratified Feldberger Haussee since 1985. Prior to manipulation, nutrient load to the lake had declined due to waste water removal. Planktivorous fish were reduced by seining and by enhancement of piscivorous fish. Changes in transparency, nutrients, phytoplankton, zooplankton and fish were documented for both the premanipulation period (1978-1985) and the manipulation period (1986-1998). Transparency increased in response to the manipulation (+54%), but strong year-to-year fluctuations were observed. These fluctuations were correlated to chlorophyll a, primary production and the proportion of piscivores in the fish community. We conclude that the success of the restoration was predominantly attributed to bottom-up forces as a result of the declining nutrient load and an intensified co-precipitation of phosphorus with calcite. However, the increased predation impact by the piscivorous fish may have caused a reduced nutrient recycling by the planktivorous fish thus contributing also to the improvement in water quality.

The water quality of the River Kennet: initial observations on a lowland chalk stream impacted by sewage inputs and phosphorus remediation

The water quality of seven sites on the upper reaches of the River Kennet round the market town of Marlborough is described and related to the introduction of phosphorus treatment of effluent from Marlborough sewage treatment works (STW). The River Kennet is mainly groundwater-fed from a Cretaceous chalk aquifer and hence the river water is calcium- and bicarbonate-bearing and has a relatively constant composition of many major water quality determinands. In-stream biological activity gives rise to marked diurnal fluctuations in pH (of approx. 0.8 units). Dissolved carbon dioxide and dissolved oxygen also show marked diurnal fluctuations. Dissolved carbon dioxide varies from approximately 10 to 70 times atmospheric pressure, indicating net release of carbon dioxide and the dominance of heterotrophic (respiratory) processes over autotrophic processes (photosynthesis). Much of the excess carbon dioxide is probably associated with carbon dioxide laden groundwater inputs and the relatively short within-stream residence times ensures only limited degassing to the atmosphere. Diurnal fluctuations in dissolved oxygen vary from approximately 20% to 200% saturation. For both dissolved carbon dioxide and dissolved oxygen, the amplitude of fluctuations is much lower during the winter period, when biological activity is at its lowest. The concentrations of soluble reactive phosphorus (SRP), total phosphorus (TP) and boron increase markedly just downstream of the sewage works as a result of this point source input. These concentrations slowly decline further downstream as additional groundwater inputs dilute the effluent further. The introduction of chemical treatment of sewage effluent for phosphorus reduction at Marlborough STW resulted in a marked decrease in within-river SRP and TP concentrations to levels approximately the same as those upstream of the STW. A comparison of SRP and boron concentrations reveals a reduction in in-stream SRP concentrations by approximately 75% following effluent treatment. In terms of within-river processes controlling in-stream phosphorus concentrations, previous studies have indicated that one potentially important mechanism within calcium bicarbonate bearing rivers may be related to co-precipitation of phosphorus with calcium carbonate (calcite). The present study shows that the waters are oversaturated with respect to calcium carbonate, that no equilibrium conditions exist and that phosphorus removal has led to undetectable changes in calcium carbonate oversaturation. Hence, it is concluded that the primary changes in phosphorus levels within the river is directly associated with changing point source contributions from the STW and physical dilution within the river. However (1) the results relate to only the first year of study and subsequent differences may become apparent and (2) reactions between the water column and plant and bottom sediment interfaces may be important in regulating phosphorus fluxes within the river. The results presented in this paper mark a pilot phase of a longer-term initiative and this paper provides a background setting. The paper discusses the longer-term objectives and important gaps in knowledge of the system that requires further address.

A balance analysis of phosphorus elimination by artificial calcite precipitation in a stratified hardwater lake

Elimination of phosphorus was achieved by artificial calcite precipitation in the Dagowsee, a stratified eutrophic hardwater lake. The artificial calcite precipitation was induced by hypolimnetic injection of CaO in enclosures during the summer stagnation. The hypolimnetic injection of CaO was combined with aeration for 1 day. The coprecipitation of phosphorus with calcite was shown by energy dispersive X-ray analysis. The content of phosphorus in the calcite was about 0.1 wt%. Phosphorus was homogeneously distributed throughout the precipitated calcite and throughout the calcinated particles of water and sediment. The phosphorus coprecipitation efficiency was calculated from the ratio of the decrease of phosphorus to decrease of calcium in the water according to the House's coprecipitation model.

Biological Phosphorus Removal: Effect of Low Temperature

Phosphorus is a key nutrient responsible for eutrophication. Conventional activated sludge process (ASP) removes approximately 30 to 40% phosphorus. Additional phosphorus removal has been achieved by incorporating an anaerobic stage before aerobic ASP. The application of technology, however, in cold-region countries is limited. Temperature is an important consideration in the design of any treatment process in cold regions. In this paper, the performance of biological phosphorus removal (BPR) systems at low temperatures has been reviewed. The mechanism of BPR has been considered to analyze the effect of reduced temperature. Chemical coprecipitation of phosphorus, and acetate and/or short chain fatty acid (SCFA) production may affect BPR efficiency. Both these aspects have been reviewed in systems other than BPR.

Environmental tracer analysis of winter profile development in two basins of Shagawa Lake, Minnesota

Winter profile development was studied comparatively in two basins ( z max = 14 m) separated by a 6 m sill in Shagawa Lake, Minnesota. Based on physical arguments and profile measurements, heat and solutes released from shelf sediments in the western basin cause convective instability at 8–11 m. After a mid-winter interval of instability, radon profiles indicate very low rates of vertical mixing in the benthic boundary layers following their stabilization by ferrous iron. Because of hydrographic features, two types of plunging inflows sometimes enter the western basin in late winter; one anthropogenic inflow alters the lower profiles by adding sodium, radon, and oxygen; the second modifies the mid-depth region by adding ‘weathering tracers’ (especially calcium and silicon) derived from the Ely greenstone. The oxidation of Fe 2+ diffusing upward and laterally from the sediment-water interface is accompanied by near-complete coprecipitation of phosphorus. The oxidation of Fe 2+ has only a minor effect on silicic acid, probably because of unfavorably large Si:P and preferential association of Fe(III) with phosphorus. Despite low pH and temperature, detectable amounts of Mn 2+ oxidize and precipitate above iron in the water column. Solute profiles differentially register the complex effects of hydrodynamic vs. geochemical processes, and as a consequence, affect the estimation of solute budgets in ice-covered lakes.

Phosphorfällung über Calciumcarbonat im eutrophen Wallersee (Salzburger Alpenvorland, Österreich). Coprecipitation of Phosphorus with Calcite in the Eutrophic Wallersee (Alpine Foreland of Salzburg, Austria)

AbstractBy chemical analyses at the eutrophic Wallersee (Austria) a considerable precipitation of calcite during autumn overturn was found. It is a pure anorganic calcite precipitation, caused by the loss of free carbonic acid to the atmosphere during the mixing of epilimnic and hypolimnic water.An essential coprecipitation of phosphorus with the anorganic calcite precipitation could be shown by calcium and phosphorus balances and by SEM investigations.During the epilimnic biogenic calcite precipitation (in summer) phosphorus coprecipitation makes 0.19% of the calcium fallout. Phosphorus coprecipitation increases up to 0.42 % during the anorganic calcite precipitation when autumn overturn takes place. With respect to the total phosphorus sedimentation in the lake 25 % are coprecipitated with calcite.