Phosphate Concentrations In Water Research Articles

Study of Parasitary Fauna in Tilapia of Fish Cultures in the Distrito Federal

Objective: This article discusses the parasitic fauna found in tilapia, the most produced in the DF, collected in fish farms and presents an analysis of water quality, a relative condition factor and the influence of seasonality on the average abundance of parasites. Methodology: For each acquisition campaign, ten fish were collected from each visited fish farm, totaling 180 sampled fish. The fish were collected by fishing nets with mesh 14 and transported in thermal boxes, with each specimen properly packed in a plastic bag, to ensure protection during transport to the Aquaculture Laboratory of the University of Brasília (AcquaUnB). Results and Conclusion: In the two acquisition campaigns, parasitism by Trichodina sp., Monogenoids, Ichthyophthirius multifiliis and Apiosoma sp. Infestations by Trichodina sp. presented higher prevalence and average intensity than other parasites in general, followed by infections by Monogenoides, Ichthyophthirius multifiliis and Apiosoma sp, respectively. The average abundance of Trichodina sp., monogenenoids, Ichthyophthirius multifiliis and Apiosoma sp. showed a positive correlation with temperature and the concentration of ammonium and phosphate in fish farm water. On the other hand, the average abundance of parasites showed a negative correlation with the levels of dissolved oxygen and nitrate concentration. The ectoparasites found do not directly affect human health. There was a significant difference between the average abundance of parasites found in fish collected in the months of February and August, so that the highest parasitic rates were observed in February, when there is greater rainfall in the Federal District and when the values of water parameters were findings. less suitable.

Lanthanum hydroxide showed best application potential in La-based materials based on its stable phosphate adsorption properties in complex water environments

Three lanthanum morphology materials encompassing all lanthanum composites were synthesized by the direct precipitation method, and their phosphate adsorption order was determined as La2(CO3)3 > La(OH)3 > La2O3. Further comparison of the adsorption performance between La2(CO3)3 and La(OH)3 revealed that the former exhibited a twofold higher rate of adsorption compared to the latter. The presence of SO42−, HCO3−, Mg2+, and HA in the water led to a decrease in the phosphate adsorption of La2(CO3)3 and La(OH)3, while Ca2+ enhances the adsorption of phosphoric acid by both materials. Compared to La2(CO3)3, La(OH)3 exhibited stronger resistance against coexisting ions. The pH was the limiting factor for phosphate adsorption in both cases, and their adsorption capacity decreased significantly as the pH increased. The phosphate adsorption mechanism of La2(CO3)3 was ligand exchange to form inner-sphere complexes, while the phosphate adsorption mechanism of La(OH)3 involved ligand exchange, inner-sphere complexation, and electrostatic attraction. The stability of La(OH)3 exhibited superior performance compared to that of La2(CO3)3 over 5 adsorption-desorption cycles. Although La2(CO3)3 had a higher initial phosphate adsorption capacity than La(OH)3, its phosphate adsorption capacity decreased by 40 % after five adsorption-desorption cycles, while that of La(OH)3 decreased by 2.3 %. Additionally, the amount of La(OH)3 adsorbed after five cycles was 25.6 % higher than that of La2(CO3)3. Therefore, La(OH)3 performs better regeneration adsorption than La2(CO3)3. Furthermore, a smaller dosage of La(OH)3 was required compared to La2(CO3)3 in a test aimed at lowering the actual phosphate concentration in water to 0.5 mg/L. In summary, La(OH)3 is a more suitable substrate for cyclic adsorption for phosphorus removal than La2(CO3)3 and has better potential for practical application. In conclusion, La(OH)3 proves to be a more suitable substrate for cyclic adsorption in phosphorus removal compared to La2(CO3)3 and exhibits superior potential for practical application.

Preparation of PEI/La2O3/Polypropylene fiber filter for household water purifiers and investigation of its phosphate reduction and bacterial control

It has been accepted that limiting phosphate is a prerequisite for bacterial inactivation in tap water. La2O3 nanoparticles were loaded onto polypropylene (PP) fibers through the method of melt spinning. Hydrophilic modification of the adsorbent surface was performed using polyethyleneimine (PEI) to prepare PEI/La2O3/PP. The results indicated that the optimal loading amount of La2O3 was 1 %, and the optimal concentration of PEI was 1 %. The successful loading of La2O3 resulted in a roughened fiber surface and increased fiber diameters. After PEI modification the water contact angle was reduced from 98° to 50°. The pHzpc of PEI/La2O3/PP was determined to be 8.3. The co-existing ions have little effect on phosphate adsorption. Phosphate adsorption can be well described by Redlich-Peterson model with a maximum KR-P of 3.98 × 10−5 L/mg. Adsorption kinetics fit well with the pseudo-second-order reaction equation. The activation energy (Ea) is determined to be 57.9 kJ/mol, providing the evidence of chemical nature of the reaction involving phosphate ions on the surface of PEI/La2O3/PP. The PEI/La2O3/PP adsorbent can reduce the phosphate concentration in tap water to below 0.01 mg/L, leading to a reduction in Escherichia coli concentration from approximately 10,000 CFU/mL to around 10 CFU/mL. The survival rates of Escherichia coli in a multi-nutrient environment are higher than in a single phosphate source environment. Our research provides a new feasible approach for ensuring microbial water quality safety in household water purifiers.

Impacts of Agricultural Practices (Pesticides and Fertilizers) and Amalnala Stream on Amalnala Lake in Gadchandur, India

Amalnala lake is situated in the Gadchandur town of Chandrapur district in Maharashtra, India. The lake water was turning green in colour in the month of september. This study gives an insight into the causes and factors responsible for the greening of the lake adjacent to Manikgarh limestone mine in the month of September. It was noted that, phosphate concentration in lake water showed rise after July (2020, 2021) and peaked in August (2020, 2021). The phosphates were mainly contributed by organophosphate pesticides such as monocrotophos, profenofos, and chlorpyrifos, which were identified by liquid chromatography triple quadrupole mass spectrometry (LC MS/MS). The rise in phosphates showed complete correlation with the rainfall and chlorophyl a (chl a) content in September (2020, 2021). Similarly, the nitrate concentration of the lake showed peak in August (2020, 2021) followed by the rise in chl a content in September (2020, 2021). Chemical oxygen demand (COD) and biological oxygen demand (BOD) of the lake was calculated and represented in terms of COD/BOD. The COD/BOD were highest in September (2020, 2021). Positive correlation was observed between the pH, total dissolved solids, and electrical conductivity of Amalnala Lake and Amalnala Stream which flows into the lake. This stream mainly carries the contaminants from open cast Manikgarh limestone mines to Amalnala Lake. Chl a was mainly contributed by two dominant species of cyanobacteria, Phormidium species CCALA 726 which was identified by 16S rRNA sequencing and Microcystis aeruginosa which was identified by using the keys given by Desikachary and Komarek and Anagnostidis. This study thus concluded that the pesticides, nitrates, and Amalnala Stream contributed in the growth of cyanobacteria which causes the greening of the lake.

Cyclic Voltammetry Method for Analysis of Phosphate Concentration in Water

Phosphate is a nontoxic element but a limiting element for productivity. Several methods have been established to analyze the phosphate concentration in water. This study aims to analyze phosphate concentration in water using the voltammetry method using cyclic voltammetry. Cyclic voltammetry is an electroanalytical method that measures the current outcome of oxidation-reduction reactions in response to the potential. The current outcome is directly proportional to the phosphate concentration in the solution. The calibration curve was formed from the KH2PO4 standard solution using concentrations of 0.1 mg/L, 0.2 mg/L, 0.4 mg/L, 0.8 mg/L, and 1.6 mg/L. The voltammogram showed that the analyte does not have an anode peak current (Ipa), which means that the analyte solution did not have an oxidation reaction, so the cathode peak current (Ipc) value was used. Based on the calibration curve, the linear regression graph with a straight-line equation is y = -0,00000645632x - 0,000208737 with R2 of 0,99737. Meanwhile, this cyclic voltammetry method was validated by calculating the LOD and LOQ values; the results are 0.1034 mg/L and 0.3134 mg/L, respectively. Hence, based on the analysis of phosphate concentration in water samples, this method works satisfactorily and is suitable for routine analysis because of its advantages.

Nutrient dynamics, carbon storage and community composition on artificial and natural reefs in Bali, Indonesia

Artificial reefs are now commonly used as a tool to restore degraded coral reefs and have a proven potential to enhance biodiversity. Despite this, there is currently a limited understanding of ecosystem functioning on artificial reefs, and how this compares to natural reefs. We used water sampling (bottom water sampling and pore water sampling), as well as surface sediment sampling and sediment traps, to examine the storage of total organic matter (as a measure of total organic carbon) and dynamics of dissolved inorganic nitrate, nitrite, phosphate and ammonium. These biogeochemical parameters were used as measures of ecosystem functioning, which were compared between an artificial reef and natural coral reef, as well as a degraded sand flat (as a control habitat), in Bali, Indonesia. We also linked the differences in these parameters to observable changes in the community structure of mobile, cryptobenthic and benthic organisms between habitat types. Our key findings showed: (1) there were no significant differences in inorganic nutrients between habitat types for bottom water samples, (2) pore water phosphate concentrations were significantly higher on the artificial reef than on both other habitats, (3) total organic matter content in sediments was significantly higher on the coral reef than both other habitat types, and (4) total organic matter in sediment traps in sampling periods May and September were higher on coral reefs than other habitats, but no differences were found in November. Overall, in terms of ecosystem functioning (specifically nutrient storage and dynamics), the artificial reef showed differences from the nearby degraded sand flat, and appeared to have some similarities with the coral reef. However, it was shown to not yet be fully functioning as the coral reef, which we hypothesise is due its relatively less complex benthic community and different fish community. We highlight the need for longer term studies on artificial reef functioning, to assess if these habitats can replace the ecological function of coral reefs at a local level.

Microalgae-mediated tandem culture of shrimp and bivalve: an environmental and health co-benefits solution for phosphorus recovery and emission reduction

Phosphorus (P) accumulation in aquaculture systems is damaging our environment beyond acceptable levels. Devising strategies to potentially recover P from aquaculture systems in a reusable bioresource form is paramount and aligns with circular economy policies. In this study, we constructed two culture models, monoculture (Mon) and tandem culture (Tan), using Exopalaemon carinicauda and Mercenaria mercenaria. By monitoring the performance of rearing organisms, P dynamic patterns, and pollutant emissions, we found that: i) Compared to the Mon system, the Tan system demonstrated no differences in the performance of E. carinicauda and M. mercenaria, suggesting that the Tan model was viable in terms of fishery yield; ii) P in the Tan system could be efficiently recovered and removed from water and sediment, as indicated by the lower phosphate concentration in water (0.01 mg L−1), and the decrease in labile P in surface sediment (from 0.04 to 0.02 mg L−1). A combination of assimilatory and dissimilatory processes, mediated by phototrophic (bait-microalgae) and heterotrophic organisms (bivalves), appeared to be the primary mechanism for P utilization and removal; iii) The Tan system reduced pollutant emissions four times lower than the Mon system due to its minimal tailwater discharge (10%, 230 L). The emissions of total P, phosphate, total organic carbon, ammonium, and chemical oxygen demand from the Tan systems were 19 mg m−2 d−1, 2 mg m−2 d−1, 2 g m−2 d−1, 38 mg m−2 d−1, and 11 g m−2 d−1, respectively, 1.3, 1.7, 1.4, 1.3, and 1.2 times lower than those from the Mon systems. The eco-friendly Tan culture model fully exploited the resources of pond culture, a solution with environmental and health co-benefits for P recovery and emission reduction.

A novel electric spark precipitation and electrospinning strategy to prepare cerium hydroxide nanocomposite for phosphate uptake from aqueous solutions

Phosphorus is a main cause of eutrophication in water bodies, the use of adsorbents to reduce phosphate concentration in water is considered an effective way to combat eutrophication. Herein, a new and effective strategy for phosphorus removal with a PAN based cerium hydroxide nanocomposite (CHP) is shown, we combined electrospinning and spark ablation techniques, where an electrospun fiber membrane polyacrylonitrile (PAN) was used as a carrier, spark ablation produced clean nano-cerium aerosol embedded in it as the active ingredient, and a combined hydrothermal method to develop PAN based cerium hydroxide nanocomposite (CHP), the crystal size of ceria nanoparticles was 120–210 nm. CHP can capture phosphate selectively with a maximum adsorption capacity of 86.7 mg·P/g, which is higher than that for most cerium-based adsorbents and is easily separated from the liquid with high efficiency and economy. The adsorption mechanism showed that CeO2 plays an important role in phosphorus adsorption through oxidation, reduction, and ligand exchange. Compared to mesoporous structures, fibrous structures are more favorable for reducing the aggregation of nanoparticles (NPs) and adsorption of large phosphate species. The spark ablation method immobilized active cerium dioxide NPs very stably on the fiber with high efficiency and limited environmental impact. In conclusion, our results have promising applications for lake eutrophication treatment.

Tonian Carbonates Record Phosphate‐Rich Shallow Seas

AbstractThe early‐middle Neoproterozoic is thought to have witnessed significant perturbations to marine P cycling, in turn facilitating the rise of eukaryote‐dominated primary production. However, with few robust constraints on aqueous P concentrations, current understanding of Neoproterozoic P cycling is generally model‐dependent. To provide new geochemical constraints, we combined microanalytical data sets with solid‐state Nuclear Magnetic Resonance, synchrotron‐based X‐ray Absorption Near Edge Structure spectroscopy, and micro‐X‐ray Fluorescence imaging to characterize the speciation and distribution of P in Tonian shallow‐water carbonate rocks. These data reflect shallow water phosphate concentrations 10–100× higher than modern systems, supporting the hypothesis that tectonically‐driven influxes in P periodically initiated kinetically‐controlled CaCO3 deposition, in turn destabilizing marine carbonate chemistry, climate, and nutrient inventories. Alongside these observations, a new compilation and statistical analysis of mudstone geochemistry data indicates that, in parallel, Corg and P burial increased across later Tonian continental margins until becoming decoupled at the close of the Tonian, implicating widespread N‐limitation triggered by increasing atmospheric O2.

Investigation of Impact of Phosphate Fertilizer Applied to Paddy Fields on Water Quality of Nearby Reservoirs

Phosphorous (P) is an essential element to plant growth and development necessitating P fertilizer applications for agricultural crops for better yields. Paddy, the main food crop of Sri Lankans is a fertilizer intensive crop where phosphorus nutrition is achieved via triple super phosphate applications. Since water circulating system of paddy fields are connected to other water bodies this soluble P can contaminate the nearby waterbodies. To detect the extent of P fertilizer leaching from paddy fields, a lysimeter experiment was carried out in the Low Country Intermediate zone, Sri Lanka for four consecutive growing seasons from 2015 to 2016. Paddy fields under two management practices; control run-off and continual run-off conditions were selected for the study. The farmers practice the Department of Agriculture recommended fertilizer application schedules. Lysimeters were placed in a Randomized Complete Block Design with triplicates at upper and lower ends of the gradient of the each site. Water samples were collected below the root zone, at a depth of 30 cm, irrigated, run-off, nearby water reservoirs and analyzed for water soluble of phosphate. The highest concentration of total phosphate in leached water (0.88 mg/L) did not exceed the drinking water standard threshold level of 2 mg/L of Phosphate. The quantified leached total Phosphate amount for controlled run-off condition and continual run-off condition were 0.49 ± 0.10 kg/ha and 0.46 ± 0.04 kg/ha, respectively without statistically significant differences. It represented 2% of the applied P fertilizer content of both sites. This indicates that paddy cultivation under both the conditions does not pose a threat to water quality of the nearby water bodies if the farmers adhere closely to the Department of Agriculture recommended fertilizer schedules.

The Release of Pollutants through the Bleeding of Cemented Phosphogypsum Backfill: Link to Protocols for Slurry Preparation

The present study investigated the effects of protocols for slurry preparation on the release of pollutants into bleeding water from cemented phosphogypsum (PG) backfill. Backfill slurry was prepared using four different protocols in which different parameters varied, including binder/PG ratio, solid concentration, binder type and mixing procedure. The concentrations of phosphate, fluoride and sulfate and the pH values of the obtained bleeding water were measured. The results demonstrated that the slurry preparation protocols affected the quantities of pollutants through the concentrations of pollutants in bleeding water and the bleeding rate. On the one hand, the binder/PG ratio was the key factor influencing the concentrations of all pollutants in bleeding water. Comparatively speaking, the binder type and mixing procedure had an obvious influence on the fluoride concentration but had little influence on the phosphate and sulfate concentrations in the bleeding water. On the other hand, the protocols for slurry preparation affected the bleeding rate by determining the water retention and water content of the backfill slurry. The most effective protocol for slurry preparation for cemented PG backfill could reduce the bleeding rate and enhance the immobilization of pollutants, minimizing the phosphate concentration in bleeding water to below 0.2 mg/L. However, it appeared that the fluoride concentration was still tens of milligrams per liter (over the limit of 10 ten milligrams per liter), to which attention should be paid.

A novel La(OH)3 decorated co-graft tannin and polyethyleneimine co-coating magnetic adsorbent for effective and selective phosphate removal from natural water and real wastewater

Our study synthesized La(OH)3 decorated co-graft tannin and polyethyleneimine (PEI) co-coating magnetic composites (La@TP@Fe3O4). Dual organic modification with co-grafted tannin and PEI can significantly enhance the material's charge density, allowing La@TP@Fe3O4 to maintain a high phosphate adsorbability at a wide pH range (3.0–11.0). La@TP@Fe3O4 achieved a maximum theoretical phosphate adsorption capacity of 363.64 mg/g at 25 °C under pH 3.0 and was consistent with the Langmuir model, reaching adsorption equilibrium in 20 min. Phosphate adsorption was less affected by various coexisting ions with >90% of phosphate removal maintained after five cycles. La@TP@Fe3O4 could be quickly separated by magnetic force with negligible La and Fe leakages. Besides electrostatic attraction, inner-sphere complexation and weak precipitation contributed to phosphate uptake on La@TP@Fe3O4, as demonstrated by X-ray absorption near edge structure (XANES) analysis. Importantly, low La@TP@Fe3O4 doses could quickly decrease phosphate concentrations in natural water and wastewater to meet regulatory requirements, thus highlighting the potential applicability of La@TP@Fe3O4 for phosphate removal.

Determination of phosphate levels in the southern part of Al-Hammar marsh water by flow injection analysis

Flow Injection Analysis (FIA) was applied to determine phosphate concentration in water of the southern part of Al-Hammar marsh water from July 2007 to July 2008. A linear line was obtained over the range 0.25- 1.75 μg/ml of phosphate with regression coefficient for seven points is 0.9999. The detection limit was 0.075 μg/ml with % R.S.D for ten replicate analysis of 1.0 μg/ml phosphate is 0.511% and the dispersion coefficient in the flow system is 5.4. The samples can be analyzed at rates exceeding 72 sample per hour .It was noted that phosphate concentration ranged 0.295 - 1.450 μg/ml, whereas the maximum phosphate concentration was recorded in spring 2008 and the minimum in autumn 2008.
 

Global Patterns and Controls of Nutrient Immobilization on Decomposing Cellulose in Riverine Ecosystems

AbstractMicrobes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low‐nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low‐nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature‐dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter.

Field Determination of Phosphate in Environmental Water by Using a Hand-Powered Paper Centrifuge for Preconcentration and Digital Image Colorimetric Sensing.

Phosphate concentration in natural water has been used as a water quality indicator, as it is one of the major nutrients for aquatic plants. However, the traditional phosphomolybdenum blue (PMB) method has limited sensitivity for visual or camera-based detection, leading to underestimation of the phosphate concentration. We present an ultralow-cost, rapid field preconcentration and digital image colorimetric sensing of low-concentration phosphate method for water analysis. A novel hand-powered paper centrifuge (paperfuge) is used for sample preparation and preconcentration. This paperfuge is made of two circular paper discs and a string. Six centrifuge tubes (CTs) originally used as glue dispensing tips with a sample capacity of ∼230 μL, are loaded on the paperfuge. After sampling, phosphate in the water sample is reacted to form PMB. Then, the reacted sample is drawn into a CT using an autopipette before the CT bottom is sealed by glue. After Oasis® HLB sorbents are added through the top of the CT, the CT top is also sealed with glue. The HLB sorbents adsorb PMB and are accumulated in the CT tip through centrifugation. The CT tips are cut and analyzed with the ImageJ software. It was found that the blue color intensity of sorbents is in a linear relationship to the phosphate concentration, with a linear range of 0–5 μM (r2 = 0.9921) and limit of detection of 0.19 μM. In addition, this method has been applied to in-field water analysis. The results are in agreement with the standard PMB method.

Mitigation of CyanoHABs Using Phoslock® to Reduce Water Column Phosphorus and Nutrient Release from Sediment.

Cyanobacterial blooms can be stimulated by excessive phosphorus (P) input, especially when diazotrophs are the dominant species. A series of mesocosm experiments were conducted in a lake dominated by a cyanobacteria bloom to study the effects of Phoslock®, a phosphorus adsorbent. The results showed that the addition of Phoslock® lowered the soluble reactive phosphate (SRP) concentrations in water due to efficient adsorption and mitigated the blooms. Once settled on the sediments, Phoslock® serves as a barrier to reduce P diffusion from sediments into the overlying waters. In short-term (1 day) incubation experiments, Phoslock® diminished or reversed SRP effluxes from bottom sediments. At the same time, the upward movement of the oxic–anoxic interface through the sediment column slightly enhanced NH4+ release and depressed N2 release, suggesting the inhibition of nitrification and denitrification. In a long-term (28 days) experiment, Phoslock® hindered the P release, reduced the cyanobacterial abundance, and alleviated the bloom-driven enhancements in the pH and oxygen. These results suggest that, through suppression of internal nutrient effluxes, Phoslock® can be used as an effective control technology to reduce cyanobacteria blooms common to many freshwater systems.

A Colorimetric Dip Strip Assay for Detection of Low Concentrations of Phosphate in Seawater.

Nutrient pollution remains one of the greatest threats to water quality and imposes numerous public health and ecological concerns. Phosphate, the most common form of phosphorus, is one of the key nutrients necessary for plant growth. However, phosphate concentration in water should be carefully monitored for environmental protection requirements. Hence, an easy-to-use, field-deployable, and reliable device is needed to measure phosphate concentrations in the field. In this study, an inexpensive dip strip is developed for the detection of low concentrations of phosphate in water and seawater. In this device, ascorbic acid/antimony reagent was dried on blotting paper, which served as the detection zone, and was followed by a wet chemistry protocol using the molybdenum method. Ammonium molybdate and sulfuric acid were separately stored in liquid form to significantly improve the lifetime of the device and enhance the reproducibility of its performance. The device was tested with deionized water and Sargasso Sea seawater. The limits of detection and quantification for the optimized device using a desktop scanner were 0.134 ppm and 0.472 ppm for phosphate in water and 0.438 ppm and 1.961 ppm in seawater, respectively. The use of the portable infrared lightbox previously developed at our lab improved the limits of detection and quantification by a factor of three and were 0.156 ppm and 0.769 ppm for the Sargasso Sea seawater. The device’s shelf life, storage conditions, and limit of detection are superior to what was previously reported for the paper-based phosphate detection devices.

Using modified quartz sand for phosphate pollution control in cemented phosphogypsum (PG) backfill

Cemented phosphogypsum (PG) backfill technology is a new alternative for massive disposal of PG as well as to provide a safe underground mining workplace. However, phosphate in bleeding water and leachates of backfill might be discharged into its surrounding environment. To reduce phosphate pollution with source control concept, modified quartz sand (MQS) was used during the mixing of backfill slurry. Experimental results showed that when the MQS was added in the backfill slurry, phosphate concentrations in the bleeding water decreased significantly with mixing time, which was attributed to a synergetic effect of MQS adsorption and binder hydration. As a result, phosphate concentration in the MQS-added backfill could be reduced to 0.3 mg/L in 20 min, therefore ensuring the phosphate concentration in bleeding water below the first grade discharge standard (0.5 mg/L, GB 8978–1996) in a short mixing time. In comparison, the time needed for control group to meet this discharge standard was over 60 min. Then, through phosphate adsorption static experiments, it is found that the MQS adsorption process was in accordance with the Langmuir model and pseudo-second-order kinetic model, illustrating that the MQS was a monolayer chemical adsorption for phosphate in the cemented PG backfill system. Furthermore, by monitoring the leachates of backfill with and without MQS, the phosphate concentrations were always less than 0.05 mg/L, indicating that the addition of MQS had no adverse effect on the phosphate release in the long run. Besides, the addition of MQS can promote hydration process and optimize aggregate gradation to enhance strength development of backfill.

Unravelling phosphate adsorption on hydrous ferric oxide surfaces at the molecular level

The thorough understanding of the adsorption mechanism of phosphate on hydrous ferric oxides is necessary to deal with the environmental issues related to high phosphate concentrations in soils and open water. In this work, we consider three different adsorption geometries (monodentate and bidentate chemisorption and physisorption) and calculate the adsorption geometries and related adsorption energies at optPBE-vdW level. Using the Maxwell-Boltzmann distribution, it is estimated that about 83% of the phosphate molecules is in a monodentate chemisorption configuration, while 17% is physisorbed. Furthermore, theoretical infra-red spectra are obtained and compared to equivalent experimental spectra, supporting the conclusion that mainly monodentate chemisorption and physisorption occur. Most interestingly, a weighed infra-red spectrum is then calculated, using the weights from the Maxwell-Boltzmann distribution, showing a very good comparison with the experimental spectra.

Influence of phosphate dosing on biofilm development on Drinking Water Distribution Systems infrastructure surfaces

Phosphate is added to drinking water by UK water companies as a treatment to prevent the corrosion and metal leaching, like lead, in pipes. However, phosphate is a nutrient for microorganisms, and it can favour biofilm formation in Drinking Water Distribution Systems (DWDS), which can alter the water quality and safety. This study analyses the effect of phosphate addition on biofilm formation over different materials and its consequences for drinking water quality by i) using controlled experimental pipeline facility representative of a real-scale DWDS with high-density polyethylene coupons and ii) using a small-scale DWDS biofilm reactors with lead coupons. Biofilms developed over one month were exposed to the effect of different phosphate dosing and compare with UK normal water phosphate concentrations. During the experiment, physico-chemical analysis of water and microbial analysis of biofilms was carried out. Sequencing analysis of the 16s rRNA gene, from extracted DNA obtained from biofilms, provided information on any bacterial changes, and Scanning Electron Microscopy gave information about the biofilm organization. The results indicate that microorganisms find more difficult to establish and develop biofilms under high phosphate dosing, resulting in biofilms with less cells. Also, some physico-chemical parameter seems to be affected by phosphate dosing, like chlorine and lead. It is expected that differences in the biofilm community will be found depending on phosphate dosing. This study will provide information on the effect of phosphate on biofilm development in different pipes materials, which will facilitate to adjust an optimal phosphate dose to prevent plumbosolvency in DWDS.