Complete Phosphate Removal Research Articles

Development of a bionanotechnological phosphate removal system with thermostable ferritin

Phosphate removal to ecologically desired levels of <0.01 mg/L is currently dependent on large overdosing of metal salts and production of large amounts of chemical sludge. The present study focuses on the development and performance of a new bionanotechnological phosphate removal system, based on sorption of oxoanions by nanoscale ferric iron particles stabilized within thermostable ferritin from the hyperthermophilic archaeon Pyrococcus furiosus (PfFrt). Laboratory studies show that this thermostable protein nanocage has fast kinetics for phosphate uptake at very low concentrations by catalytic oxidation of iron. In this study we demonstrate essentially complete phosphate removal with a capacity of approximately 11 mg/g PfFrt. Ferritin can easily be immobilized and is amenable to fast and efficient regeneration, making recovery of phosphate possible. The phosphate removal process with PfFrt is, due to its high affinity, able to reach ecologically desired phosphate levels and in addition it is cost competitive with existing techniques.

Phosphate removal from source separated urine by electrocoagulation using iron plate electrodes

The aim of this study was to investigate the effects of current density, gap between electrodes, urine dosage, dilution and hydrolysis on phosphate removal from human urine by electrocoagulation technique using iron as electrodes. It was shown that, although a high current density and a long electrolysis time favored the removal of phosphate, an appropriate value for these two parameters can be obtained by taking into account the consumption of energy and iron in addition to P removal. In this study, current density 40 mA/cm2 and electrolysis time 20 min were shown to be optimal for 1.0 L pure urine to achieve nearly a complete removal (98%) efficiency of phosphate under the conditions of electrode area 160 cm2, the stirring speed 150 rpm, and the gap between electrodes 5 mm. Increase of gap between electrodes had little effect on phosphate removal, although it increased the energy consumption dramatically. The use of a high urine dosage reduced the efficiency of phosphate removal but increased the amount of removed phosphate. When pure urine was diluted with tap water, use of a higher tap water proportion for dilution expedited the electrolysis to achieve a nearly complete removal of phosphate in solution, but dilution caused the increase in energy consumption. It was also revealed that the hydrolysis of urine prior to electrocoagulation treatment impeded phosphate removal.

Phosphate removal in marine electrolytes by zeolite synthesized from coal fly ash

The aim of this study was to examine the influence of seawater electrolytes on removal of phosphate by zeolite synthesized from fly ash (ZFA). A low-calcium ZFA was initially saturated with Na +, Mg 2+, Ca 2+, Al 3+, and Fe 3+. Al- and Fe-ZFA showed nearly complete removal of phosphate regardless of the major seawater electrolytes, pH, and salinity. This result was explained primarily on the basis of the adsorption mechanism through the formation of inner-sphere complexes. The remaining ZFAs showed lower phosphate removal performance, in general with the order of Ca-ZFA > Mg-ZFA > Na-ZFA. Compared with pure water, increase of electrolyte concentration or salinity initially enhanced phosphate uptake but then reduced phosphate removal. The individual presence of major seawater electrolytes all facilitated the retention of phosphate, with CaCl 2 being the most effective. The mechanism for phosphate removal by Na-, Mg-, and Ca-ZFA was due mostly to precipitation. Repeated batch equilibration experiments indicated that, compared with pure water, ZFA had greater sorptive capacity for phosphate (except for Ca-ZFA, whose capacity decreased slightly) and had lower reversibility for sorbed phosphate in marine electrolytes. In conclusion, our results suggest that presence of seawater electrolytes had roughly no effect, or even positive effects, on the removal of phosphate by ZFA.

Removal of phosphate from secondary effluent with Fe 2+ enhanced by H 2O 2 at nature pH/neutral pH

Removal of phosphate in secondary effluents was investigated in presence of Fe 2+/H 2O 2. The effect of H 2O 2-dose, Fe-dose and initial phosphate concentration were assessed. The results indicated that Fe 2+/H 2O 2 could greatly increase the removal of phosphate compared with those achieved by Fe 2+ alone. For initial phosphate concentration of 0.97–3.75 mg P/L, phosphate removal rates of 50–60% were observed at 1:1 molar addition of Fe(II). However, a 125% excess of Fe-dose was necessary for complete phosphate removal. The experimental data demonstrated that removal of phosphate with Fe 2+/H 2O 2 was higher than that observed with ferric coagulation alone. This fact suggested that in situ formed Fe(III) having much affinity for ligand phosphate. Chemical co-precipitation was considered as the dominant mechanism about phosphate removal in presence of Fe 2+/H 2O 2. The electron paramagnetic resonance (EPR) spectra tests in secondary effluents showed that Fe 2+/H 2O 2 could produce an increasing hydroxyl radical concentration with a decrease in both H 2O 2 dosage and phosphate concentration. Fe 2+/H 2O 2 had the potential to be utilized for removal of phosphate due to the lower cost and the higher phosphate removal capability.

Phosphorus immobilization in Lake Głęboczek following treatment with polyaluminum chloride

Abstract In 2001-2003, a survey was conducted of the effectiveness of restoration in the heavily eutrophic polymictic Lake Głęboczek, located in Tuchola. The application of the phosphorus inactivation method with polyaluminum chloride PAX 18 resulted in the complete removal of phosphates, and in a considerable (up to 50-60%) reduction of total phosphorus in the lake water. The sorptive capacity of the bottom sediments was enhanced after the restoration, particularly in the top layer (0-5 cm). An increase of the aluminum content and of mineral forms of phosphorus was observed, mainly the aluminum-bound fraction (at its greatest, by over 330%). The amount of mobile phosphorus in the sediments decreased by 40%. The evidence of the durable immobilization of phosphorus in the aquatic ecosystem was the limited phosphorus release from the bottom sediments. This was confirmed by a significant decrease of total phosphorus in the interstitial waters (from 4-6 mg dm-3 to 2-3 mg dm-3), and by a practically complete removal of phosphates from the near-bottom waters.

Desalination of domestic wastewater effluents: phosphate removal as pretreatment

Water shortage has become a global issue and not only a problem relevant to arid zones. In the past decade desalination of sea and brackish water has been found to be a technically and economically acceptable solution for water shortage. More recently, desalination of wastewater effluents has also begun to be considered for sustainable water reclamation and reuse. Performance of membrane desalination processes, such as reverse osmosis (RO), is restricted by different fouling and clogging constraints, including inorganic scaling as well as organic fouling and biofouling. Utilization of effluents for desalination introduced to the membrane systems new feed water characteristics with reduced salinity but higher concentration of dissolved organic matter and predominant inorganic ions that are less common in sea water. Phosphate scaling is found to be a main obstacle for effluents desalination, mainly due to the lack of appropriate antiscalants to cope with its precipitation, especially at high recovery rates. This work was aimed to study the chemical coagulation of phosphate from wastewater effluents as a pretreatment for RO desalination. Based on preliminary jar test experiments, sodium aluminate (SAL) at concentrations of 20–30 mg/L, was found as an efficient coagulant for phosphate and turbidity reduction. SAL coagulation was tested either as simultaneous phosphate removal during membrane bioreactor (MBR) treatment or as postremoval of phosphate from secondary effluents from activated sludge process, followed by microfiltration. Both alternative treatments resulted in almost complete phosphate removal (≥99%). Batch desalination of both kinds of pretreated effluents showed also that calcium carbonate was a second scaling agent upon phosphate removal. The simultaneous MBR-coagulation, which in addition to complete phosphate removal displayed a significant reduction of alkalinity (75%), produced higher quality effluents and reduced the effect of calcium carbonate scaling, as compared to the post-coagulation of secondary effluents. Furthermore, the simultaneous MBR-coagulation process showed no detrimental effects on the MBR membrane performance or on the biological activity and avoided the need of an additional sedimentation or filtration step prior to RO. In conclusion, the MBR-chemical coagulation process seems to be a technically feasible pretreatment of domestic effluents for further desalination.

Enhanced biological phosphorus removal for high-strength wastewater with a low rbCOD:P ratio

In order to assess the feasibility of enhanced biological phosphorus removal (EBPR) for dairy processing wastewater, which in New Zealand have rbCOD:P ratios that can be as low as 13:1, a sequencing batch reactor treating a synthetic wastewater with a COD VFA of 800 mg/l (representing a dissolved air flotation (DAF) treated, pre-fermented dairy wastewater with a raw COD of 3000 mg/l) was operated at COD:P ratios of 25:1, 15:1 and 10:1. Full (>99%) phosphate removal was achieved for COD:P loadings of 25:1 and 15:1. The trial using 10:1 COD:P loading showed less consistency but still achieved 82% phosphate removal. Based on further analysis of the final trial this study proposes that the minimum COD:P loading for complete phosphate removal is 13:1 indicating that EBPR could indeed be feasible for effective treatment of dairy processing wastewaters. With regard to the type of COD consumed, propionate was found to be favoured over acetate as a substrate. Further research into increasing the propionate content of pre-fermented dairy wastewaters is suggested.

Evaluation of steel slag for organic and inorganic removals in soil aquifer treatment

Basic oxygen furnace slag (BOFS) was evaluated as an additive to the soil aquifer treatment (SAT) in the laboratory column tests and the characteristic behaviors of organics and inorganic compounds through the columns were examined with both natural soil and the mixture of soil and slag. It was obvious that the slag could contribute more removals of DOC under both unsaturated and saturated conditions of SAT operation possibly due to its larger surface area. The molecular weight fractions of less than 1 kDa was greatly degraded during the unsaturated SAT operation by biodegradation and the molecular weight fractions of higher than 10 kDa was also significantly reduced after unsaturated SAT by adsorption. It was indicated that the steel slag seemed to play an effective role in reducing the refractory organics during saturated SAT. The macroporous XAD resin isolations showed the increase of hydrophilic fractions with a decrease in the hydrophobic and transphilic fractions through SAT. The use of steel slag resulted in adverse effect on the nitrification due to high pH (about 11) and the relative redox potential measurement showed that the steel slag provided a non-oxidative environment in SAT columns. Almost complete removal of phosphate was achieved during unsaturated and saturated SAT operations with a relatively low hydraulic loading rate and effective adsorption by steel slag. A 20–30% increase of sulfate was observed in slag-containing unsaturated columns whereas the saturated 100% slag columns exhibited 68% decrease of sulfate concentration.

Why the limiting nutrient differs between temperate coastal seas and freshwater lakes: A matter of salt

Comparison of bottom‐water chemistry in the marine‐limnic habitat gradient shows greater phosphorus availability in marine waters, primarily because of enhanced iron sequestration by sulfide. In the oxidative hydrolysis of iron and the concomitant precipitation of phosphate, a minimum of two iron atoms are needed to precipitate one phosphate molecule (Fe : P = 2). However, dissolved Fe : P &lt; 2 predominates in anoxic marine waters, therefore leaving some phosphate in solution after oxygenation because of a shortage of dissolved iron for phosphate coprecipitation by iron oxyhydroxide. In contrast, anoxic bottom waters in most freshwater lakes show Fe : P &gt; 2, allowing almost complete phosphate removal on oxygenation. This difference is a consequence of the high sulfate content of sea salt, and a main reason why nitrogen normally limits net primary production in temperate coastal waters, in contrast to the predominant phosphorus limitation of near‐neutral lakes.

Endoglucanase V and a phosphatase from Trichoderma viride are able to act on modified exopolysaccharide from Lactococcus lactis subsp. cremoris B40

EPS B40 from Lactococcus lactis subsp. cremoris consists of a repeating unit of →4)-β- d-Glc p-(1→4)-[α- l-Rha p-(1→2)][α- d-Gal p-1-PO 4-3]-β- d-Gal p-(1→4)-β- d-Glc p-(1→. A phosphatase from Trichoderma viride was able to release phosphate, but only after removal of rhamnosyl and galactosyl residues by mild CF 3CO 2H treatment. Purified endoV from T. viride was able to act on the backbone of the polymer, but only if rhamnosyl substituents and phosphate had been removed. After complete removal of phosphate and partial removal of rhamnosyl residues by HF treatment, incubation with endoV resulted in a homologous series of oligomers. Purification of these oligomers and subsequent characterisation by NMR demonstrated that endoV was able to cleave the β-(1→4) linkage between two glucopyranosyl residues when the galactopyranosyl residue towards the nonreducing end is unsubstituted. The mode of action of endoV on HF-treated EPS B40 is discussed on the basis of the subsite model described for endoV [J.-P. Vincken, G. Beldman, A.G.J. Voragen, Carbohydr. Res., 298 (1997) 299–310].

Polyphosphate-accumulating and denitrifying bacteria isolated from anaerobic-anoxic and anaerobic-aerobic sequencing batch reactors

In this study, phosphate-accumulating bacteria achieved complete phosphate removal in two different systems: an anaerobic-anoxic sequencing batch reactor and an anaerobic-aerobic sequencing batch reactor. This result shows that phosphate-accumulating bacteria in the A2 SBR can use nitrate as terminal electron acceptor instead of oxygen. Phosphate-accumulating bacteria accumulated phosphate with a rates between 30 and 70 mg P/L/h in the A/O SBR and between 15 and 32 mg P/L/h in the A2 SBR. Twenty denitrifying isolates were screened from A2 SBR and nine from A/O SBR. Identification of these isolates by the Biolog system and the API 20 NE identification kit revealed that the most active denitrifiers in both SBRs reactors were species of Ochrobactrum, Pseudomonas, Corynebacterium, Agrobacterium, Aquaspirillum, Haemophilus, Xanthomonas, Aeromonas, and Shewanella. The most active phosphate accumulating and denitrifying bacteria were identified as Agrobacterium tumefaciens B, Aquaspirillum dispar, and Agrobacterium radiobacter. This study showed that the active phosphate accumulating-bacteria were also the most efficient denitrifying bacteria in both reactors.

Phosphate removal from aqueous solutions using red mud wasted in bauxite Bayer's process

Abstract The red mud wasted from the Guinean bauxite refinery was studied for phosphate removal from model aqueous solutions of potassium orthophosphate (OPh) and sodium tripolyphosphate (TPPh). The red mud has been treated with concentrated sulphuric acid. After filtration of the acid suspension, the activated mud was washed (pH 7), dried and ground to powder. The influence of acid to mud ratio, and contact time between them, on the extent of phosphate removal has been studied. The importance of the preliminary acid treatment of the red mud was established by parallel experiments using both raw and activated red mud. The dose of red mud added to the aqueous solutions, the contact time between them and initial concentrations of phosphates in the solutions for the complete removal of phosphates have been determined. Regression models describing the process for both types of phosphate solutions have been deduced.

Removal of phosphate from aqueous and wastewater samples using aluminum salts

Abstract Batch laboratory scale experiments were conducted to investigate the removal of phosphate from aqueous and municipal wastewater samples by addition of Al2(SO4)3.18H2O. The effect of pH, Al‐dose and initial phosphate concentration were assessed. Optimum phosphate removal, 51% for stoichio‐metric Al‐dose, was observed at pH 6. However, a 151% excess of Al‐dose was necessary for complete phosphate removal. Phosphate removal from municipal wastewater samples was slightly higher than that observed for the aqueous solutions. A chemical precipitation mathematical model was developed and tested with the available experimental data. The model considered 16 chemical equilibrium equations and the mass balance equations for aluminum and phosphorus. The chemical equilibrium equations included: (1) The co‐precipitation of two solid phases containing aluminum and phosphorus. (2) The formation of 9 aluminum containing soluble complexes and polymers. (3) The formation of 2 aluminum and phosphorus containing compl...

The relationship of biomass to phosphate uptake by Acinetobacter junii in activated sludge mixed liquor

The involvement of Acinetobacter in biological excess phosphate removal from the activated sludge process is widely accepted, though its role is not yet clearly defined. To better understand why activated sludge systems remove phosphate, different cell concentrations of Acinetobacter junii (10 4, 10 5, 10 6, 10 7, 10 8 cells·ml −1 initial biomass) were used as inoculum in a mixed liquor medium containing sodium acetate. The phosphate uptake capacity was dependent on the biomass concentration. Low initial biomass concentrations triggered the release of phosphate once transferred into the mixed liquor. Release of phosphate increased during active growth and uptake occurred when cells reached the stationary growth phase. High initial biomass concentration of Acinetobacter junii (10 8 cells·ml −1) resulted in uptake of phosphate during the entire duration of the experiment leading eventually to complete phosphate removal.

Effects of phosphate residues on the excellent emulsifying properties of phosphoglycoprotein phosvitin.

The effects of phosphate residues in phosvitin on its emulsifying properties were investigated. The emulsifying properties, especially the emulsion stability, of phosvitin were much superior to those of bovine serum albumin which is an excellent emulsifier. The emulsifying activity and emulsion stability of phosvitin were greatly decreased by the partial removal of phosphate with phosphatase and by the complete removal of phosphate with alkaline treatment. In addition, the emulsifying properties were decreased by the blocking of phosphate in phosvitin with calcium ion. These results suggest that the electrostatic repulsive force of phosphate in phosvitin significantly affects its emulsifying properties.

Aquacultural approaches to recycling of dissolved nutrients in secondarily treated domestic wastewaters—I Nutrient uptake and release by artificial food chains

Wastewater based artificial food chains composed of sequential monocultures of a suspended unicellular green alga, of an herbivorous cladoceran crustacean, and of an herbivorous or a carnivorous teleost fish and of filamentous green algae were studied in an effort to find efficient, potentially economically viable mechanisms for the biological capture (tertiary treatment) of nutrients (especially nitrate and phosphate) in wastewaters processed by small to medium size two-stage treatment plants that primarily handle domestic and agricultural wastes. All experiments were carried out on laboratory scale systems with a low technology approach to keep apparatus and procedures as simple and reliable as possible. Among all organisms tested as components of the artificial food chains only the unicellular green alga Scenedesmus, the filamentous green algae Cladophora and Ulothrix, the cladoceran crustaceans Daphnia magna and Daphnia pulex, and the teleost fishes Notemigonus crysoleucas, Pimephales promelas and Notropis lutrensis were found to be suitable. Unmodified secondarily treated domestic effluents were both iron deficient and lacking in buffering capacity necessary for optimal algal growth. Additions of both ferrous iron (1 ppm) and carbon dioxide (5%) were required to achieve good quality cultures suitable for feeding cladocerans. Most removal of nutrients occurred in the first algal stage of the food chain. Nitrate removal averaged 78%, phosphate removal 55% in buffered algal cultures. In unbuffered cultures nitrate removal was 30%, phosphate removal 98%. The near complete removal of phosphate in unbuffered algal cultures was probably due to physico-chemical precipitation of phosphate complexes formed as a result of high pH levels (pH > 10) reached within 24 h of culture initiation. Cladoceran and fish stages added nutrients (mostly ammonia and phosphate) back into the effluent. A final stage of Ulothrix and Cladophora algae removed nutrients regenerated by cladocerans and fishes. A 12 h light–12 h dark cycle statistically significantly reduced levels of nutrient removal by both unbuffered and buffered algal cultures below removal rates measured in algae cultured in continuous light. Daily harvesting rates of 25–75% of culture volumes had no significant effect upon removals of nitrate by buffered algal cultures; phosphate removals were inversely proportional to harvesting rates in these cultures. Important theoretical and technical points are discussed.

Advanced purification of sewage works effluent using a combined system of lime softening and flotation

A lime softening flotation process is described for the purification of secondary treated sewage effluent to potable quality. Excess lime treatment is used as a coagulant in the flotator, and micro bubble aeration is achieved by centrifugal pump action. Flotation is followed by recarbonation and contact stabilization on ferric hydroxide, before sand filtration. ABS is removed by foam fractionation and ammoniacal nitrogen by “breakpoint” chlorination. Active carbon filtration is applied as a polishing stage to remove residual ABS and chloronous tastes and odours. The use of excess lime has the advantages of a sterilizing action, low cost and complete removal of phosphates. An ultimate reduction of total dissolved solids is also achieved. The importance of Mg(OH) 2 and Fe(OH) 3 for entrainment of suspended CaCO 3 in the flotator and stabilizer is emphasized. The aeration technique used appears to have economic advantages in comparison with conventional dissolved air flotation. Tentative cost figures for a 1 million gal/day demonstration plant are derived.