Magnesium Ammonium Phosphate Precipitation Research Articles

Nitrogen removal from tannery wastewater by protein recovery

Nitrogen removal from wastewaters has gained importance in recent years. In this paper protein precipitation and recovery potential of leather tanning industry wastewaters were experimentally evaluated. A protein profile for all sources was prepared. Liming was determined to be the most important protein source. Composite samples were made up to assess the protein precipitation applications. Isoelectric pH precipitation yielded around 50% protein removal between the optimum pH interval of 2.1-3.8. FeCl3 proved to be a very effective means of protein removal providing over 60% efficiency. Polyelectrolyte precipitation did not yield satisfactory results. Magnesium ammonium phosphate precipitation followed by acid precipitation of protein provided 85% ammonia removal in addition to 50% protein removal.

Struvite precipitation in anaerobic swine lagoon liquid: effect of pH and Mg:P ratio and determination of rate constant

Because of increased concern about surface water eutrophication from nutrient-enriched agricultural runoff, many swine producers are encouraged to decrease application rates of waste-based P. Precipitation and subsequent removal of magnesium ammonium phosphate (MgNH 4PO 4 · 6H 2O), commonly known as struvite, is a promising mechanism for N and P removal from anaerobic swine lagoon effluent. The objectives of this research were to (i) quantify the effects of adjusting pH and Mg:P ratio on struvite precipitation and (ii) determine the rate constant pH effect for struvite precipitation in anaerobic swine lagoon liquid. Concentrations of PO 4-P in liquid from two anaerobic swine lagoons were determined after 24 h of equilibration for a pH range of 7.5–9.5 and Mg:P ratios between 1:1 and 1.6:1. Struvite formation reduced the PO 4-P concentration in the effluents to as low as 2 mg l −1. Minimum concentrations of PO 4-P occurred between pH 8.9 and 9.25 at all Mg:P ratios. Struvite precipitation decreased PO 4-P concentrations by 85% within 20 min at pH 9.0 for an initial Mg:P ratio of 1.2:1. The rate of PO 4-P decrease was described by a first-order kinetic model, with rate constants of 3.7, 7.9, and 12.3 h −1 at pH 8.4, 8.7 and 9.0 respectively. Our results indicate that induced struvite formation is a technically feasible method to remove N and P from swine lagoon liquid and it may allow swine producers to recover nutrients for off-farm sale.

Recovery of ammonium-nitrogen from landfill leachate as a multi-nutrient fertilizer

Leachates generated in Hong Kong landfill sites contain high strength of ammonium-nitrogen (NH 4 +-N) in the range of 2000–5000 mg l −1, which could be used to produce nitrogen-fertilizer. To recover the NH 4 +-N from the leachate, a lab-scale study was performed to investigate the efficiency of magnesium ammonium phosphate (MAP) precipitation using three combinations of chemicals: MgCl 2·6H 2O+Na 2HPO 4·12H 2O, MgO+85% H 3PO 4 and MgSO 4·7H 2O+Ca(H 2PO 4)·H 2O. The results indicated that the NH 4 +-N was recovered by 92, 36 and 70%, respectively, using the selected chemicals at pH 9.0 and a molar ratio of Mg:N:P=1:1:1. The MAP precipitate (MgNH 4PO 4·6H 2O) as struvite was examined by scanning electron microscopy and the results showed that the MAP precipitate had a typical morphology of elongated tubular and short prismatic crystals. The MAP precipitate was also analyzed by energy dispersive spectroscopy and the analytical results indicated its composition of 4.9% N, 8.6% Mg and 16% P, which was similar to the standard struvite composition of 5.7% N, 9.9% Mg and 12.6% P. To investigate the fertility of the MAP precipitate, a set of pot trial tests was conducted. Four quick-growth vegetables, Chinese flowering cabbage ( Brassica parachinensis), Chinese chard ( Brassica rapa var. chinensis), water spinach ( Ipomoea aquatica) and water convolvulus ( Ipomea aquatica, I. reptans), were planted in sandy clay (Red Earth) and the MAP precipitate was applied as a fertilizer. The germination and growth of the selected vegetables in the pots with MAP showed significantly greater rates than those in the pots without MAP as control tests. The experiment also demonstrated that over-dosing of about 2–8 times of MAP in the soil did not cause any problems with water spinach ( Ipomoea aquatica) growth, due to its limited solubility in water. MAP application as a fertilizer did not result in more heavy metals in the vegetables than those from soil and model fertilizer, whereas the higher levels of P and Mg in the vegetables would stimulate vegetables’ growth. This study confirmed the feasibility of recovering NH 4 +-N from landfill leachate effectively by chemical precipitation, and also the feasibility of applying the MAP precipitate as a multi-nutrient fertilizer for vegetable growth.

Struvite precipitation from anaerobically treated municipal and landfill wastewaters

A two-stage treatment system including upflow anaerobic sludge blanket reactor pre-treatment combined with a chemical post treatment system such as magnesium ammonium phosphate (MAP) precipitation was proposed as a comparable alternative to conventional biological treatment. In this study, anaerobically pre-treated domestic wastewater, domestic wastewater mixed with 2% and 3% of leachate by volume and raw leachate were further treated chemically with MAP precipitation. MAP precipitation was both applied at the stoichiometric ratio (Mg:NH4=PO4; 1:1:1) and above the stoichiometric ratio (1.1:1:1 and 1.1:1:1.1) on domestic wastewater + 3% leachate mixture. Maximum NH4-N removal of 68% was achieved at the pH of 9.2 at the stoichiometric ratio, whereas at the same pH value 70 to 72% NH4-N removal was obtained above the stoichiometric ratio. Additional ammonia recovery studies were conducted on Fenton's oxidation applied effluents before MAP precipitation and no significant additional ammonium removal was achieved. However, by the application of Fenton's oxidation high additional COD removals were obtained. Consequently, chemical treatment by MAP precipitation and/or Fenton's oxidation after anaerobic treatment yielded very effective removals for COD and NH4-N in domestic wastewaters + leachate mixtures.

A new process for the combined treatment of municipal wastewaters and landfill leachates in coastal areas

One of the most convenient methods for leachate control is to treat landfill leachates with domestic wastewaters. In this framework, a two-stage treatment system including anaerobic pre-treatment combined with a chemical post-treatment system such as ammonia stripping and/or Magnesium Ammonium Phosphate (MAP) precipitation can be comparable with a conventional secondary biological treatment. In this study, 2.5% and 2% of leachate by volume was mixed with domestic wastewater as the feed for the mesophilic Upflow Anaerobic Sludge Bed Reactor (UASBR). pH, feed strength and hydraulic retention time (HRT) were monitored for the evaluation of the performance of the anaerobic process. The HRT's varied from 0.76 to 0.52 d and 58% and 85% COD removal efficiencies were obtained at Organic Loading Rates (OLR) of 0.63 and 2 kg COD/m3.d respectively. The average biomass (VS) concentration in the reactor increased from 40 g/l to 50 g/l during the study. Effluents from the UASBR were further treated chemically either with lime for ammonia stripping or with MAP precipitation. MAP precipitation was applied both at the stoichiometric ratio (Mg:NH4:PO4 = 1:1:1) and above the stoichiometric ratio (Mg:NH4:PO4 = 1:1:1.3). Maximum NH4 removal of 66% was achieved at the pH of 9.3 at the stoichiometric ratio, whereas 86% NH4 removal was obtained at the pH of 9.3 above the stoichiometric ratio. Alternatively, ammonia stripping was applied either to the effluents directly taken from the anaerobic reactor or to the effluents to which MAP precipitation was applied stoichiometrically. Ammonia stripping was conducted for 24 h and 89% NH4 removal was observed at the end of 24 h. Consequently, this study indicates that anaerobic pre-treatment combined with chemical post-treatment (MAP) produced high quality of effluent comparable to the conventional biological treatment especially in terms of N and P levels.

MAP Precipitation from Landfill Leachate and Seawater Bittern Waste

The leachates generated at Hong Kong landfill sites contain high strength of ammonium-nitrogen (NH4 +-N) over 3,000 mg l−1 and are generally inhibitive to most biological treatment processes. To remove the NH4 +-N from the landfill leachates and also recover the nitrogen as a struvite fertilizer, a lab-scale study was performed to investigate the feasibility of NH4 +-N removal and struvite crystallization using different magnesium sources. Three combinations of chemicals, MgCl2·6H2O+Na2HPO4·12H2O, MgO+H3PO4 and MgSO4·7H2O+Ca(H2PO4)·H2O, were first used at different molar ratios to precipitate NH4 +-N from the leachate. The experimental results indicated that NH4 +-N was removed by 92%, 36% and 70% respectively at pH 9.0 and a molar ratio of Mg:N:P−=1:1:1. Two synthetic seawater bittern wastes containing Mg2+ at 9,220 mg l−1 and 24,900 mg l−1 respectively were then used as a magnesium source, while 85% H3PO4 chemical was used as a phosphorus source. The results revealed that NH4 +-N was removed by 80% and 72% respectively, while a molar ratio of Mg:N:P=1:1:1 was applied. In the final stage of experiments, the magnesium-ammonium-phosphate (MAP) precipitates were examined by SEM, EDS and XRD. The SEM micrographs of the MAP precipitates showed a typical morphology of elongated tubular and short prismatic crystals. The EDS and XRD results indicated that the chemical composition of the MAP precipitates depended on the chemicals used and experimental conditions. The study confirmed that the recovery of NH4 +-N from landfill leachate and seawater bittern wastes could be effectively achieved by MAP precipitation to obtain struvite crystals with a composition of 5.1%N, 10.3%Mg and 16.5%P.

Assessment of magnesium ammonium phosphate precipitation for the treatment of leather tanning industry wastewaters

Magnesium ammonium phosphate (MAP) precipitation has a potential for ammonium removal from industrial wastewaters. Application basis of this recent method of treatment has not been fully determined. In this study application of MAP precipitation to leather tanning wastewaters has been experimentally evaluated. Five alternative places of MAP precipitation in leather tanning wastewater treatment scheme tested were; instead of plain settling, after plain settling, after polyelectrolyte added plain settling, within the chemical precipitation and after biological treatment. Among these alternatives MAP application instead of plain settling and within the chemical precipitation were found to be most favourable and efficient by reducing the nitrogen load to the level of nutrient requirement in the biological stage. pH 9.0-9.5 and stoichiometric magnesium and phosphate doses were determined to be optimum conditions for MAP precipitation.

Ammonia recovery from high strength agro industry effluents

The aim of the study was to investigate ammonia recovery from high strength agro industry effluents involving significant amounts of ammonia, by applying magnesium ammonium phosphate (MAP) precipitation technology. Two types of industrial effluents have been tested in the study. The first plant was an opium alkaloid processing industry and the second one was a baker's yeast industry. High chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and unacceptable dark brown color characterized effluents from both industries. Effluents from the biologically treated opium alkaloid and baker's yeast industries were both applied at the stoichiometric ratio (Mg:NH4:PO4 = 1:1:1) and above the stoichiometric ratio (Mg:NH4:PO4 = 1.1:1:1.1) to MAP precipitation. NH4 removals of 61-80% were achieved at the pH of 9.2 at the stoichiometric ratio, whereas 83% NH4 removal was obtained at the pH of 9.2 above the stoichiometric ratio. Experimental studies performed on both anaerobically and/or aerobically treated baker's yeast and opium alkaloid industry effluents have clearly indicated that MAP precipitation was an appropriate treatment option for NH4 removal or struvite recovery from high ammonia content agro industry effluents. Additional ammonia recovery studies were conducted on ozonated and Fenton's oxidation applied effluents and these have also indicated that the amounts of struvite and the quality of MAP precipitate was increased significantly. In this framework, MAP sludge recovered from combined biological and Fenton's oxidation treatment effluents were considered as a more valuable slow release fertilizer for agricultural use.

Assessment of source-based nitrogen removal alternatives in leather tanning industry wastewater

Nitrogen is an important parameter of leather tanning wastewaters. Magnesium ammonium phosphate (MAP) precipitation is a chemical treatment alternative for ammonia removal. In this study, a detailed source-based wastewater characterisation of a bovine leather tannery was made and nitrogen speciation as well as other basic pollutant parameter values was evaluated. This evaluation has led to definition of alternatives for source-based MAP treatment. MAP precipitation experiments conducted on these alternatives have yielded over 90% ammonia removal at pH 9.5 and using stoichiometric doses. Among the alternatives tested liming-deliming and bating-washing was found to be the most advantageous providing 71% ammonia removal.

Optimalisation of Magnesium Ammonium Phosphate Precipitation and Its Applicability to the Removal of Ammonium

Among the physico-chemical abatement technologies, mainly acid scrubbers have been used to control NH3-emission. The disadvantage of this technique is that it yields waste water, highly concentrated in ammonia. In this report, the applicability of the magnesium ammonium phosphate (MAP) process to regenerate the liquid phase, produced by scrubbing NH3-loaded waste gases, was investigated. In the MAP process, ammonium is precipitated as magnesium ammonium phosphate, which can be used as a slow release fertilizer. The influence of a number of parameters, e.g. pH, kinetics, molar ratio NH(+)4/Mg2+/PO(3-)4 on the efficiency of the formation of MAP and on the ammonium removal efficiency was investigated. In this way, optimal conditions were determined for the precipitation reaction. Next to this, interference caused by other precipitation reactions was studied. At aqueous NH(+)4-concentrations of about 600 mg l(-1), ammonium removal efficiencies of 97% could be obtained at a molar ratio NH(+)4/Mg2+/PO(3-)4 of 1/1.5/1.5. To obtain this result, the pH was continuously adjusted to a value of 9 during the reaction. According to this study, it is obvious that the MAP-precipitation technology offers opportunities for ammonium removal from scrubbing liquids. The practical applicability of the MAP-process in waste gas treatment systems, however, should be the subject for further investigations.

Optimalisation of Magnesium Ammonium Phosphate Precipitation and its Applicability to the Removal of Ammonium

Among the physico-chemical abatement technologies, mainly acid scrubbers have been used to control NH3-emission. The disadvantage of this technique is that it yields waste water, highly concentrated in ammonia. In this report, the applicability of the magnesium ammonium phosphate (MAP) process to regenerate the liquid phase, produced by scrubbing NH3-loaded waste gases, was investigated. In the MAP process, ammonium is precipitated as magnesium ammonium phosphate, which can be used as a slow release fertilizer. The influence of a number of parameters, e.g. pH, kinetics, molar ratio NH4+/Mg2+/PO43- on the efficiency of the formation of MAP and on the ammonium removal efficiency was investigated. In this way, optimal conditions were determined for the precipitation reaction. Next to this, interference caused by other precipitation reactions was studied. At aqueous NH4+-concentrations of about 600 mg 1-1, ammonium removal efficiencies of 97% could be obtained at a molar ratio NH4+ /Mg2+/PO43- of 1/1.5/1.5. To obtain this result, the pH was continuously adjusted to a value of 9 during the reaction. According to this study, it is obvious that the MAP-precipitation technology offers opportunities for ammonium removal from scrubbing liquids. The practical applicability of the MAP-process in waste gas treatment systems, however, should be the subject for further investigations.

Conditions influencing the precipitation of magnesium ammonium phosphate

Struvite precipitation in wastewater treatment works has caused substantial operational problems since the early 1960s. Struvite, magnesium ammonium phosphate hexahydrate (MgNH 4PO 4·6H 2O), is a white inorganic crystalline mineral that precipitates in places with increased turbulence such as pumps, aerators and pipe bends. Batch experiments were conducted to examine the influence of a number of physical and chemical parameters on struvite crystallisation. This was undertaken by dosing a medium of de-ionised water with varying concentrations of Mg 2+, NH 4 + and PO 4 3− ions. Preliminary experiments found that struvite could be precipitated out of solution at pH 10 and increasing the ion concentration stoichiometrically could increase crystal yield. Increasing the NH 4 + concentration increased purity of the precipitate. As reaction time was increased from 1 to 180 min, crystal size was found to increase from 0.1 to 3 mm.

Stability of enhanced biological phosphorus removal and composition of polyphosphate granules

The influence of varying Ca- and Mg-concentration of the influent wastewater on the enhanced biological phosphorus removal was investigated in an anaerobic-aerobic bench-scale plant. The artificial enhancement of the Mg-concentration in the influent from 15 to 24 mg l −1 and 31 mg l −1, respectively, caused a raise of the mean P-removal efficiency from 85 to 97%. The P-elimination was very stable in time. A chemical precipitation of magnesium ammonium phosphate could be excluded. The elemental composition of polyphosphate granules was investigated by electron microscopy and energy dispersive X-ray spectroscopy. The elements Ca, Mg and K were the principal metal components of polyphosphate granules. Concerning the metal composition, different types of granules could be distinguished. The quantitative ratios of Ca, Mg and K varied in dependence on the influent concentration of these metals. A relation between the Mg/Ca-ratio of the granules and the efficiency of enhanced biological phosphorus removal can be supposed.

Struvite precipitation potential for nutrient recovery from anaerobically treated wastes

Geochemical equilibrium speciation modeling was used to determine optimum conditions for precipitation of magnesium ammonium phosphate, or struvite, for the recovery of nutrients from anaerobically digested wastes. Despite a wide range of pH values with the potential to precipitate struvite, the optimum pH was determined to be 9.0. Bench experiments conducted on effluent from an anaerobic sequencing batch reactor (ASBR) treating swine wastes achieved a maximum of 88% ammonia removal at a pH of 9.5 with added magnesium and phosphate to achieve an ammonium: magnesium: phosphate molar ratio of 1:1.25:1. Struvite precipitation was performed on a continuous basis in a pilot-scale ASBR treating swine wastes. Through the addition of supplemental magnesium and phosphate, the ammonia concentration was reduced from 1500 mg/L as nitrogen to less than 10 mg/L. The supenatant from the struvite precipitation clarifier was recycled to the feed of the ASBR without adverse impact, simulating on-farm effluent reuse as flush water.

ATP production from adenine by a self-coupling enzymatic process: high-level accumulation under ammonium-limited conditions.

To improve ATP production from adenine, we optimized cultivation and reaction conditions for the ATP producing strain, Corynebacterium ammoniagenes KY13510. In the conventional method, 28% NH4OH has been used both to adjust pH during cultivation and reaction, and to provide nitrogen for cell growth. In the ATP-producing reaction, high concentrations of inorganic phosphate and magnesium ion are needed, which form magnesium ammonium phosphate (MgNH4PO4) precipitate. To keep inorganic phosphate and magnesium ions soluble in the reaction mixture, it was indispensable to add phytic acid as a chelating agent of divalent metal ions. Under such conditions, 37 mg/ml (61.2 mM) ATP was accumulated in 13 h (Appl. Microbiol. Biotechnol. 21, 143 1985). If ammonium ion was depleted from the reaction mixture to avoid MgNH4 PO4 formation, we expected that there was no need to add phytic acid and ATP accumulation might be improved. Therefore, we obtained the cultured broth of C. ammoniagenes KY13510 strain with low ammonium ion content (less than 1 mg/ml as NH3) by the method that a part of alkali solution (28% NH4OH) for pH control was replaced with 10 N KOH. Using this culture broth, ATP producing reaction was done in 2-liter jar fermentor, controlling the pH of the reaction mixture with 10 N KOH. Under these conditions, the rate of ATP accumulation improved greatly, and 70.6 mg/ml (117 mM) ATP was accumulated in 28 h. The molar conversion ratio from adenine to ATP was about 82%. Phytic acid was slightly inhibitory to ATP formation under these ammonium-limited conditions.

Characterization and Treatment of Textile Printing Wastewaters

Textile printing is becoming an important wastewater source as the water-based materials replace the organic solvents. The wastewaters originating from this operation are often strong and may contain toxics, although their volume is quite low. In this study, a textile printing plant was evaluated to assess pollution characteristics and treatment alternatives. Rotation printing wastewaters were found to be relatively diluted compared with other printing wastewaters, having a COD of around 800 mg l−1 and responded with a high efficiency to both chemical precipitation and biological treatment. On the other hand, tube and item printing wastewaters contained solvents as well as high COD and TKN. Chemical treatment and aeration used as a pretreatment resulted in over 90 % COD removal together with high degree of color and solvent removal. Biological treatment following pretreatment resulted in an effluent COD of 250-500 mg l−1. Nitrogen removal in the pretreatment stage was also assessed using magnesium ammonium phosphate (MAP) precipitation and air stripping. Results of the study were evaluated considering alternative treatment schemes.

Ammonia removal from young landfill leachate by magnesium ammonium phosphate precipitation and air stripping

Leachate from sanitary landfills is a strong wastewater in terms of organic matter and ammonia. Organic matter can be reduced by anaerobic plus aerobic treatment; however, ammonia reduction by nitrification often poses problems due to inhibition. In this study, ammonia removal by physical chemical treatment from young leachate and anaerobically treated young landfill leachate was experimentally investigated. Magnesium ammonium phosphate precipitation (MAP) and ammonia stripping at pH 12 provided ammonia removals over 90 and 85% respectively. Up to 80% COD removal was obtained with MAP precipitation of raw leachate.

Ammonium removal from landfill leachate by chemical precipitation

The landfill leachate in Hong Kong usually contains quite high NH 4 +–N concentration, which is well known to inhibit nitrification in biological treatment processes. A common pre-treatment for reducing high strength of ammonium (NH 4 +–N) is by an air-stripping process. However, there are some operational problems such as carbonate scaling in the process of stripping. For this reason, some technical alternatives for NH 4 +–N removal from leachate need to be studied. In this study, a bench-scale experiment was initiated to investigate the feasibility of selectively precipitating NH 4 +–N in the leachate collected from a local landfill in Hong Kong as magnesium ammonium phosphate (MAP). In the experiment, three combinations of chemicals, MgCl 2·6H 2O+Na 2HPO 4·12H 2O, MgO+85% H 3PO 4, and Ca(H 2PO 4) 2·H 2O+MgSO 4·7H 2O, were used with the different stoichiometric ratios to generate the MAP precipitate effectively. The results indicated that NH 4 +–N contained in the leachate could be quickly reduced from 5618 to 112 mg/l within 15 min, when MgCl 2·6H 2O and Na 2HPO 4·12H 2O were applied with a Mg 2+:NH 4 +:PO 4 3− mol ratio of 1:1:1. The pH range of the minimum MAP solubility was discovered to be between 8.5 and 9.0. Attention should be given to the high salinity formed in the treated leachate by using MgCl 2·6H 2O and Na 2HPO 4·12H 2O, which may affect microbial activity in the following biological treatment processes. The other two combinations of chemicals [MgO+85% H 3PO 4 and Ca(H 2PO 4)2·H 2O+MgSO 4·7H 2O] could minimise salinity after precipitation, but they were less efficient for NH 4 +–N removal, compared with MgCl 2·6H 2O and Na 2HPO 4·12H 2O. COD had no significant reduction during this precipitation. It was found that the sludge of MAP generated was easily settled within 10 min to reach its solids content up to 27%. The other characteristics including capillary suction time (CST) and dry density (DD) of the MAP sludge were also tested. The experimental results indicate that the settled sludge is quite solid and can be directly dumped at a landfill site even without any further dewatering treatment.

Full scale experiences with anaerobic/aerobic treatment plants in the food and beverage industry

In Germany, there are currently 125 full-scale anaerobic treatment plants treating industrial wastewater. This paper describes the operational experiences of several industries (beet sugar, starch, pectin brewery, distillery, vegetable, potato processing) which undertake anaerobic wastewater treatment, with particular emphasis on specific wastewater problems and their solutions. Also presented are experiences with the handling of high nitrate concentrations, with the treatment of mixtures of industrial wastewater from different origins, with the chance to prevent the emergence of lime, magnesium ammonium phosphate (MAP) or aluminium precipitation. This paper deals as well with the first EGSB reactor (Expanded Granular Sludge Bed) at a German potato processing factory as well as the first municipal wastewater treatment plant combined with a separate anaerobic stage to treat a wastewater mixture from several small factories.

Full scale experiences with anaerobic/aerobic treatment plants in the food and beverage industry

In Germany, there are currently 125 full-scale anaerobic treatment plants treating industrial wastewater. This paper describes the operational experiences of several industries (beet sugar, starch, pectin brewery, distillery, vegetable, potato processing) which undertake anaerobic wastewater treatment, with particular emphasis on specific wastewater problems and their solutions. Also presented are experiences with the handling of high nitrate concentrations, with the treatment of mixtures of industrial wastewater from different origins, with the chance to prevent the emergence of lime, magnesium ammonium phosphate (MAP) or aluminium precipitation. This paper deals as well with the first EGSB reactor (Expanded Granular Sludge Bed) at a German potato processing factory as well as the first municipal wastewater treatment plant combined with a separate anaerobic stage to treat a wastewater mixture from several small factories.