Simultaneous Recovery Of Phosphorus Research Articles

High-efficiency anaerobic digestion of soybean curb residue with simultaneous phosphorus recovery by Mg[sbnd]Fe layered double hydroxides addition

Anaerobic digestion of food waste faces several technical problems, such as process failure caused by over-acidification, low heating value of biogas, and high treatment cost of liquid digestate. Layered double hydroxides (LDH) are expected to simultaneously enhance biogas production and quality and immobilize soluble phosphorus in AD due to their excellent anion exchange capability. This study first verified the above hypothesis, indicated by a dramatically enhanced methane yield of 17 folds under a high substrate load and a high quality of generated biogas with 89 % methane content and 90 % lowered hydrogen sulfide. Meanwhile, the soluble phosphorus was efficiently reduced to 3 mg/L after AD. Moreover, the calcined product of LDH showed comparable performance, indicating the possibility of reusing LDH in the AD process. The above results implied the great potential of LDH as a multifunctional material for enhancing the efficiency of waste treatment and energy/resource conversion in the AD process.

Simultaneously converting synthetic fresh urine into high-quality artificial phosphate ores and urea solution: A novel coupled system of electrochemical selective separation plus induced precipitation

Both the sustainable development and environmental protection urge a demand of new paradigm to recover high-quality nutrients from source-separated urine, but the simultaneous recovery of phosphorus and nitrogen is difficult due to the complex composition. Herein, a coupled system consisting of a flow-electrode capacitive desalination and magnesium-air fuel cell (FCDI-MAFC) was proposed to accomplish electrochemical selective separation plus induced precipitation. The results showed that ionic species in urine were effectively separated from the non-ionic components to generate a urea solution with purity up to 99.7%. Ionic species were converted into artificial phosphate ores (APOs) with a phosphate content of 98.2%. The mass proportion of struvite in the APOs exceeded 90%. The energy consumption also decreased by 13% over five batches of operation. The overall results provide a novel method for the electrochemical selective separation and recovery of high-quality nutrients from complex wastewater.

Simultaneous phosphorus recovery from wastewater and sludge by a novel denitrifying phosphorus removal system

A novel process was proposed for simultaneous denitrification and phosphorus (P) recovery. The increased nitrate concentration facilitated the activity of denitrifying P removal (DPR) in P enrichment, which stimulated P uptake and storage, making P more readily accessible for release into the recirculated stream. The total P content in the biofilm (TPbiofilm) rose to 54.6 ± 3.5 mg/g SS as the nitrate concentration increased from 15.0 to 25.0 mg/L, while the P concentration of the enriched stream reached 172.5 ± 3.5 mg/L. Moreover, the abundance of denitrifying polyphosphate accumulating organisms (DPAOs) increased from 5.6% to 28.0%, and the increased nitrate concentration facilitated the process of carbon, nitrogen, and P metabolism due to the rise in the genes involved in critical functions of metabolism. Acid/alkaline fermentation analysis indicated that the EPS release was the primary P-release pathway. Additionally, pure struvite crystals were obtained from the enriched stream and fermentation supernatant.

A novel Electrolysis-integrated anammox system for intensified nitrogen removal and simultaneous phosphorus recovery as vivianite

A novel electrolysis-integrated anammox (Ele-anammox) process was developed for intensified nitrogen removal and concomitant phosphorus recovery from nutrient-rich wastewater. By conducting a parallel experiment, average removal efficiencies of total nitrogen (TN) and total phosphorus (TP) in Ele-anammox reactor reached 90.69% and 95.02% respectively, showing increases of 7.76% and 79.08%, as compared to the traditional anammox process. Anammox reaction and synergetic denitrification were mainly responsible for the reinforced N-removal. Successions of microbial communities revealed that Candidatus Kuenenia declined markedly while Candidatus Brocadia was enriched in Ele-anammox system, suggesting that electrical environment provided Candidatus Brocadia with a competitive advantage over other anammox bacteria. Based on the proposed current control strategy (the applied current was calculated to match the influent P loading), precise release of soluble Fe2+ could be achieved by anodic oxidation. Various elemental analysis methods, including the standards, measurements and testing (SMT) protocol, energy dispersive X-ray spectroscopy (eSEM-EDX), X-ray fluorescence spectrometry (XRF) and inductively coupled plasma emission spectroscopy (ICP-OES), jointly indicated that the solid phase of Ele-anammox was primarily Fe-P precipitation, which showed a similar Fe:P ratio with vivianite (Fe3(PO4)2·8H2O, 1.5). X-ray diffraction (XRD) analysis further validated the in-situ crystallization of vivianite, and semi-quantification implied a vivianite content of 85%. Mössbauer spectroscopy showed at least 51.48% ∼ 59.11% of iron was bound in vivianite, while impurity occupation and potential oxidization may impair the purity of P-recovery products, which should be concerned in future practice.

A comparative study on simultaneous recovery of phosphorus and alginate-like exopolymers from bacterial and algal-bacterial aerobic granular sludges: Effects of organic loading rate

The effects of organic loading rate (OLR) on simultaneous phosphorus (P) and alginate-like exopolymers (ALE) recovery from bacterial aerobic granular sludge (AGS) and algal-bacterial AGS were examined and compared during 70 days’ operation. With the increase of OLR (0.6–1.2 g COD/(L·day)), both AGS showed good settleability and granular strength with P bioavailability > 92% (Stage III). The moderate increase in OLR had a positive influence on simultaneous recovery of P and ALE. On day 60, the contents of ALE and guluronic acid/guluronic acid (GG) blocks reached the highest in algal-bacterial AGS, about 13.37 and 2.13 mg/g-volatile suspended solids (VSS), respectively. Meanwhile, about daily 0.55 kg of P is estimated to be recovered from the wastewater treatment plant with a treatment capacity of 10,000 m3/day. P mass balance analysis during ALE extraction from both AGS was conducive to further evaluation of P removal pathway and its application potentials.

Simultaneous recovery of phosphorus and nitrogen from inorganic fertilizer wastewater

ABSTRACT Conventional method for removal of N and P from industrial wastewater by biological treatment requires a long hydraulic- retention- time (HRT) and strict conditions for protecting the microorganisms. This study focuses on N and P recovery by struvite (MgNH4PO4 .6H2O) precipitation method which is a fast chemical process. In order to control the specs of the sample, a simulated wastewater solution was prepared according to the parameters of inorganic fertilizer wastewater. The influence of pH (7-9), Mg/P molar ratio (1-1.6) and N/P molar ratio (1.2-2) in struvite recovery efficiency was evaluated and the obtained struvite samples were characterized using X-ray diffraction (XRD), scanning electron micrograph (SEM). Response surface methodology (RSM) was utilized in Box-Behnken experimental design and data analysis to obtain a mathematic for P and N recovery. The XRD and SEM results confirmed the formation of struvite structure with the particle size about 7-50 micrometers. The obtained struvite contained nutrients N, P2O5 and MgO which can be used directly in fertilizer formulation. The mathematic models for P recovery and N recovery were obtained from analyzing experimental data with p-value <0.05. Basing on the proposed parameters (pH=9, Mg/P=1.4 and N/P=1.2) obtained from the mathematic model, 98% of phosphorous from an actual fertilizer wastewater sample (pH=8.3, N/P=1.2, P=2.98 g L−1 ) can be recovered. The obtained mathematic model and the suggested technical conditions can be applied for simultaneous recovery ammonium and phosphate from practical wastewater with high concentrations such as in fertilizer industry.

Simultaneous recovery of phosphorus and alginate-like exopolysaccharides from two types of aerobic granular sludge

Wastewater treatment plants are expected to realize not only pollutants removal from wastewater but also resources recovery such as phosphorus (P) and alginate-like exopolysaccharides (ALE) from the produced sludge. In this study, ALE extraction and fractionation from the same activated sludge-derived bacterial aerobic granular sludge (AGS) and algal-bacterial AGS were performed in addition to P fate examination during ALE recovery. Results showed that the ALE content recovered from algal-bacterial AGS was 8.81 ± 0.02 mg/g-volatile suspended solids (VSS), about 2.8 times higher than that from bacterial AGS when fed with the same synthetic wastewater. Moreover, the mannuronic acid to guluronic acid (MG) blocks accounted for the largest proportion of ALE from the two granular sludges. In particular, the extracellular polymeric substances (EPS) extracted from bacterial and algal-bacterial AGS contained about 25.10 ± 1.85 and 19.53 ± 0.04 mg-P/g-SS, respectively, and both granular sludges possessed high P bioavailability of 97–99%.

Simultaneous electrochemical degradation of organophosphorus pesticides and recovery of phosphorus: Synergistic effect of anodic oxidation and cathodic precipitation

To address future phosphorus scarcity and organophosphorus pesticides discharge associated environmental problems, a filter-press type electrochemical system was developed for acephate, a typical organophosphorus pesticide, degradation and simultaneous recovery of phosphorus. In this reaction system, boron-doped diamond (BDD) mediated anodic oxidation could transform acephate into ortho-phosphate (o-PO4) and then o-PO4 was precipitated with Ca2+ at the cathode surface in the form of hydroxyapatite induced by the local basic environment. The phosphorus recovery efficiency raised from 57 % to 92 % within 180 min by elevating current density from 5 to 30 mA/cm2, accompanying the enhanced acephate mineralization efficiency from 77% to 97%. These enhancement trends were attributed to the increased yield of BDD(•OH) and higher local pH near the cathode, respectively, at higher current density applied. Phosphorus recovery efficiency swelled by 15% with solution pH decreasing from 9.0 to 4.0 since anodic oxidation of acephate into o-PO4 was favorable in the acid solution. Moreover, phosphorus recovery was seriously depressed in the initial reaction stage with the presence of Mg2+, whereas bicarbonate posed the negative effect over the whole reaction process. Unexpectedly, the presence of Cl− inhibited the degradation of acephate since highly oxidative •OH was consumed by Cl−. In general, the electrochemical strategy of “anodic oxidation-cathodic precipitation” has been demonstrated practicable for phosphorus recovery from the organophosphorus wastewater.

Simultaneous phosphorus recovery, sulfide removal, and biogas production improvement in electrochemically assisted anaerobic digestion of dairy manure

Anaerobic digestion (AD) produces renewable biogas from organic-rich waste streams, but the resultant digestate has to be subject to further nutrient recovery processes for better valorization. In this study, an electrochemical treatment unit using stainless steel mesh electrodes was integrated with an up-flow anaerobic sludge blanket (UASB) reactor to treat liquid dairy manure for simultaneous phosphorus (P) recovery, methane production improvement, and hydrogen sulfide (H2S) removal. The 36-d batch AD trial showed that a large portion of total P and reactive P were removed from the liquid dairy manure and were recovered mainly on the cathode deposits in the form of phosphate-bearing minerals. In the continuous USAB trial with an applied voltage of 1.0 V, 65.1% of the total P in the feeding manure was removed, of which 96.7% was achieved by sludge bed accumulation and 3.3% in the cathode deposit. Increases in both biogas production rate (13.0%) and methane yield (10.9%) were observed in the electrochemically assisted UASB system as compared to the one without electrochemical treatment. The electrochemical assistance helped decrease the H2S concentration in biogas by 20.8% at an applied voltage of 0.5 V and by 50.3% at 1.0 V. This electrochemically assisted UASB system can produce more biogas with less H2S content and recover P-enriched sludge in the sludge bed and the cathode deposit.

A proposal of low-cost technology for nutrient recovery from leachate of anaerobic digester at a biological wastewater treatment plant

Removal of nutrients from wastewater with simultaneous recovery of phosphorus (P) and nitrogen (N) in the form assimilable by plants is possible by the precipitation of ammonium magnesium phosphate (struvite). This method benefits environmental protection but has not been widely implemented in Wastewater Treatment Plants (WWTPs). One of the reasons is the high costs of available technologies. The aim of the work is to investigate the low-cost methods of reduction and recovery of nutrients from wastewater. It involves the precipitation of struvite from phosphate-rich leachate from WWTP fermentation chambers. The reaction was carried out in the prototype of a simple horizontal reactor, ensuring the possibility of collecting sediment in the funnel. A cheap waste magnesium salt was used to precipitate the struvite, which significantly reduced the costs of its acquisition. The reduction of P exceeded 80% in most of performed tests in leachate waters. The precipitant removed from the reactor has the character of sludge with a significant degree of hydration (85%). After drying, it is a dusty powder with an average P content of 40% and a total N content of 8% and a trace of heavy metals. It was proposed to mix the obtained aqueous form of struvite sediments with compost produced from excessive sludge, without drying it. Studies have shown that one percent of struvite admixture in compost results in an increase of P and N content by 13% and 2.7%, respectively.

Simultaneous recovery of phosphorus and nitrogen from sewage sludge ash and food wastewater as struvite by Mg-biochar

The drawback of biochar as a soil ameliorant is its low-nutrient content while the bottleneck of struvite production is its high chemical cost. This drew the idea of using designed biochar for nutrient recovery from nutrient-rich wastewater as struvite. Mg-biochar was used for simultaneous P and N recovery from sewage sludge ash (SSA) and food wastewater (FW) by using ground coffee bean (GCB) and palm tree trunk (PTT) waste. PTT Mg-biochar could recover 92.2% of PO43−-P and 54.8% of NH4+-N while GCB Mg-biochar could recover 79.5% of PO43−-P and 38.6% of NH4+-N. Adsorption, precipitation and cation-exchange mechanisms are involved in the Mg-biochar for the simultaneous recovery of PO43−-P and NH4+-N as struvite. Mg-biochars also showed higher struvite selectivity than the control samples. This method not only supports waste recycling and pollution mitigation but also highlights economical struvite production and the benefits of CO2 sequestration.

Two-stage nanofiltration for purification of membrane bioreactor treated municipal wastewater – Minimization of concentrate volume and simultaneous recovery of phosphorus

This study evaluates the usability of a novel two-stage tertiary nanofiltration process concept for further purification of membrane bioreactor (MBR) permeate from municipal wastewater treatment and minimization of nanofiltration concentrate volume. In addition to water purification, the studied process aims to recover phosphorus from the second stage. The process concept for tertiary wastewater treatment includes two nanofiltration modules in series, where first stage is a nanofiltration of MBR permeate with a spiral-wound element and in the second stage a minimization of the NF concentrate is done by shear-enhanced nanofiltration combined with spontaneous precipitation and removal of precipitates from the concentration process. A volume reduction factor (VRF) of 300 was achieved with the studied process concept. The average permeabilities of the NF270 membranes used in both stages were 4.3 L/(m2 hbar) (first stage, spiral wound module) and 8.9 L/(m2 hbar) (second stage, high shear rate module). The two-stage NF process efficiently decreased the chemical oxygen demand (COD) and total organic carbon (TOC) content of the treated water, giving retentions higher than 99% for COD and 97% for TOC. About 52% of phosphorus was spontaneously precipitated as calcium phosphate (presumably as hydroxyapatite, purity 80%) at the second stage of the process. High turbulence (rotor tip speed 13.7 m/s) at the membrane surface during the second stage tertiary filtration prevented the formation of inorganic scale and membrane fouling. Precipitation occurred in the settling tank after the filtration when the turbulent flow conditions subsided. This enabled the continuation of the filtration to a high VRF value of 300 despite the significant calcium and phosphorus concentrations. The results presented here confirm that shear-enhanced nanofiltration is a promising approach for efficient minimization of the NF concentrate volume, as well as for simultaneous phosphorus recovery without the need for precipitation chemicals.

Simultaneous recovery of phosphorus with nickel purification in nickel-plating wastewater via Fe/C activated H2O2 oxidation

The recovery of phosphorus (P) from wastewater has attracted substantial attention with the atrophy of global P resource. In the current work, the simultaneous recovery of P with the removal of nickel (Ni) via iron/activated carbon (Fe/AC) and hydrogen peroxide (H2O2) form nickel-plating wastewater was achieved. The isotherm reaction showed a maximum P recovery of 99.99% with an equilibrium concentration of P of 0.12 mg/L, which was lower than the limitation of discharge regulation (China national regulation, 0.5 mg/L). The optimal conditions for P recovery were 0.25 mol/L H2O2, a Fe/AC mass ratio of 1:1, an at 60 °C, which led to the ratio of P in the form of FePO4 in the residue to be 77%. Moreover, the Fe/AC microelectrolysis coupling to H2O2 promoted Fe2+ production from Fe0 and improved the circulation of Fe2+, which improved the production of hydroxyl radicals with increasing pH and consequently enhanced oxidation efficiency of hypophosphite. The FePO4 was found the major form of phosphate in the precipitate. The highest removal rate of nickel was 89%, which was attributed to its precipitation at high pH and adsorption on to iron hydroxides and activated carbon. Nickel purification was achieved by further coagulation as the equilibrium concentration of Ni was lower than 0.1 mg/L. Therefore, our work provides a promising approach for simultaneous recovery of P and removal of Ni from electroplating wastewater.

An experimental study on the recovery of potassium (K) and phosphorous (P) from synthetic urine by crystallization of magnesium potassium phosphate

In this study, the simultaneous recovery of phosphorus (P) and potassium (K) from synthetic urine by crystallization of magnesium potassium phosphate hexahydrate (MPP) was studied. A series of conditional experiments were performed to examine the effects of phosphate and magnesium dosages, solution pH, and the presence of Na+, NH4+, and Ca2+ ions on the MPP crystallization. The results revealed that the dosages of phosphate and magnesium had a marked effect on the MPP crystallization. Separate excess of magnesium was not beneficial for the formation of MPP, while the simultaneous excess of magnesium and phosphate could significantly improve the efficiency of MPP precipitation. The optimum pH for MPP crystallization was determined to be 11. At this pH, the presence of Na+, NH4+, and Ca2+ in the aqueous solution markedly influenced MPP crystallization. The effects of NH4+ and Ca2+ on the removal of K were far greater than that of Na+. Moreover, in the crystal seeding technique on MPP crystallization, the K- and phosphate-removal efficiencies were found to increase by about 10%, with an increasing dosage of the preformed MPP from 0 g/L to 30 g/L. Thus, a continuous-flow MPP precipitation process is recommended for the treatment of synthetic urine and real urine as the results demonstrated that the phosphate and K could be efficiently removed from both the urine types.

Nutrient removal and energy production in a urine treatment process using magnesium ammonium phosphate precipitation and a microbial fuel cell technique

Urine pretreatment has attracted increasing interest as it is able to relieve the nitrogen and phosphorus overloading problems in municipal wastewater treatment plants. In this study, an integrated process, which combines magnesium ammonium phosphate (MAP) precipitation with a microbial fuel cell (MFC), is proposed for the recovery of a slow-release fertilizer and electricity from urine. In such a two-step process, both nitrogen and phosphorus are recovered through the MAP process, and organic matters in the urine are converted into electricity in the MFCs. With this integrated process, when the phosphorus recovery is maximized without a dose of PO(4)(3-)-P in the MAP precipitation process, removal efficiencies for PO(4)(3)-P and NH(4)(+)-N of 94.6% and 28.6%, respectively, were achieved with a chemical oxygen demand (COD) of 64.9% accompanied by a power output of 2.6 W m(-3). Whereas removal efficiencies for PO(4)(3)-P and NH(4)(+)-N of 42.6% and 40%, respectively, and a COD of 62.4% and power density of 0.9 W m(-3) were obtained if simultaneous recovery of phosphorus and nitrogen was required through dosing with 620 mg L(-1) of PO(4)(3-)-P in the MAP process. This work provides a new sustainable approach for the efficient and cost-effective treatment of urine with the recovery of energy and resources.