Phosphorus Recovery from the Ash of Sewage Sludge Using NaOH by Heat Treatment-II—Reuse of the Alkali Water Generated by Phosphorus Recovery

The phosphorus recovery from the incinerated ash using NaOH by the heat treatment,was investigated.In this method,non-reacted NaOH containing alkali water was generated with the phosphorus recovery.In order to find out the best method for reuse of the alkali water,the alkali water was mixed with new reagent of NaOH,and the phosphorus recovery was carried out.The phosphorus was recovered as a sodium phosphate,and the recovery rate was almost the same even with the reuse of the alkali water.

Phosphorus Recovery from Dehydrated Water Sludge by Incineration Using Alkali Metal Compounds

In order to recover the phosphorus from the waste water sludge,the dehydrated sludge was mixed with the reagent of NaOH,KOH or Na2CO3,and incinerated at 750℃ or 900℃.Phosphorus in the incinerated ash of the sludge was dissolved by the addition of water,and recovered by the evaporation of the phosphorus resolved water.The recovered phosphorus was confirmed to be an alkali metal phosphate,and the recovery rate reached about 75%regardless any combination of the reagents(NaOH,KOH or Na2CO3).

Influence of temperature and Fe_(2)O_(3)on phosphorus recovery from dephosphorization slag by reduction

The reduction and recovery of P_(2)O_(5)in dephosphorization slag were examined to establish a new recycling process for dephosphorization slag.The dephosphorization slag is obtained from the dephosphorization furnace in the duplex converter process,and the content of P_(2)O_(5) in the dephosphorization slag can reach 9 wt.%.The dephosphorization slag is considered to be a prospective resource of phosphorus due to its high content of P_(2)O_(5).To explore the effects of temperature and Fe2O3 content in slag on phosphorus recovery from dephosphorization slag,the experimental slag was reduced by carbon powder in a resistance furnace.The results show that the temperature and content of Fe2O3 in slag have a significant effect on the reduction in P_(2)O_(5),and the reduction and recovery ratios of P_(2)O_(5) in slags increase with the increase in the experimental temperature and content of Fe_(2)O_(3),reaching 94.41%and 83.09%,respectively.It has been indicated that phosphorus recovery from dephosphorization slag using carbothermic reduction has significant environmental and economic benefits.

Environmental sustainability opportunity and socio-economic cost analyses of phosphorus recovery from sewage sludge

Although phosphorus(P)recovery and management from sewage sludge are practiced in North America and Europe,such practices are not yet to be implemented in China.Here,we evaluated the environmental sustainability opportunity and socio-economic costs of recovering P from sewage sludge by replacing the current-day treatments(CT;sludge treatment and landfill)and P chemical fertilizer application(CF)in China using life cycle assessment and life cycle costing methods.Three potential P recovery scenarios(PR1‒PR3:struvite,vivianite,and treated sludge)and corresponding current-day scenarios(CT1‒CT3 and CF)were considered.Results indicated that PR1 and PR2 have smaller environmental impacts than the current-day scenarios,whereas PR3 has larger impacts in most categories.PR3 has the lowest net costs(sum of internal costs and benefits,39.1-54.7 CNY per kg P),whereas PR2 has the lowest external costs(366.8 CNY per kg P).Societal costs for production and land use of 1 kg P by P recovery from sewage sludge(e.g.,∼527 CNY for PR1)are much higher than those of P chemical fertilizers(∼20 CNY for CF).However,considering the costs in the current-day treatments(e.g.,∼524 CNY for CT1),societal costs of P recovery scenarios are close to or slightly lower than those of current-day scenarios.Among the three P recovery scenarios,we found that recovering struvite as P fertilizer has the highest societal feasibility.This study will provide valuable information for improved sewage sludge management and will help promote the sustainable supply of P in China.

A new strategy for obtaining highly concentrated phosphorus recovery solution in biofilm phosphorus recovery process

Recovery of phosphorus(P)from wastewater is of great significance for alleviating the shortage of P resources.At present,the P recovery process is faced with the problem of excessive organic carbon consumption when obtaining a P-concentrated recovery solution.This study proposed a new strategy to obtain a more highly concentrated P recovery solution with minimal carbon consumption by strengthening the P storage capacity of the biofilm.A biofilm sequencing batch reactor(BSBR)process was modified to treat synthetic wastewater.The effect of the dissolved oxygen(DO)concentration on the P storage capacity of the biofilm was investigated at DO concentrations of DO 3.5 mg/L(P_(L))and DO 6.5 mg/L(P_(H)).The results showed a maximum P storage of 101.2 and 149.6 mg-P/g-mixed liquid suspended solids under the two conditions.Strengthening the P storage capacity of the biofilm resulted in a net increase in the P recovery rate,which was as high as 66.96%in a harvesting cycle,and total soluble P>220 mg/L in the P recovery solution was successfully achieved.Meanwhile,the carbon cost of P recovery in the BSBR was reduced to 41.57 g-chemical oxygen demand/gP,and the carbon utilization efficiency was enhanced.To highlight the new strategy,the P recovery performance of the BSBR was given and the relationship between P content and anaerobic P release was discussed.In addition,the changes in the microbial communities under P_(L) and P_(H) conditions were analyzed.

Effect of sodium alginate on phosphorus recovery by vivianite precipitation

There are good prospects for phosphorus recovery from excess sludge by vivianite crystallization while a large number of extracellular polymeric substances in sludge will have impact on vivianite precipitation.In this study,as a representative of extracellular polymeric substance,the effect of sodium alginate(SA)on phosphorus recovery by vivianite precipitation under different initial SA concentrations(0–800 mg/L),p H values(6.5–9.0)and Fe/P molar ratios(1:1–2.4:1)was investigated using synthetic wastewater.The results showed that SA in low concentrations(≤400 mg/L)had little inhibitory effect on the phosphorus recovery rate.However,when the concentration of SA was larger than 400 mg/L,the phosphorus recovery rate decreased significantly with increasing SA concentrations.The inhibition rate of 800 mg/L SA was about 3 times as large as that of 400 mg/L SA.It was worth noting that the inhibitory effect of SA on vivianite precipitation decreased with increasing initial p H and Fe/P molar ratios.Additionally,SA has no obvious influence on the composition of products,but the morphology of harvested crystals was transformed from branches to plates or rods in uneven sizes.

A review of phosphorus recovery from different thermal treatment products of sewage sludge

Phosphorus(P)is an indispensable element of living organisms and plays an irreplaceable role in the growth of crops.As a non-renewable element,the reserves of phosphorus rock,the primary source of phosphorus in nature,are facing the danger of exhaustion.As a phosphorus-rich solid waste,sewage sludge has gradually become a main renewable phosphorus resource.The combination of effective recycling of phosphorus and innocuous disposal of sewage sludge can not only alleviate the crisis of phosphate rock resources shortage but also reduce the environmental hazards of sewage sludge.This study reviewed the application of thermal treatment in sewage sludge disposal.Besides the advantages of reducing waste volume,decom-posing organic pollutants,generating valuable byproducts,it can also significantly promote the recycling of phosphorus.Studies have shown that thermal treatment(incineration,pyrolysis,and hydrothermal)can enrich phosphorus in the products and transform the speciation of phosphorus to increase the bioavailability.The physical and chemical properties of different thermal treatment products and the speciation of phosphorus are different.The transformation and migration of phosphorus affect the efficiency of subsequent phosphorus recovery and reuse.At the same time,this study compared several general phosphorus recovery methods(wet extraction,thermochemical,and electrochemical methods),and further summarized the advantages and disadvantages of various methods and application conditions.This review summarizes recent advances in phosphorus recovery from sewage sludge,identifies challenges and knowledge gaps,and provides the foundation for future research aimed at achieving efficient,economic,and eco-friendly reclamation of phosphorus in sewage sludge.

Effect of saline water ionic strength on phosphorus recovery from synthetic swine wastewater

Declining worldwide phosphate rock reserves has driven a growing interest in exploration of alternative phosphate supplies. This study involved phosphorus recovery from swine wastewater through precipitation of struvite, a valuable slow-release fertiliser. The economic feasibility of this process is highly dependent on the cost of magnesium source. Two different magnesium sources were used for phosphorus recovery: pure magnesium chloride and nanofiltration(NF) saline water retentate. The paper focuses on the impact of ionic strength on phosphorus recovery performance that has not been reported elsewhere. Experimental design with five numerical variables(Mg/P molar ratio, pH, PO_(4)^(3-)-P, NH_(4)^(+)-N, and Ca^(2+) levels) and one categorical variable(type of magnesium source) was used to evaluate the effect of ionic strength on phosphorus removal and struvite purity. The experimental data were analysed using analysis of variance(ANOVA) and principal component analysis(PCA). Results indicated that a magnesium source obtained from NF retentate was as effective as MgCl_(2) for struvite precipitation. It was also revealed that ionic strength had a more positive effect on struvite purity than on phosphorus removal. Within the range of parameters studied in this research, high ionic strength, high p H and wastewater with high phosphate, high ammonium and low calcium contents were found to be the most favourable conditions for struvite precipitation. Findings from this study will be beneficial to determine the feasibility of using high ionic strength saline water, such as NF seawater retentate, as a magnesium source for phosphorus recovery from wastewater that is rich in ammoniumnitrogen and phosphate.

Recovery and Upgrading of Phosphorus from Digested Sewage Sludge as MAP by Physical Separation Techniques

Physical separation apparatuses;a vibrating screen, a 4-inch hydrocyclone and a Multi-Gravity Separator (MGS) were used to recover phosphorus as MAP (magnesium ammonium phosphate, MgNH4PO4.6H2O) from anaerobic digested sludge of two sewage-treatment plants A and B. For plant A, the MAP grade increased from 0.08% to 88.9% with 90.4% recovery and for plant B, the grade increased from 0.11% to 73.8 with 93.2% recovery. The collected MAP products containing impurities such as organic materials and heavy metals were further upgraded through dry and wet magnetic separation tests at different magnetic flux densities. A dry magnetic separator was tested on both MAP products (MAP-A and MAP-B), while the wet magnetic separation process was exclusively experimented for the removal of impurities from MAP-B. Feed samples, as well as magnetic and nonmagnetic products were analyzed by absorption spectroscopy, XRD, ICP-AES, polarizing microscope observation, and SEM-EDX. The grade of MAP products could be improved by about 4% - 9% after magnetic separation (the most appropriate magnetic force being 15,000 Gauss). During both dry and wet magnetic separation processes, not only heavy metals have been removed, but also nonmagnetic constituents like Al, Ba, and Ca. This may be attributed to the attachment of fine magnetic particles on the nonmagnetic surfaces, rendering them magnetic properties.

Temporal Dynamics and Performance Association of the Tetrasphaera-Enriched Microbiome for Enhanced Biological Phosphorus Removal

Tetrasphaera have been recently identified based on the 16S ribosomal RNA(rRNA)gene as among the most abundant polyphosphate-accumulating organisms(PAOs)in global full-scale wastewater treatment plants(WWTPs)with enhanced biological phosphorus removal(EBPR).However,it is unclear how Tetrasphaera PAOs are selectively enriched in the context of the EBPR microbiome.In this study,an EBPR microbiome enriched with Tetrasphaera(accounting for 40%of 16S sequences on day 113)was built using a top-down design approach featuring multicarbon sources and a low dosage of allylthiourea.The microbiome showed enhanced nutrient removal(phosphorus removal~85%and nitrogen removal~80%)and increased phosphorus recovery(up to 23.2 times)compared with the seeding activated sludge from a local full-scale WWTP.The supply of 1 mg·L^(-1)allylthiourea promoted the coselection of Tetrasphaera PAOs and Microlunatus PAOs and sharply reduced the relative abundance of both ammonia oxidizer Nitrosomonas and putative competitors Brevundimonas and Paracoccus,facilitating the establishment of the EBPR microbiome.Based on 16S rRNA gene analysis,a putative novel PAO species,EBPR-ASV0001,was identified with Tetrasphaera japonica as its closest relative.This study provides new knowledge on the establishment of a Tetrasphaera-enriched microbiome facilitated by allylthiourea,which can be further exploited to guide future process upgrading and optimization to achieve and/or enhance simultaneous biological phosphorus and nitrogen removal from high-strength wastewater.

Study on the Recycling of P in Phosphogypsum Leachate

After washing and curing, P is transported from the phosphogypsum to the leachate during the phosphogypsum detoxification process, providing two ideas for phosphorus recovery from phosphogypsum leachate: 1) preparation of calcium hydrogen phosphate for feed;2) preparation of calcium phosphate. A ready-to-use calcium oxide slurry was used to recover P from phosphogypsum leachate at a slurry concentration of 20% and a quantitative link between calcium to phosphorus ratio and fixation rate was fitted by mixed use batch experiments, reaction kinetics and thermodynamics, and theoretical calculations were used to demonstrate that phosphorus cannot be completely reused in the preparation of calcium hydrogen phosphate. The findings demonstrated that: a) the residual phosphorus concentration was in the range of 1300 - 1500 mg/L for the preparation of type I feed grade calcium hydrogen phosphate from phosphogypsum leachate;b) the P removal effect could reach 99.99% for the preparation of calcium phosphate from phosphogypsum using the theoretical equation: fixation rate = 87.91 - 10.96(Ca/P) + 3.22(Ca/P)2 (R2 = 0.9954);c) The procedure follows the suggested secondary kinetics, and according to the Freundlich isothermal model, the reaction process is under the control of the chemical reaction, with a reaction index of 0.7605. This study can be used as a theoretical guide for the recovery of P from phosphogypsum leachate, the preparation of products to bring about economic by-products, and the purification of wastewater for reuse.

Cell surface-expression of the phosphate-binding protein PstS:System development,characterization,and evaluation for phosphorus removal and recovery

Simultaneous overabundance and scarcity of inorganic phosphate(Pi)is a critical issue driving the development of innovative water/wastewater treatment technologies that not only facilitate Pi removal to prevent eutrophication,but also recover Pi for agricultural reuse.Here,a cell-surface expressed high-affinity phosphate binding protein(PstS)system was developed,and its Pi capture and release potential was evaluated.E.coli was genetically modified to express PstS on its outer membrane using the ice nucleation protein(INP)as an anchoring motif.Verification of protein expression and localization were performed utilizing SDS-polyacrylamide gel electrophoresis(SDS-PAGE),western blot,and outer membrane separation analyses.Cell surface characterization was investigated through acid-base titration,X-ray photoelectron spectroscopy(XPS),and Fourier transform infrared spectroscopy(FTIR).These tests provided information on the macromolecular structure and composition of the bacteria surface as well as the proton-exchange properties of the surface functional groups(i.e.,pKa values).Phosphate desorption and adsorption batch experiments were conducted to evaluate the effects of temperature,pH,and ionic strength on phosphate capture and release.The PstS surface-displayed cells demonstrated greater potential to release and capture phosphate compared to non-modified cells.Higher temperatures up to 40℃,basic pH conditions(pH=10.5),and higher ionic strength up to 1.0 mol/L KCl promoted 20%-50%higher phosphate release.

Preparation and characterization of MgO hybrid biochar and its mechanism for high efficient recovery of phosphorus from aqueous media

Conversion of organic waste into engineered metal-biochar composite is an effective way of enhancing biochar’s efficiency for adsorptive capture of phosphorus(P)from aqueous media.Thus,various strategies have been created for the production of metal-biochar composites;however,the complex preparation steps,high-cost metal salt reagent application,or extreme process equipment requirements involved in those strategies limited the large-scale production of metal-biochar composites.In this study,a novel biochar composite rich in magnesium oxides(MFBC)was directly produced through co-pyrolysis of magnesite with food waste;the product,MFBC was used to adsorptively capture P from solution and bio-liquid wastewater.The results showed that compared to the pristine food waste biochar,MFBC was a uniformly hybrid MgO biochar composite with a P capture capacity of 523.91 mg/g.The capture of P by MFBC was fitted using the Langmuir and pseudo-first-order kinetic models.The P adsorptive capture was controlled by MgHPO4 formation and electrostatic attraction,which was affected by the coexisting F−and CO_(3)^(2−)ions.MFBC could recover more than 98%of P from the solution and bio-liquid wastewater.Although the P-adsorbed MFBC showed very limited reusability but it can be substituted for phosphate fertiliser in agricultural practices.This study provided an innovative technology for preparing MgO-biochar composite against P recovery from aqueous media,and also highlighted high-value-added approaches for resource utilization of bio-liquid wastewater and food waste.

Adsorption and recovery of phosphate from water by amine fiber,effects of co-existing ions and column filtration

A weak-base adsorption fiber,acrylic amine fiber(AAF),was prepared for removal and recovery of phosphate from water.The adsorption properties of the AAF for phosphate and effects of co-existing ions were investigated using batch and column filtration experiments,scanning electron microscope,and Fourier transform infrared techniques.Experimental results showed that AAF had a high phosphate adsorption capacity of 119 mg/g at pH 7.0.The effects of calcium,sulfate,carbonate,nitrate,and fluoride showed that sulfate and calcium inhibited phosphate adsorption.However,AAF showed higher binding affinity toward phosphate than sulfate.Column filtration results showed that AAF could filter 1420 bed volumes of tap water containing 1.0 mg-P/L of phosphate.The saturated AAF could be regenerated using 0.5 mol/L hydrochloric acid solution and reused.After desorption,phosphate was recovered through precipitation of hydroxyapatite(Ca5(PO4)3OH).The easy of regeneration,good adsorption performance,and the fiber morphology of AAF make it an attractive alternative for phosphate recovery from multiple water sources.

Selection of cost-effective magnesium sources for fluidized struvite crystallization

Struvite crystallization has been considered a promising approach to recover phosphorus from wastewater. However, its practical application is limited, probably because of the high cost of magnesium(Mg). In this study, a comprehensive economic analysis was conducted using five Mg sources(MgCl_2, MgSO_4, MgO, Mg(OH)_2, and bittern) during the operation of a pilot-scale fluidized bed reactor(FBR), using swine wastewater as the case matrix. First, the economic operating conditions were investigated, and subsequently, the performance and the costs of the five Mg sources were compared. The results indicated that the FBR could be operated most economically at pH of 8.5 and Mg to phosphorus(Mg/P) molar ratio of 1.5. Under these conditions, no significant differences in phosphorus removal and product quality could be found between the five Mg sources. Selecting the most economical Mg source was thus highly dependent on the prices of the reagents and Mg sources. Low-solubility Mg sources were preferable when NaOH was priced higher, while high-solubility Mg sources proved more economical when HNO_3 was expensive. The bittern was the most economical choice only when the distances for total inorganic orthophosphate removal and struvite recovery were shorter than 40 and 270 km, respectively. The current study provides an overview of the economic selection of an Mg source, which can help reduce the cost of struvite crystallization.

Raceway pond cultivation of a new Arthrospira sp.ZJWST-S1 in digested piggery wastewater treated by MBR and ozonation

A new Arthrospira strain named Arthrospira sp.ZJWST-S1 was isolated from a local digested piggery wastewater(DPW)storage pool in Jiaxing City,Zhejiang Province,China.It possessed good stain resistance against contaminants in DPW,which was pretreated with a membrane bioreactor(MBR).The strain was identified as Arthrospira platensis(A.platensis)based on its morphological characteristics and the 16S rDNA sequencing analysis.The effect of chrominance on growth of A.platensis ZJWST-S1 was investigated in a field raceway pond filled with MBR effluent or MBR effluent decolorized with ozonation.After ozonation,the chrominance of MBR effluent was decreased from 700 mg Pt/L to 150 mg Pt/L.Two runs of cultivation showed that A.platensis ZJWST-S1 grew faster in the ozone decolorized MBR effluent,the averaged biomass concentration being 0.907 g/L after 10 days of cultivation,close to that in a Zarrouk medium(0.969 g/L).By comparison,the biomass grew much slower in the non-decolorized MBR effluent(0.624 g/L).The pollutant removal was also benefited from the accelerative growth of A.platensis ZJWST-S1 in the decolorized MBR effluent.Almost all ammonium,61.2%of nitrate and 68.1%of phosphate were removed by the A.platensis ZJWST-S1 in the decolorized MBR effluent,much higher than the corresponding values of almost all ammonium,25.4%of nitrate and 36.5%of phosphate in the MBR effluent.Furthermore,the Arthrospira biomass harvested from the ozone decolorized MBR effluent after 10 d cultivation was with crude protein content of 59.1%±3.5%in dry algae powder.The content of Pb,As,Cd and Hg in biomass was also low enough to meet the Chinese Arthrospira Standard for Animal Feed(GB/T 17243-1998).This study showed that the new strain A.platensis ZJWST-S1 possessed potential to be used for producing animal feed and simultaneous removal of nitrogen and phosphorus in DPW.