Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite...Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.展开更多
Phosphorus is an irreplaceable and depletable element. Furthermore, it has an almost one-way circulation on earth, so it is necessary to close the phosphorus cycle loop. Phosphorus could be recovered as struvite, whic...Phosphorus is an irreplaceable and depletable element. Furthermore, it has an almost one-way circulation on earth, so it is necessary to close the phosphorus cycle loop. Phosphorus could be recovered as struvite, which is a good slow-released fertilizer for agriculture. The supernatant of anaerobic digestion used to treat sludge from wastewater treatment plant is one main source from which phosphorus can be recovered. Studies have proven that phosphorus recovery from digester supematant is a feasible choice to preserve phosphorus rock technically and economically. A modified ＂PHOSNIX＂ P-recovery process was applied under the operating conditions of a 9.0 pH value and a 1.8 mg： P ratio with the influent of the centrate coming from the sludge centrifuge of the Songjiang Wastewater Treatment Plant in Shanghai. More than 80% influent phosphorus was recovered as struvite. Crystal products with good purity and low heavy metal content were gained. The largest crystal had a length of up to 0.26 mm. It was found in our study that the reaction time did not play an important role in crystal growth. Therefore, the optimization of the reaction condition for crystal growth should be examined in future study.展开更多
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 ou...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.展开更多
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 w...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).展开更多
Leveraging seawater toilet flushing system in Hong Kong,China,a Seawater-based Urine Phosphorus Recovery(SUPR)process that integrates ureolysis and phosphorus(P)recovery was proposed in our earlier work.In this study,...Leveraging seawater toilet flushing system in Hong Kong,China,a Seawater-based Urine Phosphorus Recovery(SUPR)process that integrates ureolysis and phosphorus(P)recovery was proposed in our earlier work.In this study,a thermodynamic model was applied to evaluate the effects of ureolysis and the seawater-to-urine mixing ratio(S/U ratio)on P precipitation in the SUPR system.The results suggested that effective P recovery was thermodynamically feasible across a wide range of S/U ratios,with elevated pH levels resulting from ureolysis being critical for P precipitation.Furthermore,a SUPR reactor was developed to validate this process.When the hydraulic retention time(HRT)exceeded 3 h and the S/U ratio was lower than 3:1,more than 98%of P could be recovered without urine storage,chemical dosage,or external mixing.Further decrease in the HRT and increase in S/U ratio caused flushing out of fine precipitates,resulting in a relatively low P recovery efficiency.However,this could be advantageous when downstream urine nitrification is implemented,as dilution of urine can alleviate the inhibitory effects of free ammonia and free nitrous acid,as well as overcome the P limitation problem,thus facilitating urine nitrification.Consequently,there is a trade-off between optimizing P recovery and nitrification efficiencies.展开更多
Phosphorus（P） is a limited resource, which can neither be synthesized nor substituted in its essential functions as nutrient. Currently explored and economically feasible global reserves may be depleted within gener...Phosphorus（P） is a limited resource, which can neither be synthesized nor substituted in its essential functions as nutrient. Currently explored and economically feasible global reserves may be depleted within generations. China is the largest phosphate fertilizer producing and consuming country in the world. China’s municipal wastewater contains up to 293,163 Mg year of phosphorus, which equals approximately 5.5% of the chemical fertilizer phosphorus consumed in China. Phosphorus in wastewater can be seen not only as a source of pollution to be reduced, but also as a limited resource to be recovered. Based upon existing phosphorus-recovery technologies and the current wastewater infrastructure in China, three options for phosphorus recovery from sewage sludge, sludge ash and the fertilizer industry were analyzed according to the specific conditions in China.展开更多
Struvite crystallization is a promising method to remove and recover phosphorus from wastewater to ease both the scarcity of phosphorus rock resources and water eutrophication worldwide. To date, although various kind...Struvite crystallization is a promising method to remove and recover phosphorus from wastewater to ease both the scarcity of phosphorus rock resources and water eutrophication worldwide. To date, although various kinds of reactor systems have been developed, supporting methods are required to control the stmvite fines flushing out of the reactors. As an intrinsic property, aggregation is normally disregarded in the struvite crystallization process, although it is the key factor in final particle size and therefore guarantees phosphorus recovery efficiency. The present study developed a method to analyze the characteristics of struvite aggregates using fractal geometry, and the influence of operational parameters on struvite aggregation was evaluated. Due to its typical orthorhombic molecular structure, struvite particles are prone to crystallize into needle or rod shapes, and aggregate at the comers or edges of crystals. The determined fractal dimension （Dpf） of struvite aggregates was 1.52-1.31, with the corresponding range of equivalent diameter （d0.5） at 295.9-85.4 Ixm. Aggregates formed in relatively low phosphorus concentrations （3.0-5.0 mmol/L） and mildly alkaline conditions （pH 9.0-9.5） displayed relatively compact structures, large aggregate sizes and high aggregation strength. Increasing pH values led to continuous decrease of aggregate sizes, while the variation of Dpf was insignificant. As to the aggregate evolution, fast growth in a short time followed by a long steady stage was observed.展开更多
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 ob...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.展开更多
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...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.展开更多
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...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.展开更多
Microwave（MW） hybrid processes are able to disrupt the flocculent structure of complex waste activated sludge,and help promote the recovery of phosphorus as struvite.In this study,to optimize struvite yield,（1） th...Microwave（MW） hybrid processes are able to disrupt the flocculent structure of complex waste activated sludge,and help promote the recovery of phosphorus as struvite.In this study,to optimize struvite yield,（1） the characteristics of matter released in MW-hybrid treatments were compared,including MW,MW-acid,MW-alkali,MW-H2O2,and MW-H2O2- alkali.The results showed that selective release of carbon,nitrogen,phosphorus,Ca^2＋,and Mg^2＋ achieved by sludge pretreatment using MW-hybrid processes.MW-H2O2 is the recommended sludge pretreatment process for phosphorus recovery in the form of struvite.The ratio of Mg^2＋：NH4^＋-N：PO4^3--P was 1.2：2.9：1 in the supernatant.（2） To clarify the effects of organic matter on struvite recovery,the composition and molecular weight distribution of organic matters were analyzed.Low molecular weight COD was found to facilitate the removal rate of NH4^＋-N and PO4^3-P via crystallization,and the amorphous struvite crystals（〈1 kDa） from the filtered solutions had high purity.Therefore,the present study reveals the necessity of taking into consideration the interference effect of high molecular weight organic matters during struvite crystallization from sewage sludge.展开更多
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 struvi...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.展开更多
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...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.展开更多
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 oppor...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.展开更多
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, MgNH<sub>4</sub>PO<sub...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, MgNH<sub>4</sub>PO<sub>4.</sub>6H<sub>2</sub>O) 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.展开更多
Shortage in phosphorus （P） resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultur...Shortage in phosphorus （P） resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar （Ca-Mg/biochar） application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca-Mg/biochar was rich in organic functional groups and in CaO and MgO nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca-Mg/biochar could be accelerated by nano-CaO and nano-MgO particles and reached equilibrium after 360min. The process was endothermic, spontaneous, and showed an increase in the disorder of the solid-liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63 mg/g. The P adsorption selectivity of Ca-Mg/biochar could not be significantly influenced by the typical pH level of biogas fermentation liquid. The nano-CaO and nano-MgO particles of Ca-Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca-Mg/biochar were in the order of Ca-Mg/B600 〉 Ca-Mg/B4S0 〉 Ca-Mg/B300. Results revealed that postsorption Ca-Mg/biochar can continually release P and is more suitable for an acid environment.展开更多
The releasing characteristics of phosphorus, nitrogen compounds, organics, and some metal cations during thermal treatment of excess sludge were investigated. It was found that during heating not only phosphorus, but ...The releasing characteristics of phosphorus, nitrogen compounds, organics, and some metal cations during thermal treatment of excess sludge were investigated. It was found that during heating not only phosphorus, but also nitrogen compounds, organics, and some metal cations could be released in abundance. The maximum orthophosphate （ortho-P） release of about 90 mg/L in concentration was observed at 50℃ in 1 h. Except for volatile fatty acids （VFAs）, comparatively little total nitrogen （TN）, total organic carbon （TOC）, and metal cations were released at the same time. Such results might favor further process of phosphorus recovery. VFAs were considerably released only at 50℃. Acetic, butyric, and propionic acid were the most abundant components in turn and their releasing profiles exhibited good linear relationship with time （R2 = 0.9977, 0.9624, and 0.8908, respectively）. The concentrations of Mg^2＋ and K^＋ increased with time and temperature during thermal treatment, but Ca^2＋ decreased. The release of Mg^2＋ and K^＋ agreed well with TP release （R^2 = 0.9892 and 0.9476, respectively）. Temperature in the experimental range had very little impact on the linear relationships, especially of Mg^2＋. Moreover, the parameter of mixed liquor suspended solids （MLSS） was found to be an important factor for thermal sludge treatment as the released ortho-P and total phosphorus （TP） at 50℃ increased more than one-fold when MLSS was increased from 4000 to 8000 mg/L.展开更多
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 enha...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.展开更多
Phosphorus （P） is an element vital for all living organisms, yet the world＇s reserves of phosphate rock are becoming depleted. This study investigated an effective P recovery method from sludge ash via struvite pre...Phosphorus （P） is an element vital for all living organisms, yet the world＇s reserves of phosphate rock are becoming depleted. This study investigated an effective P recovery method from sludge ash via struvite precipitation. Results showed that more than 95% of the total P content was extracted from sludge ash by applying 0.5 mol/L HC1 at a liquid/solid ratio of 50 mL/g. Although heavy metal leaching also occurred during P extraction, cation exchange resin efticiently removed the heavy metals from the P-rich solution. Orthogonal tests showed that the optimal parameters for P precipitation as struvite would be a Mg：N：P molar ratio of 1.6：1.6：1 at pH 10.0. X-ray diffraction analysis validated the formation of struvite. Further investigations revealed that the harvested precipitate had a high struvite content （97%）, high P bioavailability （94%）, and low heavy metal content, which could be considered a high quality fertilizer.展开更多
For phosphorus （P） recovery from wastewater, the effect of humic substances （HS） on the precipitation of calcium phosphate was studied. Batch experiments of calcium phosphate precipitation were undertaken with syn...For phosphorus （P） recovery from wastewater, the effect of humic substances （HS） on the precipitation of calcium phosphate was studied. Batch experiments of calcium phosphate precipitation were undertaken with synthetic water that contained 20 mg/L phosphate （as P） and 20 mg/L HS （as dissolved organic carbon, DOC） at a constant pH value in the range of 8.0-10.0. The concentration variations of phosphate, calcium （Ca） and HS were measured in the precipitation process; the crystalline state and compositions of the precipitates were analysed by powder X-ray diffraction （XRD） and chemical methods, respectively. It showed that at solution pH 8.0, the precipitation rate and removal efficiency of phosphate were greatly reduced by HS, but at solution pH ≥9.0, the effect of HS was very small. The Ca consumption for the precipitation of phosphate increased when HS was added; HS was also removed from solution with the precipitation of calcium phosphate. At solution pH 8.0 and HS concentrations ≤3.5 mg/L, and at pH ≥ 9.0 and HS concentrations ≤ 10 mg/L, the final precipitates were proved to be hydroxyapatite （HAP） by XRD. The increases of solution pH value and initial Ca/P ratio helped reduce the influence of HS on the precipitation of phosphate.展开更多
基金Project supported by the High Level Returned Overseas Chinese Scholars (No. 2005-118)the Returned Overseas Chinese Scholars (No. 2004-99)the Innovation Fund of Chinese Research Academy of Environmental Sciences (No. 2004-021).
文摘Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.
文摘Phosphorus is an irreplaceable and depletable element. Furthermore, it has an almost one-way circulation on earth, so it is necessary to close the phosphorus cycle loop. Phosphorus could be recovered as struvite, which is a good slow-released fertilizer for agriculture. The supernatant of anaerobic digestion used to treat sludge from wastewater treatment plant is one main source from which phosphorus can be recovered. Studies have proven that phosphorus recovery from digester supematant is a feasible choice to preserve phosphorus rock technically and economically. A modified ＂PHOSNIX＂ P-recovery process was applied under the operating conditions of a 9.0 pH value and a 1.8 mg： P ratio with the influent of the centrate coming from the sludge centrifuge of the Songjiang Wastewater Treatment Plant in Shanghai. More than 80% influent phosphorus was recovered as struvite. Crystal products with good purity and low heavy metal content were gained. The largest crystal had a length of up to 0.26 mm. It was found in our study that the reaction time did not play an important role in crystal growth. Therefore, the optimization of the reaction condition for crystal growth should be examined in future study.
文摘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.
文摘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).
基金supported by the Excellent Young Scientists Fund of National Natural Science Foundation of China(No.52222008)the Science and Technology Development Fund,Macao SAR,China(No.0026/2022/A1)+2 种基金the Shenzhen Science and Technology Innovation Committee(No.EF2023-00072-FST)the Research Grants Council of Hong Kong Special Administrative Region,China(No.T21-604/19-R)the Hong Kong Innovation and Technology Commission,China(No.ITC-CNERC14EG03).
文摘Leveraging seawater toilet flushing system in Hong Kong,China,a Seawater-based Urine Phosphorus Recovery(SUPR)process that integrates ureolysis and phosphorus(P)recovery was proposed in our earlier work.In this study,a thermodynamic model was applied to evaluate the effects of ureolysis and the seawater-to-urine mixing ratio(S/U ratio)on P precipitation in the SUPR system.The results suggested that effective P recovery was thermodynamically feasible across a wide range of S/U ratios,with elevated pH levels resulting from ureolysis being critical for P precipitation.Furthermore,a SUPR reactor was developed to validate this process.When the hydraulic retention time(HRT)exceeded 3 h and the S/U ratio was lower than 3:1,more than 98%of P could be recovered without urine storage,chemical dosage,or external mixing.Further decrease in the HRT and increase in S/U ratio caused flushing out of fine precipitates,resulting in a relatively low P recovery efficiency.However,this could be advantageous when downstream urine nitrification is implemented,as dilution of urine can alleviate the inhibitory effects of free ammonia and free nitrous acid,as well as overcome the P limitation problem,thus facilitating urine nitrification.Consequently,there is a trade-off between optimizing P recovery and nitrification efficiencies.
基金supported by the Chinese Government Graduate Student Overseas Study Program by the China Scholarship Council(CSC)
文摘Phosphorus（P） is a limited resource, which can neither be synthesized nor substituted in its essential functions as nutrient. Currently explored and economically feasible global reserves may be depleted within generations. China is the largest phosphate fertilizer producing and consuming country in the world. China’s municipal wastewater contains up to 293,163 Mg year of phosphorus, which equals approximately 5.5% of the chemical fertilizer phosphorus consumed in China. Phosphorus in wastewater can be seen not only as a source of pollution to be reduced, but also as a limited resource to be recovered. Based upon existing phosphorus-recovery technologies and the current wastewater infrastructure in China, three options for phosphorus recovery from sewage sludge, sludge ash and the fertilizer industry were analyzed according to the specific conditions in China.
基金supported by the Hi-Tech Research and Development Program(863)of China(No.2011AA060902)the Xiamen Science and Technology Planning Project(No.3502Z20132016)
文摘Struvite crystallization is a promising method to remove and recover phosphorus from wastewater to ease both the scarcity of phosphorus rock resources and water eutrophication worldwide. To date, although various kinds of reactor systems have been developed, supporting methods are required to control the stmvite fines flushing out of the reactors. As an intrinsic property, aggregation is normally disregarded in the struvite crystallization process, although it is the key factor in final particle size and therefore guarantees phosphorus recovery efficiency. The present study developed a method to analyze the characteristics of struvite aggregates using fractal geometry, and the influence of operational parameters on struvite aggregation was evaluated. Due to its typical orthorhombic molecular structure, struvite particles are prone to crystallize into needle or rod shapes, and aggregate at the comers or edges of crystals. The determined fractal dimension （Dpf） of struvite aggregates was 1.52-1.31, with the corresponding range of equivalent diameter （d0.5） at 295.9-85.4 Ixm. Aggregates formed in relatively low phosphorus concentrations （3.0-5.0 mmol/L） and mildly alkaline conditions （pH 9.0-9.5） displayed relatively compact structures, large aggregate sizes and high aggregation strength. Increasing pH values led to continuous decrease of aggregate sizes, while the variation of Dpf was insignificant. As to the aggregate evolution, fast growth in a short time followed by a long steady stage was observed.
基金supported by the National Natural Science Foundation of China(Nos.51778390,51938010)Natural Science Foundation of Jiangsu Province(No.BK20171219)+1 种基金the Graduate Research and Innovation Projects of Jiangsu Province(No.KYCX19_2032)Financial support was also provided by the Collaborative Innovation Center of Water Treatment Technology and Material of Jiangsu Province and the National and Local Joint Engineering Laboratory of Municipal Sewage Resource Utilization Technology。
文摘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.
基金supported by the State Key Laboratory of Eco-hydraulics in the Northwest Arid Region of China(No.2016ZZKT-8)。
文摘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.
基金the National Natural Science Foundation of China(Grant No.51621005)Key research and development plan of the Yunnan Science and Technology Department(2018IB026).
文摘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.
基金financially supported by the Major Science and Technology Program for Water Pollution Control and Treatment of China (No. 2015ZX07203-005, 2012ZX07202-005)the National Natural Science Foundation of China (No. 51008297)
文摘Microwave（MW） hybrid processes are able to disrupt the flocculent structure of complex waste activated sludge,and help promote the recovery of phosphorus as struvite.In this study,to optimize struvite yield,（1） the characteristics of matter released in MW-hybrid treatments were compared,including MW,MW-acid,MW-alkali,MW-H2O2,and MW-H2O2- alkali.The results showed that selective release of carbon,nitrogen,phosphorus,Ca^2＋,and Mg^2＋ achieved by sludge pretreatment using MW-hybrid processes.MW-H2O2 is the recommended sludge pretreatment process for phosphorus recovery in the form of struvite.The ratio of Mg^2＋：NH4^＋-N：PO4^3--P was 1.2：2.9：1 in the supernatant.（2） To clarify the effects of organic matter on struvite recovery,the composition and molecular weight distribution of organic matters were analyzed.Low molecular weight COD was found to facilitate the removal rate of NH4^＋-N and PO4^3-P via crystallization,and the amorphous struvite crystals（〈1 kDa） from the filtered solutions had high purity.Therefore,the present study reveals the necessity of taking into consideration the interference effect of high molecular weight organic matters during struvite crystallization from sewage sludge.
基金This research was financially supported by the Department of Chemical and Materials Engineering,Faculty of Engineering,the University of Auckland。
文摘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.
基金the National Natural Science Foundation of China(Grant Nos.51704080,51874102 and 52074093)the National Key Research and Development Program of China(Grant No.2019YFC1905200).
文摘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.
基金This study was funded by the National Key R&D Program of China(2018YFE0106400)the National Natural Science Foundation of China(42122059 and 41977324)the Natural Science Foundation of Tianjin(20JCYBJC01080).The support from Aalborg University was also acknowledged.
文摘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.
文摘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, MgNH<sub>4</sub>PO<sub>4.</sub>6H<sub>2</sub>O) 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.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120008120013)the National Natural Science Foundation of China (No. 31401944)+2 种基金the Beijing Natural Science Foundation (No. 6144026)the China Scholarship Council (No. 201206355006)the Chinese Universities Scientific Fund of China Agricultural University (No. 2011JS169)
文摘Shortage in phosphorus （P） resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar （Ca-Mg/biochar） application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca-Mg/biochar was rich in organic functional groups and in CaO and MgO nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca-Mg/biochar could be accelerated by nano-CaO and nano-MgO particles and reached equilibrium after 360min. The process was endothermic, spontaneous, and showed an increase in the disorder of the solid-liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63 mg/g. The P adsorption selectivity of Ca-Mg/biochar could not be significantly influenced by the typical pH level of biogas fermentation liquid. The nano-CaO and nano-MgO particles of Ca-Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca-Mg/biochar were in the order of Ca-Mg/B600 〉 Ca-Mg/B4S0 〉 Ca-Mg/B300. Results revealed that postsorption Ca-Mg/biochar can continually release P and is more suitable for an acid environment.
文摘The releasing characteristics of phosphorus, nitrogen compounds, organics, and some metal cations during thermal treatment of excess sludge were investigated. It was found that during heating not only phosphorus, but also nitrogen compounds, organics, and some metal cations could be released in abundance. The maximum orthophosphate （ortho-P） release of about 90 mg/L in concentration was observed at 50℃ in 1 h. Except for volatile fatty acids （VFAs）, comparatively little total nitrogen （TN）, total organic carbon （TOC）, and metal cations were released at the same time. Such results might favor further process of phosphorus recovery. VFAs were considerably released only at 50℃. Acetic, butyric, and propionic acid were the most abundant components in turn and their releasing profiles exhibited good linear relationship with time （R2 = 0.9977, 0.9624, and 0.8908, respectively）. The concentrations of Mg^2＋ and K^＋ increased with time and temperature during thermal treatment, but Ca^2＋ decreased. The release of Mg^2＋ and K^＋ agreed well with TP release （R^2 = 0.9892 and 0.9476, respectively）. Temperature in the experimental range had very little impact on the linear relationships, especially of Mg^2＋. Moreover, the parameter of mixed liquor suspended solids （MLSS） was found to be an important factor for thermal sludge treatment as the released ortho-P and total phosphorus （TP） at 50℃ increased more than one-fold when MLSS was increased from 4000 to 8000 mg/L.
基金supported by the Key Research and Development Program of Zhejiang(2022C03075)National Natural Science Foundation of China(22241603)Zhejiang Provincial Natural Science Foundation of China(LR22D010001)。
文摘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.
基金supported by the National Natural Science Foundation of China (No. 20977066)the Specialized Research Found for Doctoral Program of Higher Educationof China (No. 200802470029)the Major Science and Technology program for Water Pollution Control and Treatment (No. 2008ZX07316-002)
文摘Phosphorus （P） is an element vital for all living organisms, yet the world＇s reserves of phosphate rock are becoming depleted. This study investigated an effective P recovery method from sludge ash via struvite precipitation. Results showed that more than 95% of the total P content was extracted from sludge ash by applying 0.5 mol/L HC1 at a liquid/solid ratio of 50 mL/g. Although heavy metal leaching also occurred during P extraction, cation exchange resin efticiently removed the heavy metals from the P-rich solution. Orthogonal tests showed that the optimal parameters for P precipitation as struvite would be a Mg：N：P molar ratio of 1.6：1.6：1 at pH 10.0. X-ray diffraction analysis validated the formation of struvite. Further investigations revealed that the harvested precipitate had a high struvite content （97%）, high P bioavailability （94%）, and low heavy metal content, which could be considered a high quality fertilizer.
基金The German Research Foundation (DFG-Graduiertenkolleg 366) Grant Program for the High-Level Returned Scholars fromAbroad, Ministry of Personnel of China (No. 2004-2005)
文摘For phosphorus （P） recovery from wastewater, the effect of humic substances （HS） on the precipitation of calcium phosphate was studied. Batch experiments of calcium phosphate precipitation were undertaken with synthetic water that contained 20 mg/L phosphate （as P） and 20 mg/L HS （as dissolved organic carbon, DOC） at a constant pH value in the range of 8.0-10.0. The concentration variations of phosphate, calcium （Ca） and HS were measured in the precipitation process; the crystalline state and compositions of the precipitates were analysed by powder X-ray diffraction （XRD） and chemical methods, respectively. It showed that at solution pH 8.0, the precipitation rate and removal efficiency of phosphate were greatly reduced by HS, but at solution pH ≥9.0, the effect of HS was very small. The Ca consumption for the precipitation of phosphate increased when HS was added; HS was also removed from solution with the precipitation of calcium phosphate. At solution pH 8.0 and HS concentrations ≤3.5 mg/L, and at pH ≥ 9.0 and HS concentrations ≤ 10 mg/L, the final precipitates were proved to be hydroxyapatite （HAP） by XRD. The increases of solution pH value and initial Ca/P ratio helped reduce the influence of HS on the precipitation of phosphate.
