Method For Phosphorus Recovery Research Articles

Efficient phosphorus recovery from waste activated sludge: Pretreatment with natural deep eutectic solvent and recovery as vivianite

Recycling phosphorus from waste activated sludge (WAS) is an effective method to address the nonrenewable nature of phosphorus and mitigate environmental pollution. To overcome the challenge of low phosphorus recovery from WAS due to insufficient disintegration, a method using a citric acid-based natural deep eutectic solvent (CA-NADES) assisted with low-temperature pretreatment was proposed to efficiently release and recover phosphorus. The results of 31P nuclear magnetic resonance (NMR) confirmed that low-temperature pretreatment promoted the conversion of organic phosphorus (OP) to inorganic phosphorus (IP) and enhanced the effect of CA-NADES. Changes in the three-dimensional excitation-emission matrix (3D-EEM) and flow cytometry (FCM) indicated that the method of CA-NADES with low-temperature thermal simultaneously release IP and OP by disintegrating sludge flocs, dissolving extracellular polymeric substances (EPS) structure, and cracking cells. When 5 % (v/v) of CA-NADES was added and thermally treated at 60 °C for 30 min, 43 % of total phosphorus (TP) was released from the sludge. The concentrations of proteins and polysaccharides reached 826 and 331 mg/L, respectively, which were 6.30 and 14.43 times higher than those of raw sludge. The dewatering and settling of the sludge were also improved. Metals were either enriched in the solid phase or released into the liquid phase in small quantities (most efficiencies of less than 10 %) for subsequent clean recovery. The released phosphorus was successfully recovered as vivianite with a rate of 90 %. This study develops an efficient, green, and sustainable method for phosphorus recovery from sludge using NADES and provides new insights into the high-value conversion of sludge.

Economic feasibility and direct greenhouse gas emissions from different phosphorus recovery methods in Swedish wastewater treatment plants

Phosphorus (P) is a finite, non-renewable resource that is a critical component of fertilizers; therefore, recovering P from municipal wastewater can provide an alternative sustainable source of this nutrient. This work analyses economic impacts and greenhouse gas emissions of P recovery in Swedish municipal wastewater treatment plants. The study examines different scenarios, including P recovery technologies in individual plants and hubs, and considers various P-rich streams (supernatant, sludge, and ash) in plants, different plant sizes, and multiple sludge management strategies such as land application, incineration, and hydrochar production, under current market conditions. The goal is to identify and offer solutions tailored to local conditions, addressing both technical opportunities and strategies to reduce costs.The results show varying recovery rates: 5 % from supernatant, 36–65 % from sludge, and 17 % from sludge ash relative to total P in wastewater. Despite technical feasibility, P recovery costs are not covered at current market prices of P, indicating a lack of financial incentive, especially for smaller treatment plants. The least expensive recovery method costs about 7 k€/t P for ash, compared to 30–187 k€/t P for supernatant, however with the latter coming with the co-benefit of mitigated greenhouse gas emissions. The emissions from studied plants range from 84 to 123 kt CO2 eq (CO2 equivalent) for supernatant, 94–141 kt CO2 eq for sludge, and 75–102 kt CO2 eq for ash among different P recovery methods. Comparatively, P recovery methods from supernatant showed the lowest emissions, while the lower emissions range for ash is due to the consideration of fewer plants. Developing hub networks and converting sludge into products like hydrochar are crucial for attracting investments, enhancing P recovery, and leveraging economies of scale. Results highlight the urgency for localized strategies and proactive policy interventions to reconcile economic and environmental objectives in P recycling. Furthermore, P recovery from wastewater treatment plants, although more resource-intensive than mineral fertilizer, promotes circularity in the food chain and mitigates the risk of eutrophication.

Improved agro-industrial waste utilization in biogas and fertilizer production ensuring CO2 sequestration

The global food crisis approach encourages finding new sources of replenishment of the phosphorus deficit in agriculture, making the unconventional sources of phosphorus particularly relevant. Despite numerous studies of phosphorus recovery methods, the need to increase the content of nutrients in the organo-mineral fertilizers obtained via anaerobic digestion of sewage activated sludge from municipal wastewater still exists. The greatest success in this area has been achieved by the biotechnologies which ensure the simultaneous production of biogas and biofertilizers. The present study proposes a sustainable technology for anaerobic digestion with the simultaneous capture of carbon dioxide and sodium carbonate production. It involves pre-comminution of the organo-mineral substrate (vegetal waste, activated sludge, phosphorus-containing component, and cheese whey) facilitating anaerobic digestion, and extraction of CO2 from biogas by absorption with a 10 % NaOH solution. Biomethanation reaction was found to have the first order with the activation energy of 24.8 kJ/mol, whereas the carbon dioxide absorption degree is proportional to the CO2 content in biogas. The results showed good potential for increasing the efficiency of both phosphorus recovery from municipal wastewater and anaerobic digestion to produce valuable products, including high-purity bio-methane (96 vol. % CH4), concentrated (∑NPKCa 53 %) organo-mineral fertilizer from digestate and soda ash. Obtained fertilizer increased potato yield by 35 wt. %. The study demonstrates a novel concept of carbon dioxide cycle looping in biogas production, as well as reducing greenhouse gas emissions by converting up to 98.7 % of CO2 into an additional marketable product – sodium carbonate, which contains 99 % Na2CO3.

Phosphorus recovery methods from secondary resources, assessment of overall benefits and barriers with focus on the Nordic countries

Phosphorus (P) recovery and recycling play a crucial role in improving resource efficiency, sustainable nutrient management and moving toward circular economy. Increasing demand for fertilizers, signs of geopolitical constraints, and high discharge of P to waterbodies are the other reasons to pursue the circularity of P. Various research have been carrying out and several processes have been developed for P-recovery from different resources. However, there is still a huge unexplored potential for P-recovery specially in the regional framework from the four main P-rich waste resources: food waste, manure, mining waste, and sewage sludge. This study reviews recovery methods of P from these secondary resources comprehensively. Additionally, it analyzes the Nordic viewpoint of P-cycle by evaluating Nordic reserves, demands, and secondary resources to gain a systematic assessment of how Nordic countries could move toward circular economy of P. Results of this study show that secondary resources of P in Nordic countries have the potential of replacing mineral fertilizer in these countries to a considerable extent. However, to overcome the challenges of P-recovery from studied resources, policymakers and researchers need to take decisions and make innovation along each other to open the new possibilities for Nordic economy.

Phosphorus recovery alternatives for sludge from chemical phosphorus removal processes – Technology comparison and system limitations

Several approaches have recently been proposed in the literature for P recovery after metal precipitation, but a robust comparison of these approaches in a techno-economic framework is still lacking. Five phosphorus recovery methods using sewage sludge or sludge ash as feed material were compared based on their specific operational recovery cost by scaling the processes to unified size and operational conditions. The selected technologies were (1) wet leaching + struvite precipitation, (2) magnetic vivianite separation, (3) sludge melt gasification, (4) the thermochemical sodium sulfate process, and (5) white phosphorus recovery. The analyses were based on the literature values in addition to a plant-wide model used to estimate chemical consumption and phosphorus and metal-related sludge properties. The technologies were assessed by operational cost, end-product quality, recovery efficiency, and technology maturity. The choice of the recovery process is dependent on the precipitant used in the wastewater treatment processes. Technologies using sewage sludge ash, (4) and (5), had the highest recovery efficiency, technical maturity, and product quality, but they require mono-incineration. Technology (3) had better recovery efficiency than (1), but the end-product had much lower P content. Technology (2) had the lowest recovery efficiency among all the compared technologies, however, it produced an end-product with the second highest P content. The operational costs were calculated for energy and chemical costs for same scale and operational conditions. The specific recovery cost ranges from 6 to 38 €/kgPrecovered.

Side-Stream Phosphorus Recovery in Activated Sludge Processes

Precipitation of mineral phosphates from wastewater treatment processes is an excellent method for phosphorus recovery, leading to the formation of compounds with high fertilizing value. Conventionally, P-precipitation processes are mostly applied to supernatant of anaerobic sludge digestates, due to their high P and N residual contents. This study concerns P-recovery in a pilot-scale side-stream reactor from aerobic (activated sludge) wastewater liquor. The effect of process retention time and pH was determined using sodium hydroxide and calcium hydroxide as alternative pH buffer reagents, in both synthetic and real wastewater. Equilibrium mass balance calculations were first applied to estimate the theoretical final composition of P-precipitates under different process conditions; then, actual precipitation experiments were carried out with synthetic wastewater to define optimal process operating parameters in controlled conditions. Results showed that phosphorus precipitation was affected mainly by solution pH and did not significantly depend on the reactor’s retention time. These findings were validated by operating the process with real wastewater: on average, 61.2% and 90.4% phosphorus precipitation (recovery) were achieved at pH = 8.5 and 9.0 under a controlled Mg:NH4:P molar ratio of 5:5:1, using sodium hydroxide as acidity buffer. The main fraction of final precipitates consisted of calcium phosphate compounds, while struvite, bobierrite and calcite showed up in smaller proportions. It was also shown that dosage of calcium hydroxide for pH adjustment, without any other chemicals for molar ratios adjustment of the solution, has great potential for P recovery in the form of a calcium phosphate-rich precipitate, usable for fertilizer, with 75.6% phosphorus removal in mineral form at pH = 8.5. The process is much less costly to operate than struvite precipitation, and more energetically sustainable. This scheme could be ideally suited for application in facilities operating under an enhanced phosphorus removal process scheme.

Biological recovery of phosphorus from waste activated sludge via alkaline fermentation and struvite biomineralization by Brevibacterium antiquum.

Struvite biomineralization is a promising method for phosphorus recovery from wastewater treatment plant streams, and the growth of responsible microorganisms in mixed cultures is one of the most critical points for applying this process in pilot and full-scale. This study aimed to investigate the growth and bio-struvite production of Brevibacterium antiquum in mixed sludge culture. Alkaline fermentation was applied at different pH conditions to enhance the phosphorus content of sludge for an efficient recovery, and pH 8 was determined as the most feasible considering the phosphorus release and sludge characteristics. Growth optimization studies showed that NaCl's presence decreases the growth rate of Brevibacterium antiquum and bio-struvite production. At the same time, pH in the range of 6.8-8.2 did not alter the growth significantly. In addition, studies showed the ability of Brevibacterium antiquum in unsterilized fermented sludge centrate to grow and recover the phosphorus as struvite. Thus, our results indicated the potential of struvite biomineralization in full-scale wastewater treatment plants.

Phosphorus Recovery Methods from Secondary Resources, Assessment of Overall Benefits and Barriers with Focus on the Nordic Countries

Phosphorus Recovery Methods from Secondary Resources, Assessment of Overall Benefits and Barriers with Focus on the Nordic Countries

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, decomposing 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.

Optimization of induced crystallization reaction in a novel process of nutrients removal coupled with phosphorus recovery from domestic wastewater

AbstractPhosphorus removal and recovery from domestic wastewater is urgent nowadays. A novel process of nutrients removal coupled with phosphorus recovery from domestic sewage was proposed and optimization of induced crystallization reaction was performed in this study. The results showed that 92.3% of phosphorus recovery via induced Hydroxyapatite crystallization was achieved at the optimum process parameters: reaction time of 80 min, seed crystal loads of 60 g/L, pH of 8.5, Ca/P mole ratio of 2.0 and 4.0 L/min aeration rate when the PO43--P concentration was 10 mg/L in the influent, displaying an excellent phosphorus recovery performance. Importantly, it was found that the effect of reaction temperature on induced Hydroxyapatite crystallization was slight, thus favoring practical application of phosphorus recovery method described in this study. From these results, the proposed method of induced HAP crystallization to recover phosphorus combined with nutrients removal can be an economical and effective technology, probably favoring the water pollution control and phosphate rock recycle.

Particle size based recovery of phosphorus from combined peat and wood fly ash for forest fertilization

Correlations between the concentrations of P, K, and As with particle size in fly ash from power plants were examined with a viewpoint to obtain fractions suitable for forest fertilization. Fly ash samples from several CHP plants were fractionated by using four sieves and the five fractions were analyzed by ICP-OES; it was found that both P and K are concentrated in smallest size (<45μm) fractions. Some fly ash samples were found to contain As in excess of the legal limit of 40mg/kg, but even in these cases it was possible to obtain size fractions that pass the legal limit while containing useful amounts of P and K. Fractionating fly ash into different sizes is identified as a viable phosphorus recovery method for obtaining legally acceptable fractions for forest fertilization.

Environmental Benefits and Burdens of Phosphorus Recovery from Municipal Wastewater.

The environmental benefits and burdens of phosphorus recovery in four centralized and two decentralized municipal wastewater systems were compared using life cycle assessment (LCA). In centralized systems, phosphorus recovered as struvite from the solids dewatering liquid resulted in an environmental benefit except for the terrestrial ecotoxicity and freshwater eutrophication impact categories, with power and chemical use offset by operational savings and avoided fertilizer production. Chemical-based phosphorus recovery, however, generally required more resources than were offset by avoided fertilizers, resulting in a net environmental burden. In decentralized systems, phosphorus recovery via urine source separation reduced the global warming and ozone depletion potentials but increased terrestrial ecotoxicity and salinization potentials due to application of untreated urine to land. Overall, mineral depletion and eutrophication are well-documented arguments for phosphorus recovery; however, phosphorus recovery does not necessarily present a net environmental benefit. While avoided fertilizer production does reduce potential impacts, phosphorus recovery does not necessarily offset the resources consumed in the process. LCA results indicate that selection of an appropriate phosphorus recovery method should consider both local conditions and other environmental impacts, including global warming, ozone depletion, toxicity, and salinization, in addition to eutrophication and mineral depletion impacts.

The Relevance of Phosphorus and Iron Chemistry to the Recovery of Phosphorus from Wastewater: A Review

The addition of iron is a convenient way for removing phosphorus from wastewater, but this is often considered to limit phosphorus recovery. Struvite precipitation is currently used to recover phosphorus, and this approach has attracted much interest. However, it requires the use of enhanced biological phosphorus removal (EBPR). EBPR is not yet widely applied and the recovery potential is low. Other phosphorus recovery methods, including sludge application to agricultural land or recovering phosphorus from sludge ash, also have limitations. Energy-producing wastewater treatment plants increasingly rely on phosphorus removal using iron, but the problem (as in current processes) is the subsequent recovery of phosphorus from the iron. In contrast, phosphorus is efficiently mobilized from iron by natural processes in sediments and soils. Iron-phosphorus chemistry is diverse, and many parameters influence the binding and release of phosphorus, including redox conditions, pH, presence of organic substances, and particle morphology. We suggest that the current poor understanding of iron and phosphorus chemistry in wastewater systems is preventing processes being developed to recover phosphorus from iron-phosphorus rich wastes like municipal wastewater sludge. Parameters that affect phosphorus recovery are reviewed here, and methods are suggested for manipulating iron-phosphorus chemistry in wastewater treatment processes to allow phosphorus to be recovered.

Environmental and resource implications of phosphorus recovery from waste activated sludge

Phosphorus is an essential mineral resource for the growth of crops and thus necessary to feed the ever increasing global population. The essentiality and irreplaceability of phosphorus in food production has raised the concerns regarding the long-term phosphorus availability and the resulting food supply issues in the future. Hence, the recovery of phosphorus from waste activated sludge and other waste streams is getting huge attention as a viable solution to tackle the potential availability issues of phosphorus in the future. This study explores the environmental implications of phosphorus recovery from waste activated sludge in Denmark and further elaborates on the potential availability or scarcity issue of phosphorus today and 2050. Life cycle assessment is used to assess the possibility of phosphorus recovery with little or no environmental impacts compared to the conventional mining. The phosphorus recovery method assessed in this study consists of drying process, and thermal gasification of the waste activated sludge followed by extraction of phosphorus from the ashes. Our results indicate that the environmental impacts of phosphorus recovery in an energy efficient process are comparable to the environmental effects from the re-use of waste activated sludge applied directly on farmland. Moreover, our findings conclude that the general recommendation according to the waste hierarchy, where re-use of the waste sludge on farmland is preferable to material and energy recovery, is wrong in this case. Especially when phosphorus is a critical resource due to its life threatening necessity, lack of substitution options and potential future supply risk originating due to the high level of global supply concentration.

Phosphorus recovery: minimization of amount of pharmaceuticals and improvement of purity in struvite recovered from hydrolysed urine

Struvite (MgNH4PO4·6H2O) is normally used as a fertilizer in agriculture, where struvite crystallization from hydrolysed human urine is a simple and reliable method for phosphorus (P) recovery. Human urine, however, contains high amount of pharmaceuticals, which may cause health risk for applications. This research investigates the possibility of decreasing the amount of pharmaceuticals (tetracycline, demeclocycline and oxytetracycline) in struvite crystals recovered from synthetic and human urines by focusing on storage time, and of increasing the quality of struvite production. Urines were stored for different times up to 15 days prior to recovery of phosphorus by two steps, spontaneous precipitation and struvite crystallization. The morphology of spontaneous precipitates and struvite crystals was observed. Spontaneous precipitation removed around 17–24% of phosphate from synthetic and human urines, while pharmaceuticals were removed with a quite high amount at a short storage time (5 days) and this amount decreased with increasing the storage time (10 and 15 days). Urines with>70% remaining phosphates were re-used for struvite crystallization by adding extra magnesium. It was found that maximum P-recovery efficiency could be achieved from struvite crystallization at 5-day storage time, 70% and 68% of remaining P in the separated supernatant from synthetic and human urines, respectively, whereas less than 1% pharmaceuticals remained in the struvite crystals from both samples. This indicates that the procedure in this work is a good method for phosphorus recovery, in which high struvite purity (>99%) is obtained with low amount of pharmaceuticals.

Effects of Organic Coexisting Impurities on Phosphorus Recovery from Animal Manure Wastewater by Struvite Crystallization

Struvite crystallization is an efficient method for phosphorus recovery from animal manure wastewater. However, large amount of organic coexisting impurities, contained in animal manure wastewater, might influence struvite crystallization. In this study, the effect of typical organic matter contained in animal manure wastewater, such as butyric acid, fulvic acid, tetracycline, on phosphorus recovery was examined. The following conclusions were drawn: (1) with an increase in butyric acid concentration in animal manure wastewater, phosphorus recovery efficiency did not change significantly; (2) with an increase in fulvic acid concentration in animal manure wastewater, phosphorus recovery efficiency decreased obviously; (3) with an increase in tetracycline concentration in animal manure wastewater, phosphorus recovery efficiency decreased slightly.

Phosphorus recovery from sewage sludge ash through an electrodialytic process

The electrodialytic separation process (ED) was applied to sewage sludge ash (SSA) aiming at phosphorus (P) recovery. As the SSA may have high heavy metals contents, their removal was also assessed. Two SSA were sampled, one immediately after incineration (SA) and the other from an open deposit (SB). Both samples were ED treated as stirred suspensions in sulphuric acid for 3, 7 and 14days. After 14days, phosphorus was mainly mobilized towards the anode end (approx. 60% in the SA and 70% in the SB), whereas heavy metals mainly electromigrated towards the cathode end. The anolyte presented a composition of 98% of P, mainly as orthophosphate, and 2% of heavy metals. The highest heavy metal removal was achieved for Cu (ca. 80%) and the lowest for Pb and Fe (between 4% and 6%). The ED showed to be a viable method for phosphorus recovery from SSA, as it promotes the separation of P from the heavy metals.

Phosphorus recovery from fosfomycin pharmaceutical wastewater by wet air oxidation and phosphate crystallization

Fosfomycin pharmaceutical wastewater contains highly concentrated and refractory antibiotic organic phosphorus (OP) compounds. Wet air oxidation (WAO)-phosphate crystallization process was developed and applied to fosfomycin pharmaceutical wastewater pretreatment and phosphorus recovery. Firstly, WAO was used to transform concentrated and refractory OP substances into inorganic phosphate (IP). At 200 °C, 1.0 MPa and pH 11.2, 99% total OP (TOP) was transformed into IP and 58% COD was reduced. Subsequently, the WAO effluent was subjected to phosphate crystallization process for phosphorus recovery. At Ca/P molar ratio 2.0:1.0 or Mg/N/P molar ratio 1.1:1.0:1.0, 99.9% phosphate removal and recovery were obtained and the recovered products were proven to be hydroxyapatite and struvite, respectively. After WAO–phosphate crystallization, the BOD/COD ratio of the wastewater increased from 0 to more than 0.5, which was suitable for biological treatment. The WAO–phosphate crystallization process was proven to be an effective method for phosphorus recovery and for fosfomycin pharmaceutical wastewater pretreatment.

Nitrogen and Phosphorus Recovery from Wastewater and the Supernate of Dewatered Sludge

Excessive nitrogen and phosphorus supply to freshwater negatively affects water quality and ecosystem balance through a process known as eutrophication. This can lead to increased wastewater treatment costs, a reduction in the biological diversity and recreational value of natural water bodies. Besides, algal blooms can result in loss of livestock and human health issues. Therefore, efficient and reliable nitrogen and phosphorus removal methods are required. In wastewater containing relatively high concentrations of nitrogen and phosphorus (e.g. wastewater from chemical fertilizer plant, the supernate of dewatered sludge, etc.), these elements are difficult to remove economically to reach the appropriate compliance limits by biological methods. On the other hand, both nitrogen and phosphorus are nutrients for the plants, and recently, nitrogen and phosphorus recovery by precipitation (e.g. struvite) has drawn much attention, because nitrogen and phosphorus precipitates can be utilized as a fertilizer and both phosphorus and ammonium can be simultaneously removed. Thus, this review summarized nitrogen and phosphorus recovery methods, during which nitrogen and phosphorus compounds can be used as a raw material for the fertilizer industry, including the options of struvite and hydroxyapatite formation and other feasible using options. In this article most important patents are also discussed.

Floc-forming properties of polyphosphate accumulating organisms in activated sludge

The physico-chemical characteristics of polyphosphate-accumulating organisms (PAO) involved in enhanced biological phosphorus removal (EBPR) was investigated in order to find a novel method for phosphorus recovery. If the physico-chemical characteristics of PAO are different from those of other main floc components, it may be possible to enrich PAO in bulk water or in the floc material for improved recovery of phosphorus. A combination of shear tests, chemical manipulation, and quantification of PAO by fluorescence in situ hybridization was applied. The microcolony strength of both Rhodocyclus-related PAO and Actinobacteria-related PAO was generally high as no treatment could break up more than 20% of all PAO in microcolonies. In contrast, it was possible to remove 20-40% of the organic matter and other bacterial cells by applying a high pH value or adding EDTA. With that a selective enrichment of PAO in the remaining floc material was possible. The feasibility of applying this selective PAO enrichment in flocs remains to be evaluated in full-scale plants for P-recovery.