Nutrient Recovery Research Articles

Innovative Approach to Sustainable Fertilizer Production: Leveraging Electrically Assisted Conversion of Sewage Sludge for Nutrient Recovery

Innovative Approach to Sustainable Fertilizer Production: Leveraging Electrically Assisted Conversion of Sewage Sludge for Nutrient Recovery

Air Gap Membrane Distillation for Nutrient and Water Recovery from Marine Culture Wastewater for Improved Water Reclamation.

Valuable nutrients such as ammonium and phosphate exist in teensy concentrations in marine-culture wastewater (MCW), causing their recovery challenging with inefficient conventional methods. Air gap membrane distillation (AGMD) is systematically explored for the first time to recover nutrients and pure water from low-nutrient MCW. This study assessed the AGMD performance in resource recovery by conducting a thorough investigation and optimization of various parameter conditions. Concerning the findings, AGMD satisfactorily inhibits ammonia transfer from the feed stream to the permeate stream by optimizing operating parameters specifically feed temperature and pH. A higher feed temperature improves water recovery, and feed pH is critical in nutrient recovery. In particular, high pH promotes the transformation and transport of ammonia through the membrane, whereas low pH inhibits ammonia transport, encouraging the creation of pure water. Maintaining an acidic feed solution decreases membrane fouling by increasing the solubility of calcium phosphate, hence boosting water recovery. Nevertheless, higher pH levels encourage fouling by allowing solid phosphate particles to form more readily. While at lower pH, ammonium phosphate fertilizers might be generated in the retentate solution by improving NH4+ and PO43- recovery under optimal conditions. The findings reveal that the AGMD system provides a novel method for treating MCW while also improving nutrient and pure water recovery.

Techno-economic analysis of nutrient recovery from urine: Centralized treatment of hydrolyzed urine vs. decentralized treatment of fresh urine

The centralized process integrating “Thermal NH3 stripping → Na-chabazite adsorption → Struvite precipitation” has been proposed for nutrient recovery from hydrolyzed urine. Meanwhile, a decentralized approach involving Na-chabazite and biochar adsorption has been suggested for fresh urine, followed by urea hydrolysis and the subsequent centralized integration of struvite precipitation and thermal stripping. However, a systematic comparison of nutrient recovery processes for fresh and hydrolyzed urine, evaluating both technical viability and financial feasibility, is lacking. This study addresses the gap by thoroughly examining both scenarios over a 30-year project, using Université Laval as a case study. It provides a comprehensive roadmap for techno-economic assessment, offering guidance for evaluating nutrient recovery processes prior to scaling up. The decentralized process achieved higher recovery efficiencies for nitrogen and phosphorus, at 89.4 % and 98.7 %, respectively. Financially, the decentralized scenario demonstrated its advantage in the lower initial investment requirement, thereby generating higher gross profits compared to the centralized scenario. As a result, it is projected to reach the break-even point in the 21st year, demonstrating its potential economic feasibility. Sensitivity analysis indicated that a 20 % increase in urine inflow rate and the price of urea-enriched biochar could further enhance the economic viability of both processes. Beyond financial considerations, both scenarios have the potential to reducing the contaminant loading rate in the downstream wastewater treatment plants and promote nutrient recovery and recycling.

Treatment of digested blackwater using a submerged microfiltration membrane system or a drum filter

After energy recovery from blackwater via anaerobic digestion, technologies such as struvite precipitation and ammonia stripping can be used to enhance nutrient recovery. However, the presence of suspended solids, organics and metals, can negatively impact the nutrient recovery processes. This study examined the treatment of digested blackwater, applying either a ceramic microfiltration membrane or a drum filter, operating in parallel in a source-separated wastewater plant. The digestate as well as the permeates from the membrane and drum filter were sampled regularly and evaluated. In general, the ceramic membrane proved to be more efficient in improving the quality of digested blackwater in comparison to the drum filter. The ceramic membrane reduced total suspended solids to below the detection limit, while the drum filter achieved 74 % removal. The membrane removed 74 %, 85 % and 76 % of TOC, BOD7 and COD-Cr, respectively, higher than the corresponding treatment with the drum filter, which removed 41 %, 42 % and 34 %, respectively. No significant differences in phosphate and ammonium concentrations (P-value = 0.05), before and after both treatment methods were observed. The membrane removed particulate-bound metals (As, Cd, Cr, Cu, Ni, Pb and Zn) up to 25 %, 95 %, 87 %, 95 %, 66 %, 90 % and 98 %, respectively. The drum filter achieved lower removal for particulate-bound As, Cd, Ni, Pb and Zn for 25 %, 79 %, 44 %, 56 % and 86 %, respectively. The removal of metals is critical to maintain struvite purity and prevent the struvite contamination due to co-precipitate of these metals.

Innovative ammonia harvesting from wastewater: A controlled closed-loop process at high pH for enhanced nutrient recovery

This study presents a new, sustainable, high-pH recirculating batch process for the regeneration of NH4+-laden cation exchange resins, while recovering the ammonia as a pure, reusable, solid salt (NH4Cl). The process efficiently recycles a minimal volume of regeneration solution while reducing NaCl consumption between cycles. The regeneration solution, containing a high concentration of NaCl maintained at high pH (pH > 11) allows Na+ to replace the desorbed NH4+, which, due to the high pH, completely transforms into NH3. Real time pH monitoring of the regeneration solution and the column effluent provided accurate tracking of the regeneration rate and allowed concise endpoint determination. Ammonia was recovered by evaporation of the exhausted regeneration solution followed by sublimation (and thereafter deposition) of NH3 and HCl, which produced pure NH4Cl salt.The optimal working conditions for the cation exchange regeneration were identified as 1 M NaCl, pH 12.0, and regeneration solution volume of 1 bed volume. Single-column application of six adsorption-regeneration cycles (no zeolite replacement) showed that the process conditions do not degrade the resin’s adsorption performance. Cost assessment of two possible ammonia recovery options indicated that while stripping NH3 from the regeneration solution and reabsorbing it in an acidic solution is operationally easier, the sublimation-based approach yields a more valuable product. For an optimized sublimation approach, a low regeneration solution volume, combined with a high resin capacity for NH4+, are essential.This process demonstrates a sustainable solution for ammonia salt recovery from wastewater, offering a circular approach that does not only add an important control to the regeneration step, but also harvests ammonia as a reusable product.

Nutrient retention and availability of biochars prepared by co-pyrolysis of vinasse with sugarcane filter cake

The disposal of vinasse, a nutrient-rich by-product of ethanol production, is challenging because of the low pH and emissions of harmful gases and smells. Here, biochars were produced by pyrolysis of mixtures of filter cake and vinasse (0.25 w/v to 1 w/v) at 550℃. The effects of filter cake to vinasse ratios on the biochar yield, pH, ash content, total nutrient (P, K, Ca, and Mg) content, and nutrient availability were investigated. Increasing the filter cake to vinasse ratio increased the biochar yield and ash content and lowered the biochar pH from 10.3 for 0.25-BC to 8.2 for filter cake biochar (FC-BC). Lower filter cake to vinasse ratios increased the total K content from 7.9 g∙kg‒1 for FC-BC to 75.9 for 0.25-BC. Nutrient recovery in the biochars was high (79.5% to 130.2%). Whereas P, Ca, and Mg extractability in water was <5%, the K extractability was 80% for 0.25-BC and decreased to 7.6% for FC-BC. Extractability of K, P, Ca, and Mg in 2% formic acid from vinasse-containing biochars was high (>50%). These results highlight the potential suitability for use in agricultural applications. Conversion of vinasse into value-added biochar could reduce waste treatment cost and improve soil health.

Transforming Irrigated Agriculture in Semi-Arid and Dry Subhumid Mediterranean Conditions: A Case of Protected Cucumber Cultivation

Pressure from population growth and climate change stress the limited water resources in the Mediterranean region and threaten food security and social stability. Enhancing food production requires the transformation of irrigation systems and enhancement of local capacity for sustainable water and soil management in irrigated agriculture. The aim of this work is the conversion of traditional irrigation practices, by introducing the practice of optimal irrigation scheduling based on local ET estimation and soil moisture monitoring, and the use of continuous feeding by fertigation to enhance both water and nutrient use efficiency. For this, two trials were established between August and November 2023 in two different pedoclimatic zones (Serein and Sultan Yacoub) of the inner Bekaa Plain of Lebanon, characterized by semi-arid and dry subhumid conditions and different soil types. Greenhouse cucumber was tested to compare the prevailing traditional farmers’ practices with the advanced, technology-based, methods of water management. Results showed a significantly higher amount of water applied by the farmers to the protected cucumber, with a potential for average saving of 105 mm of water applied in each season by improved practices. Water input in the traditional practices revealed potential stress to plants. With more than 20% increase in cucumber yield by the transformed practices, a general trend was observed in the fertilization approach and amounts, resulting in lower nutrient recovery in the farmer’s plots. The science-based practices of water and nutrient management showed higher application and agronomic water use efficiency of full fertigation, exceeding 60%, associated with double and triple higher nitrogen use efficiency, compared to those results obtained by the traditional water and fertilizer application methods. The monitored factors can contribute to severe economic and environmental consequences from nutrient buildup or leaching in the soil–groundwater system in the Mediterranean region.

Improving Prediction of Nutrient Recovery via Struvite Precipitation from Organic Waste Digestate

Improving Prediction of Nutrient Recovery via Struvite Precipitation from Organic Waste Digestate

Spent coffee ground biochar for phosphate adsorption in water: Influence of pyrolysis temperature and iron-coating activation method

A substantial portion of the phosphorus utilized in crop and food production is dispersed into soil and water, posing a challenge to the management of eutrophication and sustainable nutrient recovery. This research focuses on the reclamation of phosphate from polluted water through affinitive adsorption on biochar derived from spent coffee grounds (SCG). SCG were subjected to pyrolysis within a N2-purged vertical furnace across a temperature range of 300–550 °C, with a 1-h holding time. The adsorption capability of SCG biochar was systematically investigated and experimental data were interpreted using Langmuir and Freundlich isotherm models. Notably, the biochar pyrolyzed at 450 °C and activated with a Fe/biochar mass ratio of 2:1 demonstrated the highest adsorption capacity (0.87 mg P/g biochar) when exposed to the highest initial phosphate concentration in the solution (15 mg P/L). Comparative analyses revealed that the removal efficiency of non-activated SCG biochar was considerably lower (5.7%) compared to the corresponding activated biochar (up to 17.3%). This highlights the significant increase in adsorption capacity facilitated by the introduction of ferric chloride. Furthermore, phosphate desorption experiments were conducted to assess the biochar's phosphorus release characteristics and stability. The results demonstrate the positive outcomes of upcycling SCG waste material as a pollutant sorbent and the potential to diminish reliance on chemical fertilizers through the recovery of Fe-phosphate-enriched SCG biochar.

The Potential of Acid Hydrolysis as Pre-Treatment for Improved Nutrient Recovery from Domestic Wastewater

The Potential of Acid Hydrolysis as Pre-Treatment for Improved Nutrient Recovery from Domestic Wastewater

Co-hydrothermal carbonisation of sewage sludge and kitchen waste: Influence of process parameters

This study assessed the impact of process temperature and time on the co-hydrothermal carbonisation (co-HTC) of kitchen waste and sewage sludge. To address the limitations of using a single feedstock and to circumvent the energy costs associated with pre-drying, the two organic feedstocks were mixed at a 1:1 ratio (wet basis). Co-HTC experimental runs were conducted in the temperature range of 180 °C–260 °C for 1, 3, and 5h durations. Co-HTC for sewage sludge and kitchen waste (1:1 ratio) at 260 °C temperature for 3h duration demonstrated optimal energy enrichment with a maximum energy and carbon densification of 1.50 and 1.47, respectively. The thermogravimetric analysis (TGA) revealed that the hydrochar (HC) produced at 260 °C temperature for 3h duration underwent multistage decomposition with stable intermediates due to the formation of more stable aromatic structures and a heat energy of 21.29 kJ g−1 at 292.87 °C. At the optimal reaction conditions, the process water (PW) exhibited a high volatile fatty acids (VFA) and total kjeldahl nitrogen (TKN) concentration of 1420 mg L−1 and 431.2 mg L−1, indicating its potential for simultaneous energy recovery through anaerobic digestion and nutrient recovery.

Removal of Inorganic Pollutants and Recovery of Nutrients from Wastewater Using Electrocoagulation: A Review

Water pollution is a major concern due to its detrimental effects on the environment and public health. The particular danger of inorganic pollutants arises from their persistent toxicity and inability to biodegrade. Recently, electrocoagulation (EC) has been demonstrated as an alternative sustainable approach to purifying wastewater due to the increasingly strict pollution prevention rules. In particular, EC has been used to remove inorganic pollutants, such as Cr, Zn, Pb, or As. EC has emerged as a sustainable tool for resource recovery of some inorganic pollutants such as N and P that, when recovered, have value as plant nutrients and are critical in a circular economy. These recovered materials can be obtained from diverse agricultural drainage water and recycled as fertilizers. In this work, a state-of-the-art technique is reviewed describing the advances in contaminant removal and nutrient recovery using EC through an in-depth discussion of the factors influencing the contaminant removal process, including operating pH, time, power, and concentration. Furthermore, limitations of the EC technology are reviewed, including the high-power consumption, fast deterioration of the sacrificial electrodes, and the types of contaminants that could not be efficiently removed. Finally, new emerging constructs in EC process optimization parameters are presented.

Hybrid membrane process for nutrient recovery and sodium reduction in aquaculture wastewater

The swift growth of the aquaculture industry has exacerbated nutrient discharge, leading to eutrophication, while low nutrient but high sodium content impedes effective nutrient recovery and reuse. This study presents a novel hybrid membrane-based treatment sequence comprising ammonia stripping (AS), vacuum membrane distillation (VMD), and nanofiltration in diafiltration mode (NF), designed to efficiently recover ammonia and phosphate and reduce sodium from mixed aquaculture effluents. The process achieved ammonia and phosphate recovery efficiencies of 88.74 % and over 99 %, respectively, with a corresponding sodium reduction of 99.04 wt%. The AS stage concentrated ammonia from 20.37 mg/L to 2046.67 mg/L, whereas the subsequent VMD and NF stages produced phosphate-rich (rose from 10.33 mg/L to 50.50 mg/L) and sodium-reduced retentates (decreased from 510 mg/L to 44.50 mg/L). Long-term testing over eight consecutive batches showed robust performance with ammonia flux decline by only 2.81 %, permeate flux reduction by 4.30 %, and minimal inorganic fouling, maintaining consistent permeate quality that met environmental standards. These findings underline the proposed hybrid process's potential for sustainable aquaculture wastewater management, offering substantial enhancement in nutrient and water recycling.

Comparison of STCR and Conventional Fertilizer Approaches for Improved Yield, Uptake and Nutrient Use Efficiency in Greengram

The present study investigates the effects of various fertilizer recommendation approaches on yield, nutrient uptake and nutrient use efficiency in greengram (BGS-9), conducted at ZARS, GKVK, Bengaluru during summer-2024. Soil test crop response (STCR) based fertilizer prescription equations were developed during kharif-2022 by following the methodology of Ramamoorthy et al., (1967) and were validated alongside post-harvest soil test value prediction equations. Results indicated that significantly higher seed yield (17.99 q ha⁻¹) was recorded in the STCR approach for the target yield of 15 q ha-1, where nutrients were applied through integrated approach based on actual soil test values (T3). The highest haulm yield (30.25 q ha⁻¹) was recorded in T2, which followed the STCR inorganic approach targeting 15 q ha⁻¹, based on predicted soil test values. Nutrient uptake results indicated that significantly higher nitrogen (110.73 kg ha⁻¹), phosphorus (11.39 kg ha⁻¹) and potassium (140.06 kg ha⁻¹) uptake were recorded in STCR treatments, particularly in those with an integrated approach. These treatments also validated better nutrient recovery and agronomic use efficiency compared to low, medium and high (LMH) and package of practice (POP) approaches. The findings confirm the accuracy of predicted soil test values in fertilizer prescription, indicating that repeated soil testing between crops may be unnecessary. The STCR based integrated approach provided balanced nutrient application, leading to optimal yield and nutrient uptake. This study highlights the effectiveness of STCR methodologies for efficient nutrient management and improved productivity in greengram.

Efficient resource recovery from food waste digestate via hydrothermal treatment and its application as organic fertilizer

With the continuous recognition of green, organic and non-polluting products, organic fertilizers play an increasingly vital role in agricultural production. Among them, hydrochar-based organic fertilizer has attracted widespread attention recently. The present study evaluated the potential of digestate from anaerobic digestion of food waste for the preparation of hydrochar-based organic fertilizer by straw-based, FeCl3-catalyzed hydrothermal carbonization (HTC). Under the optimal conditions, a hydrochar-based organic fertilizer with > 25 wt% humus content and limited pollution risk was successfully prepared. The pot experiment demonstrated the feasibility of improving the physicochemical properties of red soil and promoting crop growth after adding hydrochar in place of commercial fertilizer. In addition, the function of zeolite on nutrient recovery in hydrothermal liquid (HTL) was analyzed, and preparing the slow-release organic fertilizer by mixing the nutrient-rich zeolite with hydrochar in a mass ratio of 1:4 was proposed. This work has significant implications for achieving the efficient resource recovery of digestate.

Insights into multivalent metal removal-assistant anaerobic fermentation of waste activated sludge: Impact factor identification and mechanism clarification of metal removal

The study investigated the impact factors of metal removal and their role in enhancing anaerobic fermentation of waste activated sludge (WAS), aiming to identify key mechanisms. By optimizing the sludge concentration, it found that a sludge suspension solid range of 10–30 g/L significantly improved the efficiency of anaerobic fermentation, and yielded SCOD of 93.8–177.1 mg/g volatile suspension solid after 8 h, respectively, which was 3.67–4.77 times higher than the control. Correspondingly, the production of short-chain fatty acids (SCFAs) was significantly enhanced. At the optimal sludge suspension solid of 10–30 g/L, the SCFAs were 1.28–1.51 times higher than that of the control. Furthermore, the study evaluated the performance of different metal removal reagents and discovered that microporous COOH reagent outperformed gel SO3H and macroporous SO3H reagent. The macroporous COOH reagent achieved 1.54 and 1.22 times higher SCOD values and significantly enhanced the production of SCFAs, demonstrating its superiority in metal removal and fermentation enhancement. Moreover, the research revealed that sludge concentration and metal removal agent types influenced the activities of key enzymes involved in anaerobic fermentation. Additionally, the macroporous COOH reagent showed the most efficient ability to remove metal ions, contributing to increased nutrient recovery in terms of nitrogen (NH4+-N) and total phosphorus (TP) release during the acidification process. In summary, the enhancing mechanism of metal removal-assistant anaerobic fermentation was discussed from the sludge floc concentration, the skeleton structure and the ion exchange group type. The identified mechanism significantly improves fermentation efficiency and facilitate the organic recovery, representing an innovative approach for wide application in WAS management and resource recovery.

Exit control: the role of Arabidopsis hydathodes in auxin storage and nutrient recovery.

Exit control: the role of Arabidopsis hydathodes in auxin storage and nutrient recovery.

Phosphate pre-concentration from wastewater by a continuous flow bench-scale forward osmosis membrane: A circular economy approach on nutrient recovery

Phosphate is a vital element necessary for the growth and development of plants, making it a crucial element in agricultural fertilizers. Extracting phosphate from wastewater for recovery aligns with the principles of a circular economy by closing the loop on nutrient cycles. Instead of viewing wastewater as a waste product, treating it as a resource for recovering valuable nutrients like phosphate promotes a more sustainable and efficient use of resources. In this study, the phosphate from synthetic wastewater was pre-concentrated by a continuous flow forward osmosis membrane system to facilitate effective precipitation. The pre-concentration feasibility of forward osmosis was studied by changing the draw concentration, feed concentration, feed pH, and flow rate of the feed solution. With the optimum operational parameters in batch mode such as pH of 7, the draw solute concentration of 0.4 M MgSO4, the feed and draw flowrate of 0.7 L/min and 0.3 L/min, the phosphate concentration was increased from 30 mg/L to 525 mg/L after 60 min, the average osmotic flux and reverse solute flux was 2.7 L/m2/h and 0.43 g/m2/h, respectively. As operated with continuous mode, the final phosphate concentration was increased four times, the average osmotic flux was higher with 8.1 L/m2/h and the reverse solute flux was 0.86 g/m2/h, which could improve the efficiency of calcium phosphate crystallization in precipitation/ crystallization reactors. This integrated system, which includes forward osmosis as a pretreatment method followed by a precipitation process, is technically possible for application on a larger scale as a circular economy approach.

Optimizing phosphorus precipitation from acidic sewage sludge ash leachate: Use of Mg-rich mining by-products for enhanced nutrient recovery

Phosphorus recovery from Sewage Sludge Ashes (SSA) by wet chemical extraction followed by selective precipitation has gained great attention in recent years, attempting to reduce the anthropic pressure on natural reserves. This study investigates the selective precipitation process at lab- and small pilot-scales by means of two conventional and one innovative precipitating agents, the latter derived from a low-grade magnesium oxide mining by-product (LG-MgO named PC8), assessing the role of the most relevant operating parameters. Lab-scale experiments were performed on leachates obtained from bottom and fly ashes, in which several operating conditions were tested, differing in the type of precipitating agent, target pH and nutrient molar ratio. Based on experimental results, small pilot-scale experiments were conducted with Ca(OH)2 and PC8 at pH 7. Effective phosphorus precipitation was obtained at lab-scale at pH equal to 4 for high Al/P molar ratio, while SSA leachate with low Al/P molar ratio promoted improved phosphorus precipitation (>90%) only at pH higher than 8 with PC8. Small pilot-scale findings confirmed the effectiveness of PC8 in increasing simultaneously the pH and the nutrient content of the solid precipitate. The comprehensive assessment of the samples denoted compliance with the European Regulation (EU 2019/1009), which allows the formulation of different fertilizers with agronomic relevance. This is the first time that experiments from small pilot-scale tests in the field of phosphorus recovery from SSA were investigated using an innovative precipitant providing key information for the process scale-up.

Elucidating organic and nutrient transport mechanisms in polyelectrolyte modified membranes for selective nutrient recovery

This work focuses on understanding and analyzing the transport mechanisms of organics and nutrient ions (NH4+, K+) through polyelectrolyte-based membranes, aimed at the selective recovery of nutrients from nutrient-rich resources such as anaerobic digestate. In this study, commercial nanofiltration (NF) membranes were modified by the layer-by-layer (LbL) deposition of oppositely charged polyelectrolytes, utilizing a wide range of parameters such as polyelectrolyte type, deposition pH, salt (NaCl) concentration, polymer cross-linking, etc. Such modifications resulted in membranes exhibiting characteristics that indicate a trade-off relationship between nutrient passage and nutrients/organics selectivity. Our findings suggest that nutrient passage is primarily facilitated by surface charge, while size-exclusion plays a vital role in retaining the organics. Ionically crosslinked polyelectrolyte multilayer (PEM) membranes exhibit superior nutrient passage (up to ∼30 % higher) compared to commercial NF membranes, while covalently crosslinked PEM membranes achieve higher (∼12 % higher) organics rejection. In addition, membranes with such covalent crosslinking exhibit intra-nutrient (NH4+/K+) selectivity of ∼1.8, when tested with binary NH4+/K+ mixtures – a rather surprising membrane property, since both ions have similar hydrated radii. This study provides a fundamental framework of membrane design for selectively recovering nutrients from a variety of nutrient-rich sources.