Nutrient Recovery Research Articles

Soil Restoration Strategies for Sustaining Soil Productivity: A Review

Soil degradation, characterised by a deterioration in quality and a drop in ecosystem products and services, is a key impediment to obtaining the necessary increase in agricultural productivity. Soil is a living and dynamic organism that degrades when standard agricultural practices are used. Healthy soil is a crucial pillar of sustainability because it provides various ecosystem services in addition to controlling microbial activity, nutrient recovery, and decomposition. In human time spans, soil is a non-renewable resource that is vulnerable to deterioration due to complex interactions between processes, variables, and causes occurring at a variety of geographical and temporal dimensions. Accelerated erosion, depletion of the soil organic carbon (SOC) pool and biodiversity loss, loss of soil fertility and elemental imbalance, acidification and salinization are among the key soil degradation processes. The strategy aims to minimize soil erosion, boost SOC and N budgets, boost soil biota activity and species diversity (macro, meso, and micro), and improve structural stability and pore geometry. Improving soil quality (i.e., expanding the SOC pool, improving soil structure, and boosting soil fertility) can lower the hazards of soil degradation (physical, chemical, biological, and ecological) while also benefiting the environment.

Intercropped Maize and Cowpea Increased the Land Equivalent Ratio and Enhanced Crop Access to More Nitrogen and Phosphorus Compared to Cultivation as Sole Crops

Sub-Saharan African smallholder farmers face challenges due to limited access to commercial fertilizers, affecting food security. Exploring the benefits of intercropping is promising, but evaluating crop performance in specific agroecological contexts is crucial. This study in Vilankulo, Mozambique, conducted over two growth seasons (2018 and 2019), aimed to assess the benefits of intercropping maize (Zea mays L.) and cowpea (Vigna unguiculata L., Walp) (M+C) compared to maize (M) and cowpea (C) as sole crops. Key variables for comparison included dry matter yield (DMY), land equivalent ratio (LER), competitive ratio (CR), tissue nutrient concentration, nutrient recovery, and apparent N fixation (ANF). This study also examined the effects on cabbage (Brassica oleracea L.), cultivated as a succeeding crop, and soil properties. In 2018, maize plants were severely affected by drought and did not produce grain. This year, cowpea grain yields were 2.26 and 1.35 t ha−1 when grown as sole crop or intercropped. In 2019, maize grain yield was 6.75 t ha−1 when intercropped, compared to 5.52 t ha−1 as a sole crop. Cowpea grain yield was lower when intercropped (1.51 vs. 2.25 t ha−1). LER values exceeded 1 (1.91 and 1.53 for grain and straw in 2019), indicating improved performance in intercropping compared to sole crops. In 2019, CR was 1.96 for maize grain and 0.58 for cowpea grain, highlighting the higher competitiveness of maize over cowpea. Cowpea exhibited higher average leaf nitrogen (N) concentration (25.4 and 37.6 g kg−1 in 2018 and 2019, respectively) than maize (13.0 and 23.7 g kg−1), attributed to its leguminous nature with access to atmospheric N, benefiting the growth of maize in intercropping and cabbage cultivated as a succeeding crop. Cowpea also appears to have contributed to enhanced phosphorus (P) absorption, possibly due to access to sparingly soluble P forms. In 2019, ANF in M+C was 102.5 kg ha−1, over 4-fold higher than in C (25.0 g kg−1), suggesting maize accessed more N than could cowpea provide, possibly through association with endophytic diazotrophs commonly found in tropical grasses.

Effect of split application of potassium on nutrient recovery efficiency, soil nutrient balance, and system productivity under rice-wheat cropping system (RWCS)

Improving nutrient use efficiency and system productivity with a positive nutrient balance in rice-wheat cropping system (RWCS) is vital for long-term food security. Two-year field trials were conducted with the objective of computing the effect of different rates, time, method, and source of potassium (K) fertilization on nutrient recovery efficiency, nutrient balance, and system productivity in a dry direct-seeded RWCS with eight treatments. The two-split (half basal and half at panicle initiation) application of 60 kg K2O/ha resulted in 37.5% and 19.2% increase in recovery efficiency of K in rice and wheat, respectively over basal application of 60 kg K2O/ha. Besides, the split-application of K increased the nitrogen recovery efficiency in rice and wheat by 11.2% and 10.8%, respectively. Similarly, the phosphorus recovery efficiency was increased by 3.6% and 7.4% in rice and wheat, respectively. The split application of 60 kg K2O/ha also increased the K harvest index (% of the total K absorbed is transferred to grain) by 0.7% and 2.7% in rice and wheat, respectively over applying entire K at basal. Similarly, the system productivity (11.26 t/ha) was increased by 8% over applying entire K at basal. In the absence of top-dressing of K (30 kg/ha), two foliar-sprays of 2.5% K provide equal benefits of top dressing. Application of 90 kg K2O/ha lowered the K negative balance (−99 kg/ha/year) considerably compared to two-split application of 60 kg K2O/ha (−152.5 kg/ha/year). Thus, optimization of K fertilization in RWCS will increase the system productivity, nutrient use efficiency, and sustainability.

Nutrients recovery by coupled bioreactor of heterotrophic ammonia assimilation and microbial fuel cell in saline wastewater

Heterotrophic ammonia assimilation (HAA) process had been widely used in the treatment of high salt wastewater, but the electro enhanced coupling process and electron transfer process were rarely studied. In this study, a HAA process coupled microbial fuel cell (MFC) system was established to treat ammonia-containing wastewater under increasing salinity to achieve nitrogen recovery and electricity generation. Up to 95.4 % NH4+-N and 96.4 % COD removal efficiencies were achieved at 2 % salinity in HAA-MFC. The maximum power density and current density at 2 % salinity were 29.93 mW/m2 and 182.37 mA/m2, respectively. The residual organic matter in the cathode effluent was effectively removed by the anode. The increase of salinity not only enhanced the sludge settling performance and activity, but also promoted the enzyme activity and amino acid production of the ammonia assimilation pathway. Marinobacter and Halomonas were gradually enriched at the anode and cathode with increased salinity to promote ammonia assimilation and electron production. This research offered a promising solution to overcome salinity-related challenges in wastewater treatment and resource recovery.

Assessment of the effectiveness of process-induced struvite crystallization process on the recovery of nutrients from high-strength liquid digestate of an anaerobic biogas plant

This study aimed to recover magnesium (Mg2+), ammonium (NH4+) and phosphate (PO43-) as struvite from high-strength liquid digestate (LD) of an anaerobic biogas plant, where poultry manure was processed for biogas production. Effluent quality after the struvite crystallization process was investigated in terms of the change in Mg2+, NH4+ and PO43- concentrations. The change in chemical oxygen demand (COD) concentrations was also investigated to determine whether the struvite formation could help to decrease extremely high initial concentrations in the LD. Results showed that a certain level of Mg2+, NH4+, PO43-, and COD removal occurred under the optimized experimental conditions, leaving an effluent with relatively high residual concentrations. To further reduce the residual concentrations, an attempt was made by performing a secondary struvite crystallization process as a process-induced additional treatment step, which has never been investigated in the literature. The results revealed that an improved quality of effluent was achieved after the process-induced struvite crystallization process as compared to the single-step process. The morphology and the elemental composition of the produced precipitates confirmed by XRD and EDS analysis showed that the structure was typical of struvite crystals. This study clearly demonstrates that the process-induced struvite crystallization process could effectively lessen the adverse environmental impacts arising from the problematic wastes of biogas plants. The cost analysis reveals that low-cost alternative sources of Mg and PO4, such as wastes rich in Mg and/or P content, should be used instead of high purity reagents to improve the economic sustainability of the process.

Improving BioWin Modeling of Phosphorus Solubilization in Acid-Phase Digesters

BioWin 6.0 does not accurately predict phosphorus (P) speciation in acidogenic anaerobic digesters under default kinetics characterization and parameterization. The accurate modeling of acid-phase digestion is needed to predict the performance of novel nutrient recovery technologies that act on these digester effluents. The main thrust of this work was to identify and correct the causes of inaccurate P partitioning and precipitation within BioWin models of acid-phase digestion reactors. A BioWin configuration including an organic acid digester was parameterized and recalibrated based on the known traits of acid-phase digestion and then validated against a full-scale digester in a municipal wastewater treatment plant. This digester, with pH 5.14 and 61–74% solubilized P, was predicted by BioWin default parameters to have only 27% soluble P and a net formation of P precipitates. Corrections to the polyphosphate-accumulating organism decay, endogenous product decay, hydrolysis rate, and brushite behavior resulted in 67% solubilization with no precipitate formation. Cabinet configurations showed similar behavior when modified to include an acid-phase digester under default parameters, but predictions were similarly amended by our parameter changes. This improved modeling technique should allow operators to effectively characterize acid digesters for their own treatment trains and allow engineers to predict the performance of novel nutrient recovery technologies acting on acidogenic digest.

Reduced Growth in Eustoma under High Nutrient and Phytotoxic Organic Acid Concentrations and Recovery through Hot Water Conditioning of Continuously Cropped Soil

Stunted vegetative growth and delayed or absent flowering are commonly observed in eustoma (Eustoma grandiflorum) when cultivated continuously in the same greenhouse soil. These effects are likely caused by the excessive accumulation of soluble salts and/or phytotoxic organic acids in the soil. This study aimed to clarify the mechanism of continuous cropping obstacles and formulate prevention measures of eustoma. Seedlings of eustoma ‘Croma III White’ were grown hydroponically with 0%, 25%, 50%, 75%, 100% (full), 125%, 150%, 175%, or 200% strength of Johnson’s solution. Plant height, leaf area, and shoot dry weight increased steadily as solution strength increased from 25% to 125% [solution electrical conductivity (EC) of 2.4 dS⋅m−1] and then gradually decreased as solution strength further increased from 125% to 200% (solution EC of 3.8 dS⋅m−1). When grown hydroponically in 200% strength Johnson’s solution, plant height, leaf area, and root length increased with increasing equimolar mixtures of organic acids, including maleic acid, benzoic acid, malic acid, and hydroxybenzoic acid, up to 1.2 to 1.6 mM and decreased thereafter. Node number and the percentage of flower bud visibility declined beyond 1.6 mM organic acid mixtures. Plants with 2.0 and 2.4 mM organic acid mixtures had the lowest net photosynthetic rate, stomatal conductance, transpiration, and intercellular carbon dioxide concentration. Plants had normal growth and produced flower buds when the continuously cropped soil was preconditioned with 100 °C reverse-osmosis water before planting.

Enhanced nutrient recovery from anaerobically digested poultry wastewater through struvite precipitation by organic acid pre-treatment and seeding in a bubble column electrolytic reactor

Limited mineralization of organic phosphorus to phosphate during the anaerobic digestion process poses a significant challenge in the development of cost-effective nutrient recovery strategies from anaerobically digested poultry wastewater (ADPW). This study investigated the influence of organic acids on phosphorus solubilization from ADPW, followed by its recycling in the form of struvite using a bubble column electrolytic reactor (BCER) without adding chemicals. The impact of seeding on the efficiency of PO43− and NH3-N recovery as well as the size distribution of recovered precipitates from the acid pre-treated ADPW was also evaluated. Pre-treatment of the ADPW with oxalic acid achieved complete solubilization of phosphorus, reaching ∼100% extraction efficiency at pH 2.5. The maximum removal efficiency of phosphate and ammonia-nitrogen from the ADPW were 88.9% and 90.1%, respectively, while the addition of 5 and 10 g/L struvite seed to the BCER increased PO43− removal efficiency by 9.6% and 11.5%, respectively. The value of the kinetic rate constant, k, increased from 0.0176 min−1 (unseeded) to 0.0198 min−1, 0.0307 min−1, and 0.0375 min−1 with the seed loading rate of 2, 5, and 10 g/L, respectively. Concurrently, the average particle size rose from 75.3 μm (unseeded) to 82.1 μm, 125.7 μm, and 148.9 μm, respectively. Results from XRD, FTIR, EDS, and dissolved chemical analysis revealed that the solid product obtained from the recovery process was a multi-nutrient fertilizer consisting of 94.7% struvite with negligible levels of heavy metals.

Struvite-Driven Integration for Enhanced Nutrient Recovery from Chicken Manure Digestate.

This study investigated the synergistic integration of clean technologies, specifically anaerobic digestion (AD) and struvite precipitation, to enhance nutrient recovery from chicken manure (CM). The batch experiments were conducted using (i) anaerobically digested CM digestate, referred to as raw sample (RS), (ii) filtered digestate sample (FS), and (iii) a synthetically prepared control sample (CS). The research findings demonstrated that the initial ammonia concentration variations did not significantly impact the struvite precipitation yield in the RS and FS, showcasing the materials inertness process's robustness to changing ammonia concentrations. Notably, the study revealed that the highest nitrogen (N) recovery, associated with 86% and 88% ammonia removal in the CS and FS, was achieved at pH 11, underscoring the efficiency of nutrient recovery. The RS achieved the highest nitrogen recovery efficiency at pH 10, at 86.3%. In addition, the research highlighted the positive impact of reducing heavy metal levels (Zn, Cu, Pb, Ni, Cd, Cr and Fe) and improving the composition of the microbial community in the digestate. These findings offer valuable insights into sustainable manure and nutrient management practices, emphasizing the potential benefits for the agricultural sector and the broader circular economy. Future research directions include economic viability assessments, regulatory compliance evaluations, and knowledge dissemination to promote the widespread adoption of these clean technologies on a larger scale. The study marks a significant step toward addressing the environmental concerns associated with poultry farming and underscores the potential of integrating clean technologies for a more sustainable agricultural future.

Water Stress Reduction Using Superstructure-Based Mathematical Model: Synthesise a Wastewater Treatment Plant Associated with Nutrient Recovery for Palm Oil Industry

Water Stress Reduction Using Superstructure-Based Mathematical Model: Synthesise a Wastewater Treatment Plant Associated with Nutrient Recovery for Palm Oil Industry

On the thermodynamic properties of hydrolysed urine: Experimental data, predictive and correlative models for the design of concentrative urine treatment technologies

Source-separated urine contains the potential for water, nutrient and energy recovery. During the recovery of such resources, urine treatment technologies undergo temporal changes in the thermodynamic properties of urine. To inform the design of thermal, membrane and electrochemical urine treatment processes, this study experimentally measured and modelled the thermophysical properties of synthetic hydrolysed urine (vapour pressure, osmotic pressure, density, and electrical conductivity) across temperature and concentration profiles using two approaches: predictive thermodynamic equations based on an ionic speciation model and correlative modelling. The vapour pressure and osmotic pressure were accurately predicted to 14 wt% for the predictive model, within an error of 0.30% and 0.46%, respectively, while the correlative model based on the experimental data from this study demonstrated an error of <1% for both parameters across the whole range of salt concentrations and temperatures (4.5 to 32.2 wt%; 333 to 373 K). The predictive and correlative models for density and electrical conductivity showed adequate agreement with the experimental data, where error did not exceed 2.12% and 1.2%, respectively, across the entire range of concentrations and temperatures.The value of the models for the development of sustainable urine treatment technologies was demonstrated by their application to determine the optimum heating surface area of a urine evaporator and the energy requirements of a reverse osmosis process.

Simultaneous Wastewater Treatment and Resources Recovery by Forward Osmosis Coupled with Microbial Fuel Cell: A Review.

Osmotic microbial fuel cells (OsMFCs) with the abilities to simultaneously treat wastewater, produce clean water, and electricity provided a novel approach for the application of microbial fuel cell (MFC) and forward osmosis (FO). This synergistic merging of functions significantly improved the performances of OsMFCs. Nonetheless, despite their promising potential, OsMFCs currently receive inadequate attention in wastewater treatment, water reclamation, and energy recovery. In this review, we delved into the cooperation mechanisms between the MFC and the FO. MFC facilitates the FO process by promoting water flux, reducing reverse solute flux (RSF), and degrading contaminants in the feed solution (FS). Moreover, the water flux based on the FO principle contributed to MFC's electricity generation capability. Furthermore, we summarized the potential roles of OsMFCs in resource recovery, including nutrient, energy, and water recovery, and identified the key factors, such as configurations, FO membranes, and draw solutions (DS). We prospected the practical applications of OsMFCs in the future, including their capabilities to remove emerging pollutants. Finally, we also highlighted the existing challenges in membrane fouling, system expansion, and RSF. We hope this review serves as a useful guide for the practical implementation of OsMFCs.

Valorization of poultry slaughterhouse waste into fertilizers with designed properties.

Climate change, soil erosion, air and water pollution, or problems related to waste management are just some of the many problems in the modern world. Comprehensive solutions are sought to reduce the effects of progressive environmental degradation according to the assumptions of the concept of sustainable development. The paper presents a technological concept that may be a response to these problems. The presented solution assumes full utilization of slaughterhouse waste with the simultaneous recovery of nutrients and the production of functional fertilizing products with designed properties. Four liquid fertilizer formulations with the following composition were prepared: N - 2.30-3.64%, P2O5 - 2.18-9.66%, and K2O - 0.11-4.49%. The manufactured products were characterized by a high sulfur content and the addition of microelements. The tests carried out on plants confirmed their effectiveness similar to commercial mineral fertilizers. An increase in green matter yield of peas by 5 t/ha and maize by 2 t/ha was observed. The lack of microbiological risk associated with their use has been proven. Good efficiency with a simultaneous reduction in production costs resulting from the use of waste materials, as well as limiting the negative impact of poultry farms on the environment, make this solution an attractive alternative to mineral fertilizers, in line with the assumptions of the circular economy.

Electrochemical sulfate production from sulfide-containing wastewaters and integration with electrochemical nitrogen recovery

Electrochemical methods can help manage sulfide in wastewater, which poses environmental and health concerns due to its toxicity, malodor, and corrosiveness. In addition, sulfur could be recovered as fertilizer and commodity chemicals from sulfide-containing wastewaters. Wastewater characteristics vary widely among wastewaters; however, it remains unclear how these characteristics affect electrochemical sulfate production. In this study, we evaluated how four characteristics of influent wastewaters (electrolyte pH, composition, sulfide concentration, and buffer strength) affect sulfide removal (sulfide removal rate, sulfide removal efficiency) and sulfate production metrics (sulfate production rate, sulfate production selectivity). We identified that electrolyte pH (3 × difference, i.e., 25.1 to 84.9 μM h−1 in average removal rate within the studied pH range) and sulfide concentration (16 × difference, i.e., 82.1 to 1347.2 μM h−1 in average removal rate) were the most influential factors for electrochemical sulfide removal. Sulfate production was most sensitive to buffer strength (6 × difference, i.e., 4.4 to 27.4 μM h−1 in average production rate) and insensitive to electrolyte composition. Together, these results provide recommendations for the design of wastewater treatment trains and the feasibility of applying electrochemical methods to varying sulfide-containing wastewaters. In addition, we investigated a simultaneous multi-nutrient (sulfur and nitrogen) process that leverages electrochemical stripping to further enhance the versatility and compatibility of electrochemical nutrient recovery.

Effects of the Covid-19 pandemic on the Swedish Biogas Sector

With a growing population, the world requires solutions that provide energy, waste management, transportation, and nutrient recovery in a sustainable manner. Biogas is a local system solution that can fill these needs and make society more self-sufficient. In an increasingly uncertain world, forthcoming crises and external economic pressure will affect industries, including biogas, and lead to higher risk. To manage these uncertainties and to create resilience, knowledge needs to be gathered on how industries providing system solution, such as the biogas industry, are affected by crises. The Covid-19 pandemic offers the possibility to analyse the effects of a global crisis in real-time. The aim of this study is to investigate the effects the covid-19 pandemic had on the production, distribution, and demand of biogas in Sweden. Ten semi-structured interviews were carried out with different actors in the biogas value chain. Some key findings in the result include continued availability of substrate for biogas production but with a changed composition, increased demand for biofertilizer and small-scale production of biogas, and disturbances in biogas related policies. The underlying factors contributing to these effects can be attributed to pandemic related restrictions, disturbances in logistical chains, increased energy prices and political factors. The lessons learned are that the biogas industry should try to be decoupled from policies and review the resilience of the supply chains. If this is managed, biogas is a way forward for providing waste management, transportation fuel and nutrient recovery while facilitating the transition towards self-sufficient and sustainable societies with resilience against global crises.

Enhanced internal circulation for struvite crystallization in a novel air-lift circulation reactor with Venturi structure for ammonium recovery from wastewater

Nutrient recovery as struvite from wastewater in is quite feasible. The mystery of ammonia loss has received much attention, and inadequate struvite purity is frequently present. A struvite fluidized bed reactor (FBR) was constructed and operating conditions were optimized in order to minimize ammonia nitrogen loss. The properties of the struvite produced by the reactor and the optimum operating conditions for ammonia recovery were also assessed. According to simulations, the Venturi tube increased turbulent flow energy to 4.5 × 10−2 m2·s−2. This significantly improved the mass transfer efficiency. A significant difference between the wall shearing rate (50–319 s−1) and the fluid shearing rate (2–10 s−1) prevented the crystal particles from colliding with the vessel wall. The reactor reached stable operation under conditions of N/P = 1:1 and pH = 9.0. The purity of the obtained struvite was 96.5 %, with an ammonia nitrogen conversion rate of 89.67 %, where the struvite crystals could grow to 82 μm within 24 h. It was concluded that the new FBR with air-lift internal circulation function was feasible for improving struvite crystal growth and purification. It is possible to achieve high ammonia nitrogen recovery efficiency at low cost.

Nutrient recovery from wastewater for hydroponic systems: A comparative analysis of fertilizer demand, recovery products, and supply potential of WWTPs

Nutrient recovery from wastewater treatment plants (WWTPs) for hydroponic cultivation holds promise for closing the nutrient loop and meeting rising food demands. However, most studies focus on solid products for soil-based agriculture, thus raising questions about their suitability for hydroponics. In this study, we address these questions by performing the first in-depth assessment of the extent to which state-of-the-art nutrient recovery processes can generate useful products for hydroponic application. Our results indicate that less than 11.5% of the required nutrients for crops grown hydroponically can currently be recovered. Potassium nitrate (KNO3), calcium nitrate (Ca(NO3)2), and magnesium sulfate (MgSO4), constituting over 75% of the total nutrient demand for hydroponics, cannot be recovered in appropriate form due to their high solubility, hindering their separated recovery from wastewater. To overcome this challenge, we outline a novel nutrient recovery approach that emphasizes the generation of multi-nutrient concentrates specifically designed to meet the requirements of hydroponic cultivation. Based on a theoretical assessment of nutrient and contaminant flows in a typical municipal WWTP, utilizing a steady-state model, we estimated that this novel approach could potentially supply up to 56% of the nutrient requirements of hydroponic systems. Finally, we outline fundamental design requirements for nutrient recovery systems based on this new approach. Achieving these nutrient recovery potentials could be technically feasible through a combination of activated sludge processes for nitrification, membrane-based desalination processes, and selective removal of interfering NaCl. However, given the limited investigation into such treatment trains, further research is essential to explore viable system designs for effective nutrient recovery for hydroponics.

Enhancing the nitrogen and phosphorus content of faecal-derived biochar via adsorption and precipitation from human urine

Urine diversion in toilets is a promising strategy to maximise nutrient recovery and produce low-cost urine-derived fertilisers. There are various methods for nutrient recovery from urine, including precipitation and adsorption onto porous media, such as biochars. This study uses faecal-derived biochars to produce and, for the first time, comprehensively characterise enriched biochar fertilisers with the addition of fully hydrolysed undiluted human urine. The evolution of urea hydrolysis and nutrient content during urine storage was initially investigated over a 6-month storage period and NH4+ adsorption mechanisms studied under varying biochar doses and NH4–N concentrations. The process was further optimised by adding MgO to induce precipitation reactions, enabling the combined recovery of NH4+ and P. For NH4+ adsorption, experimental data exhibited a good fit to both the Freundlich (R2 = 0.989) and Langmuir (R2 = 0.974) isotherm models and the rate of the reaction was well described by a pseudo 2nd order kinetics model (R2 = 0.988). The NH4+ uptake was rapid during the initial 2 h of the reaction and the adsorption process reached completion after 24 h. The NH4–N adsorption capacity of the faecal-derived biochar was 19.8 mg/g and the main adsorption mechanism identified was ion exchange (K+ ↔ NH4+), as confirmed by XRD and ICP-OES. The effect of different biochar doses (0, 25, 50, 100 g/L) and MgO addition scenarios (Mg:P = 0, 1.5, 4) on N and P recovery showed that the combination of MgO (Mg:P = 1.5) with the lower biochar dose (25 g/L) produced the most NP-rich fertiliser product which was easily separated from the urine. Faecal-derived biochar had a limited adsorption capacity for P, with precipitation being the main mechanism for P recovery. When MgO was added to urine, >98% of total P was recovered via precipitation of struvite/struvite-K and substituted hydroxyapatite, as identified via SEM-EDX. Faecal-derived biochar was a successful carrier to recover the P-containing precipitates and facilitate liquid-solid separation after treatment. The findings of this study provide proof-of concept for the systemic management of source separated human excreta and pave the way for the production of marketable waste-derived fertilisers from on-site sanitation systems.

Cytoprotective alginate microcapsule serves as a shield for microalgal encapsulation defensing sulfamethoxazole threats and safeguarding nutrient recovery

Microalgal encapsulation technology is expected to broaden more possibilities for employing microalgae for upgrading conventional biological wastewater treatment. However, only limited and fragmented information is currently available on microalgal encapsulation and pollutant removal. It is ambiguous whether it hold potential for wastewater treatment. Particularly, it remains to be determined whether this technology can provide more possibilities in harsh sewage environments. Here, potential of encapsulated technology to recover nutrients from wastewater was examined, simultaneously compared with commonly adopted suspended system. Results indicate the encapsulated microalgal system showed outstanding advantages in nutrient recovery and defense against antibiotic threats. Moreover, by examining the cellular oxidative stress response and changes of the photosynthetic system, the encapsulated system exhibited potential cytoprotective advantages to microalgal cells for defensing antibiotic threats. Molecular dynamics simulation revealed that the differences among superficial aggregation between the nutrients’ ions and molecular sulfamethoxazole on the cross-linked alginate microcapsule surface dominated the nutrient recovery and cytoprotective functions. Ultimately, the molecular nature of pollutants was found to be the most critical aspect for predicting application of this microalgal microcapsule. Cytoprotective systems created with alginate microcapsules can potentially handle more diverse threats with a single type of surface charge in their outermost layer.

Eco-friendly and sustainability assessment of technologies for nutrient recovery from human urine—a review

Nitrogen (N), phosphorus (P), and potassium (K) represent the primary components of commercial NPK fertilizer and are primarily derived from finite resources through complex and expensive processes. To ensure global food security, the development of sustainable and eco-friendly procedures for fertilizer production has gained attention. Humans generally excrete urine containing 11 g of N/L, 0.3 g of P/L of P and 1.5 g of K/L, which benefit plant growth. The recovery of these essential plant nutrients from human urine has become the focal point of increasing research endeavors. Despite the potential advantages of nutrient recovery from urine, this process is complicated, and the economic implications are substantial. Furthermore, human urine may harbor undesirable contaminants, such as pathogens, pharmaceutical residues, hormones, and elevated salt levels, which could be disseminated into the environment through agriculture. This study appraised various emerging technologies for nutrient recovery from human urine, considering their challenges, environmental impact, economic viability, and the overall sustainability of the processes. This review elucidated that most nutrient recovery technologies demonstrated elevated efficiency in nutrient recovery. Nevertheless, a recurrent oversight involves neglecting the potential transfer of contaminants and pathogens into environmental matrices. The complexity of these processes and their economic feasibility vary, with some proving intricate and economically unviable. Given that no singular technology fully mitigates these challenges, integrating two or more technologies appears imperative to address drawbacks and enhance overall system performance.