Biological nitrification is a promising strategy for urine nutrient recovery, yet high salinity and ammonia can inhibit nitrifiers, delaying start-up and causing unstable performance. Meanwhile instability factors, sludge adaptation mechanisms to salinity, and nitrification performance drivers remain poorly understood, limiting strategies for rapid and stable operation. Here, this study compared three sludges-nitrifying sludge (NS1), seawater aquaculture sediment sludge (SM1), and wastewater treatment plant activated sludge (AS1). NS1 and SM1 started up faster and performed better than AS1. A more balanced AOB-NOB structure in NS1 supported higher stability, but higher salt tolerance in SM1 accelerated start-up. Besides, NH4+-related salinity stress and co-occurring ions likely constrained long-term stability and promoted NO2- accumulation, while free nitrous acid (FNA) may further inhibit NOB and exacerbated instability. Sludges salt tolerance were mediated by coordinated osmotic-regulation involving K+ uptake, Na+ extrusion, energy-coupled transport, and compatible solutes synthesis/transport (e.g., betaine, trehalose, glutamate), with Ottowia, Comamonas, Rubrivivax, and Nitrosomonas contributing synergistically. Acclimation also stimulated extracellular polymeric substance (EPS) production dominated by tryptophan-/tyrosine-like proteins, potentially enhancing sludge stability. Environmental ions driven EPS secretion and enhanced salt-tolerance potential were key determinants of nitrification performance. Building on function-oriented inoculum selection, Exogenous betaine/trehalose/glutamate exogenous supplementation could enhance salt-tolerance, which may further shorten start-up and strengthen stability of biological nitrification system for urine.

Biological nitrification is a cost-effective method for stabilizing urine and recycling plant nutrients. However, hormone-extracted urine (HEU), a low-pH urine-derived wastewater (pH similar to 5) in the pharmaceutical industry, struggles to efficiently hydrolyze urea, limiting its ability to provide a stable ammonia source for nitrification. This study proposes a strategy that integrates urease-producing bacteria (UPB)-mediated enzymatic hydrolysis with biological nitrification to address nutrient recovery from HEU. Under optimal conditions (pH 10, 25 degrees C), a 30-day continuous cultivation of UPB achieved stable urease activity (950-2510 mg N.L-1.h(-1), 92%-95% urea hydrolysis) from day 2 to day 22. By analyzing the microbial community succession and genes during the UPB cultivation process, the complete metabolic pathway of urease synthesis, secretion, and urea hydrolysis was summarized. It was found that Oligella ureolytica is the main urease-producing bacterium, and the urea transporter gene (utp) and secretion-related genes (secB/E/G) are key factors limiting the synthesis and secretion of urease. After complete hydrolysis by urease, HEU achieved stable biological nitrification, with a COD removal rate over 90%. The resulting HEU-sourced fertilizer was rich in NH4+-N, NO3--N, phosphorus, potassium (2216.55 mg N.L-1, 2610.48 mg N.L-1, 87.81 mg.L-1, and 319.30 mg.L-1), and essential micronutrients like calcium and magnesium, promoting plant growth. This study proposes an innovative approach for nutrient recovery from HEU and for achieving efficient nitrogen recovery in urine-derived wastewater under conditions similar to low pH environments.

Bioflocculants rich in polysaccharide components are beneficial for flocculation. Despite the fact that urine sludge harbors abundant polysaccharide-rich biopolymers (BPs) with notable flocculation potential, the flocculation performance of urine-derived BPs (U-BPs) remains unexplored. In this study, BPs were extracted from microbial sludges collected from three pilot-scale water treatment systems, designated as wastewater-derived BPs (W-BPs), drinking water-derived BPs (D-BPs), and U-BPs. The wastewater sludge yielded 5.25 g/day of W-BPs, the drinking water sludge yielded 1.34 g/day of D-BPs, and the urine sludge yielded 6.41 g/day of U-BPs. Among these, U-BPs exhibited the highest polysaccharide content (>56%), the most pronounced surface charge (zeta potential -14.2 mV), the largest proportion of high-molecular-weight substances (74%), and the richest variety of surface functional groups (carboxyl groups >20%, protonated amino groups >30%). Coagulation-flocculation tests showed that the U-BPs group achieved optimal removal of turbidity (>96%), DOC (>53%), and SUVA(254) (>8%), as well as substantial removal of humic acid (>83%), polysaccharide (>60%), and protein (>48%), minimizing the residual concentrations of these organics. The genes epsA, epsC, and glmS, along with the genus Paracoccus, were identified as key microbiological factors influencing the secretion and flocculation performance of U-BPs. This study underscores the pivotal role of U-BPs' favorable physicochemical properties (composed of high-molecular-weight functionalized polysaccharide chains with abundant surface charge) in coagulation-flocculation, with corresponding supporting microbiological evidence provided. This study establishes a foundation for further research on U-BPs, and redefines the value of urine-derived microbial products in resource-oriented applications.

Biological nitrification presents a sustainable approach for urine resource recovery. However, high salinity and ammonium concentrations in urine inhibit or even damage microorganisms, causing delayed start-up and unstable. This study first introduces betaine (150 mg·L⁻¹) to enhance urine nitrification by improving microbial salt tolerance and metabolic. Compared with the conventional typical process without betaine addition, introducing betaine shortened start-up time from 98 to 36 days, increased nitrification rate from 313.9 to 563.7 mg N·L⁻¹·d⁻¹, reduced nitrite accumulation, and improved resilience to water quality fluctuations. It also upregulated expression of nitrifying bacteria and related functional genes. Mechanistically, betaine stimulated extracellular polymeric substances production and regulated tryptophan and tyrosine metabolism genes, improving sludge aggregation and microbial stability. Betaine modulated genes for K⁺ uptake and Na⁺ extrusion to maintain initial osmotic balance. Subsequently, betaine promoted the uptake/synthesis of osmoprotectants (e.g., betaine and trehalose), upregulated electron transport chain genes and optimized energy metabolism. Notably, Betaine-induced multiple salt-tolerance mechanisms showed synergistic effects, with Rubrivivax sp., Paracoccus aminovorans, and Nitrobacter sp. identified as core salt-tolerant species. Even after betaine discontinuation (at day 40), high nitrification activity and salt tolerance persisted, though reduced amoABC gene abundance may constrain long-term performance. Furthermore, betaine-enhanced urine fertilizers demonstrated high nutrient recovery efficiency and reduced phytotoxicity, indicating strong potential for agricultural reuse. Overall, this study provides novel theoretical and practical insights, establishing betaine as an effective strategy for accelerating and stabilizing biological nitrification in high-salinity wastewater systems such as urine, with broad implications for sustainable treatment and resource recovery.

Heat-localized solar distillation (HLSD) is an emerging environmentally- friendly high-efficiency distillation technology for clean water production. Solar interfacial distillation (SID) and photothermal membrane distillation (PMD) are two featured HLSD processes that have attracted a lot of attentions from researchers recently. Both SID and PMD systems produce water vapor from thin film surfaces where sunlight can be absorbed and converted as localized-heat to minimize heat loss and improve heat conversion efficiency. This article offers an overview of SID and PMD, including their respective classifications and characteristics. Subsequently, the water production capacities and purification efficiencies of the two systems are compared and the influencing factors are analyzed. Moreover, this paper compares the crystallization processes between the two systems and elucidates the methods employed to prevent salt fouling and achieve salt recovery. Finally, this study highlights the current challenges and future prospects of both systems to guide future research.

Understanding the transfer of embodied emissions along trade chains is crucial for promoting sustainable economic development. Here, we constructed the provincial inventory of emissions of 6 typical air/aquatic/solid pollutants (SO2, NOX, Dust, COD, NH3-N, and Solid wastes) via a multiple regional input-output (MRIO) model. We quantified the emissions responsibilities from both producer and consumer perspectives, adopting the 'Beneficiaries are responsible' principle for allocation. Further, we calculated appropriate payments or subsidies for each province's emissions using the slacks-based Data Envelope Analysis (SBM-DEA), aiming to provide a fair and transparent reference for China's current fiscal transfer payment system. Our findings revealed significant progress in emission reductions between 2012 and 2017 by 36.64%-66.49% excluding Solid wastes. Provinces within the Yangtze River Delta and Guangdong were the primary emitters at the consumption end, while provinces in Central, Western, and Northeastern China bore the brunt of embodied emissions through trade at the production end. In 2012, a dominant emission transfer was from developed to undeveloped provinces. However, by 2017, a new trend emerged, with emissions being transferred between provinces with similar levels of financial development. The secondary industry was the largest adsorber for the emission transfer, and reductions in emissions from this sector benefited the output of provinces who experienced rapid development during 2012-2017. Based on the offsetting calculated by this work, the current transfer payments system in China is not fair for some provinces who paid more or accepted less than they deserved. Some provinces should take a more active gesture in pursing their development instead of relying upon the transfer which they do not deserve. This study provides a comprehensive understanding of emissions from various perspectives, highlighting changes in inter-provincial and inter-industrial transfer pathways, which was valuable for multi-regional management efforts aimed at aligning national economic development with ecological conservation goals.

China's staple crops face heavy metal (HMs) contamination, a widespread issue lacking a national assessment. We used machine learning (ML) to assess risks of 8 HMs in rice, wheat, and maize, and estimated a financing strategy for soil remediation via linear optimization and computable general equilibrium (CGE). The accumulation of HMs in crops depends on Soil-HMs, climate, soil properties, and crop types. Cd and Hg pose major soil pollution risks, while Cr, Pb, and Cd are the most threatening in crops. High-risk zones are located at the warm temperature and subtropical zones, with wheat most vulnerable. Over a quarter (26.77 %) of the nation's croplands are classified as high-risk, with a significant 60.89 % falling into the medium-risk category, leaving merely 12.34 % of the agricultural land in a safe condition. The estimated remediation cost is 58596.73 billion RMB and the crop loss is 808.03 billion RMB in a ten-year remediation period at the context of secure crop supply. The reallocation of social investment rather than raising new taxation for the remediation is beneficial to the GDP increase and social welfare despite some loss in the household income and enterprise income. This study provides a comprehensive evaluation for Crop-HMs risk and remediation policy, crucial for national crop security.

Solar-driven interfacial evaporation technology (SDIE) was previously proposed to produce freshwater in seawater desalination. With the environmentally-friendly merit of solar energy, researchers tried to apply this technology in other water treatments. However, the components in different water matrices are complex, various contaminants accumulate on the interface reducing evaporation efficiency or evaporating with water vapor affecting the produced water quality. The photocatalysis has good performance on the removal of these pollutants in water. Since both processes require the participation of light, researchers have proposed coupling solar-driven interfacial evaporation with photocatalysis to better solve the problem in water treatment. This review summarizes the application of the coupled processes in water treatment. Firstly, the mechanisms of interfacial photothermal conversion and photocatalytic degradation of pollutants are reviewed. Subsequently, the applications of the coupled processes in water production, contaminants removal, and disinfection for water treatment are summarized. The results show that the condensate collected through the coupled process meets drinking water quality standards. Additionally, the coupled process significantly degrades volatile organic compounds (VOCs), non-volatile organic compounds (NVOCs), and disinfects bacteria, thereby preventing surface contamination at the photothermal interface. Furthermore, the application of the coupled processes for green fuel production from water treatment is also discussed. This production process is based on water-catalyzed hydrogen production and carbon dioxide reduction. Finally, current challenges and future perspectives of the coupled processes are examined, aiming to provide theoretical foundations for future research in this field.

In recent years, source-separated urine has garnered widespread recognition as a valuable nutrient recovery resource. This paper summarizes urine components globally and related urine nutrient recovery technologies. Comparative analysis highlights the significant advantages of biological nitrification in technology, environmental impact, and economics, enabling sustainable complete nutrient recovery from urine. This review summarizes functional microorganisms involved in urine biological nitrification and evaluates the performance of various reactors, while also detailing key factors influencing biological nitrification and conducting its role in improving fertilizer safety. Considering the need for remote transport and convenient storage, the performance of urine nitrification-based concentration technologies in resource recovery was also evaluated and the effective approaches for widespread application were proposed. Nonetheless, nutrient recovery technologies based on urine biological nitrification has significant challenges to be overcome, including rapid reactor start-up, stable process operation, enhanced fertilizer safety, and industrial-scale implementation. To address these challenges, this review proposes corresponding development strategies and outlines future prospects. With the refinement of urine source separation systems and improvements of nutrient recovery technologies based on biological nitrification, urine source separation strategies and decentralized treatment methods will help to contribute to the establishment of wastewater management systems that integrate pollution control, recycling, and ecological protection.

The application of sludge-based biochar and its derivatives to remove antibiotics from aquatic media has long been recognized as an environmentally-friendly approach since it delivers the scenario of waste treatment by wastes. Despite the existence of various proposed adsorption mechanisms, a comprehensive analysis that combines macroscopic and microscopic perspectives remains insufficient. Herein, surface modification (Fe3O4) and spherization (chitosan) were employed to improve the adsorption capacity of sludge-based biochar toward tetracycline hydrochloride (TC). The as-prepared gel pellets (FeB-11) exhibited high adsorption capacity toward TC in aqueous with maximum uptake of 206.98 mg & BULL;g � 1 under 298K. The combination of characterization-based and approximate site energy distribution (ASED) methods concluded that surface complexation played the primary role in enhancing the adsorption capacity of FeB-11 for TC, while space filling, hydrogen bonding, 7c-7c interaction, electrostatic interaction and ion exchange also contributed to the adsorption process. The introduction of chitosan and Fe3O4 weakened physisorption but strengthened chemisorption, and Fe3O4 was proposed as the primary promoter for TC adsorption due to the better affinity between TC molecules and FeB-11 which Fe3O4 brought. Concentrated and high distribution frequency of adsorption sites with high adsorptive energy were the primary surface property responsible for the remarkable TC adsorption capacity exhibited by FeB-11 in the macroscopic perspective. These findings underscored the importance of combining macroscopic and microscopic perspectives to understand the prioritization among various adsorption mechanisms, other than solely proposing various mechanisms, which was useful to help design efficient adsorbents.

In this study, the long-term impacts of ciprofloxacin (CIP) on the performance as well as the microorganisms of an EBPR system were assessed in a sequencing batch reactor (SBR). The results showed that nitrogen and phosphorus removal performance was significantly inhibited (P < 0.01) by CIP. Semi-inhibitory concentration (IC50) of anaerobic phosphate release, aerobic phosphate uptake and ammonia oxidation (1.9, 1.5 and 1.2 mg·L−1) suggested that the inhibition of CIP on ammonia oxidation was the strongest. Meanwhile, the diversity and evenness of microorganisms were reduced greatly (P < 0.01) due to the toxicity of CIP. Lysobacter, however, gradually dominated because of its strong resistance to CIP. The tolerance ability of functional microorganisms related to phosphorus and nitrogen removal to CIP was as follows: nitrite-oxidizing bacteria (NOB) > phosphorus-accumulating bacteria (PAOs) > Zoogloea > glycogen-accumulating bacteria (GAOs). It was also found that tightly bound EPS (TB-EPS) concentration decreased companying with a decrease of sludge activity as CIP addition increased. Moreover, an obvious sludge granulation was observed with protein (PN) proportion increased and polysaccharide (PS) proportion decreased. Nevertheless, the results of recovery experiment showed that the deterioration of the EBPR caused by long-term exposure to CIP could be replenished within 10 days, implying the inhibitory effect of CIP on EBPR was reversible.

A significant factor for eutrophication is the excessive discharge of ammonia nitrogen. Unfortunately, traditional methods to remove ammonia nitrogen are ineffective when facing gradually strict rules. Recently, adsorption has gained interest from scholars due to its efficiency and safety in ammonia nitrogen treatment. In this study, a novel biochar, modified with magnetic iron, was synthesized through co-precipitation, which performed well in ammonia nitrogen removal. The maximum adsorption amount at 293 K of the composite that was synthesized at 80℃(MB80) was 17.52 mg·g-1. Meanwhile, the simulation results displayed a good fitting with the pseudo second order model and Langmuir model. Additionally, the adsorption mechanism could be attributed to electrostatic adsorption, porous filling, ion exchange, and hydrogen bonding. Noticeably, MB80 maintained a good performance after 5 cycles, with desirable adsorption amount of 3.18 mg·g-1. This study aimed to provide an efficient method to treat ammonia nitrogen as well as a new way to dispose of municipal sludge.

The excessive discharge of phosphate into natural water has caused serious environmental problems. Adsorption is an efficient technology for phosphorus removal from water. In this study, a novel biochar modified by chitosan, ferrous sulfate, and sodium sulfide was synthesized and performed well in phosphorus adsorption. The results of batch experiments showed that the optimum synthesized composite could adsorb 49.32 mg·g-1 of phosphate at 298 K. Meanwhile, the simulation results showed better fitting with the pseudo-second-order model and Langmuir model. The adsorption rate was dominated by three-dimensional diffusion within the inner pores. The adsorption process was defined as physic/chemisorption, while the adsorption mechanism was concluded to be electrostatic adsorption, porous filling, surface chemical precipitation, hydrogen binding, and the ligand effect. This study showed that the composite is effective in phosphorus removal from water, and we anticipate that our research will offer guidelines for adsorbent design and reveal the adsorption mechanism.

采用交替厌氧/缺氧/好氧运行的序批式活性污泥反应器(SBR),通过梯度投加电子受体NO-3,考察长期缺氧吸磷驯化下强化生物除磷(EBPR)系统的性能及除磷方式的转化.结果表明,当进水COD为300～450 mg/L、PO3-4(以P计,下同)和氨氮分别为8、14 mg/L时,驯化期间TN去除率均保持在75％以上,长期缺氧吸磷驯化对COD和氨氮的去除没有影响.硝态氮投加量为5 mg/L时,EBPR系统因电子受体投加不足除磷性能迅速恶化,增加硝态氮投加量至10 mg/L,经过近30 d的恢复,缺氧吸磷率最高可达97.67％,进一步提高硝态氮投加量至15 mg/L,系统内硝态氮的积累导致缺氧吸磷率下降.污泥吸磷小试结果表明,经缺氧吸磷驯化后,即使除磷性能欠佳的低浓度电子受体系统污泥也具有良好的反硝化吸磷能力,可见经NO-3长期驯化的缺氧吸磷系统有利于筛选以NO-3为电子受体的反硝化聚磷菌.

In this study, phosphate-rich supernatant at the end of anaerobic phase was extracted by a certain side-stream ratio for chemical precipitation to investigate the optimal conditions for phosphorus recovery. The effect of side-stream reaction on the performance of the mainstream enhanced biological phosphorus removal (EBPR) system was also explored. The experiment was carried out in a sequencing batch reactor (SBR) operated in an alternating anaerobic/aerobic mode with dissolved oxygen controlled at 1.0 mg · L-1. The results showed that the optimum magnesium source,temperature, stirring speed and reaction equilibrium time for side-stream phosphorus recovery were: MgCl2 · 6H2O, 25 °C, 150 rpm and 20 min, respectively. It was also observed that the average phosphorus removal efficiency of the mainstream system maintained as high as 90.7% during the side-stream extraction period despite insufficient time for phosphate uptake under limited dissolved oxygen condition and phosphate deprivation of polyphosphate-accumulating organisms (PAOs). Besides, the sludge settling performance of the mainstream EBPR system decreased with no sludge loss. Afterwards, phosphorus removal and sludge settling performance were restored with dismissing side-stream phosphorus recovery. This study suggested that side-stream extraction of anaerobic supernatant from a mainstream EBPR subjected to low dissolved oxygen conditions for chemical phosphorus recovery was feasible and environmentally friendly.