Stringent Discharge Research Articles

Optimization approach for sustainable decommissioning of unpiggable subsea pipelines: Insights from the Arabian Gulf.

Unpiggable pipelines, often inaccessible for traditional pigging operations, pose significant risks due to residual hydrocarbons and limited inspection options. This paper presents an optimized methodology for flushing, de-oiling, and abandoning unpiggable subsea pipelines, specifically designed to address the unique environmental and regulatory challenges in the Arabian Gulf. The paper introduces an innovative approach that integrates advanced modeling tools ‒ OLGA for internal flow assurance and CORMIX for pollutant dispersion analysis ‒ to manage oil-in-water (OIW) concentrations effectively, ensuring compliance with the stringent 15-ppm discharge limit. The proposed methodology not only mitigates residual contamination risks but also enhances operational efficiency and regulatory compliance through adaptive measures. By addressing plateauing contaminant removal rates and leveraging region-specific environmental data, the current study provides actionable guidance for sustainable decommissioning of subsea pipelines. The findings hold broad applicability for projects in environmentally sensitive marine ecosystems, hence, supporting global efforts toward environmentally responsible decommissioning practices.

Effects of wastewater on phosphorus, nitrogen, and nuisance benthic algae in nearshore regions of a large lake.

Upgrading wastewater treatment plants (WWTPs) is a global practice for achieving increasingly stringent nutrient discharge objectives set by governments to accommodate population growth and reduce surface water pollution. However, associated downstream improvements in nutrient conditions are difficult to determine in nearshore regions of large aquatic ecosystems due to complex biophysical processes. We conducted a nine-year water quality study and analyzed the data using linear mixed models (LMMs) within a Before-After-Control-Impact (BACI) framework to assess effects of an upgrade to the Duffin Creek Water Pollution Control Plant (DCWPCP) on surface water nutrient conditions and proliferation of nuisance benthic algae (Cladophora glomerata) in nearshore Lake Ontario. The DCWPCP upgrade resulted in increased effluent concentrations and loads of nitrite+nitrate (NO2+3) due to enhanced nitrification, while reducing total Kjeldahl nitrogen and ammonia+ammonium (NH3+4). However, total phosphorus (TP) in effluent only changed slightly due to operational constraints during plant upgrade. For nearshore nutrient conditions, our LMM-BACI framework revealed that, after upgrade, NH3+4 decreased at impact site relative to control sites. In contrast, following upgrade, an observed decline in NO2+3 concentrations was less pronounced at impact site compared to control sites, suggesting increased NO2+3 inputs into nearshore surface water from the DCWPCP. We could not detect obvious improvement in nearshore TP concentrations, stoichiometric ratios of total inorganic nitrogen to TP and NO2+3 to TP, or phosphorus tissue content of Cladophora, likely due to the only slight reduction in TP from the DCWPCP. Overall, our findings showed that the DCWPCP upgrade increased NO2+3 inputs, which could have important implications for nutrient management and trade-offs associated with WWTP upgrades that reduce one chemical species at the expense of another. Other researchers may find our LMM-BACI framework useful to detect localized impacts of nutrient inputs in nearshore and coastal areas where multiple physical and climate drivers influence water quality.

Enhancing nitrogen removal in combined sewage overflows by using bio-fluidized bed with ceramic waste powder carriers: effects and mechanisms.

Micron-size ceramic waste powder (< 75 μm and 75-150 μm) was used as the carrier in a high-concentration powder carrier bio-fluidized bed (HPB) to treat simulated overflow sewage (CSOs). The sludge extracellular polymers (EPS), electron transfer capacity of EPS, nitrogen removal pathways, and microbiological characteristics were analyzed to gain insights into the nitrogen removal pathways and mechanisms. The results showed that only the effluent from the HPB (< 75 μm) could meet the stringent pollutant discharge standards in China of 50 mg/L for CODCr and 15 mg/L for total nitrogen from beginning to end. Meanwhile, the electrochemical performance tests indicated that the electron accepting and donating capacities of the sludge EPS in the HPB (< 75 μm) were 42.75% and 32.73% higher than those in the conventional activated sludge, meaning that ceramic powder carriers can increase the extracellular electron transfer capacity of the sludge and accelerate the denitrification process. Also, metagenomics analysis results showed that the relative abundances of the denitrification-related Nor genes were 28-39% higher in the HPB (< 75 μm) and HPB (75-150 μm) than in the conventional activated sludge (CAS). These results show that ceramic waste powders have the potential to be used as carriers in HPB systems to treat CSOs.

Toward circular greenhouse wastewater reuse: advancements in cation exchange membranes for selective Na+/K+ separation using electrodialysis systems

ABSTRACT Driven by the growing need for alternative water sources and forthcoming stringent nutrient discharge regulations, there is growing interest in developing selective membrane solutions to facilitate circular greenhouse wastewater reuse (as emphasized in the European Union's Horizon 2020 ULTIMATE project). For electrodialysis systems, sodium (Na+) over potassium (K+) selective membranes are essential to achieve minimal liquid discharge. This study addresses the challenge of developing selective, efficient, and scalable Na+/K+ cation exchange membranes. State-of-the-art cation exchange membrane developments were reviewed and the functionalization of commercial membranes with crown ethers was identified as a promising approach. Two crown ether–modified membranes (15-crown-5 (15C5) and 18-crown-6 (18C6)) were developed, characterized, and tested in equimolar and greenhouse wastewater binary feed ratios. While the results demonstrated low overall selectivity, the 15C5-modified membrane showed a marginal enhancement in K+ selectivity, suggesting the need for further optimization. The study concludes with recommendations for the future development of Na+/K+ selective membranes, highlighting the potential of machine learning approaches to expedite progress. This research provides a foundational step toward practical and scalable Na+/K+ ion separation solutions, for achieving minimal liquid discharge in greenhouse horticulture.

Achieving dendrite-free zinc deposition by large-size anion-reinforced solvated structures for highly reversible zinc anode

The electrochemical instability of zinc anode caused by surface side reactions and irregular zinc deposition severely hinders the practical application of aqueous zinc ion batteries (AZIBs). In this work, diethylenetriaminepentaacetic acid, pentasodium salt (DTPA) was used as a novel electrolyte additive to modulate the electrochemical stability of Zn anode. The DTPA anion can strongly coordinate with Zn2+, thus enabling the formation of a unique large-size anion-enhanced solvation structure of electrolyte. In this, not only the generation of by-products on Zn anode can be effectively inhibited, but more importantly, the deposition kinetics of Zn2+ can be well regulated to induce even and stable zinc deposition. In addition, DTPA is more prone to chemically adsorbed on the surface of Zn anode than H2O, contributing to the resistance of electrochemical corrosion. Synergistically, the Zn anode demonstrates excellent cycling stability (3850 h at 1 mA cm−2, 1 mAh cm−2, and 500 h at 10 mA cm−2, 10 mAh cm−2), enhanced coulombic efficiency (99.83% upon 3500 cycles at 5 mA cm−2, 1 mAh cm−2), and high reversibility of 1050 h even at a stringent discharge depth of 80%. Particularly, the full cell assembled with NaV3O8·1·5H2O (NaVO) cathode can also operate stably for 1800 cycles at 2 A g−1 with a high capacity retain of 90.8%. This work may pave a new route to achieve high-performance AZIBs by regulating the deposition process of Zn2+ based on large-size anion-enhanced solvation structure of electrolyte.

Efficient nitrogen and phosphorus removal performance and microbial community in a pilot-scale anaerobic/anoxic/oxic (AOA) system with long sludge retention time: Significant roles of endogenous carbon source

Stringent wastewater discharge standards require wastewater treatment plants (WWTPs) to focus on enhancing nitrogen (N) and phosphorus (P) removal efficiency. Increasing sludge concentration by regulation of sludge retention time (SRT) would enhance wastewater treatment loads. However, phosphorus-accumulating organisms (PAOs) would be outcompeted by glycogen-accumulating organisms (GAOs) under long SRT, leading to a collapse of P removal. In this work, pilot-scale anaerobic-oxic-anoxic (AOA) and anaerobic-anoxic-oxic (AAO) systems with long SRT (30 d) were parallelly established for actual urban wastewater treatment. The results indicated that sludge reflux ratio, temperature, and C/N ratio significantly impact N and P removal performance of AOA and AAO systems with long SRT, and removal efficiency of AOA system significantly exceeded that of AAO system. AOA system with long SRT achieved the optimal performance at sludge reflux ratio of 200%, temperature of 25 °C, and C/N ratio of 8, with COD, NH4+-N, TN, and PO43--P removal ratio of 92.80 ± 2.24%, 97.38 ± 0.89%, 88.97 ± 2.47%, and 94.33 ± 3.27%, respectively. In addition, compared to AAO system, AOA system could save 23.08% of the aeration volume. This work highlighted that AOA system with long SRT included multiple coupled nitrogen and phosphorus removal pathways, such as autotrophic/heterotrophic nitrification, anoxic/oxic denitrification, endogenous denitrification, and denitrifying phosphorus removal. Among these, the synergistic effect of endogenous denitrification and denitrifying phosphorus removal driven by internal carbon sources contributed to satisfactory nitrogen and phosphorus removal efficiency in AOA system with long SRT.

Preparation of ZnAlLa-LDHs by one-step hydrothermal method and its adsorption properties for phosphate

Abstract Phosphate is one of the main limiting factors of water eutrophication, and the effective removal of phosphate is essential to control the eutrophication of the aquatic environment and meet the increasingly stringent phosphate discharge regulations. This study successfully prepared ZnAlLa-LDHs materials using a simple hydrothermal method using triethanolamine as a soft template, which SEM, XRD, and FT-IR characterized. The results show that ZnAlLa-LDHs is a kind of two-dimensional porous structure material; the adsorption isotherm of ZnAlLa-LDHs on phosphate conforms to the Langmuir model, and the maximum adsorption capacity is 83.333 mg g−1; the adsorption kinetics conforms to the pseudo-second-order kinetic model, and the adsorption rate is mainly controlled by chemical adsorption; the adsorption mechanism of ZnAlLa-LDHs on phosphate is mainly ion exchange and electrostatic adsorption. ZnAlLa-LDHs have an excellent effect on phosphorus in wastewater from sewage treatment plants.

Removal of heavy metals from mine water using a hybrid electrocoagulation-ceramic membrane filtration process

Mining operations must account for increasingly stringent wastewater discharge limits for various contaminants, such as heavy metals and suspended solids. In the treatment of metal-bearing wastes, electrochemical processes, including electrocoagulation (EC), are gaining popularity. At large scales, EC processes can be hindered by considerable amounts of flocculants and by sedimentation tank sizes required to properly operate. This work sought to address these concerns by evaluating EC in mine water treatment using a pilot system coupled with ceramic membrane microfiltration (MF) and ultrafiltration (UF). The use of MF and UF after EC allows for the removal of suspended solids without needing a flocculation-sedimentation process. EC evaluation was performed using field samples of mine water from a North American concentrator. Under optimal conditions, EC removed over 95 % of Cr, Co, Cu, Fe, Mn, Ni, Pb, Ti and Zn from the mine water. Effluent from EC was used as feed in MF and UF processes with ceramic membranes. The tested membranes rejected 100 % of suspended solids from the EC effluent. Permeate from the membranes was free of solids and possessed turbidities of 0.05–0.15 NTU. Filtrate from the hybrid process satisfied environmental regulations for heavy metal concentrations, offering new opportunities for reuse or discharge. The hybrid process applied in this work can thus be used in mining operations to safely discharge their water, and/or to increase their water recirculation due to environmental concerns and water shortage.

A Novel Coupling of a Biological Aerated Filter with Al3+ Addition-O3/H2O2 with Microbubble for the Advanced Treatment of Proprietary Chinese Medicine Secondary Effluent

The advanced treatment of proprietary Chinese medicine secondary effluent (PCMSE) was strongly needed with the recent implementation of a more stringent discharge standard. Based on the features of PCMSE and the reuse of Al3+from wastewater from soaking of Pinellia Ternata with alumen (WSPTA), three new combined processes were designed for the advanced treatment of PCMSE on a larger pilot scale. A pilot scale study showed that compared with two other combined processes, the new coupling of a biological-aerated filter with Al3+ addition (BAFA)-O3/H2O2 with microbubble (OHOMB) (CBAFAOHOMB) obtained the maximum pollutant removal (with removals of 91.71%, 94.64%, and 82.32% being observed for color, total phosphorus (TP), and chemical oxygen demand (COD), respectively) and acquired the lowest Al3+residual in the effluent. During CBAFAOHOMB treatment of PCMSE, the vast majority of TP elimination, 35.20% of COD removal, and 49.40% of color removal were achieved by BAFA; OHOMB obtained 64.80% of COD removal and 60.60% of color removal, and biofilm activity in BAFA slightly changed under a 10 mg/L Al3+ dose. Furthermore, microbubble aeration was more efficient in removing organics than conventional bubble aeration during O3/H2O2 oxidation, and suspended solid (SS) relatively significantly lowered oxidation ability in the OHOMB system. These results indicated that CBAFAOHOMB markedly integrated advantages of BAFA and OHOMB, and was a proposed process for the advanced treatment of PCMSE. Meanwhile, it was feasible that WSPTA was reused for PCMSE treatment as an Al3+ source.

A Review of Life Cycle Assessment of Nanomaterials-Based Adsorbent for Environmental Remediation

&lt;p&gt;Nanomaterials, known for their exceptional physicochemical properties, are used in electronics, skincare, catalysts, agriculture, and water treatment. Their small size and large surface area enable high adsorption capacities and rapid adsorption rates, effectively removing organic and inorganic pollutants from water. Designed as composites, nanomaterials enhance adsorption capacity, improve mechanical strength, and provide support matrices for retaining nanoparticles. Nanoadsorbents are particularly effective in removing toxic metals from wastewater and drinking water, targeting low concentrations of metals like arsenic, cadmium, lead, and mercury, crucial given stringent discharge regulations. However, the widespread use of nanomaterials poses potential health and environmental risks, as their production involves significant energy and material inputs, generating pollutants. Most research focuses on functionalities without considering life cycle environmental impacts. Life cycle assessment (LCA) is a comprehensive tool for evaluating these impacts, assessing products from cradle to grave, including raw material extraction, processing, manufacturing, distribution, use, maintenance, and disposal or recycling. LCA, based on the ISO 14040 series, includes four phases: goal and scope definition, life cycle inventory, life cycle impact assessment, and life cycle interpretation. This study categorizes existing research based on the four LCA phases, aiming to highlight current practices, challenges, and progress. The findings provide insights and recommendations for future research to ensure the sustainable development of nanomaterials.&lt;/p&gt;

Inhibition of phosphorus removal performance in activated sludge by Fe(III) exposure: transitions in dominant metabolic pathways.

Simultaneous chemical phosphorus removal process using iron salts (Fe(III)) has been widely utilized in wastewater treatment to meet increasingly stringent discharge standards. However, the inhibitory effect of Fe(III) on the biological phosphorus removal system remains a topic of debate, with its precise mechanism yet to be fully understood. Batch and long-term exposure experiments were conducted in six sequencing batch reactors (SBRs) operating for 155 days. Synthetic wastewater containing various Fe/P ratios (i.e., Fe/P = 1, 1.2, 1.5, 1.8, and 2) was slowly poured into the SBRs during the experimental period to assess the effects of acute and chronic Fe(III) exposure on polyphosphate-accumulating organism (PAO) growth and phosphorus metabolism. Experimental results revealed that prolonged Fe(III) exposure induced a transition in the dominant phosphorus removal mechanism within activated sludge, resulting in a diminished availability of phosphorus for bio-metabolism. In Fe(III)-treated groups, intracellular phosphorus storage ranged from 3.11 to 7.67 mg/g VSS, representing only 26.01 to 64.13% of the control. Although the abundance of widely reported PAOs (Candidatus Accumulibacter) was 30.15% in the experimental group, phosphorus release and uptake were strongly inhibited by high dosage of Fe(III). Furthermore, the abundance of functional genes associated with key enzymes in the glycogen metabolism pathway increased while those related to the polyphosphate metabolism pathway decreased under chronic Fe(III) stress. These findings collectively suggest that the energy generated from polyhydroxyalkanoates oxidation in PAOs primarily facilitated glycogen metabolism rather than promoting phosphorus uptake. Consequently, the dominant metabolic pathway of communities shifted from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism as the major contributor to the decreased biological phosphorus removal performance.

Investigation on MOS shunt LVTSCR for ESD application

Continuously scaling down ICs result in more stringent electrostatic discharge (ESD) protection design requirements. Compared with other devices, silicon-controlled rectifier (SCR) has become the first choice for its area efficiency and robustness. In order to improve the latch-up issue of SCR, various schemes have been proposed. A simple method is to extend the SCR path length, which will result in the enlarged ON resistance. Segment technology is also used to improve the holding voltage of SCR, but it will shrink the effective emitter area and lead to the serious degradation of ESD robustness. MS-LVTSCR is used to protect CMOS input ports. The circuit operating voltage is 3.3V and the gate oxide DC breakdown voltage is 19V so that considering the safety margin, the ESD window is from 3.63V to 17.1V. This work proposes a novel MOS shunt low-voltage trigger silicon-controlled rectifier (MS-LVTSCR) electrostatic discharge protection device by inserting an embedded PMOS structure. Compared with the conventional LVTSCR, the proposed MS-LVTSCR achieves 53% improvement in the holding voltage and still maintains high ESD robustness with a current level of 31.5 mA/μm without more device area consumption. In addition, both the TCAD simulation and theoretical analysis were carried out to explore the principle of current shunt effect to improve holding voltage. The extra shunt paths will weaken the conductance modulation effect of the main drift region in the main SCR path and its holding voltage can be further raised by reducing the proportion of main drift region current in the total current. We also conducted detailed studies on the mechanisms and geometry effects of this newly proposed structure via experimental validations.

Clarifying the Role of Phosphorus Management Strategies in Enhancing the Sustainability of Wastewater Treatment Plants

With the emphasis on climate change and society’s goals of carbon neutrality, wastewater treatment plants (WWTPs) are facing new challenges to be more sustainable and particularly to reduce their greenhouse gas (GHG) emissions. In addition, the increasingly stringent discharge standard, especially the phosphorus removal target, also puts lots of pressure on WWTPs. The key solution is to tailor and/or optimize the phosphorus management strategies to balance removal targets and sustainability. As such, the present study systematically summarizes and analyzes different phosphorus management approaches and their impacts on the costs and operation of whole plants. The summary shows that precipitate scaling is a common issue that can be alleviated by proper phosphorus management strategies and operation optimization. Biological phosphorus removal and chemical phosphorus removal processes have their respective advantages and disadvantages. Most importantly, each phosphorus removal process probably has countering impacts on wastewater and sludge treatment lines. Thus, the evaluation of a specific phosphorus removal process should consider all factors in choosing a suitable technology, which is also true for phosphorus recovery, and the recovery from incineration ash seems to be a trend that is more feasible from a regulatory perspective.

Improving carbon management through maximizing hydrolysis and fermentation at water resource recovery facilities

Wastewater treatment plants are transitioning from a sole focus on treatment objectives to integrated resource recovery and upcycling. Effective carbon management is critical for upcycling within a water resource recovery facility (WRRF) to produce energy or other usable products, which involves carbon diversion at primary treatment and waste activated sludge (WAS) from biological treatment processes. Many WRRFs are also driven to meet stringent effluent nutrient discharge targets while minimizing energy usage and chemical addition. Nutrient removal systems still rely on biodegradable organic carbon to support denitrification and enhanced biological phosphorus removal (EBPR). Biological nutrient removal not only requires sufficient organic substrate, but also the right type of bioavailable carbon for optimal utilization. The main objective of this pilot fermentation testing was to evaluate the most effective utilization of the range of organic-carbon rich feedstocks within a WRRF. Preliminary results suggest that a 50–50 blend of primary sludge (PS) and return activated sludge (RAS) fermentation leads to highest volatile fatty acid (VFA) yield. PS fermentation resulted in the minimum nutrients release per unit of volatile suspended solids (VSS), which makes it a best suited for biological nutrients removal WRRFs with stringent nitrogen (N) and phosphorus (P) limits. The volatile fatty acids fractions produced from different combinations of RAS and PS can impact the most suitable end use for each sludge type fermentation. PS resulted into higher levels of propionate, which are ideal for selecting phosphate accumulating organisms (PAO) over glycogen-accumulating organisms (GAO). On the other hand, for denitrification, acetate is the preferred substrate, which was most abundant with RAS only fermentation. Our research outcomes will be of value to utilities aiming to integrate the stringent effluent nutrient (N and P) discharge targets with energy and resource recovery.

The urgent need to reduce phosphorus discharges for sustainable mangrove wetland management

Phosphorus affects microbial metabolic activity, nitrogen and carbon cycling in mangrove sediment, but its influence on carbon stability and greenhouse gases emission remains unclear. This study compared greenhouse gases (CO2, N2O, and CH4) emissions from mangrove sediment receiving wastewater containing various phosphorus concentrations, and evaluated its long term effect on sediment carbon flux when phosphorus pollution is eliminated. Significant increases in greenhouse gases flux and decrease of total organic carbon and readily oxidizable organic carbon in the sediment were observed after phosphorus discharge. Specifically, the N2O flux was reduced significantly at high phosphorus levels while the CO2 flux and the microbial biomass organic carbon was increased. The copy numbers of ammonia oxidation (AOA-amoA, AOB-amoA) gene, denitrification (narG, nirK) gene and methanogenesis (mcrA) gene increased with the increasing phosphorus concentration. During the wastewater discharge period for 70 days, the global warming potential of sediment flux at high phosphorus discharge condition was more than 4 times that of the control group, and the loss of total organic carbon and readily oxidizable organic carbon was 4.66 % and 7.1 %, respectively. During the remediation period (71–101 days), the greenhouse gases flux decreased rapidly, ends up with a similar level of the control group. Our results indicate that using mangrove wetland for pollution minimization in the coastal aquaculture industry could increase greenhouse gases emisison significantly, it is therefore essential to reduce phosphorus discharges from various anthropogenic activities, and local authorities must set up more stringent discharge standards in the future.

Fe(II)-driven spatiotemporal assembly of heterotrophic and anammox bacteria enhances simultaneous nitrogen and phosphorus removal for low-strength municipal wastewater

The mainstream anaerobic ammonium oxidation (anammox) faces considerable challenges with low-strength municipal wastewater. A Fe(Ⅱ)-amended partial denitrification coupled anammox (PD/A) process was conducted and achieved a long-term and efficient nitrogen and phosphorus removal, yielding effluent total nitrogen and phosphorus concentrations of 1.97 ± 1.03 mg/L and 0.23 ± 0.13 mg/L, respectively, which could well meet more stringent effluent discharge standard of some wastewater treatment plants in specific geographical locations, e.g., estuaries. Fe(Ⅱ)-driven vivianite formation provided key nucleuses for the optimization of the spatial distribution of heterotrophic and anammox bacteria with enhanced extracellular polymeric substances as key driving forces. Metagenomics analysis further revealed the increase of key genes, enhancing anammox bacteria homeostasis, which also bolstered the resistance to environmental perturbations. This study provided a comprehensive sight into the function of Fe(Ⅱ) in mainstream PD/A process, and explored a promising alternative for synergetic nitrogen and phosphorus removal for low-strength municipal wastewater treatment.

Effect of Photocatalytic Pretreatment on the Membrane Performance in Nanofiltration of Textile Wastewater

Traditional methods like biological treatment, flocculation-coagulation, adsorption, and advanced oxidation are commonly employed for textile wastewater treatment, but their sustainability is hindered by issues such as the adverse impact of textile wastewater on microorganisms and the requirement for substantial chemical usage. In response to increasingly stringent legal discharge standards, membrane technologies are emerging as prominent alternatives for effective textile wastewater treatment. The application of photocatalysis as a pretreatment to improve effluent quality and treatment performance has shown effective results in the treatment of textile wastewater by nanofiltration (NF). However, innovative solutions are needed to improve the efficiency of UV photocatalytic reactors. Here, the TiO2/halloysite nanotube (HNT) photocatalyst was shown to completely remove dyes under UV illumination. Two wastewater samples from photocatalytic (PC) pretreatment were treated using innovative NF membranes with different contents. The study examined the impact of PC pretreatment on the flux of wastewater from a textile factory heat recovery tank, which increased from 18.32 to 27.63 L/m2.h. The membranes achieved > 98% removal in COD, while bare membrane achieved 95% removal in conductivity. The addition of s-DADPS as monomer and HNT as nanoparticles to the membranes with different compositions affected the cross-linking in the TFC layer. During the tests conducted on the water extracted from the dyeing tank, the color was completely eliminated without any loss of flux. Additionally, improvements in COD removal were observed.

Efficient Recovery of Phosphate from Water Media by Iron-Magnesium Functionalized Lignite: Adsorption Evaluation, Mechanism Revelation and Potential Application Exploration.

Selective phosphorus removal from aquatic media has become an ideal strategy to mitigate eutrophication and meet increasingly stringent discharge requirements. To achieve phosphorus control and resource utilization of low-calorific-value lignite, iron and magnesium salts were used to functionalize lignite, and iron-magnesium functionalized lignite (called IM@BC) was prepared for phosphate recovery from water media. The adsorption properties of IM@BC were systematically evaluated, especially the influence of ambient pH and co-existing ions. The kinetic, isothermal, and thermodynamic adsorption behaviors of IM@BC were analyzed. The adsorption mechanism was revealed by microscopic characterization. The potential application of phosphate-containing IM@BC (P-IM@BC) was explored. The results show that IM@BC has a strong phosphate adsorption capacity, and the maximum adsorption capacity is 226.22 mgP/g at pH = 3. Co-existing CO32- inhibits phosphate adsorption, while coexisting Ca2+ and Mg2+ enhance the effect. At the initial adsorption stage, the amount of phosphate adsorbed by IM@BC continues to increase, and the adsorption equilibrium state is gradually reached after 24 h. The adsorption process conforms to the pseudo-second-order kinetic model (PSO) and Langmuir isothermal adsorption model, and the adsorption process is mainly chemical adsorption. The phosphate absorption capacity is positively correlated with temperature (283.15 K~313.15 K), and the adsorption process is spontaneous, endothermic, and entropy-increasing. Its adsorption mechanism includes electrostatic attraction, ion exchange, surface precipitation, and coordination exchange. IM@BC can efficiently recover phosphate from actual phosphorus-containing wastewater with a recovery efficiency of up to 90%. P-IM@BC slowly releases phosphate from pH 3 to 11. Plant growth experiments showed that P-IM@BC could be used as a slow-release fertilizer to promote the root growth of cowpeas. The novelty of this work lies in the development of a highly efficient phosphate recovery adsorbent, which provides a feasible method of phosphorus control in water media and resource utilization of lignite.

Carbon Source in Tertiary Denitrification Regulates Dissolved Organic Nitrogen in Wastewater Effluent.

With global eutrophication and increasingly stringent nitrogen discharge restrictions, dissolved organic nitrogen (DON) holds considerable potential to upgrade advanced wastewater denitrification because of its large contribution to low-nitrogen effluents and stronger stimulation effect for algae. Here, we show that DON from the postdenitrification systems dominates effluent eutrophication potential under different carbon sources. Methanol resulted in significantly lower DON concentrations (0.84 ± 0.03 mg/L) compared with the total nitrogen removal-preferred acetate (1.11 ± 0.02 mg/L) (p < 0.05, ANOVA). With our well-developed mathematical model (R2 = 0.867-0.958), produced DON instead of shared (persist in both influent and effluent) and/or removed DON was identified as the key component for effluent DON variation (Pearson r = 0.992, p < 0.01). The partial least-squares path modeling analysis showed that it is the microbial community (r = 0.947, p < 0.01) rather than the predicted metabolic functions (r = 0.040, p > 0.1) that affected produced DON. Carbon sources rebuild the microorganism-DON interaction by affecting the structure of microbial communities with different abilities to generate and recapture produced DON to finally regulate effluent DON. This study revalues the importance of carbon source selection and overturns the current rationality of pursuing only the total nitrogen removal efficiency by emphasizing DON.

Analysis of Microbial Community in Circulating Cooling Water System of Coal Power Plant during Reagent Conversion

The use of phosphorus-containing chemical corrosion and scale inhibitors has been found to result in excessive phosphorus discharge and an inability to reduce the high concentration of CODcr in the circulating cooling water, thereby making it challenging to comply with increasingly stringent sewage discharge standards. This study aims to assess the practicality of utilizing biological corrosion and scale inhibitors in coal power plants’ operation, as well as investigating the correlation between water quality indicators and microbial communities during the conversion period. The data illustrates that, in comparison to the chemical method, there is a decrease in turbidity of the circulating water from 19.44 NTU to 9.60 NTU, a reduction in CODcr from 71.55 mg/L to 45.47 mg/L, and a drop in TP from 2.35 mg/L to 0.38 mg/L. Microbial community analysis during the transition period reveals that microorganisms rapidly establish a new equilibrium in the circulating water, sediment, and fiber ball, resulting in significantly different microbial community structures. The relative abundance of corrosive microorganisms such as Flavobacterium, Pedomicrobium, and Hydrogenophaga is significantly diminished in the circulating water, whilst the abundance of anaerobic microorganisms like Anaerolineaceae and Rhodopseudomonas in the sediment also declines. Conversely, there is an increased presence of microorganisms associated with contaminant degradation, such as CL500-3 and SM1A02. These findings suggest a decrease in the risk of system corrosion and an enhancement in contaminant degradation capability. This study provides evidence supporting the replacement of chemical agents with biological agents in circulating cooling water systems, contributing to more environmentally friendly and sustainable practices.