Nitrogen In Wastewater Research Articles

Performance of Limoniastrum guyonianum in nutrient removal and tolerance in Halloufa Wetland, Algeria

Phytoremediation is an effective and sustainable method for removing pollutants from wastewater. This study investigates the phytoremediation capabilities of Limoniastrum guyonianum, a halophytic Saharan plant species, for excess phosphorus and nitrogen in domestic wastewater. The plants were sourced from the “Halloufa” wetland, a wastewater discharge area in the north of El-Oued, south-eastern Algeria. The research was conducted using pilot-scale circular beds designed for phytoremediation, each with an 18-liter capacity, filled with layers of gravel and a clay-sand mixture. These beds were part of a vertical surface flow system at the National Sanitation Office (ONA) domestic wastewater treatment facility in El-Oued, Algeria. The results demonstrated significant improvements in water quality parameters. Treatment with L. guyonianum reduced pH values from 8.07 to 7.64 and decreased turbidity from 116.25 NTU to 8.87 NTU. The mean concentration values of ammonia, phosphate, and biochemical oxygen demand (BOD5) were reduced by 99.22%, 55.58%, and 78.6%, respectively. The study concludes that L. guyonianum is highly efficient in remediating nitrogen contaminants, effective in reducing phosphorus levels, and capable of lowering biochemical oxygen demand. L. guyonianum presents a nontoxic, eco-friendly, and cost-effective alternative for wastewater treatment in the “Halloufa” wetland, highlighting its potential for application in bioremediation processes.

The start-up of red blood cell-like anammox granular sludge based on substrate volume flux

Enhancing substrate transfer is crucial for promoting the nitrogen removal rate of Anammox granular sludge, as the shape of the granules significantly influences substrate diffusion. In this study, inspired by biomimicry principles, we propose a novel red blood cell-like granular sludge to increase the contact area and improve substrate transfer. The startup and operation of Anammox granular sludge in low-strength ammonia nitrogen wastewater were successfully achieved through an increase in substrate volume flux (SVF). As the SVF increased from 2.38 to 7.43L²/(g VSS·h), specific Anammox activity (SAA) rose from 0.138 to 0.483gN/(g VSS·d). The Anammox granular sludge system achieved a total nitrogen removal efficiency of 85.70% and a nitrogen removal rate (NRR) of 0.792kgN/(m³·d) after 126 days. Notably, red blood cell-like granular sludge was observed by day 116. The rise in SVF induced a granule structure more conducive to substrate transport, improving the granules' efficiency in substrate uptake and thereby enhancing their SAA. High-throughput pyrosequencing revealed that the dominant bacteria using the SVF-enhancing strategy remained anaerobic ammonium oxidizing bacteria (AnAOB) (29.53%-29.89%), with an increased diversity of species, including Candidatus Kuenenia, Candidatus Anammoxoglobus, and Candidatus Brocadia.

Utilizing Fe-C and PbO2 modified electrodes for the electrochemical treatment of pickled vegetable wastewater

The objective of this study was to enhance the treatment efficiency of chemical oxygen demand (COD), total phosphorus (TP), and ammonia nitrogen (NH4+-N) in pickled vegetable wastewater, as well as to improve the electrode's stability. Iron carbon micro-electrolysis (FeC) was employed for the pretreatment of wastewater, followed by a secondary treatment utilizing PbO2 modified electrodes in the electrochemical advanced treatment process. The optimal operational conditions for Iron‑carbon micro-electrolysis (Fe/C = 1.2:1, volume ratio of iron to water = 1:1, pH = 5.4, reaction time = 4 min). For the electrochemical method, the optimal operational conditions included a plate spacing of 2.00 cm, a degradation temperature of 65 °C, a current density of 50 mA/cm2, and a pH of 6. The optimal doping ratio of La in the Ti/SnO2-Sb2O5/La-PbO2 modified anode was found to be 10 mmol/L, with a theoretical lifespan of 5670 h. Under these conditions, the removal rates for TP, COD, NH4+-N, and salinity (as Cl−) from the pickled vegetable wastewater were 96.67 %, 70.03 %, 79.88 %, and 6.09 %, respectively.

Enrichment of marine microbes to remove nitrogen of urea wastewater under salinity stress

Salinity (NaCl) and urea concentration significantly affect the diversity, structural and physiological function of microbial communities in the biological treatment of wastewater. However, the responses of microbial in high salt and urea wastewater remain elusive. Here, we investigated microbial community function and assembly of four regions using gradient domestication experiment combined with 16S rRNA gene sequencing and statistical methods. The results showed that with the increase of salinity and urea concentration, the consortium Xiamen could still remove most urea, while the other three consortia could not. The alpha diversity of microbial community initially decreased and then increased, showing a recovery trend. After domestication, the consortium Xiamen exhibited high physiological activity and complex network structure, and the community assembly process changed from stochastic to deterministic during the domestication. Furthermore, the keystones with low abundance were associated with urea removal and important for maintain the complexity of the networks, while Arenibacter and Oceanimonas were found to be keystones in maintaining efficient urea removal in harsh environments. To sum up, environmental effects dominated by salinity and urea concentration stress drove the community assembly and species coexistence that underpinned the microbial differentiation pattern at a geographic scale. These results provided new sights for elucidate how microbial response to salinity and urea during wastewater treatment.

Optimizing anoxic/oxic intervals in intermittent aeration for STHP-AD filtrate treatment: Restoring partial nitrification and community dynamics in the SPNAD system

Currently, partial nitrification (PN) processes are commonly used to improve efficiency in high ammonia nitrogen wastewaters. However, initiating and restoring damaged PN performance is crucial for optimizing nitrogen removal efficiency without the use of chemical additives. In this study, a simultaneous partial nitrification and denitrification coupled with anammox (SPNAD) sequencing batch biofilm reactor was constructed to treat anaerobic digestion after sludge thermal hydrolysis pretreatment (STHP-AD) filtrate. The PN performance was successfully recovered through optimizing the operation mode of anoxic/oxic alternation within 120 days. Result showed that Nitrosomonas increased from 0.68 % to 3.43 %, while Nitrospira decreased to 0.06 %. The PN recovery also promoted anammox, with the only anammox bacterium of Candidatus Brocadia, detected in the mixing and biofilm sludge of 1.73 % and 1.41 %, respectively. The autotrophic denitrifying bacteria Thermomonas (increasing from 0.47 % to 23.85 %) and Truepera (rising from 2.31 % to 6.54 %) rapidly accumulated. After adjusting to the anoxic/oxic alternation ratio, the hydraulic retention time was shortened from 50 h to 37.5 h, and the oxic time was reduced to half of the initial operation. The PN recovery and anammox enrichment resulted in improving nitrogen removal approximately 20 %. Eventually, the SPNAD system realizes stable and efficient nitrogen removal with the influent nitrogen loading rate of 0.43 kgN/(m3·d), the ammonium removal efficiency of 94.73 ± 3.27 %, and the nitrogen removal efficiency of 72.98 ± 1.27 %. In this study, a new strategy using intermittent aeration while appropriately extending the oxic time was proposed to restore the system’s ability to treat STHP-AD filtrate after PN disruption.

Production of Biomass and Lipid Yields of Chlorella sp. Cultivated in Autotrophic and Mixotrophic Media

In this work, we analyze the biomass and lipid yields of Chlorella sp., when it grows in synthetic wastewater with and without nitrogen limitation and in both cases, adding glucose to both medium, autotrophic and mixotrophic. Our results confirm that it is possible to expand their possibilities of use, which range from their use for the bioremediation of bodies of water to obtaining various biofuels due to their high content of lipids and carbohydrates. It was identified that both the biomass and lipids were higher in the media with mixotrophy with 535.71 mg L-1 and 244.60 mg L-1, respectively. Similarly, the importance of nitrogen present in the growth medium was recognized as a determining variable for the accumulation of lipids in the species, while it is concluded that the use of Chlorella sp. eliminates a significant percentage of nitrogen and phosphorus present in wastewater, thereby reducing nutrient contamination. The nutrient stress to which the microalgae were subjected allowed a greater accumulation of lipids in the cells, which leads to the conclusion that in a large-scale study, Chlorella sp. It could be used as a raw material to obtain oils and their subsequent transformation into biodiesel.

Experimental Study on the Removal of Pollutants from Domestic Wastewater in a Strongly Constructed Wetland with an Applied Electric Magnetic Field

The addition of physical field enhancement measures to improve the purification effect of vertical flow artificial wetlands has gradually become popular. In this study, a vertical flow artificial wetland system reinforced by electric and magnetic fields was constructed. These fields were first optimized using finite element 3D simulation software to obtain the optimal electric and magnetic field parameters. Then, the pollutant removal effects and changes in microbial community structure were comparatively analyzed. The optimal electromagnetic field parameters (applied voltage of 15 V and applied magnetic field of 20 mT) resulted in significantly enhanced removal rates of chemical oxygen demand (COD), nitrate nitrogen (NH4+-N), total phosphorus (TP), and orthophosphorus (PO43−-P) in wastewater, with rates of 74.47%, 45.44%, 89.85%, and 90.04%, respectively. These rates were notably higher than those observed in the vertical flow artificial wetland system. The microbial community structure analysis revealed that the vertical flow constructed wetland with enhanced electric and magnetic fields exhibited (EM-VFCW) a more diverse and complex microbial community structure. Notably, the abundance of bacteria capable of removing NH4+-N and COD, including Aspergillus, Fusarium, and Actinobacteria, was significantly elevated.

Novel Venturi injector reactor design and application in ammonia nitrogen wastewater treatment

The Venturi injector reactor has a robust and durable design and is highly efficient and reliable. The flow field control in the Venturi reactor is an effective way to enhance gas−liquid mass transfer. In this study, a novel Venturi injector reactor with an expandable self-priming air inlet and a second water inlet in the diffusion section was designed by combining particle image velocimetry (PIV) experiments with a computational fluid dynamics simulation. This novel design increased the gas holdup, generated smaller and more uniform bubbles, and enhanced mass transfer. Furthermore, we applied the novel Venturi device to the biological degradation of ammonia nitrogen wastewater. The total gas holdup in the novel Venturi was higher than in the conventional Venturi injector reactor by 0.0056 on average. The minimum bubble diameter was approximately 0.71 mm. Moreover, the ammonia nitrogen removal efficiency of the novel Venturi equipment with the second inlet was 2 and 1.1 times higher than that of conventional aeration and conventional Venturi device, respectively. This study provides a theoretical basis and practical significance for improving the performance and efficient degradation of the ammonia nitrogen concentration in Venturi injector reactors.

Enhancement of the reactivation process of long-term starved anammox granular sludge with gravel balls: Microbial succession and metabolic impact

Anaerobic ammonium oxidation (Anammox) process is an economical and energy-efficient method of wastewater nitrogen removal. However, they are highly susceptible to starvation stress caused by sudden environmental changes. Rapid reactivation of starved anammox sludge is a crucial method to address seed sludge shortages and expand practical applications. This study investigated the impact of gravel balls on the reactivation of long-term starved anammox granular sludge (628 days). The results showed that gravel balls enhanced the recovery of nitrogen removal performance in starved anammox sludge, with nitrogen removal efficiency being 19.88% higher than the control group at the end of the recovery phase. The gravel balls also increased extracellular polymeric substance (EPS) secretion, contributing to the stability of the anammox system. Furthermore, the gravel balls promoted the proliferation of anammox bacteria, with the relative abundance of anammox bacteria reaching 38.25% on the 80th day. The analyses of microbial functions indicated that gravel balls facilitated cross-feeding and co-metabolism among microbes, while enhancing quorum sensing associated with anammox bacteria, forming a multifunctional community network centered on anammox bacteria. This indicates that gravel balls can effectively accelerate the reactivation process of long-term starved anammox sludge, aiding the reutilization of long-term starved anammox sludge.

Synergistic effect of reinforced cellulose nanofibrils/polyethylene glycol embedded particles in ammonia nitrogen wastewater: An in-depth microbial denitrification analysis

The encapsulation and immobilization technology provide a good growth environment for bacteria, strong protection ability, improved survival rate, and resistance to adverse environmental factors. Cellulose nanofibrils (CNF) with polyhydroxyl structure improve the elasticity, tensile properties, mechanical strength and gel strength of embedded particles through non-covalent forces. Polyethylene glycol (PEG) is a water-soluble polymer with unique carbon‑oxygen chain as the core skeleton. The ether bonds present in each unit give PEG extremely strong hydrophilicity and solubility. CNF and PEG to reinforce SA (sodium alginate) and PVA (polyvinyl alcohol)-SA embedded particle were adopted to treat ammonia nitrogen wastewater. The ammonia diffusion coefficients and oxygen diffusion coefficients of the CNF/PEG/SA and CNF/PEG/PVA-SA were 0.454 × 10−9, 0.286 × 10−9, 0.672 × 10−9 and 0.493 × 10−9 m2/s, respectively. The physicochemical properties of embedded particles were characterized by mass transfer characterization, SEM, XRD, FTIR, and BET analysis. The specific surface areas of CNF/PEG/SA and CNF/PEG/PVA-SA increased to 2.583 m2/g and 3.962 m2/g, respectively. The removal efficiency of NH4+-N, COD and TN in the CNF/PEG/PVA-SA system was 90 %, 74 % and 80 % at 30 °C. By HRT 8 h, the removal efficiency of NH4+-N, chemical oxygen demand (COD)and total nitrogen (TN) by the reinforced system was 94.35 %, 63.07 % and 73.84 %, respectively. The neutral to weakly alkaline pH range showed the highest removal efficiencies of NH4+-N, COD, and TN, at 88.51 %, 74.95 %, and 77.56 %, respectively. The half-saturation constant K was 82.98 mg/L, and the maximum ammonia oxidation rate (Vmax) was 358.92 mgN/(L-particles-h). The reinforced system showed zero-order reaction kinetics. Nonlinear fitting of each initial NH4+-N concentration and ammonia oxidation rate was carried out using the Michaelis-Menten equation. In reinforced embedded particles, microbial genomic data (KEGG; MetaCyc database annotation) analysis was conducted. The reinforced system demonstrated enhanced strength, specific surface area, mass transfer properties, resistance to adverse external environmental factors, and microbial survival rate for the effective treatment of NH4+-N wastewater.

Mitigating pesticide pollution: A comprehensive study on the biological treatment of clodinafop-propargyl and organic load in agricultural wastewater using a moving bed biofilm reactor (MBBR)

The widespread use of pesticides in modern agriculture poses significant threats to public health and the environment. Addressing the growing environmental and economic concerns requires effective strategies for removing and mitigating agricultural toxins. This study evaluates the efficiency of a Moving Bed Biofilm Reactor (MBBR) in degrading clodinafop-propargyl (CF) and reducing organic matter in a controlled laboratory setting. The research focuses on initial CF concentration and hydraulic retention time (HRT) as key factors influencing removal efficiency. The biodegradation of CF was systematically carried out using the MBBR bioreactor. Results demonstrated maximum removal efficiencies of 82.51 % for CF, 88.78 % for Chemical Oxygen Demand (COD), 89.58 % for Total Phosphorus (TP), and 86.31 % for Total Nitrogen (TN). These findings highlight the MBBR's strong capability in eliminating CF and reducing nitrogen in wastewater, positioning it as a cost-effective and environmentally sustainable solution for pesticide pollution. The novelty of this study lies in its detailed examination of the MBBR's performance under varying operational conditions, providing critical insights into its efficiency and optimization. Overall, this research offers valuable contributions to environmental engineering, presenting a promising method for treating pesticide-laden agricultural wastewater and supporting sustainable farming practices.

Reducing wastewater nitrogen loading by >90% with carbon-amended septic systems: A field demonstration in Barnstable (Cape Cod), Massachusetts

Onsite wastewater treatment systems (OWTS) are a major source of excess nutrients and co-pollutants in watersheds across the United States. In Barnstable County (Cape Cod), Massachusetts, effluent from septic systems and cesspools contributes approximately 80% of the controllable reactive nitrogen (N) load to numerous impaired estuaries and degrades water quality in the region's sole source aquifer, streams and ponds. In unsewered areas, wastewater N loads could be reduced substantially by Innovative/Alternative (I/A) septic systems designed for enhanced removal. Use, however, has been partly limited by the availability of high performing, cost effective options, while conventional septic systems continue to be installed in watersheds with well documented N impairments. This paper describes the strategic replacement of residential OWTS with two I/A models that incorporate woodchip bioreactors to enhance N removal. Systems were installed at 14 neighboring homes in Barnstable, MA, and monitored for field performance. Influent and effluent were sampled monthly and analyzed for N and phosphorus (P), among other water quality indicators. Flow to each system was continuously metered to estimate nutrient loads. Results from the first 25 months of monitoring for 13 systems with at least a full year of data are presented in terms of 1) reductions in nutrient concentrations and mass loads and 2) reliability of the systems for meeting a performance goal of total N (TN) < 10 mg/L. Discussion supports consideration of where and how these technologies may be successfully used to manage excess N in sensitive watersheds.

A novel extraction process for efficient recovery of rare earth elements from the leaching liquor of ion-adsorption type rare earth ore using unsaponified N, N-di(2-ethylhexyl)-diglycolamic acid

There are still challenges in the recovery of rare earth elements (REEs) from leaching liquor of ion-adsorption type rare earth ore. In this paper, unsaponified N, N-di(2-ethylhexyl)-diglycolamic acid (HDEHDGA) was used to develop a green extraction process for efficient separation and enrichment of REEs. The cation exchange mechanism of RE(III) extraction was proposed by slope analysis and FT-IR spectra. HDEHDGA exhibited excellent extraction performances, such as short equilibrium time, high selectivity towards RE(III) and easy stripping by 0.5 mol/L HCl solution. REEs was enriched from 287.5 mg/L to 63.30 g/L by five-stage counter-current extraction and three-stage counter-current stripping using unsaponified HDEHDGA. The enrichment factor reached 220, and the proportion of REEs was increased from 80.76 wt% to 98.82 %. The loss of REEs was controlled below 2.14 wt%. This extraction strategy helps to improve the REEs recovery and avoid ammonia–nitrogen wastewater, which demonstrates its application potential in the ion-adsorption type rare earth ore.

Resource Utilization of Rare-Earth-Rich Biomass and Ammonia Nitrogen Effluent from Mining

The post-treatment of heavy metal-enriched plants in mining areas and the purification of ammonia and nitrogen pollution in water bodies are significant for the ecological environment of ionic rare earth mining areas. Herein, we focused on the biochar production potential of Dicranopteris pedata, characterizing biochar prepared by an oxidative modification process and an iron modification process. We conducted adsorption experiments to comparatively investigate the adsorption performance of biochar on NH4+ and studied the fertilizer application and migration toxicity of the adsorbed biochar for rare earth elements (REEs). Results indicated that ~332.09 g of biochar could be produced per unit area of D. pedata under 100% clipping conditions. The Brunauer–Emmett–Teller (BET) specific surface area of oxidized biochar (H2O2BC) increased, and the pore size of iron-modified biochar increased. The adsorption behavior of biochar toward NH4+ was well represented by the pseudo-second-order and Langmuir models. H2O2BC demonstrated the strongest adsorption of NH4+ with maximum theoretical equilibrium adsorption of 43.40 mg·g−1, 37.14% higher than that of pristine biochar. The adsorption process of NH4+ on biochar is influenced by various physicochemical mechanisms, including pore absorption, electrostatic attraction, and functional group complexation. Furthermore, the metal ions in the biochar did not precipitate during the reaction process. The adsorbed NH4+ biochar promoted the growth of honey pomelo without risking REE pollution to the environment. Therefore, it can be applied as a nitrogen-carrying rare earth fertilizer in low rare earth areas. This study provides a theoretical basis and technical support for the phytoremediation post-treatment of rare earth mining areas and the improvement of ammonia nitrogen wastewater management pathways in mining areas.

An innovative process for clean ammonium-free vanadium precipitation and one-step preparation of vanadium dioxide based on hydrothermal enhancement of organic alcohols

As a transition metal oxide, VO2 has excellent optical and electrical properties and is widely used in many fields. The production of VO2 by the reduction of NH4VO3 and V2O5 will inevitably produce ammonia–nitrogen wastewater and NH3 emission during the production of NH4VO3 and V2O5, which will cause serious environmental pollution and will increase economic costs. The large-scale and low-cost synthesis of VO2 still faces great challenges. In this paper, VO2(B) was successfully prepared by a one-step hydrothermal method using NaVO3 as the vanadium source and CH3CH2OH as the reducing agent, and the optimal conditions for vanadium precipitation are as follows: vanadium concentration = 30 g/L, CH3CH2OH dosage = 20 % (percentage of solution volume), initial pH = 1, reaction temperature = 220 °C, reaction time = 12 h. The vanadium precipitation efficiency under the optimal conditions could reach 98.93 %, and the purity of VO2(B) could reach 98.59 %. The precipitation products were characterized by XRD, TG, FTIR, XPS, and SEM-EDS. The mechanism of VO2(B) preparation by ethanol reduction was proposed. This process is characterized by green, clean, and high efficiency. At the same time, the vanadium precipitation effect and vanadium precipitation products of various alcohols were studied to provide technical and theoretical support for the preparation of VO2(B).

Efficient removal of ammonia from aqueous solution using coal-based carbon membrane via electrochemical oxidation in the present of chloride ion

To tackle the escalating issue of ammonia nitrogen water pollution, developing efficient removal technologies holds paramount significance. In this work, an electrochemical membrane reactor (EMR) was constructed for the decontamination of ammonia nitrogen wastewater using the coal-based carbon membrane (CCM) as the flow-through anode. The removal efficiency and degradation mechanism of ammonia nitrogen by EMR during the treatment were investigated. It was found that, under applied voltage and in the presence of chloride ions, the CCM exhibited excellent chlorine evolution performance, and as a result, the EMR had excellent ammonia nitrogen removal efficiency. The removal of ammonia nitrogen by the flow-through EMR was following the pseudo-first-order kinetics. Analysis revealed that various operating parameters, including applied voltage, chloride ion concentration, flow rate, pH value, and initial ammonia concentration, all significantly influenced the ammonia nitrogen treatment performance of EMR. At optimal operation conditions (feed concentration of 30 mg/L, applied voltage of 2.8 V, NaCl concentration of 0.1 mol/L and flow rate of 2 ml/min), the EMR achieved a removal rate of 100 % for ammonia nitrogen with a low energy consumption (EC) of 0.0380 kW•h/g-NH4-N. The degradation mechanism analysis revealed that the primary means of ammonia removal relied on indirect oxidation mediated by OCl·, which was generated by the oxidation of Cl- on the surface of CCM within the solution under the influence of the electric field. Furthermore, the EMR demonstrated good applicability across various water matrices. In conclusion, the EMR holds considerable potential for the decontamination of ammonia nitrogen-containing wastewater.

Enhancing nitrogen removal in low C/N wastewater with recycled sludge-derived biochar: A sustainable solution

Denitrification is an important biological process in wastewater treatment plants (WWTPs). However, a low carbon-to-nitrogen (C/N) ratio limits the availability of organic carbon, potentially reducing denitrification efficiency. This study investigates the impact of sludge-derived biochar on the nitrogen removal of activated sludge for low C/N ratio municipal wastewater. Sludge-based biochar was characterized by its physicochemical properties, revealing that biochar prepared at 400 °C exhibited the highest specific surface area and the most favorable surface functional groups for electron transfer. The results from batch tests showed that adding 4 g/L of biochar dosage enhanced denitrification rates and total nitrogen (TN) removal efficiency the most. Sequencing batch reactors (SBRs) experiments further confirmed that biochar dosgae improved the removal efficiencies of COD, NH4+-N, and TN, achieving stable values of 97.2 ± 1.2 %, 99.2 ± 0.6 %, and 83.8 ± 2.4 %, respectively. Metabolic and electrochemical analyses revealed that biochar addition enhanced the activity of denitrification enzymes, increasing the ammonia oxidation rate by 12.9 ± 0.7 %, nitrite oxidation rate by 14.7 ± 1.2 %, nitrate reduction rate by 36.9 ± 1.5 %, and nitrite reduction rate by 16.4 ± 0.8 %. The relative abundance of denitrification functional genes (amoA, nirS, nirK, narG, nosZ) increased, and the activities of the corresponding enzymes (AMO, NXR, NAP, NIR) rose by 23±6 %, 53±5 %, 260±15 %, and 55±7 %, respectively. This increase in enzyme activity suggested enhanced denitrification processes, which was further supported by the 60.1 ± 3.7 % increase in electron transfer system activity (ETSA), indicating that biochar acted as an electron shuttle. This study proposes a potential sustainable approach for sludge recycling and enhanced wastewater nitrogen removal under low C/N conditions.

Effect of the main components in gasification wastewater on the surface properties of coal water slurry

AbstractCoal water slurry is an advanced and efficient clean coal technology; using gasification wastewater to prepare coal water slurry can recycle wastewater and improve energy utilization efficiency. As the complex substances in wastewater have a great influence on the slurry properties, the effects of organic matter, metal ions, and ammonia nitrogen in gasification wastewater on the surface properties of coal water slurry are studied in this paper in order to provide new ideas for slurry mechanism of coal water slurry prepared from wastewater. Results show the following: (a) Compared with ordinary coal water slurry, the concentration of coal water slurry prepared from wastewater with high organic content increased by 2.9%, while the concentration of coal water slurry prepared from wastewater with high ammonia nitrogen content decreased by 2.1%. (b) The contact angles of coal water slurry prepared with phenols, alcohols, and urethane are reduced by 2.8°, 6.3°, and 1.5°, respectively, so organic matter can change the hydrophilicity of coal particles and affect slurryability. (c) Mg2+ and Ca2+ have basically no effect on slurry. Fe3+ reduces the absolute value of Zeta potential by 33.1, and Cu3+ increases that by 22.8, as they affect the slurryability by changing the surface potential of coal particles and the absorption of additives. (d) Ammonia nitrogen influences the slurryability by changing the pH value of the slurry. The conclusion of the influence mechanism of organic matter, metal ions, and ammonia nitrogen in wastewater on slurryability can provide a technical reference for the selection of suitable wastewater to prepare coal water slurry.

Process Performance and Nutrient Removal in Fish Processing Wastewater Using a Membrane Bioreactor (MBR) Unit for Reuse for Irrigation

This study investigated the removal of nitrogen and phosphates in fish processing wastewater through process optimization of a membrane bioreactor (MBR) treatment unit. Raw process wastewater was collected from the Makindi fish farm and was pre-filtered through a mesh of 0.8 mm. The experiment was conducted at a lab scale using commercial Polyethersulfone (PES) membranes submerged in the MBR unit. The pre-filtered wastewater sample was added into a denitrification (anoxic) tank. The process was conducted through continuous recirculation between the aeration and the anoxic tank to enhance the removal of nitrogenous compounds. The recirculation flow rate was 10L/h. A hydraulic residence time (HRT) of approximately 22-25h was maintained, and the aeration rate in the aerobic tank was 100L/min. Aluminum sulphate AI2(SO4)318H2O was added continually into the anoxic tank and with constant stirring to enhance the removal of phosphates. A removal rate of 85±2% for NH4+-N, 84±1% for NO3- -N, and 69±3% for PO43--P was obtained. The nutrient concentration in the effluent was successfully reduced to an acceptable level with both nitrogenous compounds and phosphate concentrations obtained within the range of &lt; 30 mg/L and ≤ 5 mg/L as per the WHO guidelines for wastewater reuse for irrigation. The results showed a successful process optimization that can be applied to ensure optimized performance of the MBR unit thus improve its effectiveness for the treatment of fish processing wastewater. The study therefore recommends process optimization as a tool for effective removal of nutrients in the MBR system thus making it a potential recycling approach for treatment of fish processing wastewater for reuse for irrigation purposes.

Efficient removal of ammonia–nitrogen in wastewater by zeolite molecular sieves prepared from coal fly ash

Zeolite molecular sieves are potential adsorbents for wastewater treatment, characterized by high efficiency, simple process, easy regeneration, and low treatment cost. In this study, zeolite A molecular sieves were prepared using coal fly ash (CFA), which is an effective method for the utilization of CFA. The results showed that the CFA-based zeolite molecular sieves synthesized under optimized conditions exhibited excellent adsorption and removal rates (> 40%) for ammonia–nitrogen in wastewater of different concentrations and properties. The analysis of adsorption kinetics revealed that the adsorption process followed pseudo-second-order kinetics model, indicating that the adsorption of ammonia–nitrogen on zeolite is primarily controlled by chemisorption rather than physisorption. The adsorption process can be divided into two stages, with a higher adsorption rate and a smaller diffusion boundary layer thickness in the first stage, and a lower adsorption rate and an increased diffusion boundary layer thickness in the second stage. This indicates that as the adsorption proceeds, the internal diffusion resistance within the particles gradually increases, leading to a decrease in the adsorption rate until reaching equilibrium, where both the diffusion and adsorption become stable. The adsorption isotherms of ammonia–nitrogen on zeolite A conformed to the assumptions of the Langmuir model, suggesting that the adsorption mechanism primarily involves uniform monolayer adsorption on the surface without intermolecular interactions.