Environmental Technology最新文献

The effects of pH and temperature on the biodegradation of phenolics in palm oil mill effluent (POME) by a thermophilic fungus, Thermomyces lanuginosus TSP3-2, which produces polyphenol oxidase (PPO), were investigated. The fungus could degrade various phenolics in a wide pH range, 4.5-8.0. Its capability to remove individual phenolics such as phenol (8%-79%), ferulic acid (16%-28%), 4-hydroxybenzoic acid (30%-90%), protocatechuic acid (7%-100%), and gallic acid (15%-33%) was likely enhanced at neutral and alkaline pH levels. At these pH levels, the PPO activity was 91.7 and 70.8 U/L, respectively, which was twice as high as that at pH 4.5 (37.5 U/L) and pH 5.5 (38.9 U/L). Groups of phenolics were affected differently based on their chemical structure and initial concentration. With fungi, the phenolics underwent partial depolymerisation (biodegradation) and polymerisation at all tested pH levels. However, the polymerisation degree was lower than that without fungi. This transformation reaction was time-dependent in neutral and alkaline POME. In addition, a temperature between 60 and 70°C slightly improved the biodegradation of most of the phenolics by 6%-15%. At all tested temperatures, a much lower proportion of highly polymerised products were produced with fungi than without fungi. During POME treatment, the fungus also produced valuable byproducts, such as xylanase and fungal biomass protein, which are useful in numerous industries. As a result of these characteristics, this thermophilic fungus can be used for the treatment and valorisation of POME.

Permeable bricks represent an effective strategy for mitigating stormwater-runoff pollution. However, traditional permeable bricks have poor nitrogen and phosphorus removal efficiency, and there is a lack of systematic research on improving the performance of permeable bricks. This study aims to prepare an active permeable bricks (APB) with high permeability, strong compressive resistance, and efficient nitrogen and phosphate removal efficiencies by selecting brick-making aggregates and optimizing of preparation parameters. The effect of APB on removing nitrogen and phosphorus under long-term rainfall was examined, and the mechanism of nitrogen and phosphorus removal by APB was elaborated. The results demonstrated that limestone exhibits a high adsorption capacity for phosphate and ammonia nitrogen, making it suitable as a brick-making aggregate. The optimal preparation parameters for APB were identified as a water-cement ratio of 0.26, design porosity of 15%, aggregate size of 3-6 mm, and fly ash content of 20%. The permeability coefficients and compressive strengths of APB achieved 2.06 × 10^-2 cm/s and 24.02 MPa, respectively, while the average removal rates for phosphate and ammonia nitrogen were 74.46% and 21.22%, respectively. The average removal rates of phosphate and ammonia nitrogen from the APB under long-term rainfall were 74.96% and 24.08%, respectively. Phosphate was predominantly immobilized as calcium-bound phosphorus, with stable forms of phosphorus in APB accounting for 98.28%. This indicated a low risk of phosphorus release. Phosphate was primarily removed through adsorption, retention, and chemical precipitation by APB, whereas ammonia nitrogen was predominantly eliminated through adsorption and retention.

This study presents a novel and sustainable approach to enhance drinking water treatment by transforming Drinking Water Treatment Sludge (DWTS), a challenging waste byproduct, into a valuable resource. We investigated the combined coagulation-adsorption process, utilising DWTS as an adsorbent alongside alum coagulant, to address the persistent issue of dissolved natural organic matter (NOM) and turbidity removal. Our findings demonstrate that adding DWTS at a dose of 1.5 g/L effectively achieved simultaneous and significant removal of both NOM and turbidity. This integration remarkably reduced alum consumption by 46.15%, leading to more sustainable chemical usage. Furthermore, the presence of DWTS improved floc properties, evidenced by a substantial decrease in the sludge volume index (SVI) from 166.60 mL/mg to 70.40 mL/mg, and an 8.33% increase in the interface velocity of the formed flocs. This study uniquely highlights the dual benefit of DWTS in both enhancing coagulation efficiency and acting as an effective adsorbent. The combined process also significantly reduced the potential for trihalomethane formation (THMFP) by approximately 77.71%, directly addressing a critical public health concern related to disinfection by-products. This work establishes a robust framework for a circular economy in water treatment, offering a highly efficient and environmentally sound method for mitigating NOM and turbidity while valorising a waste stream.

This study investigated the use of eucalyptus ash (EA) as a partial replacement for sand in mortar properties. The EA underwent particle size reclassification (ERA) to match the particle size distribution of the sand used in the mortar mixtures. Properties of the mortar in both fresh and hardened states were evaluated, as well as the microstructure of the mortars, with substitution levels of 15%, 30%, and 50% of sand by ERA. The experimental programme included the physical and chemical characterisation of eucalyptus ash and its derivatives, including X-ray diffraction (XRD), scanning electron microscopy (SEM), consistency index, density in fresh and hardened states, capillary absorption, immersion absorption, and compressive strength. The results indicated that EA has a crystalline nature with high hygroscopicity. The reclassification process significantly reduced carbonate and pulverulent material content in the ash. Mortars with ERA tended to have more voids and absorb more water than the control. However, the compressive strength of the mortars with ERA showed similar values to the control at 7 and 28 days of curing, reaching values of 48.55 ± 0.77 MPa and 46.44 (± 0.44) MPa for 30% and 50% of ERA substitution at 28 days, respectively. Therefore, ERA provided the production of mortars with higher sustainability, with replacements of 15% and 30% being the most recommended, without significant loss in properties in the fresh and hardened state of the mortar.

The high degree of urbanization and industrialization has led to the generation of nitrogenous matter in rainwater, which poses a significant health risk when rainwater is used for drinking purposes. A solar galvanic system was fabricated using a copper and magnesium (1:1) electrode with the goal to study the removal of nitrates and ammonia from rainwater. Surface response methodology with the flow rate (3.17-8.82 mL·min^-1) and supporting electrolyte concentration (0.004 M-0.010 M sea salt) as the operating variables was used to determine the optimal conditions (0.011 and 4.7 mL·min^-1) of this process. Solar radiation at 167.72 kJ·L^-1 induced the photocatalytic degradation of nitrates, and the degradation of ammoniacal nitrogen was promoted by the generation of oxidizing agents, such as the $H{O}^{.}$ radical. The removal of nitrate and ammoniacal nitrogen, respectively, was fitted to the Behnajady-Modirshahla-Ghanbery (BMG) two-stage model. Computational fluid dynamics (CFD) modelling of the thermal and hydrodynamic processes showed that a temperature of 343.15 K and flow rate of 3.17 mL·min^-1 enabled 81.49% nitrate removal, whereas a flow rate of 6 mL·min^-1 enabled 55% removal of ammoniacal nitrogen. The residual amounts of both species complied with permissible standard limits.

In this study, first, a novel Ni catalyst was developed where 5% nickel was loaded on food waste ash and thereafter, it was used in steam gasification of food waste via two different processes: conventional overlapping process (COP) with simultaneous pyrolysis and gasification, and in-situ two-stage process (ITP) with consecutive pyrolysis and gasification. The temperature for the pyrolysis and gasification stage in ITP was maintained at around 850 °C. Both the processes (COP and ITP) were also conducted at the same temperature of 850°C with a steam flow rate of 0.73 mL/min for 100 g of the food waste sample. The processes were conducted in a downdraft gasifier with variations in catalyst content. The catalyst content in the feed-catalyst mixture was varied from 0 to 50 g, and results indicated that the use of a 50 g catalyst during COP increased the syngas yield quite significantly (∼70%). However, the results showed that the Ni catalyst did not have much effect on syngas yield from ITP, though it increased the hydrogen fraction in syngas (∼80%). The highest hydrogen fraction in syngas from COP and ITP was found to be 71.74% and 66.53% respectively. Consequently, the highest hydrogen yield of 1.3 m³/kg was obtained from COP for 50 g of catalyst in a feed-catalyst mixture. Furthermore, performance parameters such as high heating value (HHV), carbon conversion efficiency (CCE), and cold gas efficiency (CGE) were determined for performance analysis of the Ni-based catalyst in conventional and in-situ steam gasification.

An eco-sorbent polyurethane foam was made using green components, bio-polyol derived from coconut (CO) and organic kapok (KAK) fibre, as fillers in its components. The product was called COKAK foam. The foam was made using an overhead mixing method by mixing polymeric reagents, which include a blend of coconut and fossil-based polyol and organic kapok (Ceiba pentandra) fibre filler in a moulded cup. The results show that the COKAK foam was hydrophobic with a water contact angle of θ = 114°. The composite foam reaches an absorption capacity of 12.01 and 14.11 g·g^-1 for engine and bunker oil, respectively. It had highly selective absorption performance in oil-water mix systems, with water absorptions for engine and bunker oil of 0.80-0.88 and 0.55-0.65 g·g^-1 only, respectively. Highlighting the remarkable reusability of the foam to maintain its oil absorption capabilities even after 100 absorption-squeezing cycles, which is a vital but frequently overlooked feature to minimise wastes produced after use. Also, it has a high affinity for high-viscosity oil, with bunker oil having 8%-15% higher oil absorption than engine oil. The COKAK foam's simple preparation method, along with the use of sustainable alternatives in its components, is a significant step towards environmentally-friendly oil spill clean-up technologies.

Chabazite demonstrates exceptional adsorption and ion exchange capabilities, making it widely applicable in petrochemical industries, sewage treatment, and various other sectors. At present, there are more economic considerations for synthesizing chabazite. This article employs a life cycle assessment methodology to quantitatively evaluate the inputs and outputs associated with chabazite preparation by conducting an inventory analysis of the experimental process. By comparing and analysing evaluation results for chabazite synthesized from industrial waste with those from natural minerals, rice husk ash and blast furnace slag were identified as representatives of industrial solid waste, while kaolin served as a representative natural mineral. The CML-IA baseline method in Simapro software was used to compare the values of seven environmental impact categories and the use of energy contributed the most to the environment. The results show that the synthesis of chabazite from industrial waste has no environmental advantages at present. Kaolin, a kind of raw material with high silicon and aluminium content and less treatment process, is the key to reduce zeolite pollution. The evaluation results provide a basis for the selection of raw materials for the synthesis of chabazite.

Constructed wetlands (CWs) offer an affordable and sustainable solution for decentralized wastewater treatment. This study assessed horizontal subsurface flow CWs (HSSFCWs) supplemented with charcoal and ceramic media for greywater treatment in Basra, Iraq. This novel approach demonstrates significant advancements in the removal efficiency of contaminants from greywater. Four pilot-scale wetlands were run for 182 days. Bacopa monnieri was planted in the wetlands. Regular sampling of influent and effluent analyzed organics, nutrients, and heavy metals. Biochar significantly improved the removal of chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), nitrate (NO₃⁻), orthophosphate (PO₄³⁻), ammonia (NH₃), lead (Pb), zinc (Zn) and cadmium (Cd), while ceramic media enhanced total suspended solids (TSS) and total dissolved solids (TDS) removal. The combined biochar-ceramic wetland showed the highest reduction in calcium (Ca), and magnesium (Mg). Plant growth was unaffected by amendments. The treated greywater met irrigation reuse standards, highlighting the efficacy of these amendments in improving greywater quality. Biochar and ceramic media CWs exhibited superior pollutant removal compared to the control, with biochar achieving removal efficiencies of 75.60% for COD, 22.61% for NO₃-N, 90.37% for PO₄-P Ceramic media recorded the highest removal of TSS (66.99%) and TDS (50.50%). The mixed media wetland achieved the highest removal of BOD₅ (54.96%) and hardness ions. The study concludes that biochar and ceramic media are cost-effective amendments that enhance CWs for greywater treatment, supporting sustainable water reuse in small communities. These findings support the implementation of enhanced CWs for improving greywater quality and meeting irrigation guidelines.

This study investigates the efficiency of hydrogen (H₂) and lactate (HLa) generation in the co-fermentation of sugarcane vinasse and molasses, aiming to optimize operational strategies through central composite design (CCD) and response surface methodology (RSM). The tests were conducted in 1 L Duran® flasks, with a working volume of 500 mL, under thermophilic conditions (55°C) and pH 7.0. Nine conditions were evaluated by varying co-substrate concentrations (3.9 - 11.1 g COD.L^-1) and vinasse proportions (7.6 - 92.4%), identifying the most favourable conditions for H₂ and HLa production. High H₂ potential (up to 1275 mL.L^-1) was observed with 7.5 g COD.L^-1 of co-substrates and 7.6% vinasse, mainly attributed to Clostridium. Adding molasses maximized H₂ generation, while higher vinasse proportions favoured lactobacilli, increasing HLa concentration and reducing H₂. Replicability was ensured, validating tests with high H₂ generation and 75% similar results. The tests showed discrepancies in bacterial genus prevalence: the condition with 11.1 g COD.L^-1 of co-substrates and 50% vinasse favoured HLa producers (Sporolactobacillus, Lactobacillus, Bacillus), while the condition with only 7.5 g COD.L^-1 of co-substrates and 7.6% vinasse favoured H₂ producers (Clostridium, Thermoanaerobacterium, Pseudomonas). These findings guide future feeding strategies to optimize bioproduct yield, favouring the generation of target bioproducts and ensuring a holistic view of vinasse and molasses utilization for fermentative H₂ biogas production.