Environmental Science: Water Research & Technology最新文献

Phosphorus recovery from waste streams stands out as a strategic practice to ensure phosphorus availability to future generations. The release of phosphate mediated by biological sulfate reduction is an interesting bioprocess for phosphorus recovery from sewage sludge in wastewater treatment plants in which chemical phosphorus recovery is foreseen. This study investigates the effect of biological sulfate reduction at different feed sulfate concentrations (up to 8000 mg L⁻¹) on the anaerobic phosphate release from both sewage sludge and digestate as well as the impact of sulfate addition on energy recovery from the sludge via biomethane production. During anaerobic digestion, up to 62.3% of the phosphate initially present in the sludge as iron(III) phosphate was released with 8000 mg L⁻¹ feed sulfate. However, biomethane production was significantly reduced (>40%) when sulfate was added at concentrations above 100 mg L⁻¹. The use of thermal hydrolysis on the sludge digestate was found to be an effective strategy for phosphorus recovery from the sludge without compromising the biomethane production during anaerobic digestion. A phosphate release from iron(III) phosphate of up to 48.7% was obtained when adding 4000 mg L⁻¹ sulfate to the digestate previously hydrolyzed for 2 hours. Finally, the implementation potential of the proposed strategy in full-scale wastewater treatment plants is discussed.

Abuja, the capital city of Nigeria, primarily sources its drinking water from the Lower Usuma Dam Water Treatment Plant (LUD-WTP). This study aims to investigate the preservation of the physicochemical and biological properties of the treated water as it traverses the distribution network to reach the end consumers. Laboratory analyses indicate that the physicochemical parameters of the water samples comply with the guidelines set by the World Health Organization (WHO) and the Nigerian Standard for Drinking Water Quality (NSDWQ). However, bacteriological examination of samples from areas serviced by the LUD-WTP revealed the presence of E. coli, Enterobacter aerogenes, and Klebsiella bacteria, alongside a lack of residual chlorine. The study subsequently focuses on identifying vulnerabilities in the water distribution system and proposing preventive measures. The findings of this research have significant implications for managing drinking water quality in urban distribution networks, particularly in developing countries.

Slaughterhouse wastewater treatment is mainly performed using anaerobic stabilization pond systems. Despite some mathematical models for facultative ponds provided in the literature, no guidelines or mathematical equations exist to specifically size anaerobic ponds for this particular type of wastewater. In most cases, empirical knowledge or domestic wastewater treatment criteria are adapted for this purpose. This study proposes a mathematical model based on Bartha and Pramer's classical respirometry adapted to anaerobic conditions. Raw slaughterhouse wastewater was analyzed for biochemical oxygen demand (BOD) removal under steady-state conditions at varying temperatures and contact times. Results showed compatibility between the experimental conditions and data from anaerobic pond systems in operation, enabling the development of a mathematical model capable of correlating hydraulic retention time for BOD removal as a function of temperature. The model was validated using literature and field data, with a standard deviation of up to 7%, and can be used to design anaerobic stabilization pond systems over a wide temperature range (from 10 °C to 35 °C).

Faecal sludge (FS) generated from onsite sanitation (OSS) systems has become a significant pollutant that negatively impacts the environment. Environmental contamination results from the disposal of untreated FS. In semi-urban areas where numerous toilets are linked to OSS systems, such as septic tanks and single pits, faecal sludge management (FSM) becomes crucial to ensure a safe sanitation service chain. Integral to the faecal sludge management framework, treating FS is imperative, ensuring safe disposal and resource recovery. FS characterization plays a significant role in designing FS treatment plants. This case study characterized FS samples of OSS collected from Pilani, Rajasthan, India. The pH, temperature, electrical conductivity, total solids, chemical oxygen demand, faecal coliforms, total nitrogen, total phosphorus, and capillary suction time varied from 4.64 to 7.93, 20.6 to 27.5 °C, 1.857 to 6.315 mS cm⁻¹, 3430 to 95 393.33 mg l⁻¹, 4406 to 160 000 mg l⁻¹, 10³ to 10⁹ CFU ml⁻¹, 81.7 to 709.2 mg l⁻¹, 285 to 4471 mg l⁻¹, and 149 to 1256.8 seconds, respectively. The significant factors influencing the key FS characteristic parameter COD are found to be the FS age (p < 0.001) and type of OSS (p = 0.044), and for total solids, the factors affecting are identified as the FS age (p < 0.001), type of OSS (p = 0.002) and greywater dilution (p = 0.011). This case study can assist FSM stakeholders in designing FS treatment plants in Indian semi-urban towns and other developing nations with infrastructure, geographical and demographic factors, sanitation types, and FSM models similar to those in Pilani.

In this study, a novel bidentate Schiff base ligand, namely (1E,1′E,2E,2′E)-N,N′-(butane-1,4-diyl)bis(3-(2-methoxyphenyl)prop-2-en-1-imine) (L¹), and a tetradentate Schiff base ligand, namely N1,N2-bis(2-(((1E,2E)-3-(4-(dimethylamino)phenyl)allylidene)amino)ethyl)ethane-1,2-diamine (L²), were successfully synthesized through a simple procedure. The synthesized Schiff base ligands were characterized by scanning electron microscopy (SEM) analysis, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), nuclear magnetic resonance (NMR) and ultraviolet-visible (UV-vis) spectroscopy. Moreover, the thermal behavior was studied through thermogravimetric (TG)/differential thermogravimetric (DTG)/differential thermal (DT) analyses under a nitrogen atmosphere. Subsequently, the features and performances of the synthesized ligands (L¹ and L²) as electrochemical sensors for the detection of heavy metal ions (HMIs) have been investigated. A different behavior was noticed using these two ligands, with L¹ being the best candidate for developing a modified screen-printed carbon electrode (L¹/SPCE) electrochemical Pb²⁺ sensor. To improve further the performances, gold nanoparticles (AuNPs) were deposited by an electrochemical process on the L¹/SPCE platform. The developed AuNPs-L¹/SPCE sensor displayed enhanced lead ion sensing with a high sensitivity of 56.78 μA μM⁻¹ cm⁻² and a detection limit of 0.298 μM. This novel sensor demonstrated promising performances for the detection of Pb²⁺ ions in real seawater with no sample treatment.

The removal of boron from aqueous solutions offers an important opportunity to improve the management of sustainable resources. In this regard, microbial desalination cells (MDCs) are a promising bioelectrochemical approach for effective water treatment, but the integrated MDC-Donnan Dialysis (DD) process for boron removal from reverse osmosis (RO) concentrated effluents has not been investigated before. Integration of the DD process with MDC is investigated in this paper for the first time to enhance the efficiency of the process by providing pre-treatment and natural pH manipulation. Therefore, the MDC process was evaluated for boron removal from boron-containing synthetic solution, geothermal water, and RO-concentrated effluent with the help of the DD system. The highest boron removal performance, with an efficiency of 72.1% in the desalination chamber and 74.8% in the DD-feed chamber, was obtained for boron-containing synthetic solution, while the COD removal efficiency was almost 90% in all water resources. However, the maximum power density was 4818 mW m⁻² with a closed circuit voltage of 1317 mV for RO concentrated water treatment due to its high ionic strength. Moreover, the most crucial output of this study is that the pH value of the system did not need to be adjusted continuously to convert the uncharged boric acid into the borate ion in the charged form owing to better manipulation of the pH by the DD system. Overall, the integrated MDC-DD system provided promising results, presenting effective boron-containing water desalination, yeast wastewater treatment, and enhanced energy production.

One of the sources of fresh water, especially in desert and water-scarce areas is atmospheric air. Cooling the moist air and lowering its temperature to the dew point leads to the condensation of present water. This research used a thermoelectric cooler system to obtain water from humid air. Al₂O₃/water nanofluid was used to take the heat from the hot side of the thermoelectric cooler. Using a lab setting, the convective heat transfer coefficient of various nanofluid concentrations was determined. According to the findings, for high Reynolds numbers, the heat transfer coefficient of the nanofluid is between 5000 and 7000 W m⁻² K⁻¹. The effect of some parameters, such as velocity and humidity of the inlet air as well as the nanofluid concentration, on the amount of harvested water was studied experimentally and numerically. The results showed that increasing air humidity led to an increase in the amount of water obtained and the system's performance coefficient. The maximum amount of extracted water at a relative humidity of 20% and air temperature of 35 °C was obtained at 51.3 ml h⁻¹ at the inlet air velocity of 1.4 m s⁻¹ and using a nanofluid of 5 wt%. The velocity of inlet air had a significant effect on the performance coefficient of the system. Increasing the velocity from 1.1 to 1.6 m s⁻¹ increased the COP by about 30%. In general, the research results showed that thermoelectric coolers could be used as portable devices to extract fresh water from the air, even with low humidity.

Sewage sludge (SS) thermochemical treatment is considered as an effective management scheme in the transition to low carbon and sustainable development from conventional SS treatment. According to temperature and atmosphere, SS thermochemical treatment technologies are primarily categorized into thermal hydrolysis (TH), medium-temperature pyrolysis carbonization (MPC), high-temperature pyrolysis carbonization, gasification incineration, and incineration. Herein, the life cycle assessment (LCA), energy efficiency analysis (EEA), and cost–benefit analysis (CBA) methods were used to examine the environmental, energy, and economic performances of the five different SS thermochemical technologies. The LCA results indicate that MPC is environmentally favorable, with incineration being the most impactful in terms of environmental burden, MPC has a global warming potential (GWP) index of 163.63 kg CO₂ eq., significantly lower than the 306.37 kg CO₂ eq. impact generated by incineration. The EEA results show that the energy recovery rate increases with the temperature of thermochemical treatment. Economically, MPC has the best economic benefits, the CBA and environmental-CBA results are 97.39 and 87.17 RMB per tonne, respectively. Ultimately, scenario analyses illustrate that technological improvements by adding inorganic–organic separation pretreatment before MPC are beneficial to the reduction of environmental indicator values, especially by up to 42.48–44.21% in terms of ecological and human health hazards, with an additional economic benefit of 10.22%.

In this research, a two-stage reaction system was developed, incorporating a moving bed biofilm reactor (MBBR) and a photocatalytic reactor. This was based on the preparation of suspended graphitic carbon carriers, with the aim of investigating the system's efficacy in removing low-concentration tetracycline wastewater. Initially, the preparation conditions for the novel floating composite photocatalyst were optimized. Then the photocatalytic reaction system was constructed using this photocatalyst to remove convective dynamic tetracycline wastewater. The maximum degradation rate of tetracycline wastewater, with an influent concentration of 50 mg L⁻¹, achieved in the photocatalytic reaction system was 99.32%. Subsequently, the working conditions of the bio-MBBR reaction system were optimized, including chemical oxygen demand (COD) and filler feeding rate. The optimal reaction conditions were then selected and combined with the photocatalytic reaction system to investigate the treatment effect on tetracycline wastewater of varying concentrations. The results indicated that even when the concentration of tetracycline (TC) in the influent water remained at 3 mg L⁻¹ for 11 days, the average removal rates of TC, COD, total phosphorus (TP), total nitrogen (TN), and ammonia nitrogen (NH₄⁺-N) were still 92.25%, 87.43%, 87.49%, 66.81%, and 95.72%, respectively. This suggests that the MBBR coupled photocatalytic reactor has a significant removal effect on wastewater containing low concentrations of antibiotics.

This study focuses on the removal of uranium ions from nuclear wastewater by fabricating inorganic–organic hybrid cyclic and linear polyphosphazene based polymers. Synthesized HCP-A and HCP-B had BET surface areas of 497.06 m² g⁻¹ and 410.75 m² g⁻¹, respectively, while the pore size distribution (PSD) was in the range of 1–20 nm. The maximum removal efficiency of uranium by HCP-A and HCP-B for a lab prepared sample was found to be 97.6% and 95.2%, respectively, at pH 6, a contact period of 80 minutes, an adsorbent weight of 0.6 g, and a temperature of 25 °C, while for a nuclear wastewater sample, it was 83.9% and 79.8%, respectively. Lone pair–cation interactions, metal ligand complexation, hydrogen bonding, cation–pi interactions and electrostatic interactions were responsible for adsorption. The point of zero charge (PZC) for both HCPs was at pH 4.6. The optimal uranium uptake capacities of HCP-A and HCP-B were found to be 714.28 mg g⁻¹ and 555.56 mg g⁻¹, respectively. The Freundlich model was the best match for uranium adsorption by both HCPs, with R² values of 0.9775 and 0.9931, respectively. Adsorption kinetics study exhibited that it fitted a pseudo 2nd order kinetic model with R² values of 0.9446 for HCP-A and 0.9882 for HCP-B. The uranium uptake process was found to be spontaneous and exothermic in nature. For HCP-A and HCP-B, a Gibbs free energy (ΔG) of −1.516 kJ mol⁻¹ and −0.27 kJ mol⁻¹, enthalpy change (ΔH) of −41.59 kJ mol⁻¹ and −40.65 kJ mol⁻¹, and entropy change (ΔS) of −0.134 kJ mol⁻¹ K⁻¹ and −0.136 kJ mol⁻¹ K⁻¹, respectively, were observed. The reusability of HCPs with a minor decrease (2% and 1%) in their adsorption capability suggests that they can be used in industrial level applications.