Air, water, and soil pollution are worldwide problems. Of these, heavy metals and organic dyes are the main targets for removal. Graphene oxide (GO), especially functionalized GO, has shown great application potential for the removal of contaminants from wastewater. This study used Santa Barbara Amorphous-15 (SBA-15) with amino acid to functionalize GO, not only to increase the adsorption sites, but also chelate with heavy metals to improve the adsorption efficiency. The optimal experimental conditions for Cu2+ adsorption were obtained by response surface methodology (RSM): pH=5.8, C0=38.38 mg/L, M=0.56 g/L, and T=35.68°C. The optimum experimental conditions for MB adsorption were pH=10.24, C0=82.70 mg/L, M=0.33 g/L, and T=35.27°C, and absorption rates all above 70%. Also, the adsorption mechanism, desorption, and reusability of the complexes are reviewed. Finally, the application potential of GO/SBA-15 as an adsorbent in the field of industrial wastewater treatment is summarized and its prospects are discussed.

Polycyclic aromatic hydrocarbons (PAHs) have been detected in municipal and industrial wastewater, and are widely known as a toxic and carcinogen contaminant to human health. Currently, PAHs are treated by suspended growth bacteria in the municipal and industrial wastewater, but this method is not effective due to the washed-out effect of the bacteria from the aeration treatment. Therefore, this study investigates the attached bacteria on biofilm surface to enhance the biodegradation of PAHs. Phenanthrene (phe) and Rhodococcus zopfii (R. zopfii) were selected as the target contaminant and bacteria due to their presence and an abundancy in the wastewater. Surface characterization study of the natural biofilm was conducted using Fourier transform infrared spectroscopy (FTIR) and environmental scanning electron microscope (ESEM). Chemical functional groups present on the surface of the natural biofilm were hydroxyl (O-H), carbonyls (C═O), and alcohol (C─ O). These chemical functional groups provide sources of carbon for R. zopfii. Pore sizes of the natural biofilm were in the range of 1.97 to 20.60 μm, and they provide shelter for R. zopfii to grow and enhanced biodegradation rate of phe. The biodegradation kinetics of phe by R. zopfii with the natural biofilm (kwith biofilm: 0.26 mg/L/day) was increased 1.52 times compared with without the natural biofilm (kwithout biofilm: 0.17 mg/L/day) within 7 days. The biodegradation of the phe by the R. zopfii with the natural biofilm was significantly affected by difference of pH conditions (pH 7–9). The greatest biodegradation kinetic rate of phe was observed at pH 7 (kwithbiofilm: 0.441 mg/L/day) compared with other pH conditions. Phe was significantly transformed to catechol, coumarin, and phthalic acid via dihydroxylation reaction. This study provides new knowledge on the role of the natural biofilm as a shelter for R. zopfii to grow and enhance biodegradation kinetic of phe by R. zopfii in the wastewater treatment system.

There has been a recent increase of interest in sewer network water quality, both for pollutants and wastewater epidemiology. Of particular interest is the ability to perform cost-effective small-scale monitoring to understand the sewer network and perform source localization (the process of identifying the sources of materials of interest within the network), enabling prioritization of combined sewer overflow (CSO) interventions and targeted response to the detection of infectious diseases. Rhodamine WT fluorescent dye tracing was carried out in the combined sewer networks of four UK cities, for which network geometries were available. Over 100 dye concentration profiles were recorded, from which discharge, travel time (velocity), and dispersion were quantified. A simplified hydraulic and water quality (conservative solute transport) modeling approach was used to investigate dispersion further. A theoretical method for calculating dispersion over a reach with nonuniform properties was derived and used with the models and recorded data to develop a method for estimating the dispersion coefficient in sewers. Novel simultaneous injections into multiple manholes within one sewer network were conducted. Modeling of these injections validated the modeling approach and explained the measured concentration profiles, demonstrating both the potential of hydraulic and solute transport modeling and the new dispersion coefficient predictor for source localization. Such modeling can be used to develop sewer network “fingerprints” and source location probability plots based on residence time distribution (RTD) theory to maximize information from limited water quality monitoring. This will aid managers and operators in identifying potential intermittent sources of material within the network.

A floating breakwater can significantly reduce the wave invasion of marine structures and provide a safe construction environment and service environment for wave attenuation protection for marine structures. With the development and utilization of marine resources, the application of floating breakwaters in engineering is becoming more and more important; research on integrated systems of a floating breakwater and wave-energy converter (WEC) is also valuable. However, existing research has not yet systematically improved the influencing factors of wave attenuation performance of floating breakwaters and the summary of the wave attenuation mechanism; there are few summaries about the integration of floating breakwaters and wave-energy converters. Therefore, the research progress on the wave attenuation performance and wave-energy integration of floating breakwaters is reviewed and summarized. Firstly, according to the structural shape, floating breakwaters are divided into three types: box type, floating cylinder type, and other types. Secondly, the wave attenuation performance of three types of breakwaters and the research progress of floating breakwater-WEC integrated devices are discussed and reviewed. Finally, the problems to be solved in the study of various breakwaters and the key directions for future research are summarized. This review is helpful to deepen the cognition and understanding of wave attenuation performance of floating breakwater and floating breakwater-WEC integration devices, which can provide reference for the optimization research and engineering application of floating breakwaters.

Chlorine is commonly used in disinfection processes in wastewater treatment plants. The chlorine solution is typically dosed by turbulent mixing through multiport jet diffusers. The chlorine reacts with the inorganic and organic nitrogenous compounds at a fast rate (in the order of 1 s or less), and a significant portion of the dosed chlorine can be rapidly consumed by the reactions instead of destroying the pathogens. Despite extensive previous research, the chlorine consumption in the complex sewage flow remains an elusive problem. Field-scale experiments have been carried out to study the chlorine consumption in the turbulent mixing of dense chlorine jets with the primary treated sewage effluent of the Stonecutter’s Island Sewage Treatment Works (serving a population of 5.7 million). Based on jet theory and the field tests, it is proposed to discharge the chlorine jets at a location of highest velocity to minimize the contact time of the sewage with high concentration chlorine. Full-scale in-plant experiments demonstrated that significant savings in chlorine can be achieved with optimal jet diffuser design and placement; at nominal applied chlorine dosages of 12 and 20 mg/L in winter and summer, respectively, the chlorine demand can be reduced by up to 30% compared with the conventional dosing design. The relatively simple dosing reconfiguration results in significant savings in chlorine and energy, reduces harmful impact to the environment, and improves plant operation reliability. The chlorine demands from daily operations are well-correlated with the results of the field-scale models. Predictions of the chlorine demand as a function of applied dosage and temperature were obtained from the collective field data.

Ca–Al-layered double hydroxide (Ca/Al-LDH) is an excellent sorbent for wastewater decontamination and is widely used in the treatment of this phosphate and fluoride-containing wastewater. In this study, we propose a strategy using the wastes generated from treating high-concentration phosphate wastewater process to treat fluoride wastewater to maximize the value of LDH. The effects of environmental parameters such as reaction time, initial fluoride and phosphate concentrations, adsorbent concentration, and pH were investigated. The experimental results showed that when the initial F- concentration was 10 mg L−1, the removal rates of F- were over 90%. To further understand the adsorption mechanism of F- on solid waste, we employed characterization methods such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR), which were also able to characterize the adsorption products before and after the reaction. It was found that hydroxyapatite was formed after the removal of phosphate, while fluorapatite was formed at the F-substituted hydroxyl position after the removal of fluorine. The adsorption process of fluorine removal is a spontaneous endothermic adsorption process. This study shows that Ca/Al-LDH can be a promising material with a high development value, and the new strategy of sequentially removing phosphorus and fluorine using this material can maximize the value of this adsorbent.

Enhanced biological phosphorus removal (EBPR) is a growing, succeeding, and recognized process for removing phosphorus biologically from wastewater. Four sequencing batch reactor (SBR) plants with capacities of 120, 87.5, 50, and 3 million L per day (MLD) from different Indian locations were analyzed for EBPR. The 120 MLD Varanasi, 87.5 MLD Mumbai, and 50 MLD Gurgaon plants were working effectively for EBPR; >75% total phosphorus (TP) removal was observed at milligrams of readily biodegradable chemical oxygen demand (rbCOD) per milligram TPremoved of 12.0, 14.4, and 18.6, respectively; however, the 3 MLD Roorkee SBR was working mainly as adequate nitrogen removing technology at milligrams rbCOD/mg TPremoved<8. The linear increasing trend was observed between rbCOD/COD (%) and EBPR (%) at R2=0.99 (p<0.05 and r=0.99) in plants. Optical microscopic examinations were performed to identify the intracellular polymers [poly-β-hydroxybutyrate (PHB) and polyphosphates] in the EBPR sludge. This study focuses on optimizing the SBR designs (selector and non-selector based) for EBPR and identifying the relationships between wastewater characteristics and phosphorus removal governed by typical microbial functions with the perspective of optimizing decentralized treatment systems of India.

Pressure sewer networks offer a flexible alternative to more traditional gravity-based systems for the conveyance of wastewater. Some of the issues associated with pressure sewer networks (e.g., odor, septicity) arise from inappropriate design assumptions. Daily inflow volumes are a crucial part of the design of pressure sewer systems; gravity design parameters are presently used to design pressure sewer networks in New Zealand. This study analyzed flow data from six representative pressure sewer networks (approximately 24% of operating pump units in New Zealand) to identify the daily inflow volumes per connected pump unit. The results indicated that the median inflow volume was approximately 410 L/pump unit/day. This inflow is much lower than current council design standard assumptions, which range from 650 to 1,000 L/pump unit/day. Pressure sewer network designs using higher daily loading rates may result in oversized networks that are detrimental to the network’s operation and performance, especially for meeting minimum self-cleansing velocities and wastewater retention times. The data collection period included the first COVID-19 lockdown in New Zealand. Four lockdown levels were introduced, with Level 4 and Level 3 being the most restrictive and requiring all but essential workers to stay and work from home. Levels 1 and 2 allowed people to return to their place of work. The data indicated that the Level 4 lockdown period caused a 25% increase in daily inflow volumes. In comparison, the Level 3 and 2 lockdown periods increased the daily inflow volumes by 20% and 15%, respectively. The analysis also included the networks’ wet-weather responses. Minor rain events did not significantly affect the daily inflow volumes. However, gravity networks that have been retrofitted with pressure sewer networks may be more subject to aging or damaged laterals and illegal stormwater connections, both of which are likely to result in a more significant wet-weather response. The paper also discusses the issues associated with an overreliance on standardized design methods without understanding their proper application and the pitfalls of adopting gravity sewer design assumptions for pressure sewer network designs. The findings of this paper will further allow determination of the sensitivity of network design outcomes, performance, and maintenance requirements to the design methods and assumptions for pressure sewer networks, not only in New Zealand but in any country that uses the technology.

Stack emissions have increased the carbon footprint by devastating impacts on human lives and vegetation as well as reducing the ozone layer to amplify the possibility of global warming. So the extent of emitted gases in the atmosphere or on the ground and possible conversion pathways of gases are of interest to understand the advection, diffusion and dispersion patterns, acid rain precursor formation, ozone layer depletor generation, and scopes of air pollution regulation development. A number of factors such as atmospheric stability conditions, wind velocity, stack height, downwind distance from the stack, vertical distance from ground level, and ambient temperature of the surrounding environment of the plume were studied to depict the advection, diffusion, and dispersion pattern of gases and particles in the atmosphere. The plume could travel downwind distances of 10.5 and 1,720 km in stability conditions A and D, respectively, for high mass emission (HME), although wind velocity and stack height had significant impacts on dispersion and deposition pattern. Ambient temperature, turbulence, and density gradient could similarly play important roles in mixing and the ultimate fate and transport of plume elements. The magnitude of vertical dispersion of the plume might influence the formation of acid rain precursors and depletion of the ozone layer in the troposphere and stratosphere. Ozone layer stability depends not only on atmospheric chlorine and nitrogen elements but also on increasing temperature due to the presence of heat-trapping elements where about 0.0011%/day and 0.00035%/day of the ozone layer may change at −25°C and −50°C in the atmosphere, respectively. Currently available scientific literature has not discussed the influence of all these factors on the advection and dispersion of pollutants and ozone depletion by heat-trapping elements.

In wastewater treatment design, it is common practice to test aeration equipment in clean water first, and then extrapolate the result to wastewater via a correction factor. In addition to the many variables, such as the organic loading and physicochemical properties of the water, that affect its magnitude, there is evidence that biochemical reactions play an important role in oxygen transfer in wastewater. The proposed model for in-process oxygen transfer is based on the novel concept of a resistance to gas transfer due to the microbial activity in the field. The hypothesis proposed in this study is that the alpha factor α, or the relative mass transfer coefficient, which is the ratio of the mass transfer coefficient in wastewater KLaf to the mass transfer coefficient in water KLa, is independent of microbial activities in an aeration basin, and the corresponding performance ratio in terms of efficiencies is the same function as α=OTEf/OTE, where subscript f denotes field water characteristics. The common approach is to report the OTEf from off-gas measurements in the field and translate this value to KLaf, giving α as the ratio OTEpw/OTE that gives only a false or apparent alpha, where the subscript pw denotes process water undergoing biological stabilization due to microbial metabolism. The field-determined OTEpw is affected by the respiration rate R, which is dictated by the microbial activity, which is mathematically associative to the transfer process by addition and not associative by multiplication with a scalar quantity. A gas-phase mass balance for oxygen around a completely mixed aeration tank confirmed the association nature of the alpha factor. Examination of test data extracted from the literature indicates that the field-determined OTEpw is indeed affected by the respiration rate R. Using the data collected from previous investigators, the alpha factor has a consistent magnitude of about 0.8 for domestic sewage.