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This review assesses the leachate quality from waste disposal sites in tropical climate zone. Through this review, data from 228 leachate samples from 145 waste disposal sites from 18 countries in the tropical region were analyzed. The 12 types of sites were considered for the analysis based on the climatic conditions, age, and the operating condition of the site. Tropical rainforest, tropical monsoon, and tropical savanna climates were identified for the climatic zone classification. Age of site was classified as young and old. The operating conditions were classified as engineered landfill and open dump site. Eighteen leachate quality parameters were included in the analysis. Leachate pollution index indicated that young sites from tropical rainforest zone and tropical monsoon zone have higher pollution potential, while the pollution potential in tropical savanna zone did not demonstrate considerable difference in pollution potential in terms of age of the landfill. Considering the operating method of the sites, open dumpsites pose higher pollution potential. Positive correlation could be seen among biological oxygen demand, chemical oxygen demand, total dissolved solids, and total Kjeldahl nitrogen. pH negatively correlated with organic pollutants as well as heavy metals. Analysis of emerging contaminants present in landfill leachate is limited in tropical region; thus, it is recommended to conduct studies on emerging contaminants. Further, the leachate treatment options considered in tropical region are discussed in this review.

Sustainable agricultural practises ensure production of quality products having negligible environmental impacts replacing conventional techniques. Supercritical carbon dioxide (SC−CO2) extraction, a replacement to flammable, toxic, non-ecological solvent extraction was carried out in this study to extract γ-oryzanol, a potent bioactive ingredient, from defatted rice bran. The response surface methodology was applied to optimize the handling parameters such as temperature, pressure and CO2 flow rate . Extraction of γ-oryzanol is investigated at low pressures (such as 15, 20 and 25 MPa) compared to previous studies. The highest (optimum) yield of γ-oryzanol was 36,000 mg.kg−1 at 10 w/w% of ethanol as co-solvent and the corresponding temperature, pressure and CO2 flow rate were 48.9 °C, 23.9 MPa and 29.8 g.min−1, respectively. The techno-economic assessment using Aspen plus software evaluated the return of investment of the plant processing 3000 tonnes of rice bran per year accounts for a net present value almost double the investment cost having a payback period of around 5 years.

In order to address freshwater scarcity, seawater desalination technologies have been widely studied in recent years. However, the disposal of desalination brine which contains an even higher concentration of salts than seawater can potentially damage the surrounding environment. Therefore, alternative approaches aiming to recover valuable resources from desalination brine have been conducted. Three resources that can be recovered have been studied in this paper, which are minerals, freshwater and energy. The techniques to recover minerals can be divided into pressure-driven techniques, thermal-driven techniques, electro-driven techniques and other techniques. The water recovery techniques employ mainly membrane/thermal integrated hybrid processes, while the energy recovery techniques such as pressure retarded osmosis (PRO) and reverse electrodialysis (RED) utilize the salinity gradient energy (SGE) to generate energy. The valuable mineral products have also been reviewed in this paper in terms of recovery methods, performance of processes and product quality. The reviewed products are sodium salts (NaCl, NaOH, Na2SO4), lithium salts (LiCl, Li2CO3), magnesium salts (struvite, Mg(OH)2, MgSO4, MgO), calcium salts (CaSO4, CaCO3) and other minerals (U, Rb, Cs). Based on the cost and revenues of each technique, an economic comparison has been conducted along with the cost analysis of operating desalination plants.

One of the most broadly used models for membrane fouling is the Hermia model, which separates this phenomenon into four blocking mechanisms, each with an associated parameter n. These mechanisms are complete blocking (n=2), intermediate blocking (n=1), standard blocking (n=3/2), and cake formation (n=3/2). The original model, which was obtained through experimental data, is given by an Ordinary Differential Equation (ODE) dependent on n. At the time, this ODE was only solved for these four values of n, which limits the effectiveness of the model when adjusted to experimental data. This paper aims to not only mathematically prove the original Hermia model but also to broaden the scope of this model for any real number n by using the original ODE, the equations of fluid mechanics, and the properties of single and multivariable calculus. The extended Hermia model (EHM) is given by a power law for any n≠2 and is given by an exponential function at n=2. To better test the model, we have performed the model fitting of the EHM and compared its performance to the original four pore-blocking mechanisms in 6 micro- and ultrafiltration examples. In all examples, the EHM performed consistently better than the four original pore-blocking mechanisms. Changes in the blocking mechanisms concerning transmembrane pressure (TMP), crossflow rate (CFR), crossflow velocity (CFV), membrane composition, and pretreatments are also discussed.

The textile industry produces a high volume of wastewater rich in toxic and harmful chemicals. Therefore, it is necessary to apply wastewater treatment methods such as membrane bioreactor (MBR) to achieve high efficiency, process stability, small footprint, and low maintenance costs. This work performed a study on a synthetic textile wastewater treatment using an enhanced membrane bioreactor (eMBR) equipped with two anoxic and one aerobic reactor and a UV disinfection unit. The results showed 100% removal of total suspended solids, 81.8% removal of chemical oxygen demand, and 96% removal of color. The SEM analysis indicated that the pores of the membrane were blocked by a compact and dense gel layer, as observed by the presence of the fouling layer. According to these results, an eMBR hybrid system is a suitable option for treating synthetic textile wastewater. Opportunities to increase the efficiencies in the removal of some pollutants, as well as stabilizing and standardizing the process are the improvements which require further investigations.

Wastewater treatment plants (WWTPs) are key components for the capture of microplastics (MPs) before they are released into natural waterways. Removal efficiencies as high as 99% may be achieved but sub-micron MPs as well as nanoplastics have been overlooked because of analytical limitations. Furthermore, short MP fibres are of concern because of their low capture rate as well as the lack of understanding of their influence on purification system efficiency. This study has investigated the impact of poly(ethylene terephthalate) (PET) short nanofibres on the performance of polyvinylidene fluoride (PVDF) ultrafiltration membranes during cross-flow operation. Model MP fibres with an average length of 10 ± 7 μm and a diameter of 142 ± 40 nm were prepared via a combination of electrospinning and fine cutting using a cryomicrotome. The manufactured MPs were added to both pure and synthetic domestic wastewater at a concentration of 1 mg.L

The goal of the present study is to treat industrial wastewater containing sodium aluminate using a chemically inert polyurea (PU) based thin film composite (TFC) reverse osmosis (RO) membrane to promote water reclamation and zero liquid discharge (ZLD). Pretreatment was carried out to reduce the pH of the effluent from 12.5 to 7.1. The TFC RO membrane was fabricated by coating PU on Polyethersulfone (PES) substrate by interfacial polymerization (IP). The surface and cross-sectional morphologies of the membrane were characterized using scanning electron microscopy (SEM). The indigenously synthesized membrane was effective in the removal of total dissolved solids (TDS), chemical oxygen demand (COD), colour and electrical conductivity. The experiments were conducted by varying the feed composition of the wastewater. The maximum water recovery and flux were found to be 74% and 73.9 L/m2·h. RO process using PU membrane exhibited significant potential for cost effective, safe and pollution-free treatment of sodium aluminate industrial effluent.

Over the past few years, supercritical water oxidation (ScWO) has shown great potential for application to landfill leachate treatment, providing substantial organic matter degradation in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC). However, the conversion of ammonia, which is present at high concentrations in leachates, is the rate-limiting step during ScWO and usually requires large amounts of oxidants, the addition of catalysts, or severe operating conditions. Aiming at proposing a treatment system that effectively removes both organic matter and ammonia from leachate, this paper evaluates the intensification of the ScWO process through ion exchange with zeolite. Thus, ScWO was operated under a pressure of 23 MPa at 600 and 700 °C, without the addition of oxidants. The zeolite (clinoptilolite) was used without any modification inside a glass column. The ScWO (600 °C)/zeolite system removed 90% ammoniacal nitrogen (NH3-N), 100% nitrite (NO2-N), 98% nitrate (NO3-N), color, and turbidity, 81% TOC, and 74% COD, suggesting that this system is a promising alternative for leachate treatment. However, the final NH3-N and COD values were slightly above the limits (20 and 200 mg L−1, respectively) stipulated by the Brazilian environmental legislation. These results suggest that further improvements are still required for the application of the intensified ScWO to be feasible. Notably, ammonium-saturated clinoptilolite is amenable for regeneration or can be applied to soil as a slow-release fertilizer.

Various studies provide information about the high potential of using hollow fiber membrane contactors (HFMCs) for the recovery of dissolved methane from anaerobically treated wastewater effluent and the effects of different operating conditions on their performance. However, majority of those studies evaluated HFMCs at bench scale under favorable conditions, i.e. clean water as feed under short-term operations. This study evaluated the performance of porous HFMC and dense HFMC (in terms of dissolved methane removal efficiency and methane desorption flux) subjected to anaerobic feed during long-term operation of one month. The study will provide better understanding of the performance of HFMCs with conditions expected at large-scale wastewater treatment systems. From the results, the decrease in the performance of HFMCs and the increase in the mass transfer resistance per week under varying feed flux were determined. These relationships were utilized in a numerical model to incorporate the effect of long-term operation to evaluate the performance of upscaled HFMCs. The fit of the model with the experimental data with one month of operation was evaluated and the relative errors were 11.9 % and 15.3 % for porous HFMC and dense HFMC, respectively. Moreover, results showed that dense HFMC will provide better performance than porous HFMC if it were to be operated longer than two weeks before cleaning. The net energy for porous HFMC and dense HFMC were optimized to be 0.07 and 0.02 kWh·d

Solid waste Management: There are two articles in this section. Shi et al. (2021) investigated the unbalanced status and multidimensional influences of municipal solid waste management in Africa. It was identified that economic growth, urbanization and geographical location are the most critical factors influencing the unbalanced statue of MSW management in Africa.

Made available in DSpace on 2022-04-28T19:42:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) This study reports an alternative method for black liquor treatment with potential for energy and process savings in the paper and pulp industry. Gasification of black liquor was carried out under sub- and supercritical conditions, varying the black liquor feed composition (0.10, 2.55 and 5.00 wb%) and temperature (350, 425 and 500 °C). Liquid products were identified by high resolution mass spectrometry (FT-Orbitrap MS) and compounds belonging to classes O3 and O4 were found to be the most representative in the products of reactions performed at 500 °C. The mass spectra results also revealed the overall selectivity of reactions, where decarboxylation and demethoxylation reactions were favored under subcritical and supercritical conditions, respectively. Among the gaseous products, hydrogen and methane were produced with maximum of 69.04 and 28.75 mol%, respectively, at 2.55 wb% and 425 °C. The proposed thermodynamic modelling of the reaction system satisfactorily predicted the gas phase behavior of the system. In the economic analysis, the simulated conditions indicated that the main energy requirements for a scaled-up black liquor gasification process are related to the necessary heat exchangers and pressurizing of the black liquor solution. Furthermore, the cost of the black liquor gasification is around 0.06 US$ per kg of feed stream. Liquid and gaseous products from gasification could be obtained at a cost of 56.64 US$ and 3.35 US$ per tonne of stream, respectively. Therefore, black liquor gasification is an interesting route for obtaining combustible gases and value-added bioproducts. Department of Chemical Engineering State University of Maringá (UEM) Petroleum and Energy from Biomass Research Group (PEB) Chemistry Department Federal University of Sergipe (UFS) Department of Chemical Engineering Federal University of Maranhão (UFMA) School of Chemical Engineering State University of Campinas (UNICAMP) Department of Energy Engineering São Paulo State University (UNESP) Department of Chemical Engineering Technological Federal University of Paraná (UTFPR) School of Engineering & Water: Effective Technologies and Tools (WETT) Research Centre RMIT University Department of Agronomy State University of Maringá (UEM) Department of Energy Engineering São Paulo State University (UNESP) CAPES: 180/2019–00 CNPq: 202519/2020–1 CAPES: 88887.338

Made available in DSpace on 2022-04-28T19:44:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-12-01 The demand for lithium-ion batteries (LIBs) is exponentially rising driven by the increasing variety of their applications, which includes consumer electronics, stationary energy storage, and especially electromobility. To meet this increasing demand, recycling becomes necessary since, in addition to reducing the environmental impact of the LIBs, it mitigates the challenges of scarcity of lithium (Li) and other valuable metals such as cobalt (Co), nickel (Ni), and manganese (Mn). In this paper, we propose and demonstrate a technology for recycling LIB cells that recovers active materials and other elements contained in LIB cells. The reported technology, which we denominated RecycLib, employs hydrometallurgy and can be applied to lithium cobalt oxide LiCoO2 (LCO) with cylindrical and prismatic geometries, as well as lithium nickel manganese cobalt oxide LiNixCoyMnzO2 (NMC) cells. Experimental characterization reveals recovery efficiency rates of the cathodic metallic oxide higher than 90 % for LCO (with 98 % purity in the case of cylindrical LIB cells and 80 % for prismatic cells) and 80 % for NMC LIB cells (with 85 % purity) employing relatively inexpensive reagents with low environmental hazardous potential and sub-processes designed according to Circular Economy precepts. Therefore, it is envisaged that the proposed technology to show a low potential for environmental impact, low operating costs, and high work safety, thus favoring industrial scalability. Center for Advanced and Sustainable Technologies (CAST) São Paulo State University (UNESP) Campus of São João da Boa Vista Programa de Pós-Graduação em Engenharia Química Universidade Estadual de Maringá (UEM) School of Engineering and Water: Effective Technologies and Tools Research Centre RMIT University Melbourne VIC 3000 Center for Advanced and Sustainable Technologies (CAST) São Paulo State University (UNESP) Campus of São João da Boa Vista

High strength synthetic wastewater containing 5 mg L−1 of lead was studied for treatment using an A2O MBR system. The system showed 99% removal of ammonia and COD, a maximum removal of 52% of total phosphorus and an average minimum removal of 72% of total nitrogen. A maximum lead removal of 98% was achieved for hydraulic retention time (HRT) of 144 h, which decreased to 85% when the influent COD concentration was decreased. Mass balance for lead revealed that much of its removal was through accumulation by the biomass present in the anaerobic and anoxic tanks. Comparative study on virgin PSf and GO blended PSf membrane showed that the GO blended membrane lasted 1.4 times longer than the other. SEM-EDS of membranes showed lead peaks on the fouled and un-fouled sections of the membranes indicating the association of lead with the foulant and the role of membrane in lead separation. Good separation efficiency was achieved irrespective of the membranes used.

Maintaining the discharge standards of biologically-treated wastewater is essential in order to protect receiving water bodies from secondary pollution. If unexpected faults happen in an activated sludge process that is used as biological treatment, it would affect the quality of the receiving water body. Thus, in this paper, an improved particle filter (PF) algorithm, based on a variable frequency mutation (VFM) strategy is proposed for the process faults diagnosis. This is inspired by the frequency conversion for energy-saving application in the industrial process; an adaptive frequency conversion operator has been incorporated into the mutation operation of immune algorithm to reduce the system operating costs. Then, the resampling process of PF algorithm was replaced by particle mutation based on the previously calculated information for securing the diversity and the effectiveness of the particle; lastly, a VFM-based PF algorithm for system states estimation and fault diagnosis was established. This algorithm not only effectively increases the adaptability of the particle to changes of the system state, but also conductively solves the problems of the degeneracy in the traditional PF algorithm and the diversity weakening caused by resampling operation. Simulation results show that the algorithm can effectively improve the estimation accuracy of the nonlinear system states. The application results of faults diagnosis in the activated sludge process show that it can accurately diagnose the occurrence of faults. Therefore, the proposed method has great practical significance in wastewater treatment plants to avoid problems caused by unexpected faults.

Continuous increase in the world’s population is posing serious threat to the fresh water reserves all over the world. Seawater desalination processes have been proven to be one of the most promising processes to supplement the increasing demand for fresh water, due to the limitless nature of seawater. One of the biggest problems related to the membrane desalination process is the fouling and scaling of reverse osmosis (RO) membrane. Among all the foulants, silica is considered to be one of the most difficult inorganic foulant to deal with in membrane desalination due to its chemical complexity. This study compares some of the most commonly used pretreatment techniques of silica removal, analyses the characteristics of dissolved silica in both brackish water and seawater bodies, along with silt density index (SDI) tests. It was found that silicate salts are difficult to be dissolved in brackish water and seawater, and the fouling propensity of membrane is not a function of silica concentration (from 15–200 mg/L) in the feed water. Also, Al3+ exhibited superior silica removal efficiency than Fe3+, and a removal efficiency of 90.2% was reported when using electrocoagulation on brackish water where the silica concentration was around 28 mg/L.

Compared to the traditional activated sludge process, the membrane bioreactor (MBR) has several advantages such as the production of high-quality effluent, generation of low excess sludge, smaller footprint requirements, and ease of automatic control of processes. The MBR has a broader prospect of its applications in wastewater treatment and reuse. However, membrane fouling is the biggest obstacle for its wider application. This paper reviews the techniques available to predict fouling in MBR, discusses the problems associated with predicting fouling status using artificial neural networks and mathematical models, summarizes the current state of fouling prediction techniques, and looks into the trends in their development.

Membrane bioreactor technology includes the integration of biological wastewater treatment and physical separation by membrane filtration. When analyzing the system performance, efficiency of biological processes, physical separation and membrane fouling must be taken into consideration. Over the years, mathematical modelling of wastewater treatment has evolved and is being used extensively to optimize the performance of treatment systems. A Number of attempts have been made towards the development of mathematical models for membrane bioreactors and most of these models have not considered the effect of soluble microbial products on membrane fouling. Also the effect of periodic membrane cleaning was neglected. In this study, an integrated mathematical model was developed for the membrane bioreactor. A biological model based on activated sludge processes (extended with biopolymer kinetics) and a physical model with cake layer kinetics and membrane fouling have been combined. In order to overcome the drawbacks of previous attempts of modelling, the influence of soluble microbial products and extracellular polymeric substances are considered in the model integration. Further, the physical processes of the sludge removal and membrane cleaning which have strong influence on membrane fouling are considered in the model. “AQUASIM”, a computer program for the identification and simulation of aquatic systems, was used for solving the processes. Calibrated and validated model enables the prediction of the system performance and membrane fouling under different operating conditions.