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Graft copolymer of natural rubber (NR) and styrene to used as a blend with styrene-butadiene for green tire can be produced via three techniques: emulsion polymerization (EP), electron beam irradiation (EB), and gamma ray irradiation (GR). Products from all techniques had similar cross-linking properties; leading to similar mechanical properties. Therefore, producing the graft copolymer using less resources is the best choice as it is a cleaner production. This paper compared the environmental impact assessment of these three production processes. SimaPro version 7.3 software using Eco-indicator 99 method for environmental impact assessment was used throughout this study. The functional unit (FU) used was 100 g of grafted rubber product, with the considered system boundary starting from raw materials for the production of a specified product and continuing to the end of copolymerization processes (cradle-to-gate). The results indicated that, at the laboratory scale, the EB technique had the largest contribution of environmental impacts, followed by EP and GR techniques. However, operating at the maximum capacity led to an overall reduction of all impacts. The reduction was improved by 86.32% for EB and by 60.5% for GR. However, production by EB still contributed the highest overall environmental impact, while GR contributed the least. In decreasing order of significance, the main impacts of EB were resources (R), human health (HH), and ecosystem quality (EQ). The essential factors which caused these impacts were, in decreasing order of significance, the usages of electricity, NR, and styrene. Therefore, GR method was the choice for scaling up the green production process in both saving the electricity usage and for improvement in the environmental impacts.

In 2015, the milk quota system that is in place in Europe is to be abolished, instigating an increase in milk production. This increase will aid in addressing the world's ever growing demand for food, but will incur increased stresses on the environmental impact and sustainability of the dairy industry. In this paper, an environmental life cycle assessment, which is performed in order to estimate the global warming potential (GWP) associated with 11 dairy products in the Republic of Ireland, is presented. The primary aim of the study is to examine the GWP associated with the processing of raw milk into the various products. However, the GWP contribution from dairy farms producing the raw milk is also included. Therefore, the system boundary utilised in this study is cradle-to-processing factory gate (dairy, farm, raw milk transportation and dairy processing). Furthermore, when performing the analysis, the 11 dairy products are clustered into 6 product groups: fluid milk (whole milk, skimmed and semi-skimmed milk); butter; cheese; cream; milk powders (buttermilk powders, whole milk powders, skimmed milk powders, and chocolate crumb); and whey powders (whey powders and proteins). The total GWP was calculated for each product group and mass allocation was used to derive the GWP of each product within that group. Data from 12 companies (18 dairy processing plants), which account for approximately 92% of the cow's milk processed in the Republic of Ireland, was used in this study to accurately assess the Irish dairy processing industry. From the analysis, it was found that raw milk production accounted for between 80.8% and 97.3% of the total GWP, depending on the amount of raw milk per kg of product. Additionally, raw milk transportation accounted for approximately 0.4% of the GWP, with the remainder contributed by the processing phase. The main contributor to GWP in the processing phase was direct energy use within the plant (electricity, natural gas and other fuel), which accounts for between 91 and 98% of the GWP, depending on the product. Furthermore, even though raw milk production is the most significant contributor to the total GWP of each dairy product, it was observed that energy use and water consumption in the processing phase were of the same magnitude as that of the production phase.

The world today is facing challenging crises like depletion of fossil fuels and environmental pollution. Biofuels can be an alternative solution to fossil fuels. Iran hosts a variety of weather conditions and its soil can grow different types of plants suitable for production of liquid biofuels. In this regard, the present research is an in-depth attempt to explore the potentials of Khuzestan Province as an agriculture hub of Iran to produce liquid biofuels. The studied biodiesel sources included oilseeds, animal fats and fish wastes, and the sources of bioethanol were wheat, sugarcane, sugar beet, rice, barley, maize, alfalfa, potato, grapes, apple, date and other local citrus fruits including orange, grapefruit, sweet lemon, sour lemon and sour orange. Results showed that the province's production potential was 1.04 Gl of bioethanol. A 5% addition of ethanol to gasoline (i.e. E5) can save 63.5 Ml of gasoline throughout the province. The estimated biodiesel production from animal fat- and oil-containing products and fish wastes is about 56 Ml in this province that can supply 2% of its total diesel fuel requirement. The estimated fat-based biodiesel production of Iran is 332.56 million liters. By adding the biodiesel production from oilseeds, Iran can produce 1.27 Gl of biodiesel fuel. This amount can supply 4.2% of the country's total diesel fuel consumption. The results for bioethanol and biodiesel production show promising alternatives. As a result of sound management of agricultural residues, E5 (5% ethanol, 95% gasoline) for SI engines and B2 (2% biodiesel and 98% diesel fuel) for diesel engines can be commercially produced as they impose no modifications to these engines.

Poor sanitation due to improper treatment of human excreta, and energy scarcity are global problems with only partial solutions. Thus, feasible conversion of human excreta into safe, reusable “products” and renewable energy could be advantageous. The research objectives were to study the properties and major chemical processes occurring during hydrothermal carbonization of raw human excreta with typical solids content, as well as exploring potential use of the resulting hydrochar and aqueous phase. Human excreta (often considered as black water) were hydrothermally carbonized in a set of nine 50-mL laboratory batch reactors under a range of severities, a single parameter obtained from a coalification model that represents the combination of temperature and time. Three temperatures (180, 210 and 240 °C) and reaction times (30, 60 and 120 min) were used. The physicochemical characteristics such as yield, elemental composition, organic matter and calorific value of the hydrochar (solid phase) were studied. Aqueous phase was characterized for carbon, nitrogen, macro and micronutrients composition. In addition, the potential use of the hydrochar and aqueous phase were studied. There was high correlation between severity factor and carbon content (R2 = 0.95) and calorific value (R2 = 0.89). Hydrochar yield decreased with increasing severity from 69 to 56%. Calorific values increased from 24.7 to 27.6 MJ/kg, falling within the calorific range of sub-bituminous coal. The aqueous phase demonstrated high nitrogen concentration, reaching up to 8178 mg/L total nitrogen, while N:P:K ratios were similar to those of commercial fertilizers. Pilot scale experiments resembled the results found in laboratory scale experiments for both hydrochar and aqueous phase and fitted the regression curves obtained from the severity factor. It is postulated that hydrothermal carbonization of human excreta could potentially serve as a sustainable sanitation technology with a closed-loop cycle approach while recovering energy and nutrients.

A novel degumming approach by using steam treatment is proposed to minimize water pollution and consumption in silk wet processing. Sericin removal of Bombyx mori silk fibers was carried out with pressurized steam. The degumming ratio, fine structure and physical properties of the degummed silk fibers as well as energy efficiency were investigated to elucidate the degumming effects of steam treatment. Compared to the conventional neutral soap and sodium carbonate (Na2CO3) degumming methods, sericin can be removed by steam treatment without any chemicals, and the degumming ratio as well as physicochemical properties of the degummed silk fibers maintained at a desirable level. Energy efficiency and cost analysis showed that steam degumming is more energy-efficient and economical than the conventional chemical degumming methods. Results showed that steam treatment is a feasible silk degumming method with the benefits of reduction in water pollution and energy consumption.

Given the high ammonia nitrogen (NH3-N) concentration and low biological oxygen demand/chemical oxygen demand (BOD/COD) ratio (

Textile dyeing effluent has been the focus of considerable research because of its adverse effects on aquatic biota. Here, we present the first comprehensive study of a combined permanganate and ozone (KMnO4 O3) technique to treat different kinds of textile dyeing wastewater. We investigated the effects of process parameters on TOC and COD removal and the toxicity of the wastewater after KMnO4 O3 treatment. The synergistic mechanism involved in the KMnO4 O3 process is also discussed. The results indicate that KMnO4 O3 treatment is efficient in treating many kinds of textile dyeing wastewater. The TOC, COD, and toxicity were reduced by approximately 70%, 80%, and 34.4–95.5%, respectively, using a KMnO4 dosage of 1.5 mM, an O3 dosage of 10 mg/L, a pH value of 7, and a reaction time of 30 min. Furthermore, biodegradability was increased to 0.33–0.68. The combined use of KMnO4 and O3 provided synergetic and complementary advantages. On the one hand, oxidation of pollutants on suspended solid surfaces and in the aqueous phase was enhanced by the stirring action of O3 molecule bubbles. On the other hand, small molecular organic compounds and fine particles were coagulated by KMnO4 and its intermediate oxidations. X-ray photoelectron spectroscopy results indicate that the valence state of manganese changed after KMnO4 O3 treatment, and the manganese intermediate catalysing O3 process contributed to the removal of 20% of COD and 19% of TOC. It was therefore determined that the KMnO4 O3 treatment is a promising method for use in the treatment of textile dyeing wastewater.

Recycling of petrochemical by-products is important for environmental protection and sustainable utilization of resources. In this study, petrochemical by-product was analyzed and used for the first time as a cost effective frother in flotation separation of molybdenum to replace terpineol. A significant improvement in molybdenum recovery was achieved by replacing terpineol with petrochemical by-products as frother. Properties of the petrochemical by-product and terpineol solutions, such as foaming, bulk rheology, and foam stability, were investigated through surface tension and rheological measurements. The properties of the petrochemical by-product solution are generally better than that of terpineol. In addition, results obtained in bench-scale flotation showed that the recovery of molybdenum substantially improved by 2.5% in the locked-cycle tests when the concentration of the petrochemical by-product was 100 g/t. Industrial tests showed that the molybdenum recovery obtained by using petrochemical by-products increased by 2.55% which can lead to about 6918192 RMB (1001113 USD) net profit per year. Therefore, these encouraging results suggest that petrochemical by-products can effectively be utilized in mineral processing plants as frothers, and interestingly, Jinduicheng Molybdenum Industry Co., Ltd, China is one that started to use it in industrial production by replacing terpineol.

A floating phytobed system based on plants of Chrysopogon zizanioides and Typha angustifolia (Consortium CT) was effective in the removal of Scarlet RR Dye (150 mg/L) and a textile effluent, with rates of 89 and 87%, respectively, within a 60-h period, which demonstrates a higher elimination rate than an individual plantation. In addition, the treatment of textile effluents with the floating phytobed linked to microbial fuel cells was enhanced in terms of color reduction, chemical oxygen demand, biological oxygen demand, total dissolved solids and total suspended solids up to 82, 75, 75, 67 and 70%, respectively. Moreover, it produced a power of 0.0769 W/m2 at current density of 0.3846 A/m2. Terminal restriction length polymorphism community analysis documented 37 new genera which have a probable role in efficient treatment as well as power generation. Induction in the activities of oxidoreductase, high performance thin layer chromatography and gas chromatography-mass spectroscopy analyses of treated Scarlet RR dye confirmed the biotransformation. Toxicity evaluated on gill histology of Lamellidens marginalis and inter simple sequence repeat marker assessment confirmed the decreased toxicity of Scarlet RR after phyto-transformation.

Producción Científica, Sugar beet pulp (SBP) is the major by-product in sugar industry. To make profit out of this undervalued residue, the FASTSUGARS process was proposed as a solution, combining the advantages of supercritical water as hydrolysis medium with very short reaction times in the so-called ultrafast reactors. Operating at 390 °C, 25 MPa and reaction times between 0.11 and 1.15 s it was possible to convert SBP into sugars and to obtain a lignin-like solid fraction. The highest yields of C-6 and C-5 sugars (61 and 71% w/w, respectively) were obtained at 0.11 s with the lowest yield of degradation products. The solid product obtained at 0.14 s was thoroughly analyzed by acid hydrolysis, TGA and FTIR analysis to prove its enhanced thermal properties and aromaticity. The FASTSUGARS process demonstrated being a versatile and promising technology to be integrated in the future biorefineries., Ministerio de Economía, Industria y Competitividad (Project CTQ2013-44143-R and CTQ2016-79777-R)

A parametric study employing Taguchi's design of experimental technique was conducted to produce a value added novel biochar mix from three different origin feedstock and evaluate the effect of process parameters on biochar quality. Three feedstocks sourced from different origins (macroalgae: Sargassum sp, agricultural waste: rice husk and lignocellulosic waste: pine wood) were mixed in a definite proportion and pyrolyzed following the L4 experimental layout. Results indicated that temperature and mixing ratio were the most influential contributing factor. A temperature of 500 °C and 70% algae mix was the optimum condition to get an enhanced biochar in terms of thermal stability, aromaticity, pH balance, ash content and yield. Among the 4 Taguchi combination char S3 stands out as the best condition that resulted in high aromaticity, 40% high ash content, highly alkaline pH (10.3), 1–2% higher nitrogen and sulfur content. Potential application of biochar in agronomy as a soil ameliorant and/or in contaminant remediation as an adsorbent is suggested.

The manufacturing of energetic compounds (explosives), such as 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and 3-nitro-1,2,4-triasol-5-one (NTO), generates large volumes of wastewater containing organic pollutants, which are also rich in nutrients, mainly nitrogen. These wastewaters are subject to regulatory compliance and require treatment prior to their release into local water bodies. An approach is proposed to recover nutrients and water from wastewaters prior to treatment by growing microalgae with the aim to reduce the energy footprint of the munitions production facility by producing algae-based biofuels. In order to assess the feasibility of implementation of the proposed approach, ten different fully characterized untreated wastewaters with various levels of organic and inorganic carbon and nitrogen content were assessed for microalgae toxicity using Scenedesmus obliquus ATCC® 11477 as target microorganism. Toxicity experiments were performed in microplates for six days at 25 °C, 120 rpm orbital mixing speed, under a 14:10 h light: dark photoperiod, and 68 μmol photons/m2s of light intensity. The results indicate that the majority of the wastewater streams assessed could be used as nutrient media with no pretreatment while only three of the streams required chemical treatment due to their high growth inhibition characteristics. From the toxicological results obtained, a site specific mixture prepared by blending of the different untreated waste streams was tested for Scenedesmus obliquus growth. It was observed that this microalga can reach 5 × 107 cells/mL over six days of incubation in the wastewater mixture containing up to 24 mg/L RDX and 28 mg/L NTO. This strain exhibited similar growth patterns in the wastewater mixture as compared to the control sample, suggesting the potential feasibility of using untreated, energetic-laden industrial wastewater along with carbon dioxide [CO2 (atmospheric or flue gases)] for microalgae biomass production.

In order to reduce solid content and to recover value from municipal solid waste materials, laboratory-scale batch hydrothermal deconstruction tests were carried out under subcritical wet oxidation conditions. Treatments of the selected solid waste materials (plastics, timber, tyres, cardboards, and sanitary items) were carried out at a temperature range from 240 to 280 °C with initial pressure of 35 bar oxygen. A substantial solid reduction was observed for the wastes through the wet oxidation deconstruction process, which breaks down the physical structure of the waste materials and segregates the solids into useable process outputs, such as acetic acid. At 280 °C, more than 90% of total suspended solids were successfully reduced and at least 1500 mg/L of acetic acid was produced for each individual material. The mixture of materials representing a non-recyclable municipal solid waste stream produced approximately 2930 mg/L of acetic acid. Soluble chemical oxygen demand showed different trends for different materials due to competing effects of solubilisation and oxidation. The high concentrations of acetic acid product offer opportunities for recovery and re-use if effectively managed therefore such a process can provide a significant commercial and environmental benefit.

Combustion of Mazut in power plant generates sulfur oxides (SOx) and nitrogen oxides (NOx) that need to be controlled in accordance with the European standard. Most of the pollutant removal methods are effective in removing only one contaminant but not both SOx and NOx. In this work, a combined approach is studied to simultaneously control SOx and NOx from combustion of Mazut fuel. This combined approach is consisted of the Mazut Nano-Emulsion usage instead of regular Mazut, as well as, wet flue gas desulfurization or FGD system installation. The wet FGD system removes the SOx by 80.3% but has no influence on NOx. The water content equals to by 10% of Mazut volume is used to synthesize the Mazut Nano-Emulsion at optimum performance. The dimensions of fuel droplet are in nano scale (63.7 nm in width and 123 nm in diameter). The Mazut Nano-Emulsion usage removes the NOx and SOx by 30.8% and 42.2%, respectively. The approach of Mazut Nano-Emulsion usage and wet flue gas desulfurization leads to simultaneous reduction of SOx and NOx in accordance with the European standard. Results show that the combined approach decreases the SOx and NOx 79.8% and 78.3%, respectively that satisfied the European standard.

In order to minimise the environmental, social and economic impacts caused by the mining activity, this work proposes the use of iron ore tailings from tailings dams (IOT) as pigment in the production of a paint for buildings – the Sustainable Paint. The waste originates from the mining activity in the state of Minas Gerais. For this work, it was used in its raw state, subjected only to drying and lump breaking. In addition to IOT and water, four types of binders were tested: polyvinyl acetate (PVA) resin (in the form of ordinary white glue), acrylic resin, hydrated lime for painting and high early strength Portland cement. Binder contents ranged from 0% to 50% over the mass of IOT. For the evaluation of the mixtures, four main parameters were used: cost, colour homogeneity, abrasion resistance, and durability to external exposure, using the colour difference methodology ΔE (Delta-E). The results of binder evaluations were compared among themselves and with conventional paints from a brand recognised by the Brazilian Association of Paint Manufacturers. The Sustainable Paint presented reddish colour; suitable opacity; satisfactory results regarding durability at a significantly lower cost. In general, the blends with IOT, especially those using PVA as binder, have proved to be promising alternatives for paintings prepared in situ. It is noticeable the wide potential of use of this pigment by communities affected by iron ore tailings dams throughout Brazil and worldwide.

In the present study, an optimized process involving integrated events of flue gas CO2 sequestration and wastewater utilization was developed for improved microalgal biomass production in a cleaner fashion. An artificial neural network (ANN) combined with genetic algorithm (GA) optimization tool was employed for predicting optimal process conditions for enhancing the biomass of the green microalga, Scenedesmus sp., using domestic wastewater as culture medium and coal-fired flue gas as carbon source in an integrated process chain. A 24 central composite design involving four independent process parameters such as light intensity, photoperiod, temperature and initial pH as input variables with biomass productivity as the output was used to construct a non-linear ANN model followed by GA tool to predict optimal combinations of process conditions. Among the tested neural network architecture, 4-12-1 ANN topology was found to be the optimal network architecture in terms of maximum correlation coefficient (R = 0.9947) and minimum mean square error as the performance indexes. On employing the optimized ANN model as fitness function in GA tool, the optimum values of the process parameters for efficient biomass production were as follows: light intensity = 124 μmol m−2 s−1, photoperiod; L:D = 17:7 (h), temperature = 27.5 °C and initial pH = 9.5. These parameters improved the algal biomass productivity by about 57%, CO2 sequestration rate of 578.1 ± 23.1 mg L−1 d−1 and chemical oxygen demand (COD) reduction of 95.9 ± 2.4% were achieved. The optimized process yielded biomass with lipid content and productivity of 34.6% and 106.4 mg L−1 d−1 respectively. The biofuel assessment from the fatty acid methyl ester profile obtained also conformed to the international standard specifications for biodiesel.

This study presents a thermoeconomic and environmental assessment of the extraction of lipids and proteins from wet microalgal biomass in a 3G biorefinery by two different technologies: supercritical fluid extraction (SFE) and low-pressure solvent extraction (LPSE). Simulation tools were used to study a sugarcane biorefinery producing ethanol from sugarcane juice (1G) and bagasse (2G); the microalgal growth in an open pond; and the processing of microalgal biomass into lipids, proteins and synthetic natural gas (SNG). Supercritical water gasification (SCWG) of microalgal biomass enables an increase in biofuel production of 10.2% MJ when no extraction process is considered and of 1.9% MJ when LPSE is considered. The heat demand of the proposed biorefinery with LPSE was increased by 87.8% compared with the demand of the sugarcane biorefinery without microalgal growth and processing. When the SFE process is considered, the heat demand of the overall process increased 3.2 times. SFE for wet microalgae processing is not economically attractive, as it increases the total investment by 71%. The CO2 flow used in the SFE process demonstrated to be a key factor in the thermoeconomic viability of the process. Regarding the wet processing of microalgae prior to SCWG, the best alternative studied was the use of LPSE technology.

Centrifugal mother liquid (CML) is a typical poorly biodegradable organic wastewater generated during the production of polyvinyl chloride (PVC). A method of treating PVC centrifugal mother liquid by a high efficiency internal circulation aerobic biofilm reactor (four reactors lined up together) is presented in this study. The optimized technique was tested and evaluated in a lab and in a plant scale system. The effect of chemical oxygen demand (COD) removal efficiency was studied under different hydraulic retention time (HRT): 40, 20, 17, 14 and 12 h, respectively. Considering the efficiency and removal rate, the best HRT was 14 h. At HRT of 14 h, the average volume loading was 0.326 kg COD/(m3∙d). During the product shift from TL-1000 to TL-800 (two kinds of PVC products with different polymerization degree), the treatment efficiency of the system was not affected. Compared with the plant scale system, the results showed that in the lab setup the removal rates of centrifugal mother liquid of TL-1000 (total organic carbon (TOC) = 70–75 mg/L) and TL-800 (TOC = 20 mg/L) were 90%–95% and 80%–90%, respectively. While in the plant scale system, the removal rates of centrifugal mother liquid of TL-1000 and TL-800 were 80%–90% and 65%–80% (effluent TOC 7.5–12 mg/L), respectively. Biofilm formation by the microbial reproduction as well as intensive filamentous bacteria settlements were observed.

Palm Oil Mill (POM) effluent is the primary discharge from the industrial clarifiers during POM processing and a potential substrate for methane production. However, due to its rich content of sulfate components, the initial fermentation phase of anaerobic digestion is highly acidifying which leads to severe performance losses, digester's instability, and even culture crash. This study introduces a new reactor design, shear-loop anaerobic contact stabilization (SLACS) system to enhance the methane productivity of POM substrate. The treatment profiles, including the influence of feed COD/SO42− ratio, pH and sulfide inhibition was examined for the shear-loop anaerobic bed (SLAB) and the anaerobic plug flow (APF) units of the SLACS system which functions as a dissimilatory sulfate reduction phase and a methanogenic phase, respectively. Experimental observations indicated that methane (CH4) production, COD and sulfate removal were influenced by the feed COD/SO42− ratios. In addition, the performance of the one-stage domesticated digestion of POM substrate was compare with the two-stage domesticated SLACS system. During two-stage domestication, methane productivity was 256 mL g−1 VS, a 32% methanogenic proficiency higher than that of the one-stage digestion. The SLAB unit had great advantage in averting the toxic inhibitory effect of sulfide and non-ionized H2S accumulation on the microbial community structure and the two-stage SLACS system could proficiently enhance the substrate utilization efficiency and energy recovery from POM substrates, thus enhancing methanogenesis.

The treatment of an industrial wastewater (Efmix) composed of sanitary wastewater (91.5%), pretreated wastewater from pesticide production (3.8%) and hazardous waste landfill leachate (4.7%) was investigated in a moving bed biofilm reactor (MBBR) at a hydraulic retention time of 6 h. Treated effluent was then mixed with surface water (EfMBBR + SW) in a 1:9 volumetric ratio and physicochemical processes (coagulation/flocculation, sedimentation, rapid sand filtration and cartridge filter) were applied in lab-scale to reproduce the industrial water treatment plant and verify the efficiency of the combined process for wastewater reclamation. During the 90 days of operation, the moving bed biofilm reactor was efficient and stable regarding the removal of organic matter (64–89% in terms of chemical oxygen demand) and ammonium nitrogen (89–98%). Even with a fluctuating inlet chemical oxygen demand (230–721 mg/L), values below 100 mg/L were always achieved after biological treatment. Ammonium nitrogen (1.3 ± 0.6 mg NH4+-N/L) and nitrate (20 ± 4 mg NO3⁻-N/L) concentrations in treated wastewater showed that nitrification took place without inhibition throughout the bioreactor operation. Advanced treatment results indicated that a microfiltration or ultrafiltration unit must be coupled to the existing conventional reverse osmosis pretreatment in the water treatment plant in order to improve water quality concerning SDI15, turbidity and color, and thus allow for total reclamation of the industrial complex wastewater. An integrated conventional-microfiltration/ultrafiltration system could achieve high turbidity (99.9%) and apparent color (96.7%) removal to produce high quality water for reverse osmosis, minimizing membrane fouling problems and, consequently, the operational costs.

This study presents the effect of certain porous materials on the production of biogas from the anaerobic co-digestion of a mix of sheep manure (20 wt.%) and cheese whey (80 wt.%). These porous materials are custom-made from recycling agricultural and forestry wastes - almond shells, walnut shells, kenaf fibre, and charcoal. The manufacturing cost is therefore low. They are crushed and sieved, and then fed into the bioreactor to form a fixed bed in order to make a greater surface available for bacterial adhesion, and thus increase the microbial population in the reaction medium. The ultimate objective is to increase biogas production, i.e., to maximize the energy yielded by the codigestion of this mixture. The conclusion drawn from the results of the study was that the greatest long-term (for reaction times over 168 days) biogas production is obtained when using charcoal as the porous material. There was a 27.82% increase in methane (CH4) production compared with the biomethanization of the mixture without any porous material in the reactor (control experiment), and a 50% reduction in chemical oxygen demand (COD). The study of the economic viability of an industrial plant, based on previous results, showed that the period of return on investment (PRI), net present value (NPV), and internal rate of return (IRR) economic parameters are highly favourable. In particular, with the use of charcoal, a PRI of 8 years and an IRR of 10% are achieved.

The aim of this research is to identify the operational conditions and performance of low cost tubular digesters producing biogas from the slaughterhouse wastewater treatment. Three full scale sequenced tubular digesters (of more than 8 m3 each), operating in a slaughterhouse in Cochabamba (Bolivia), have been monitored during one year. The Organic Load Rate (OLR) varied from 0.04 to 1.13 kgSV/m3d (0.04–1.07 kgCOD/m3d), and the Hydraulic Retention Time (HRT) from 3.2 to 87.4 days. The passive solar heating design considered drove the slurry temperature to 27 °C, 8 °C more than mean ambient temperature. The first digester has been filled with soda bottle plastic rings in order to increase the internal effective surface and evaluate, obtaining that an increment in 67% of the internal effective surface, more than doubles the biogas production and enables higher OLRs. A Biogas Production Rate (BPR) peak of 0.2 m3/m3d was observed for OLR = 0.37 kgSV/m3d, HRT = 9.7d and Specific Biogas Production (SBP) = 0.55 m3/kgSV. COD removal achieves values above 70% from HRT>19 d. A comparison with other anaerobic digestion technologies demonstrates that low cost tubular digesters with biofilm carriers, are competitive for OLR

Recently, the valorization of the lignin fraction in the biorefinery scheme is getting more and more attention as the use of this component for the production of bio-based chemicals is crucial for the success of the integral development of lignocellulosic biorefinery processes. The present work includes the exergy performance and the economic analysis of a process for catechols production using lignin extracted from olive tree pruning. Energy and exergy calculations were obtained from the process simulation with Aspen Plus®. The exergy analysis was applied to identify the units associated with the main irreversibilities and exergy losses. The process investment and operating costs were determined as well as the derived catechol market price. The calculated total plant capital investment was about 4.9 M$ for a plant capacity of 2544 kg feedstock/day. The estimated catechol price was 1100 $/t with a valorization ratio of 3.02. These results place the product in a competitive position in the market.

In the nitrophosphate process of fertilizer production, rare earth elements (REE) can be recovered as a REE phosphate concentrate. In this process, after digestion of apatite in concentrated nitric ...

The treatment of recalcitrant bio refractory pollutants especially common in wastewater emanating from the tannery industries is a major challenge to the industries due to the absence of an efficient treatment technology, high operational costs as well as in view of the stringent rules imposed by the various environmental and governmental regulatory bodies. This study reports the degradation of organic pollutants present in tannery waste effluent (TWE) using hybrid hydrodynamic cavitation (HC) such as HC + ozone (O3), HC + hydrogen peroxide (H2O2) and HC + Fenton's reagent. HC treatment alone caused a reduction of 14.46% chemical oxygen demand (COD), 12.60% total organic carbon (TOC), 10.01% total dissolved solids (TDS) and 34.82% total suspended solids (TSS) of the TWE samples at the optimum inlet pressure of 500 kPa within 120 min. It also caused an increase in biodegradability index (BI) value from 0.33 to 0.43 indicating increased biodegradability, whereas dilution of the TWE samples did not enhance the HC process efficiency. HC combined with O3 was effective as COD and TOC reduction increased to 26.81% and 17.96% respectively at the optimum loading of 7 g/h of O3. HC combined with H2O2 also significantly enhanced the degradation efficiency to a maximum of 34.35% COD and 19.71% TOC reduction due to the enhanced generation of hydroxyl radicals. However, HC combined with Fenton's process was found to be the most efficient hybrid process for the treatment of TWE at a maximum reduction of 50.20% COD and 32.41% TOC respectively at FeSO4.7H2O/H2O2 ratio of 1:3 (w/w). The requirement of H2O2 per g of COD reduction for HC + Fenton reduced to 1.95 g/g compared to the requirement of 3.02 g/g for HC + H2O2 process. Moreover, HC + Fenton's treatment increased the BI value from 0.28 to 0.46, which is an increase by 64% compared to an increase by 30% using HC alone. These hybrid techniques enhanced the BI of treated TWE and therefore may be used as a pre-treatment tool by integrating into existing biological treatment units in the conventional effluent treatment plants, in order to cause enhanced degradation of highly bio-recalcitrant organic pollutants. Other enhanced benefits include higher rate of mineralization of organic matter with lower cost of treatment. Hybrid HC + Fenton was the most energy efficient approach than HC process with a 75% reduction in the energy requirement and 56% reduction in treatment cost per mg of COD reduction of TWE.

The anaerobic digestion of municipal sewage was studied at psychrophilic temperatures (19 °C and 17 °C) in three up-flow anaerobic sludge bed reactors (UASB). A pulsed feeding system was operated for 430 d, during which different hydraulic retention time (HRT) (6, 8, 10, 12, 14, 18, 24 and 36 h) were tested. Granulation of the sludge was observed under the pulsed feeding strategy and a 6 h HRT. Low hydrolysis rates were obtained at HRTs lower than 10 h, as a result of an increased solids accumulation inside the reactor. An HRT of 14 h was identified as the most suitable HRT under the studied temperatures (19 °C and 17 °C), with methane yields of 136 and 117 mL CH4/g of removed chemical oxygen demand (CODremoved), respectively.

The aim of this study was to estimate the energy potential of sewage sludge co-digestion with grease trap waste. The semi-continuous process was carried out at lab scale bioreactors under mesophilic conditions where, in contrast to the literature data, the reactor was operated at a significantly shorter hydraulic retention time (10 days). The concentration of grease trap waste was increased up to 54% in the feedstock on a volatile solids content basis. Although, significant variations in the organic loading rate were observed, the biogas production and methane yield increased with a larger addition of fat-rich waste. Despite the fact that the concentration of long chain fatty acids obtained in the present study significantly exceeded the accepted level inhibiting the fermentation process, it had no negative impact on process performance. The calculated energy balance showed that the addition of grease trap waste will provide an increased production of biogas. As shown the energy balance, as the ratio of biogas-derived energy to energy consumed, after co-substrate introduction of the co-substrate improved by about 30%. Furthermore, implementation of the co-digestion process at the wastewater treatment plant may lead to an increased recovery degree of wastewater treatment plant energy consumption via electric energy supplied by methane combustion, even up to 100% in comparison to anaerobic digestion of sewage sludge alone.

Spent lithium-ion batteries have caused global concern owing to their rich resource metal content and high potential for polluting the environment. In the present study, a green, efficient, and simple process was developed to recycle and detoxify Li, Mn, Cu, Al, Co, and Ni from spent lithium-ion mobile phone batteries using adapted Aspergillus niger. The adaptation of Aspergillus niger to heavy metals improved the production of organic acids and the leaching efficiency of metals compared to unadapted fungi. Moreover, it decreased the time required to enter the logarithmic phase and increased the speed of acid production. In the presence of spent lithium-ion battery powder, gluconic acid was the main lixiviant produced by the adapted fungi. At a pulp density of 1% (w/v), the adapted Aspergillus niger leached 100% Li, 94% Cu, 72% Mn, 62% Al, 45% Ni, and 38% Co. The results of SEM, FTIR, XRD, EDX, and mapping analyses of the original spent battery powder and bioleached residue confirmed the effectiveness of fungal metabolites to leach the metals of spent lithium-ion mobile phone batteries.

Anaerobic co-digestion of solid wastes with activated sludge for biogas production is an alternative and effective cleaner process of energy production from waste matter. This study comprehensively evaluated the suitability of Tea Powder Waste as an alternative co-substrate for higher biogas production. Biochemical Methane Potential analyses were performed on the anaerobic co-digestion of carbon-rich organic solid waste and Tea Powder Waste with the presence of Methanogens in activated sludge. The process parameters for the co-digestion of organic waste with Tea Powder Waste were optimized in order to achieve higher biogas production. Biogas producing reactors, with the organic wastes and methanogens activated sludge, were maintained under a mesophilic temperature (35 ± 2 °C) for 60 days retention period. The influence of various process parameters on the production of biomethane were analyzed. The optimized feed ratio of 1:2:1 (FFV: TPW: MAS) showed higher methane yield. Nitrogenous compounds present in Tea Powder Waste increased the methane production by four folds. The co-digestion of wastes showed 65% yield when compared to 40% yield as in mono-digestion of wastes.

Palm oil mill effluent is a highly polluting and corrosive liquid waste generated from crude palm oil processing. Its varying characteristics depending on the crop season and loading rate of the milling process complicate the handling of anaerobic digestion of palm oil mill effluent. To ease monitoring and aid decision making to handle operation anomalies, this study adopts Adaptive Neuro-Fuzzy Inference System with hybrid learning algorithm and subtractive clustering to predict the output from a thermophilic high-rate anaerobic digester treating palm oil mill effluent. Influent pH, chemical oxygen demand, organic loading rate and historical data of effluent pH, chemical oxygen demand and total suspended solids were utilized to build the model for output prediction of treated effluent (pH, chemical oxygen demand and total suspended solids). Trained models were validated with experimental data. The models were able to predict the effluent pH, chemical oxygen demand and total suspended solids satisfactorily with average error of less than 8.32% and standard deviation of less than 7.65% with closely followed pattern between the actual values and simulated results. The viability of adaptive neuro-fuzzy inference system in modelling palm oil mill effluent using thermophilic high-rate anaerobic digester is further demonstrated by coefficient of determination, R2 of 0.82, Root Mean Square Error of 0.0377, Index of Agreement of 0.95 and d-factor of 0.0496.

Gravity-driven membrane (GDM) filtration is a promising technology for decentralized drinking water treatment due to its low energy requirements and simple operation. The reduced flux observed in GDM systems relative to other membrane treatment techniques remains a vital obstacle to their wider application. With the goal of further improving membrane flux and permeate quality, three simple and practical technologies have been examined as pre-treatments for GDM systems, (i) slow filtration with granular activated carbon (GAC), expected to remove both biodegradable and non-biodegradable contaminants, (ii) slow filtration with modified fiber ball (MFB), expected to promote biodegradation of organic compounds and (iii) microfiltration (MF), expected to reject suspended substances and particles. Results indicated that stable permeability increased by approximately 230%, 150% and 100% in GDM systems employing GAC, MFB and MF pre-treatments compared to the control. The dissolved organic compounds (DOC) were removed by approximately 60% and 30% in GAC/GDM and MFB/GDM, while MF/GDM and GDM control were not effective at DOC removal. Correlations between the stable flux and extracellular polymeric substances (EPS) concentration (R2 > 0.9) indicated that reduction of EPS should be responsible for the flux improvements. Tracing the fate of florescent foulants illustrated that the EPS was mainly secreted/converted by the microbes colonizing within the bio-fouling layer of the GDM system. During long-term filtration, assimilable organic compounds (AOC) which can serve as nutrients for the growth of microbes within the bio-fouling layer were efficiently consumed (>50%) by the biological pre-treatments. This reduction in AOC was linked with a reduction in the growth/activity of bacteria within the bio-fouling layer of GDM system and a reduction in EPS accumulation. Overall, biological pre-treatments can significantly enhance the flux and water quality produced by a GDM system without significantly increasing the operation and maintenance. These improvements in flux and water quality can hopefully spark wider adoption of GDM as an economical and environmentally-friendly technology for decentralized drinking water treatment.

Generally the exhaust dyeing process utilizes a large amount of energy, time and high liquor ratio. On the contrary, the microwave irradiation can be used for the exhaust dyeing that consumes less energy and less time. In this research, the environmental friendly technique, the microwave irradiation, is used to dye cotton fabric at lower liquor ratio through the exhaust dyeing process and it is compared with the conventional dyeing method. The exhaustion percentage, fixation percentage, and color strength values have been measured and a suitable recipe is obtained. It is found that the microwave technique facilitates the process by minimizing the dyeing time and maximizing the exhaustion percentage, fixation percentage, and color strength values. Furthermore, the microwave technique is considered as a green technique and higher exhaustion and fixation percentages indicate that there is comparatively less residue dye in the effluent. XRD and SEM tests also performed to analyze whether the microwave has affected the morphological structure but from the results, there is not a considerable difference observed. Finally, the colorfastness tests have been carried out and compared with the conventionally dyed samples and the results are almost the same for both techniques. Hence the microwave technique is providing almost the same quality product by using less time with the environment friendliness.

A new synthetic route was developed to create an azo-based reactive disperse dye containing the vinyl sulphonyl reactive group. This dye was used to colour wool and cotton fibres using scCO2 as the dyeing medium. The optimum dyeing process was carried out with water pre-treatment at 90 °C and 140 bar during a 60 min dyeing time. Under optimal conditions, which are relatively moderate for supercritical dyeing processes, the dyed wool fabrics produced uniform dyeings with high colour strength and fastness properties. These wool dyeings provided good colour strength and fixation properties (fixation of 99.4%). Cotton also showed good colour strength results. Crucially, the process did not produce any dyeing effluent. Furthermore, there is a potential to modify a wide scope of disperse dyes using the thiol group via this synthetic method without the need for further purification.

Oxy fuel combustion technique has been in practice since last three decades powered mainly by coal or other fossilized fuels. A similar technique was applied to biomass thermochemical conversion keeping in consideration zero carbon and renewability features of biomass. Experimental investigation of combustion characteristics of lignocellulose based biomass including maize stalk, wheat straw, rice husk and groundnut hull has been carried out in this study. Objective was to determine the behavioral changes in fuel inherent nitrogen during combustion and its distribution between elemental nitrogen (N2) or nitrogen oxides (NOx) after the combustion. Approximately isothermal conditions with temperature range from 700 °C to 1200 °C and various oxidizer atmospheres comprised of mainly oxygen with corresponding nitrogen or carbon-dioxide gases were opted for the experimental work. Results revealed that average 78% relative NOx reduction efficiency for four selected biomasses (81.69% maize stalk; 68.69% wheat straw; 88.64% rice husk & 72.99% groundnut hull) was achieved under 21% O2/79% CO2 atmosphere over the corresponding 21% O2/79% N2 atmosphere. Through enhancing O2 ratio in oxy biomass combustion atmosphere i.e. 30% O2/70% CO2 and comparing NOx reduction efficiency with its corresponding 30% O2/70% N2 atmosphere; an average relative NOx reduction efficiency of 80.49% i.e. (maize stalk: 78.94%, wheat straw: 79.11%, rice husk: 88.60%, groundnut hull: 75.30%) was attained. It was concluded that oxygen played key role in achieving satisfactory reduction in NOx emissions.

Dilute acid (DA) pretreatment results in the formation of inhibitory compounds and pseudo-lignin along with the burden of unnecessary materials like ash, extractive, lignin or their condensed products that reduces the conversion efficiency of cellulose to monomeric sugar. Indian Oil Corporation Limited (IOCL) has developed a modified pretreatment (MP) in order to reduce the enzyme dosage during ethanol production. This method uses extraction of biomass in water and varying alkali concentration of 0.2, 0.4 and 0.5%, prior to pretreatment as a strategy to reduce the enzyme dosage and improve the ethanol yield. The environmental and economic impact of these MP scenarios in comparison with conventional pretreatment (CP) is studied. The ethanol production increases from 218 to 267 L using MP. The introduction of extraction step prior to DA pretreatment fulfills the objective of reducing enzyme dosage by 23–39%. However, overall life cycle assessment (LCA) results revealed that performance of MP2, MP3 and MP4 is on a negative side in all the environmental impact categories as compared to CP due to the use of alkali, where a huge amount of emissions are released during the production stage. Overall, MP1 using water as a media for extraction is the most environmentally suitable pretreatment process for ethanol production. Life cycle costing (LCC) results showed that cost of 1 L ethanol production could be lowered down from 0.87 to 0.70 United States Dollar (USD) using MP1 scenario. From an environment and economic perspective, it is recommended to use only water as an extraction media for biomass, as this can reduce the enzyme dosage, emissions and cost.

This study was focused on the application of various chemical and electrochemical advanced oxidation processes (AOPs/EAOPs) as a polishing step for the remediation of a textile wastewater, concerning its discharge into the environment and its reuse in the textile industry. The textile wastewater was previously subjected to biological treatment, clarification and filtration. The following processes were compared: hydrogen peroxide (H2O2) photolysis with ultraviolet C (UVC) radiation (H2O2/UVC), anodic oxidation (AO), AO with electrogenerated H2O2 (AO-H2O2) and AO-H2O2 with UVC radiation (AO-H2O2/UVC). Furthermore, the influence of H2O2 concentration on the H2O2/UVC process and the influence of current density on the AO-H2O2/UVC process were evaluated. The efficiency of the AOPs/EAOPs was assessed in terms of decolorization and mineralization. The decolorization ability of the various processes up to 25–30 min of reaction could be arranged in the following sequence: AO > AO-H2O2/UVC ≈ H2O2/UVC > AO-H2O2. For treatment times above 25–30 min, the AO-H2O2/UVC and H2O2/UVC processes provided higher decolorization than the AO process. Complete color removals were found, contrasting with a maximum mineralization of 39%, thereby indicating the presence of recalcitrant non-colored organic compounds. The German color discharge standards were achieved after 5–9 min of reaction for all processes, whereas the Brazilian color discharge limit was reached after 10 min of reaction for the AO process, 20 min for the AO-H2O2/UVC and H2O2/UVC processes, and 35 min for the AO-H2O2 process. The feasibility of using the recycled textile wastewater in textile processing was proved for scouring, bleaching and dyeing processes, taking into account hydrophilicity, color difference and whiteness index. The treatment times required for reuse purposes applying the H2O2/UVC process were equal or higher than the ones necessary for discharge purposes: 45 min for scouring, 20 min for bleaching, and 30 min for dyeing.

Bleaching technology by ozone dissolved in water offers alternative measures to prevent pollution in the textile industry for sustainable development at organizational and economic levels. In this paper, jeans fabric was treated with ozone injected in water combined with ultrasound and H2O2. Effectiveness of Fenton process regarding dye degradation was also tested with confirmation of hydroxyl radicals detected by fluorescence and electron paramagnetic resonance (EPR) spectroscopy. Results showed that individual ozone was more effective regarding the bleaching of the jeans samples than the hydroxyl radicals especially when coupled with ultrasound. The mechanical action of ultrasonic cavitations enhanced the diffusion of ozone through the fabric which increased the degradation of the indigo dye. The fading degree of samples treated with ultrasound and 100 g/Nm3 of ozone for 60 min in acidic condition reached 64.49 which gave a full bleach appearance. Scanning electron microscopy (SEM), ultimate tensile strength and fastness tests were performed in order to evaluate the effect of such treatment on the cotton fabric. The said tests proved that moderated concentrations of ozone caused no damage to the cotton fiber and results were very close to those obtained with ordinary bleaching processes.

Coal fly ash (CFA) is an industrial by-product derived from coal combustion in thermal power plants. This abundant and low cost by-product is generally reemployed as an additive in the building industry. This work explores the possibility of recovering CFA as an adsorbing material for the removal of anionic surfactants dissolved in water, on the basis of data about concerning its embodied energy. Indeed, Although the CO2 footprint of CFA and activated carbon is comparable, CFA shows an extremely lower embodied energy with respect to activated carbon, the most used widely used material for surfactant removal. Surfactant are widely used in several detergents products, and enter into the environment through the discharge of sewage effluents. In this paper, Sodium Dodecyl Sulfate (SDS) is used as a model surfactant. Upon careful optimization of the CFA/SDS mass ratio, it was found that CFA is able to remove SDS from water with efficiency up to 96%. SDS adsorption onto the CFA surface was investigated and results point to a three-step mechanism, which stops with the final formation of a CFA supported SDS bilayer. There are two main results: first, the first one in the era of raw materials scarcity, the choice of to investigate the employ employment of a material in terms of its embodied energy must be considered; second, the second result this work opens new perspectives in the field of anionic surfactant removal.

Reactive dyeing of cotton generates a great deal of coloring wastewater containing residual dyes, electrolyte, alkali, and other auxiliaries. Especially for the effluent from the first/initial spent dyeing bath, it may be comprised of as high as 60% of the initial dye dosed, 30–90 g/L of sodium chloride or sodium sulfate, and plenty of sodium carbonate, making it to be the most contaminative effluent among the entire reactive dyeing process. This paper presents a new alternative to regenerate the waste effluent from the first spent dyeing bath through catalytic ozonation with novel catalysts for reuse of the effluent in successive dyeing. Two novel ozonation catalysts, mesoporous carbon aerogel and its supported cobalt oxide nanoparticles, were successfully prepared and used in catalytic degradation of residual dyes in waste effluents with ozone. Degradation efficiency was determined by both decolorization and chemical oxygen demand removal. The result showed novel catalysts could improve both of these two targets. For chemical oxygen demand removal, carbon aerogel supported cobalt oxide strikingly enhanced the efficiency by 30% on the whole comparing to ozonation alone (approximately 50%) without the catalyst. Waste effluents after catalytic ozonation were thereafter reused in successive dyeing in the same process. It has been validated that the waste effluent was successfully regenerated and can be additionally reused twice without sacrificing fabric quality, which cannot be realized in ozonation alone. Color difference of the fabric dyed with the regenerated effluent was within the acceptable tolerance, and excellent levelness and equal colorfastness had also been achieved. This is probably the first study to investigate the feasibility of regenerating highly polluting dyeing effluents for reuse by catalytic ozonation with carbon aerogel materials. With novel catalysts, it could be speculated that catalytic ozonation is a promising technology for in-situ regeneration of waste effluents in textile dyeing plant for reuse.

Electrical and electronic waste (e-waste), is an emerging and fast growing waste stream in the world. Among all the e-waste, cathode ray tubes (CRTs) are significantly recyclable in principle, but in practice, recycling is often inefficient because of limits imposed by hazardous behavior, recycling technologies, and the composition of glass. These topics were studied in this paper based on their characteristics and concluded the recycling challenges and most recent developed recycling technologies that could improve recycling rates. As a global society, we are currently far away from a closed-loop material system because the demand for CRT glass closed-loop recycling is extremely limited. However, much improvement is possible through recent developed recycling technologies but the challenge for the future is to transfer these environmentally friendly and energy-saving technologies into practice.

The interest in nanocellulose made from woody biomass has been growing rapidly; however, detailed studies on the environmental performance of nanocellulose have only been reported on a few occasions. To fulfill this gap, the environmental performance of nanofibrillated cellulose fabricated from thermo-groundwood (removal of extractives, lignin and hemicelluloses, TEMPO oxidation and homogenization processes were included) was evaluated by means of a Life Cycle Assessment. The results show that the purification process contributes more than 95% of the impact. It is associated with a relatively high consumption of electrical energy and ancillary chemicals, i.e., cyclohexane and acetone. The global warming potential of 1 kg of nanofibrillated cellulose is as high as 800 kg CO2 equivalents. Even in the case that in addition to the extractives and the hemicelluloses also lignin is considered as a potentially valuable co-product, and the latter takes over some of the burden, the impact of nanofibrillated cellulose remains relatively high, at around 400 kg CO2 equiv. per kg of nanocellulose. While the primary energy consumption is around 19.000 MJ per kg of nanofibrillated cellulose, or 10.100 MJ in the case that the lignin is considered as a potentially valuable co-product. The study also had a methodological goal, i.e., the impact indicators were calculated using the three most relevant evaluation methods: ILCD/PEF, CML 2001 and ReCiPe 2016. These three methods show similar results for the impact on global warming and acidification. However, in the case of impacts on some other indicators, significant deviations in the obtained impact scores were observed with respect to the results for the three methods. Taking into account the background data of the methods, ReCiPe 2016 was found to be the most up-to-date method and can currently be considered as the preferable Life Cycle Impact Assessment method.

It is very challenging to treat raw pistachio processing wastewater (PPW) by one step process due to its high chemical oxygen demand (COD) and total phenols (TP). In this study, electrochemical (EC) process and anaerobic digestion are combined to improve treatment efficiency. Central composite design (CCD) was used in EC experimental design with three factors at three levels of the independent variables. Impact of current density (50─100 A/m2), electrode distance (2─6 cm), and reaction time (60─300 min) on the removal of COD and TP were systematically investigated. A maximum removal efficiency of 43.7 and 56.4% of COD and TP, respectively, was obtained with the current density of 100 A/m2, electrode distance of 6 cm, and reaction time of 293 min. Specific energy consumption (SEC) was measured as 7.80 kWh/kgCOD for the same experimental conditions. In order to achieve further treatment, a batch anaerobic reactor was combined with EC process to produce biogas. COD and TP removal efficiency were measured in the anaerobic reactors at appropriate time intervals (0, 10, 25, 30, 40, and 50th d) and biochemical methane potential (BMP) tests lasted up to 50 d. BMP enhancement of raw PPW was found as 35.7 and 16.5% for electrocoagulated PPW under maximum COD and TP removal efficiency condition (100 A/m2 current density, 6 cm electrode distance, and 293 min reaction time) and under cost driven approach condition (53 A/m2 current density, 2 cm electrode distance, and 182 min reaction time) compared to raw PPW. The results showed that pre-treated PPW with EC process had the highest COD and TP removal efficiencies and enhanced the biochemical methane production, by decreasing the concentration of total phenols in the PPW. Energy balance revealed that EC under cost driven approach condition combined with anaerobic digestion can be used as an energy positive process for the treatment of PPW.

The citric acid wastewater treatment produces a large quantity of sludge, which contains more organic matter and is more difficult to be dewatered by mechanical devices, compared to the municipal wastewater sludge. Fenton conditioning was a highly effective and affordable approach to improving the dewaterability of citric acid wastewater sludge while preserving the fertilizing properties. The optimal condition of Fenton treatment was pH 5.0, H2O2 dose of 20 mg g−1 dry solids, and Fe2+ dose of 80 mg g−1 dry solids. Capillary suction time was reduced from 19.3 s to 10.7 s, and the water content of sludge cake was reduced from 85.3% to 73.8% under this condition. There was no significant difference in capillary suction time and the water content of sludge cake reduction by Fenton treatment between the lab-scale and scale-up experiments. The mechanism investigations of extracellular polymeric substances, zeta-potential, particles size, and morphological changes of the sludge samples conditioned by Fenton treatment under the optimal condition demonstrated that the enhanced coagulation by Fenton treatment was the mechanism dominating the sludge dewaterability improvement. Most critically to the citric acid wastewater sludge, the majority of fertilizing properties of the sludge were preserved after Fenton treatment. The volatile suspended solids, total organic carbon, total nitrogen, potassium and phosphorus were mostly maintained in the solid phase. The cost of Fenton reagents under the optimal condition was approximately 49 US$/t dry solids, which made Fenton treatment a cost reasonable approach to citric acid wastewater sludge conditioning.

The integration of pyrolysis and prepositive anaerobic digestion could be a solution to improve energy recovery from sewage sludge. However, it is not clear whether this integrated pathway always outperforms the two single technologies when dealing with different types of sludge. In this study, the integrated pathway is compared with anaerobic digestion and pyrolysis from the points of view of life cycle environmental impacts and energy efficiency. In addition, the effect of the organic content in the feed sludge on the performance of the three pathways is investigated. The results indicated that the environmental impacts of the three pathways are heavily dependent on their energy inputs and outputs. The single pyrolysis pathway exhibited the lowest energy efficiency and the heaviest environmental burden, and only the sludge with volatile solids in total solids (VS/TS) higher than 63% allowed the system generate a net energy output. The integrated pathway had better environmental performance and energy efficiency than single pyrolysis because prepositive anaerobic digestion enhanced the conversion of sludge organic matter to energy. When sludge VS/TS exceeded 61%, the integrated system exported surplus heat. Anaerobic digestion performed the best among the three pathways because it required no energy and material expenditure for thermal drying and pyrolysis. Also, a VS/TS of 52% in the feed sludge corresponded to the balance point for equal energy input and output. Therefore, anaerobic digestion should be the first choice when designing a sewage sludge disposal system. The integrated pathway is an alternative for high organic content sludge because of its high conversion rate of sludge to energy.

In order to meet the requirements of decentralized sewage treatment in rural China, a source-sorted treating method was proposed, including a black water pre-treating anaerobic baffled reactor (ABR), an anoxic filter (ANF), a novel multi-stair waterwheel driving rotating biological contactors (ms-wdRBCs) and constructed wetlands (CW). The ms-wdRBCs were utilized to post-treat mixture of digested black water and raw grey water with the ANF. Key parameters of ANF/ms-wdRBCS were identified founded on the nutrient removal performance, especially nitrogen removal, for further application in the project. Besides, the ANF/ms-wdRBCs coupling device was operated 10 weeks at the optimum parameters to confirm its performance on contamination removal. The coupling device performed well on chemical oxygen demand (COD), total nitrogen (TN), and ammonia (NH4+-) removal. When running under 150% reflux ratio, 1 h HRT of each-stair wdRBC and 7.11 h HRT of ANF, the removal efficiency of COD, TN, NH4+- and total phosphorus (RTP) were 88.40 ± 2.16%, 52.33 ± 3.80%, 88.14 ± 2.30% and 34.11 ± 7.00%, respectively. The NH4+-/ NO3−- concentration ratio of effluent was approximately 3 which was certificated to be beneficial to plants growth in CW. Although the removal efficiency of TP was only 34.11 ± 7.00%, the phosphorus was partly retained to contribute to plants growth in CWs. Overall, the entire four-part system achieved outstanding pollutant removal efficiencies, while the selected plants in CW also gained benefits back. Low construction and operating cost, simple management and easy maintenance of the system ensure the application in rural areas.

The objective of this research is to enhance concrete produced with high content of fly ash (FA) and recycled concrete aggregates (RCA), individually and jointly, with low (with superplasticizer) and high (without superplasticizer) water to binder ratio (w/b), according to their chloride ion penetration resistance (CIPR)-related service life and embodied energy (EE). For that purpose, the EE was determined for the production of 1 m3 (declared unit) of concrete considering the primary energy, non-renewable (PE-NRe) of the “Cumulative Energy Demand” environmental impact assessment method, and the CIPR of concrete are considered the conditioning factors. The environmental assessment of the mixes was evaluated by considering the Life Cycle Assessment (LCA) standardized methodology. In addition, the assessment was mostly made either according to the local Life cycle inventory (LCI) data or environmental product declaration (EPD) report and selected according to NativeLCA methodology on typical conditions in Portugal. Generally, the CIPR of concrete decreases when the RCA content increases, and the opposite occurs by replacing cement with FA. After 28 days, the rate of CIPR development of the concrete made with incorporating both FA and RCA is higher than that of concrete containing either FA or RCA. Therefore, it is positive to use simultaneously RCA and FA in concrete. This rate increased even more when SP was used. Furthermore, the EE significantly reduced with increasing replacement level of cement and coarse natural aggregates (NA) with FA and coarse RCA, respectively. Nonetheless, the changes in EE caused by the incorporation of SP and fine RCA are small. In term of the influence of combining FA and RCA in low and high w/b concrete, the EE linearly changed with each individual effect. Nevertheless, the optimal solution of mixes by means of both EE and CIPR (measured by the yearly EE of the mixes relative to the reference concrete) does not necessarily consider the one that requires less EE or that has higher CIPR. According to this parameter, the best-case scenario is always the low w/b mixes with high volumes of RCA and FA, followed by the corresponding high w/b mixes.

Microalgae cultivation is arousing interest for its ability to provide biomass for food, feed and energy. Microalgae are more efficient in converting solar energy into biomass than terrestrial plants, and microalgae cultivated in a mixotrophic mode showed a higher biomass productivity. This work aimed to evaluate the environmental impacts of the cultivation of microalgae in autotrophy and mixotrophy and to define under what conditions mixotrophic cultivation gives the best environmental performance. To make this comparison, primary data of Chlorella vulgaris cultivation in autotrophy and mixotrophy were used. The scenarios considered were autotrophy (Scenario 1); mixotrophic cultivation on cheese whey, (Scenario 2); and mixotrophic cultivation using dairy wastewater (cheese wastewater) (Scenario 3). In addition, since commercial nitrogen fertilizers are one of the major contributors to the environmental impact of Chlorella production, two other scenarios were modelled: autotrophy on recovered nitrogen from digestate (Scenario 4) and mixotrophic culture on recovered nitrogen and carbon (Scenario 5). The mixotrophic growth of microalgae was shown to be an environmentally effective process (i.e. it showed a decrease of the impact categories), when the organic carbon provided had no other allocation and could be considered free of a cost burden. The cultivation of microalgae on recovered nitrogen and recovered carbon was found to decrease the CO2 emission by almost 60% and similar decreases were obtained for the other impact categories in comparison with autotrophy. A value of CO2 emission equal to 1.05 kg CO2 eq. kg−1 of microalgae was achieved for Scenario 5, and a decrease of more than 50% was assessed for the impact categories: Marine eutrophication, Human toxicity, Freshwater ecotoxicity, Marine ecotoxicity and Fossil fuel depletion.

Food wastage is a relevant problem all over the world. Remains of prepared foods increase the waste of resources due to energy and labor used in their preparation. However, food waste has a high energy potential can be converted in the form of methane via anaerobic digestion. This study evaluated the potential for recovery of energy contained in food wastes and presented a way to stablish the anaerobic digestion process using solely food waste. For this purpose, a prototype anaerobic digester was used of complete mixture with a volume of 408 L, 15% of total solids, temperature of 29.4 °C and an agitation system. The system was operated at steady state for 51 days in hydraulic retention time of 103 days, volatile solids and chemical oxygen demand of 0.80 g L−1 rd−1. According to the literature, the stabilization period presented typical inconvenient of food wastes digestions processes, that was solved monitoring at more frequent intervals the volatile fatty acids and with the maintenance of a compatible volume of organic load according with the size of the reactor. It was obtained a reduction of 90% in volatile solids and 82% in chemical organic demand. The methane production was 0.51 L.g−1CODc, 0.44 L.g−1VSc and volumetric yield of 0.32 L.L−1rd−1, representing 59% of the composition of the biogas. The adequate levels of agitation frequency, feeding load, temperature and C/N ratio were found in this study using the prototype anaerobic biodigester.

Recycled aggregates obtained from construction and demolition waste is known to have lower strength performance than natural aggregate concrete. Several studies have been conducted during the past decade to reduce the adverse effects of recycled aggregates on the strength properties of recycled aggregate concrete. The present study is in continuation of the similar approach, contributing towards the improvement of the recycled aggregate concrete properties with waste derived silicon rich char as a cement replacement from 0.1 to 0.75% of total volume of concrete. Concrete was produced with 100% recycled coarse aggregates and wash-mix sand. It was observed that rice husk and enhanced poultry litter char; both improved the compressive and splitting tensile strength at 0.1% of total volume. Rice husk char at 0.1% produced highest compressive and splitting tensile strength with 17% and 3% increment respectively. On the other hand, enhanced poultry litter and rice husk at 0.75% replacement produced optimum flexural strength than the rest of char mixes. Char was also found to reduce water absorption up to 0.5% of total volume and reduced the permeable voids in recycled aggregate concrete by creating dense structure. Based on the findings, we conclude that waste derived char can potentially enhance the properties of recycled aggregate concrete with marginal amount of cement content replacement while simultaneously acting as carbon storage.

Utilization of heterogeneous catalyst in the biodiesel production process can minimize the cost of separation process and subsequently reduce the biodiesel price. This study aims at developing a low-priced heterogeneous catalyst CaO/SiO2 prepared from cheap and abundant wastes of eggshell and peat clay for the production of biodiesel from wasted cooking oil. CaO catalyst was capable to produce biodiesel with the yield of 78%. The presence of silica as a support generated from waste of peat clay improved the biodiesel yield to 91%. The optimum reaction time was 60 min and the biodiesel yield increased with temperature. A reaction mechanism during transesterification process was proposed based upon the characterization analysis. The mechanism suggested that the silica contributed in the esterification reaction and the CaO played a positive role in biodiesel production via transesterification. The kinetic study confirmed the proposed mechanism. The pre-exponential factor (A) and activation energy (Ea) were 5.44 × 108 min−1 and 66.27 kJ/mol. The proposed reaction mechanism and kinetic study lead to an essential step of biodiesel production for further research development or application at a larger scale.