Recent advances in photocatalytic treatment of pollutants in aqueous media

Photocatalysis can be an excellent solution for resolving the world's energy and environmental problems. It has a wide range of applications for the decontamination of diverse hazardous pollutants in aqueous media. Technological progress in this research field has been achieved toward the improvement of the solar sensitivity to enhance the efficiency of pollutant decontamination. As a result, various strategies have been introduced to upgrade photocatalytic performance with the modification of prototypical photocatalyst such as doping, dye sensitization, semiconductor coupling, mesoporous supports, single site, and nano-based catalysts. In this review, a brief survey is presented to describe those strategies based on the evaluation made against various pollutants (such as pharmaceuticals, pesticides, heavy metals, detergents, and dyes) in aqueous media.     

Decolorization of Remazol Black-B using a thermotolerant yeast, Kluyveromyces marxianus IMB3

The ability of Kluyveromyces marxianus IMB3 to decolorize Remazol Black-B dye was investigated. The effect of environmental conditions, such as pH and temperature were examined. No noticeable effects on decolorization were observed when pH varied from 3.0-5.5. Maximum colour removal, 98%, was achieved at 37 degrees C. Little or no colour removal was detected when K. marxianus IMB3 was incubated under anaerobic conditions. Further investigation, in which decolorization was monitored under extreme temperatures and low pH (to inhibit growth) and using ten fold dense inoculum, revealed that decolorization was due to biosorption to the yeast cells and not due to a metabolic reaction.     

Tackling environmental issues in industrial ceramic sintering of sewage sludge: odors and gas emissions

The inertization of sewage sludge in ceramic matrices to be used in structural or red ceramic material for buildings has proved to be a good case of reuse of waste material. However, its practical application has not yet been fully implemented in real-case scenarios, and environmental concern seems to be the main hurdle to overcome for its definitive massive approval by the building industry. In this contribution, air emissions related to the sintering of ceramic bricks made of mixtures of clay with some percentage of sewage sludge have been analyzed (in terms of gases, suspended particles and odors). Tests conducted during this work have shown higher VOC emissions in samples with some percentage of sludge in their composition (still under the regulated emission limit values), and some of them (mercaptans) are associated with odor nuisances. Besides, limit emissions values were exceeded by three inorganic pollutants (suspended particles, NO_x and HCl). Measurements in an industrial scenario test showed a high variability in air pollution emissions, suggesting the need of in situ testing for definitive implementation. With the experience collected in this and several previous works in the area of emissions related to the production of added sewage sludge ceramic, some guidelines and recommendations are given to minimize the environmental impact of ceramic production plants implementing this particular waste revalorization process. Guidelines cover different aspects: workplace implementation of gas cleaning equipment; geographical context and local wind pattern analysis; monitoring of emission and immission levels; and information policy through social control participation procedures for reporting of nuisance episodes.     

Fungal dye decolourization: recent advances and future potential

Dyes released by the textile industries pose a threat to the environmental safety. Recently, dye decolourization through biological means has gained momentum as these are cheap and can be applied to wide range of dyes. This review paper focuses on the decolourization of dye wastewaters through fungi via two processes (biosorption and bioaccumulation) and discusses the effect of various process parameters like pH, temperature, dye concentration etc. on the dye removing efficiency of different fungi. Various enzymes involved in the degradation of the dyes and the metabolites thus formed have been compiled. Genetic manipulations of microorganisms for production of more efficient biological agents, various bioreactor configurations and the application of purified enzymes for decolourization, which constitute some of the recent advances in this field, have also been reviewed. The studies discussed in this paper indicate fungal decolourization has a great potential to be developed further as a decentralized wastewater treatment technology for small textile or dyeing units. However, further research work is required to study the toxicity of the metabolites of dye degradation and the possible fate of the utilized biomass in order to ensure the development of an eco-friendly technology.     

Assessment of hydrothermally modified fly ash for the treatment of methylene blue dye in the textile industry wastewater

Dyes and pigments are one of the major water pollutants and if not discharged properly cause ecological disturbance. Considering this, the current study investigates the application of thermal power plant by-product, i.e., fly ash for the elimination of a hazardous methylene blue dye from its synthetic aqueous solution. Experiments were conducted in batch mode to study the effect of pH, temperature, adsorbent dose and contact time. Highest dye removal (94.3%) was achieved at pH 10 using adsorbent dose of 10 g/L in 90 min of contact time at 40 °C. However, for cost-effective operation at neutral pH and room temperature (30 °C), it yields 89.3% dye removal having similar dose and contact time. Equilibrium isotherms for adsorption were analyzed by Langmuir and Freundlich, Temkin and Dubinin–Radushkevich isotherm equations. The results revealed that the best fit model of adsorption closely followed Langmuir adsorption. Based on adsorption isotherm models, thermodynamics parameters ΔG, ΔH and ΔS were calculated. The negative value of ΔG and ΔH revealed that adsorption process was exothermic, spontaneous and physical. The present work suggests that through simple process hydrothermally modified fly ash has the potential to be used as cost-effective and efficient adsorbent for the treatment of wastewater from textile industries.     

Azo dye biodegradation by microbial cultures immobilized in alginate beads

Microbial degradation of azo dyes usually starts in anaerobic conditions with a reductive cleavage of the azo bond, followed by an aerobic step necessary for the degradation of the aromatic amines formed. Because some reductive processes take place also in presence of molecular oxygen, a one-step azo dye degrading process has been investigated. A microbial consortium able to degrade ethyl orange in aerobic conditions has been selected and immobilized in alginate beads coated with polyacrylamide resin. Different concentrations of ethyl orange have been completely degraded in the presence of 1% glucose or starch as cosubstrates, and different beads preparation procedures have been studied to determine the best condition for microbial degradation. The catalytic activity of the immobilized consortium improved during five serial processes carried out for 30 days at room temperature. Three pure cultures were then isolated from the consortium. The one with the greatest degrading activity, a filamentous fungus, had a degradative capacity similar to that of the whole consortium.     

Behavior of a surface applied radionuclide and a dye tracer in structured and repacked soil monoliths

There has been increasing evidence in recent years about the impact of soil structure on vadose zone hydrology and the distribution of surface applied chemical substances. We have carried out a combined dye and radionuclide tracer study on two monoliths from the same location, one structured and one repacked, as part of an ongoing study to investigate the link between preferential flow, leaching of surface applied substances and their distribution within the soil.A tracer solution containing 1300 Bq/L (58)Co and 0.31 micromol/L Sulforhodamine B (SB) was added with roughly constant irrigation during a period of three weeks. The dye served as a tracer for water movement within the soil and thus allowed linkage of the radiotracer ((58)Co) with the flow pattern. Both were monitored in the outflow and measured within profile sections after monolith disassembly. Preferential flow in the structured monolith promoted the bypass and transport of both tracers, although transport was impeded at depths greater than 30 cm by compacted soil and reduced hydraulic conductivity. Eighty four percent of radiocobalt and 8% of SB were found in the upper 4 cm of the structured monolith. The homogenized monolith, on the other hand, showed mostly chromatographic infiltration and a more efficient soil filtering capacity with 91% of radiocobalt and 20% SB residing in the upper 4 cm. Furthermore no tracer was found in the outflow of the homogenized monolith during normal to high irrigation or at greater depth within the monolith. We have related flow characteristics and sorption of radiotracers by quantifying dye distributions and radionuclide activities throughout the profiles. Activities within the flow paths are up to 20-times higher than those measured in the soil matrix, and a fraction of radiocobalt follows the dye tracer in spite of cobalt's low mobility. The dye can thus be used to trace radionuclide distribution within the soil block.     

The mutagenic effect of amaranth (FD and C red no. 2) in bacteria and yeast

Although amaranth is consumed in large quantities as a food dye, its mutagenicity and/or carcinogenicity is still controversial. Therefore, the investigation of the genetic activity induced by this dye might assist in the evaluation of its possible dangers to human health. Both bacteria and yeast strains were used for testing the mutagenic activity of amaranth. When the fluctuation test was used, amaranth was found to enhance both forward and reverse mutations in bacterial strains that contain R-plasmids. Amaranth was not found to induce any genetic activity in yeast cells at 28 °C but a significant increase in mitotic gene conversions was recorded at 37 °C in both acidic and neutral media. It has been postulated that amaranth has optimal action on microbial cells at 37 °C and should be considered a weak mutagen.     

Regional environmental assessment (REA) and local Agenda 21 implementation

The implementation of sustainable development requires several support instruments. One of the major instruments in the Rio Declaration to support this process has been environmental assessment that has been given considerable emphasis as to its potential ability to help achieve more sustainable forms of development. Regional environmental assessment (REA) has shown to be effective in supporting local sustainable development process. Selected environmental assessment methods have been␣used to improve the REA exercise and provide reliable data for decision-making not only to correct environmental problems due to past unsustainable social-economic developments but also help local governments to implement Agenda 21 (AG21) plans and projects.     

Water quality analysis in rivers with non-parametric probability distributions and fuzzy inference systems: Application to the Cauca River,Colombia

The integration of water quality monitoring variables is essential in environmental decision making. Nowadays, advanced techniques to manage subjectivity, imprecision, uncertainty, vagueness, and variability are required in such complex evaluation process. We here propose a probabilistic fuzzy hybrid model to assess river water quality. Fuzzy logic reasoning has been used to compute a water quality integrative index. By applying a Monte Carlo technique, based on non-parametric probability distributions, the randomness of model inputs was estimated. Annual histograms of nine water quality variables were built with monitoring data systematically collected in the Colombian Cauca River, and probability density estimations using the kernel smoothing method were applied to fit data. Several years were assessed, and river sectors upstream and downstream the city of Santiago de Cali, a big city with basic wastewater treatment and high industrial activity, were analyzed. The probabilistic fuzzy water quality index was able to explain the reduction in water quality, as the river receives a larger number of agriculture, domestic, and industrial effluents. The results of the hybrid model were compared to traditional water quality indexes. The main advantage of the proposed method is that it considers flexible boundaries between the linguistic qualifiers used to define the water status, being the belongingness of water quality to the diverse output fuzzy sets or classes provided with percentiles and histograms, which allows classify better the real water condition. The results of this study show that fuzzy inference systems integrated to stochastic non-parametric techniques may be used as complementary tools in water quality indexing methodologies.     

Environmental impact assessment of a ceramic tile supply chain – a case study

The beginning of the twenty-first century saw a surge in the growth of construction industry, particularly the housing sector in India. This led to the growing demand of ceramic tiles. This growth is responsible for large-scale consumption of natural resources and generation of solid waste. The objective of this paper is to assess the environmental impact of vitrified ceramic floor tile supply chain by performing life cycle assessment (LCA) following international standards of ISO 14040 series guidelines. The impact has been determined by conducting a LCA using Umberto NXT software (eco-invent 3.0 database) with ReCiPe endpoint and midpoint methods. It has been found that the manufacturing stage of supply chain is generating highest impact on environment in all the categories. Impact analysis of different input resources/material shows that red oxide used in glaze preparation, electricity in manufacturing, packaging material, distribution by trucks, installation of tiles using concrete and disposal of packaging material are responsible for most of the environmental impact. This study will offer the essential quantitative assessment to recognise the phases and materials which are highly responsible for the degradation of environment so that appropriate interventions by the different stakeholders can be planed.     

Removal of dyes from an artificial textile dye effluent by two agricultural waste residues,corncob and barley husk

The use of a previously untried biosorbent, barley husk, for dye removal is compared to corncob. The effectiveness of adsorption as a means of dye removal has made it an ideal alternative to other more costly treatments. This paper deals with two low-cost, renewable biosorbents, which are agroindustrial by-products, for textile dye removal. Experiments at total dye concentrations of 10, 20, 30, 40, 50, 100, 150, and 200 mg l(-1) were carried out with an artificial effluent consisting of an equal mixture of five textile dyes. The effects of initial dye concentration, biosorbent particle size, dose of biosorbent, effective adsorbance, and dye removal kinetics were examined. One gram (per 100 ml) of < or = 600 microm corncob was found to be effective in removing a high percentage of dyes at a rapid rate (92% in 48 h). One gram of I x 4 mm barley husk was found to be the most effective weight and particle size combination for the removal of dyes (92% in 48 h). The results illustrate how barley husk and corncob are effective biosorbents concerning the removal of textile dyes from effluent.     

Energy and exergy analysis of solar hybrid adsorption refrigeration system

In this paper, performance of a solar hybrid adsorption refrigeration (AR) system is investigated experimentally. Such a system was built and tested under the conditions at National Institute of Technology Calicut, Kerala, India. The hybrid system has been designed for heating 50 l of water from 25 to 90°C as well as cooling 10 l of water from 25 to 10°C. The experimental results demonstrate that the refrigerator has a cooling capacity of 47–78 W with a cycle coefficient of performance (COP) of 0.19 and maximum possible COP of 0.45. In exergy analysis of the system, the irreversibility and exergetic efficiency of each component of the system have been calculated. The exergy analysis reveals that the main source of irreversibility is the adsorbent bed of the AR system, emphasising that the input heat energy is not utilised efficiently due to material constraints. The exergetic efficiencies of condenser, expansion device, evaporator and adsorbent bed are found as 42.3%, 79.8%, 54.7% and 11%, respectively.     

Optimum design and evaluation of hybrid solar/wind/diesel power system for Masirah Island

This paper addresses the requirements of electrical energy for an isolated island of Masirah in Oman. The paper studied the possibility of using sources of renewable energy in combination with current diesel power plant on the island to meet the electrical load demand. There are two renewable energy sources used in this study, solar and wind energy. This study aimed to design and evaluate hybrid solar/wind/diesel/battery system in terms of cost and pollution. By using HOMER software, many simulation analyses have been proposed to find and optimize different technologies that contain wind turbine, solar photovoltaic, and diesel in combination with storage batteries for electrical generation. Four different hybrid power systems were proposed, diesel generators only, wind/diesel/battery, PV/diesel/battery, and PV/wind/diesel/battery. The analysis of the results shows that around 75 % could reduce the cost of energy by using PV/wind/diesel hybrid power system. Also, the greenhouse emission could be reduced by around 25 % compared with these by using diesel generators system that currently utilize in the Masirah Island. The solar/wind/diesel hybrid system is techno-economically viable for Masirah Island.     

Comparative toxicity of solid waste leachates to Daphnia magna

The comparative acute and chronic toxicities of municipal, industrial, coal-fired power plant, and synthetic fuel solid waste leachates to the aquatic invertebrate Daphnia magna were determined. Seventeen leachates were laboratory-derived by extraction with 0.5 N acetic acid, and one, an arsenic-contaminated groundwater, was naturally derived. The acute toxicity 48-h LC₅₀ estimates (concentrations of the test materials that killed 50% of the test organisms in 48 h) ranged from 0.0005% for a dye waste leachate to > 100% (i.e., undiluted) for a coal gasification waste leachate. The most toxic leachates were derived from a dye waste, a plater's waste, and the arsenic-contaminated groundwater, and the least toxic were from a soybean process cake waste and a coal gasification waste. Of the 16 leachates used in the 28 day chronic toxicity tests, only the arsenic-contaminated groundwater and a municipal sewage sludge significantly affected D. magna reproduction. The former material at 1.0% concentration and the sludge at 0.1% caused about an 88% reduction in the numbers of young produced by exposed females compared with controls. Generally, the industrial waste leachates were more toxic than those from the power plant and synthetic fuel wastes. Because its presence in the test materials interfered with interpretation of the results, acetic acid may not be an appropriate extraction medium for preparation of leachates.     

Experimental investigation of solar-powered desiccant cooling system by using composite desiccant “CaCl<Subscript>2</Subscript>/jute”

A solar-powered composite desiccant cooling system has been experimentally investigated. It consists of evacuated tube solar water heater, composite desiccant bed heat exchanger (CDBHE), direct evaporative cooling unit and cooling tower. The composite desiccant material has been synthesized by using iron mesh and jute layer impregnated with calcium chloride solution, and this composite desiccant is placed in shell- and tube-type heat exchanger to make CDBHE. In this desiccant cooling system, the evacuated tube solar water heater is used to produce required hot water for regeneration of composite desiccant material. A cooling tower is used to produce cooling water which is pumped into CDBHE during dehumidification process to remove heat of adsorption. Direct evaporative cooling unit is used to cool the outlet process air of CDBHE. It has been found that the average dehumidification rate increases by 54.1 % when using circulating cooling water. The COP_th of desiccant cooling system has been found to be 0.46 with a cooling capacity of 353.8 W.     

Treatment of wastewater from an oil and soap factory via dissolved air flotation

Highly polluted wastewater from oil and soap factories has been treated via coagulation followed by dissolved air flotation. Ferric chloride and alum were used as coagulants at their optimal pH value and dosages. Factors affecting the efficiency of the dissolved air flotation process, such as detention time and air-solids ratio, have been investigated. The results obtained showed that this process proved to be very efficient in removing the organic contaminants. The oil removal value reached 99.1%. The COD, BOD, and turbidity removal achieved 94.5%, 96% and 99.3%, respectively.     

Assessment of alpha activity of building materials commonly used in West Bengal, India

This paper, reports for the first time, an extensive study of alpha activity of all widely used building materials (plaster of Paris, stone chips, marble, white cement, mosaic stone, limestone, sand, granite, cement brick, asbestos, red brick, cement tile, ceramic tile and ceramics) in West Bengal, India. The alpha activities have been measured using Solid State Nuclear Track Detector (SSNTD), a very sensitive detector for alpha particles. The samples were collected from local markets of Kolkata. The measured average alpha activities ranged from 22.7+/-2.5 to 590.6+/-16.8Bqkg(-1). The alpha activity of ceramic tiles was highest and provides additional data to estimate the effect of environmental radiation exposure on human health.     

Diclofenac and its transformation products: Environmental occurrence and toxicity - A review

Diclofenac (DCF) is a prevalent anti-inflammatory drug used throughout the world. Intensive researches carried out in the past few decades have confirmed the global ubiquity of DCF in various environmental compartments. Its frequent occurrence in freshwater environments and its potential toxicity towards several organisms such as fish and mussels makes DCF an emerging environmental contaminant. At typical detected environmental concentrations, the drug does not exhibit toxic effects towards living organisms, albeit chronic exposure may lead to severe effects. For DCF, about 30–70% removal has been obtained through the conventional treatment system in wastewater treatment plant being the major primary sink. Thus, the untreated DCF will pass to surface water. DCF can interact with other inorganic contaminants in the environment particularly in wastewater treatment plant, such as metals, organic contaminants and even with DCF metabolites. This process may lead to the creation of another possible emerging contaminant. In the present context, environmental fate of DCF in different compartments such as soil and water has been addressed with an overview of current treatment methods. In addition, the toxicity concerns regarding DCF in aquatic as well as terrestrial environment along with an introduction to the metabolites of DCF through consumption as well as abiotic degradation routes are also discussed. Further studies are required to better assess the fate and toxicological effects of DCF and its metabolites and must consider the possible interaction of DCF with other contaminants to develop an effective treatment method for DCF and its traces.