Showing papers in "Environmental Technology in 1997"
TL;DR: A low-cost inorganic acid-activated clay was used as an adsorbent for the adsorption of six dyes (two basic, one acidic, one disperse, one direct dye, and one reactive) from aqueous solutions as discussed by the authors.
Abstract: A low-cost inorganic acid-activated clay was used as adsorbent for the adsorption of six dyes (two basic, one acidic, one disperse, one direct dye, and one reactive) from aqueous solutions. The adsorption capacity was comparatively high for basic dyes and was lower for disperse, direct, and reactive dyes. The equilibrium data could be well described by the Langmuir equation over the entire range of concentration (50∼500 mg dm−3). In addition, the effect of temperature on the adsorption was examined and the thermodynamic data were determined. Based on the adsorption capacity only, it was generally shown that activated clay was more effective compared to other commonly used adsorbents.
218 citations
TL;DR: In this paper, the unicellular green alga Chlorella vulgaris was immobilized in two polysaccharide matrices, namely carrageenan and alginate, in form of spherical beads and was used to treat primary settled domestic wastewater in order to eliminate the harvesting limitation.
Abstract: Excess nutrients (N and P) discharged from sewage treatment plants has been identified as one of the major pollution point sources leading to eutrophication in the coastal water. Microalgae have been demonstrated as excellent nutrients stripper from the sewage. However, its application is limited by its harvesting problem at the end of the treatment process. In this study, the unicellular green alga Chlorella vulgaris was immobilized in two polysaccharide matrices, namely carrageenan and alginate, in form of spherical beads and was used to treat primary settled domestic wastewater in order to eliminate the harvesting limitation. Growth of the algal cells in the matrices was not inhibited and the exponential growth rates were 0.420, 0.441 and 0.417 day−1 for the free, carrageenan and alginate immobilized cells, respectively. Although algal cells in the carrageenan and alginate matrix exhibited a longer lag period (2 and 3 days, respectively) than the free cells (1 day), the immobilized cells were more meta...
177 citations
TL;DR: In this article, an investigation of the treatability of a commonly used azo dye in the textile dyeing and finishing operations, Reactive Black 5, by an advanced oxidation process, to achieve an acceptable degree of destruction of the target pollutant was performed.
Abstract: Treatment of textile dyeing wastewaters by conventional methods have recently proved to be inadequate. Such methods consist of various combinations of biological, physical and chemical methods including coagulation/flocculation and carbon adsorption. The study described herein is an investigation of the treatability of a commonly used azo dye in the textile dyeing and finishing operations, Reactive Black 5, by an advanced oxidation process, to achieve an acceptable degree of destruction of the target pollutant. The research was focused on a UV/H2O2 oxidation process, where the individual effects of H2O2 concentration, initial dye concentration, and alkalinity under neutral pH on the pseudo-first order reaction rate constant were investigated. Relative removal rates of color with respect to chemical oxygen demand and total organic carbon in dye-distilled water mixture were compared; effect of bicarbonate alkalinity at neutral pH was tested. Pseudo-first order reaction rate constants and electrical energy r...
160 citations
TL;DR: In this paper, the degradation kinetics of eleven azo dyes by TiO2/UV were studied using a Rayonet photoreactor, and the experimental results indicate that positive hole oxidation is the dominant mechanism contributing to the degradation of neutral or negatively charged dyes at pH 3.
Abstract: Photocatalytic degradation kinetics of eleven azo dyes by TiO2/UV was studied using a Rayonet photoreactor. The degradation kinetics of azo dyes seems to be significantly influenced by their electrical nature, the number of azo bonds present in a dye molecule, and type of auxiliary groups attached to the azo bond. For example, trisazo dyes were the most difficult to degrade, and monoazo dyes were the most readily degradable, while the disazo dyes were in the middle range. The experimental results indicate that positive hole oxidation is the dominant mechanism contributing to the degradation of neutral or negatively charged dyes at pH 3. The degradation kinetics of positively charged basic dyes may be through reduction by electrons in the conduction bands of the excited TiO2 particles. On the other hand, hydroxyl radicals should be the major oxidation species at pH greater than 7. The pH effects on the degradation kinetics of different dyes may be due to the intrinsic reactivities of the neutral and ionize...
150 citations
TL;DR: In this article, an increasing flux of materials with time and an increased areal coverage of the benthos appears to be an increasing phenomenon in the marine environment following its use in agricultural, industrial and social activities.
Abstract: Plastic debris accumulates in the marine environment following its use in agricultural, industrial and social activities. Its ultimate fate is accomodation in sediments where it may persist for times up to centuries or longer. There appears to be an increasing flux of materials with time and an increased areal coverage of the benthos. Impacts upon bottom organisms can take many forms. Systematic monitoring tactics for the extent of seafloor coverage by plastics are yet to be incorporated into national programs.
138 citations
TL;DR: This paper presents a review of mathematical models designed to simulate leachate generation and transport in municipal solid waste landfills and finds that they become increasingly useful as more field data are obtained and used for calibration and validation purposes.
Abstract: Numerous mathematical models have been developed to simulate processes governing leachate occurrence and behaviour in landfills. The emphasis of these models have generally been on estimating leachate quantity and quality in order to control its associated environmental impacts, particularly on ground and surface water pollution, enhance methanogenesis and landfill stabilization, and provide guidance in the design of leachate control, recirculation and collection systems. These models have been successful to a limited extent, more in estimating leachate quantity than its composition, because of inherent uncertainties associated with estimating model parameters that can adequately describe the complex biological, chemical, and physical processes in landfills. They become increasingly useful as more field data are obtained and used for calibration and validation purposes. This paper presents a review of mathematical models designed to simulate leachate generation and transport in municipal solid waste landf...
121 citations
TL;DR: In this paper, the stochastic properties of Fenton's reagent in the oxidation of dichloroethylene (DCE), trichloro methylene (TCE), TCE, Tetra-CE, and DCEA were investigated and the theoretical optimal ratio between H2O2 and Fe2+ was found to be 11.
Abstract: The stoichiometry of Fenton's reagent in the oxidation of dichloroethylene (DCE), trichloroethylene (TCE), tetrachloroethylene (tetra-CE), and dichloroethane (DCEA) was investigated. The theoretical optimal ratio between H2O2 and Fe2+ is found to be 11. However, the experimentally determined optimal ratio between H2O2 and Fe2+ ranged from 5 to 11 at optimal pH of 3.5. The amount of H2O2 required for a specific percentage removal of the organic compounds depends upon the initial organic concentration to be oxidized. The accumulation of chloride ion released also depends upon the initial organic substance concentrations. The typical percentage removal of organic compounds and percentage release of chloride ion were reported at 100%, 70%, 50%, 40%, 30%, 20%, 10%, and 1%. The amount of H2O2 required to achieve a certain percentage removal follows the order of TCE < Tetra-CE < DCE << DCEA. However, the amount of chloride ion detected at a constant concentration of H2O2 follows the order of DCEA << DCE < TCE < ...
111 citations
TL;DR: In this article, the ability of rice husk to remove chromium, zinc, copper and cadmium from waste water has been investigated, and several parameters that can affect metals uptake such as particle size, pH and temperature were described.
Abstract: The ability of rice husk to remove chromium, zinc, copper and cadmium from waste water has been investigated. Several parameters that can affect metals uptake such as particle size, pH and temperature were described. At the optimal conditions, the chromium, zinc, copper and cadmium ions removal from aqueous solution are 79, 85, 80 and 85%, respectively. After the adsorption of metal ions, the analyte retained in the husk could be recovered almost completely by eluting with dilute hydrochloric acid solution. The method was applied to removal chromium, zinc, copper and cadmium present in the laboratory waste water.
94 citations
TL;DR: In this paper, bottom sediments of the central area of the Venice Lagoon (Italy) and some lagoon canals, chosen as an anaerobic reference environment, were analyzed by a sequential extraction procedure for Cr, Cu, Ni, Pb, Zn, Mn, and Fe.
Abstract: Bottom sediments of the central area of the Venice Lagoon (Italy) and some lagoon canals, chosen as an anaerobic reference environment, were analyzed by a sequential extraction procedure for Cr, Cu, Ni, Pb, Zn, Mn, and Fe. Bio-Available Phases (BAPs) and Non-Bio-Available Phases (NBAPs) have been determined in the Malamocco-Marghera Canal, to define the significant level of heavy metal contamination of the sediment. Relationships among metal distributions with Fe/Mn oxides/hydroxides and sulfides were determined in both environments, using statistical methods. The central lagoon area shows low pollution and a balanced influence of all the sediment components in the metal complexing processes, mostly due to the manganese and iron matrices. The inner canals are very polluted with heavy metals strongly bonded to H2S that form highly insoluble compounds, as demostrated through the correlation analysis. The authors suggest different procedures for lagoon restoration due to the different sediment behaviours, i....
87 citations
TL;DR: In this article, surface dust and soil samples were collected from seven selected playgrounds with different levels of traffic volume and urban development for the determination of total Cd, Cu, Pb and Zn concentrations.
Abstract: Due to the scarcity of land in Hong Kong, most of the children playgrounds are being built on marginal lands which may be subjected to serious atmospheric emission. Hence, children playing in these playgrounds are exposed to a potential health risk. The aim of this study was to evaluate heavy metal pollution in children playgrounds using surface dusts and soils as indicators. Surface dust and soil samples were collected from seven selected playgrounds with different levels of traffic volume and urban development for the determination of total Cd, Cu, Pb and Zn concentrations. The mean Cd, Cu, Pb and Zn concentrations of surface dusts were 2.63, 201, 302 and 1517 mg kg−1 respectively, whereas for soils they were 2.30, 28.4, 195 and 237 mg kg−1. The results indicated elevated concentrations of Cd, Cu, Pb and Zn in both dust and soil samples especially for those samples collected from busy commercial and industrial areas i.e., Mei Foo, Tsim Sha Tsui and North Point. Surface dusts were enriched relative to so...
84 citations
TL;DR: In this paper, coal fly ash (FA) and lagoon ash (LA) were mixed with dewatered sludge at 0, 10 and 25% w/w, and the mixtures were composted for 100 days in laboratory batch reactors.
Abstract: Alkaline coal ash residues produced from a coal-fired power plant were co-composted with sewage sludge to evaluate it's effect on heavy metal availability and the biological process of composting. Coal fly ash (FA) and lagoon ash (LA) were mixed with dewatered sludge at 0, 10 and 25% w/w, and the mixtures were composted for 100 days in laboratory batch reactors. The changes in pH, electrical conductivity (EC), CO2 production, microbial population, soluble and extractable heavy metal contents were measured during the composting period. Following an initial increase, pH started to decrease from day 7 onward till the end of the composting period for all treatments. Sludge with coal fly ash amendment had a higher pH and EC than those of the control and LA-sludge composts. Increasing fly ash amendment levels resulted in a significant reduction in DTPA-extractable Cd, Cu, Zn, Mn and Pb contents of the FA-sludge composts while the reduction was less obvious in the LA-sludge composts. No significant difference in...
TL;DR: In this article, the effect of thermal pretreatment on acidogenesis and methanogenesis during anaerobic digestion of waste activated sludge (WAS) was investigated, and the pretreatment temperature ranged from 60°C to 120°C and the holding times were 5, 10, 20, 30 and 60 minutes.
Abstract: The effect of thermal pretreatment on hydrolysis, acidogenesis and methanogenesis during anaerobic digestion of waste activated sludge (WAS) was investigated. Pretreatment temperature of WAS ranged from 60°C to 120°C and the holding times were 5, 10, 20, 30 and 60 minutes. WAS was fed into the laboratory-scale anaerobic digesters, after thermal pretreatment. The preliminary conversion step (such as death/lysis of cell and hydrolysis of WAS) was promoted through thermal pretreatment, and consequently efficiencies of acidogenic and methanogenic steps were also markedly enhanced. Thermal pretreatment at lower temperature resulted in a significant increase in methane generation and destruction of organic matter. At 60°C, when hydraulic retention time (HRT) was 8 days, an increase in approximately 52.1 % in methane generation (ml. l−1. d−1) and 26.6% in organic matter destruction was achieved (Series-I). In addition, HRT necessary for anaerobic digestion could be reduced by thermal pretreatment.
TL;DR: In this article, the order of surface affinity for Ni, followed the sequence: MnO2 > Fe(OH)3 > humic acid ∼ montmorillonite > CaCO3.
Abstract: Nickel adsorption on 5 different solid phases: amorphous-MnO2, amorphous-Fe(OH)3, CaCO3, humic acid and montmorillonite were studied. Comparative studies at pH: 6.7–8.4, using a conditional stability constant, showed that the order of surface affinity for Ni, followed the sequence: MnO2 > Fe(OH)3 > humic acid ∼ montmorillonite > CaCO3. MnO2 and Fe(OH)3 are therefore proposed as the major sinks for Ni in fresh water systems. Adsorption on montmorillonite and humic acid were described as linear. Adsorption on MnO2 was described by a Langmuir isotherm, whereas adsorption on Fe(OH)3 was described by the Redlich-Peterson model. Increasing the ionic strength decreases Ni adsorption on MnO2 and montmorillonite, whereas adsorption on Fe(OH)3 was unaffected. Adsorption on Fe(OH)3 was strongly effected by pH, in the region of 7.0 – 8.0, adsorption on MnO2 was unaffected, in the same region. The speciation calculation of Ni(II) in the pH region of 7.0 – 8.0, indicates that Ni2+ dominates at pH < 7.7, and NiCO3 0 dom...
TL;DR: In this paper, the authors used a common brown marine algae (Ecklonia radiata) for the development of an efficient biosorbent material for Cu2+ removal from waste water.
Abstract: Experimental studies showed that a common brown marine algae (Ecklonia radiata) can be used for the development of an efficient biosorbent material for Cu2+ removal from waste water. At pH 5.0, the uptake capacity of E. radiata for copper is 1.11 mmol g−1. The adsorption of copper increases as pH increases and reaches a plateau at pH 5. The copper uptake process was rapid, with 90% of the adsorption completed within 15 minutes. Presence of light metal ions in solution did not affect copper adsorption significantly. The presence of 5 mM of EDTA in solution completely inhibited the metal uptake while the effect of acetate, nitrate and chloride on metal uptake was marginal even at 20 mM concentrations of these ions. The dominant mechanism of copper biosorption is ion exchange involving Ca2+ and Mg2+ counter ions present in the algal cells. The feasibility of removing copper using the biosorbent in a packed bed system was also examined.
TL;DR: In this article, the metal bearing lignin upon a wash with 10% sulfuric acid results in elution of copious amounts of metal, which can be precipitated by addition of alkali resulting in the metal recovery.
Abstract: Lignin obtained as a byproduct from the paper and pulp industry in the form of powder and beads (obtained upon polymerization) was used for the removal of trivalent and hexavalent chromium, lead and zinc from aqueous solutions. Metal uptake as a function of time and temperature was determined. It appears that oxygen functionalities such as phenols present in lignin may serve as sites for the metal cation exchange. The metal bearing lignin upon a wash with 10% sulfuric acid results in elution of copious amounts of metal. The dissolved metals in a concentrated form in the acid can be precipitated by addition of alkali resulting in the metal recovery.
TL;DR: Assessment of the length of time spent inside the home for each family member in a sample population in the southwest of England indicated that mothers, fathers and young infants spent an average of 18.4 hours per day in the home, while in winter, infants spent longer in theHome than in the summer months.
Abstract: The study objective was to assess the length of time spent inside the home for each family member in a sample population in the southwest of England. Such information is vital in any study concerned with exposure to pollutants in the home environment, in order to calculate a dose response for a specific health effect in the individual. The design was a longitudinal observational study which started in pregnancy and was carried out for one week in each month over a 12 month period. The setting was a sample of 170 families within the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC) where indoor air pollutants were being measured. The number of hours spent in the home each day for each family member was obtained from self-report using weekly diary sheets‥ The results indicated that mothers, fathers and young infants spent an average of 18.4 (76.7%), 14.7 (61.3%) and 19.3 (80.4%) hours per day, respectively, in the home. In winter, infants spent longer in the home than in the summer months. At week...
TL;DR: Promotion of microorganism species that have a high maintenance energy by the provision of support matrices or increasing sludge retention time has the potential to prevent biomass accumulation.
Abstract: The activated sludge process is common for the treatment of wastewater. The process uses a mixed culture of microorganisms that degrade the wastewater aerobically producing carbon dioxide, water and new biomass. Some of the biomass produced is recycled and the rest requires disposal. Changing legislation, rising costs and increasing sludge production have caused a shift in emphasis from volume of wastewater turnover and maximal BOD removal to minimisation of the biomass produced. Low to zero yields are possible by extended aeration type processes and raising process operating temperature but these involve large energy inputs. Manipulation of the activated sludge process to promote the growth of protozoa, nematodes, rotifers or oligochaeta reduces biomass production by predation of the microorganisms. Promotion of microorganism species that have a high maintenance energy by the provision of support matrices or increasing sludge retention time has the potential to prevent biomass accumulation. Uncoupling of...
TL;DR: Discontinuous coupling of the ceramic microfiltration to an anaerobic primary sludge digester increased the total solids concentration of the reactor, but the reactor efficiency was not improved in terms of volumetric loading rates.
Abstract: Anaerobic digesters are widely employed at wastewater treatment works for the destruction of volatile solids present in settled primary and waste activated sludge. Membrane separation techniques afford an effective method to separate solids from the digester suspension and recycle them to the digester. A commercially available polymer ultrafiltration and ceramic microfiltration membrane were tested for filtration of anaerobic sludge. For the filtration of suspensions with similar solids concentrations, the short term fluxes reached in ceramic microfiltration (200 tot 250 l m−2 h−1) were on the average tenfold those for polymer ultrafiltration (25 l m−2 h−1). The permeate quality of the ceramic microfiltration and polymer ultrafiltration was similar. Discontinuous coupling of the ceramic microfiltration to an anaerobic primary sludge digester increased the total solids concentration of the reactor from 22 g l−1 to 35 g l−1, but the reactor efficiency was not improved in terms of volumetric loading rates. T...
TL;DR: In this article, the authors showed that there are high concentrations of copper, zinc and lead in sediment and gastropods sampled close to the pig farm but this reduced about 100 fold towards the river mouth.
Abstract: Pig farming in Malaysia has become more active over the years as it yields high annual turnover of estimated 2 billion Malaysian Ringgit. The increase in pig farming activities has brought about changes in environmental qualities in the forms of organic matter pollution and trace metals pollution. Many earlier studies have indicated the presence of high levels of trace metals in sediment from estuarine receiving effluent from pig farming. This study shows that there are high concentrations of copper, zinc and lead in sediment and gastropods sampled close to the pig farm but this reduced about 100 fold towards the river mouth. The ranges of trace metals in sediment studied are 4–670 µg g−1 for Cu, 4–550 µg g1 for Zn, 3.4–46.5 µg g−1 for Pb and 0.1–2.1 µg g−1 for Cd. While in molluscs, the levels range from 6–15 µg g−1 for Cu, 18–47 µg g−1 for Zn, 7–17 µg g−1 for Pb and 0.1–2.5 µg g−1 for Cd. The results also show that 60 to 70 percent of the Cu, Zn and Pb concentration in the sediments are from anthrophoge...
TL;DR: In this article, a synthetic layered double hydroxide (LDH: Mg-Al-CO3) was heated to 560 °C for 3 h in air, and the resulting calcined LDH (1.00 g dm−3) is used in the sorption study of aquatic CrO4 2− (concentration range: 1.0 × 10−3 − 5.0× 10 −3 mol dm −3) under CO2 free atmosphere.
Abstract: A synthetic layered double hydroxide (LDH: Mg-Al-CO3) was heated to 560 °C for 3 h in air, and the resulting calcined LDH (1.00 g dm−3) was used in the sorption study of aquatic CrO4 2− (concentration range: 1.0 × 10−3 − 5.0 × 10−3 mol dm−3) under CO2 free atmosphere. Reconstructed LDH containing intercalated CrO4 2− between interlayers was formed and this was confirmed by X-ray powder diffraction (XRD), 27Al MAS NMR, FT-IR and UV/VIS spectroscopies. The sorption of CrO4 2− by LDH resulted in increased hydroxide concentration, suggesting that ion-exchange based mechanism is involved: LDH + CrO4 2− = LDH(CrO4)+ 2OH−. The equilibrium constant (K), for sorption of CrO4 2−, based on ion-exchange with two OH− per unit LDH (composition: Mg6Al2(OH)18), of 3.1 ± 0.4 mol dm−3 was evaluated by a non-linear least squares fit procedure.
TL;DR: The occurrence of imposex was related to the distance to the main shipping routes, but not to water depth or diet of the investigated gastropod, and some gastropods affected by imposex were found within shellfish culture plots and on the fish markets.
Abstract: The study aimed to survey the presence and extent of imposex in sublittoral gastropods in relation to shipping traffic in the Gulf of Thailand and the Strait of Malacca. Females of several species of meso- and neogastropods showed a high incidence (up to 100%) of imposex at several sites. These females had a penis of variable size and a vas deferens (sperm duct), two typically male characteristics. Imposex has been found to be caused by TBT from antifouling paints. The occurrence of imposex was related to the distance to the main shipping routes, but not to water depth or diet of the investigated gastropods. TBT remains active far away from the target area and influences non-target animals. Some gastropods affected by imposex were found within shellfish culture plots and on the fish markets.
TL;DR: In this article, the authors evaluated the qualitative and quantitative characteristics of emissions from hot asphalts and bitumen that included reactive organic gases (ROGs) and particulate matter (PM).
Abstract: Asphalts are widely used in paving of roads, and water-proof sealing of building roofs, tanks and containers. This study evaluated the qualitative and quantitative characteristics of emissions from hot asphalts and bitumen that included reactive organic gases (ROGs) and particulate matter (PM). The ROGs consisted of several volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs) of environmental concern. The latter included several polynuclear aromatic hydrocarbons (PAHs) and alkanes. An experimental laboratory testing, sampling and analysis protocol was developed for obtaining efficient and cost-effective a priori estimates of asphalt emissions. The investigation identified and quantified the emissions of organics and evaluated the magnitudes as well as particle size distributions of PM emissions. The study demonstrated that the asphalt type and temperature greatly affected the emission characteristics, and that several organic compounds emitted were partitioned between gaseous and...
TL;DR: In this article, the authors used 4-aminoantipyrine as colouring agent and detected at 506 nm using visible spectrophotometer spectronic 21 to remove phenol from waste water by using rice husk.
Abstract: The study of the removal of phenol from waste water by using rice husk has been carried out. Phenol concentration was measured by using 4-aminoantipyrine as colouring agent and detected at 506 nm using visible spectrophotometer spectronic 21. Several parameters that can affect phenol uptake such as particle size, pH and concentration of reagents were described. At the optimal conditions, phenol substance removal from aqueous solution is 92%. The method was applied to removal phenol substance present in plywood industry and hospital waste waters.
TL;DR: In this paper, the authors report work on batch equilibrium and kinetic laboratory studies conducted to establish the efficiency of ammonium ion removal from wastewater effluent using a natural zeolite from the Werris Creek region in New South Wales.
Abstract: The removal of nutrients from wastewater is becoming increasingly important throughout the world. This paper reports work on batch equilibrium and kinetic laboratory studies conducted to establish the efficiency of ammonium ion removal from wastewater effluent using a natural zeolite from the Werris Creek region in New South Wales. Experiments were conducted using samples of secondary treated domestic wastewater effluent and synthetic wastewater (ammonium chloride solution). The amount of powdered zeolite added ranged from 5 to 50 g 1−1. Experiments were undertaken to characterise the zeolite in terms of its ion exchange capacity and rate of ammonium ion adsorption under various conditions. The effects of the amount of zeolite added, initial ammonium ion concentration and pH of the sample on ammonium ion removal were studied. Results were analysed using existing ion exchange models. The results indicate that a significant reduction of N as NH4 (up to 80%) can be achieved using batchwise addition of powder...
TL;DR: In this paper, the mesophilic and thermophilic anaerobic biotreatment processes treating a common substrate in laboratory scale CSTRs were compared in terms of their effluent quality.
Abstract: This study compares the mesophilic and thermophilic anaerobic biotreatment processes treating a common substrate in laboratory scale CSTRs in terms of their effluent quality The improvement in the performance and the effluent quality of these systems by temperature-staged processes, ie, mesophilic and thermophilic reactors in series, were also investigated The data presented in this paper showed that thermophilic anaerobic microorganisms had a 26% higher initial substrate utilization rates (SUR0) for COD as compared to the mesophilic ones Mesophilic bacteria, on the other hand, produced a better quality effluent as indicated by lower effluent soluble COD concentrations The results also indicated that the poor effluent quality of thermophilic anaerobic processes can be improved by a temperature-staged process configuration with a mesophilic secondary unit As high as 95% COD removal rates were achieved by the thermophilic-mesophilic staged process at an organic rate of 2 gl−1day−1 In a temperature
TL;DR: Five neogastropod species collected from a tributyltin (TBT)-polluted site near the port of Faro within the Ria Formosa on the Algarve coast of Portugal were examined in April 1996 for ‘imposex’ and no female of the fifth showed any sign of being similarly masculinised.
Abstract: Five neogastropod species collected from a tributyltin (TBT)-polluted site near the port of Faro within the Ria Formosa on the Algarve coast of Portugal were examined in April 1996 for ‘imposex’. All females of four of these species - Hexaplex trunculus, Ocenebra erinacea, Ocinebrina aciculata (all Muricidae) and Nassarius reticulatus (Nassariidae) - exhibited the characteristic development of male sex organs (penis plus vas deferens) but no female of the fifth - Columbella rustica (Columbellidae) - showed any sign of being similarly masculinised. Only two neogastropods have been previously described as lacking the imposex response to TBT exposure. These two species, along with C. rustica, can be considered as ‘zero-response’ forms. Other species can be grouped according to the maximum level of masculinisation they exhibit: level I species develop just a penis and vas deferens; in level II forms oviduct structure and function are disrupted, and in level III species ovary transformation to testis is observ...
TL;DR: In this article, the use of a sequence of biological filters; anaerobic followed by aerobic; to treat a simulated textile waste was examined and two dyes were used in its formulation, Acid Yellow 17 and Basic Red.
Abstract: Textile wastes can be difficult to treat and it is not uncommon for dye residues to impart colour and “hard” COD to the treated effluent. This paper examines the use of a sequence of biological filters; anaerobic followed by aerobic; to treat a simulated textile waste. Two dyes were used in its formulation, Acid Yellow 17 and Basic Red. Acid Yellow (25 mgl−1) was not removed by the sequence of filters and subsequent batch tests showed that it was not sorbed onto the biomass. The anaerobic filter converted some 80% of the incoming COD (2000 mgl−1) to volatile fatty acids and the overall process removed > 92% of the COD and > 99% of the Basic Red (200 mgl−1). The capability of the anaerobic filter to withstand shock loads was also examined. Of these, only the high flow rates associated with the hydraulic shock caused serious disruption to the operation of the process.
TL;DR: In this paper, an intensive composting process was employed to treat olive mill wastewater, where a mixture of extracted olive press cake and olive tree leaves was used as the solid substrate for composting.
Abstract: The evaporative capacity of an intensive composting process was employed to treat olive mill wastewater. A mixture of extracted olive press cake and olive tree leaves was used as the solid substrate for composting. The olive mill wastewater was added to the composting mass to replenish the water loss during processing in a pilot-scale topless static container reactor. The salinity content of the compost was the factor restricting the treatment of olive mill wastewater by the process. The rate of olive mill wastewater treatment achieved in this study was 2.1 1/kg starting solid substrate (dry weight -d.w.). The cumulative moisture and volatile solids content reduction during the temperature-induced aeration period of the process was 19 and 45%, respectively.
TL;DR: In this article, the suitability of advanced primary treatment (APT) for wastewater treatment in a very arid region of 85, 000 ha of poor quality soils is analyzed.
Abstract: Where there is a variation in quality and quantity of sewage, advanced primary treatment (APT) is a useful means of treating wastewater. Mexico City, which has a combined sewage network and variations of flow rates ranging from 45 m3 s−1 during the dry season to 300 m3 s−1 during the rainy season, is just such a case. The data presented in this paper show the suitability of APT for Mexico City, enabling the continued reuse of such waters in a very arid region of 85 000 ha of poor quality soils. Given the agricultural nature of the irrigation area, the objective of this treatment is determined mainly by health requirements (helminth eggs and bacterial removal) instead of the organic and nutrient contents of the effluent, which are needed for the agricultural purposes of the irrigated area. From tested conditions, alum in a dose of 100 mg l−1 and 0.2 mg l−1 of an anionic polymer produce an effluent with a helminth egg content of <1 egg l−1, which allows its use for irrigation for any kind of crop. Removal e...
TL;DR: In this paper, the authors used dissolved oxygen microelectrodes to determine the thickness of the concentration boundary layer and the hydrodynamic boundary layer above a biofilm, and found that the thickness varied from about 200 µm to about 800 µm, depending on the bulk liquid flow velocity above the biofilm.
Abstract: The thicknesses of the concentration boundary layer and the hydrodynamic boundary layer above a biofilm are critical variables in the overall performance of any biofilm system. Their values determine the degree of advective transport near the biofilm surface and the distance over which molecules must move by diffusion alone. Two factors which are thought to affect the thickness of these in a biofilm system are the velocity or Reynolds Number of the bulk fluid, and the roughness of the biofilm surface. This study shows experimentally the concentration boundary thickness above biofilms of varying roughness under various flow regimes. Using dissolved oxygen microelectrodes to determine the CBL thickness, it was found that the thickness varied from about 200 µm to about 800 µm, depending on the bulk liquid flow velocity above the biofilm. The roughness of the biofilm surface appeared to have minimal effect on CBL thickness. The study also shows, using particle image velocimetry, that the hydrodynamic boundary...