Showing papers in "Environmental Technology in 2005"
TL;DR: A novel method of pH adjustment applying NH4 +-N buffer was established and indicated that adjusting pH to 7 in the acidogenic stage in the two-phase anaerobic digestion process would increase both TS loading rate and recovery of biological energy.
Abstract: Batch and semi-continuous experiments were carried out to determine the effect of pH on hydrolysis and acidogenesis of kitchen wastes in the two-phase anaerobic digestion. The results of the batch experiment showed pH adjustment could improve both hydrolysis and acidogenesis rates of kitchen wastes. Compared with pH at 5, 9 and 11, pH 7 provided an optimum working condition for anaerobic digestion of kitchen wastes. At pH 7, about 86% of the total organic carbon (TOC) and 82% of chemical oxygen demand (COD) were solubilized and the maximum volatile fatty acid (VFA) concentration of 36g l−1 was achieved on the fourth day. The total VFA yield was 0.27 g (g total solid (TS))−1, which almost doubled the yield without pH adjustment (0.15 g (g TS)−1). The acidified products with lower concentration of lactic acid were more favorable to the subsequent methanogenesis. At pH 7, most of the protein was degraded into ammonia nitrogen (NH4 +-N), resulting in additional buffer of acidified liquid. According to this, a...
233 citations
TL;DR: It is demonstrated that distinctive community patterns from manure composts could be rapidly generated using T-RFLP analysis, and the succession of peaks in combination of increasing and decreasing peak heights at different stage of composting indicates the high potential of T- RFLP technique to monitor the dynamics of microbial communities, and their variation qualitatively and quantitatively.
Abstract: Compost processing is assumed to be related to the microbial communities present. However, methods that will evaluate these relationships are not well understood. In this study, terminal restriction fragment length polymorphism (T-RFLP) analysis was used to evaluate the diversity of PCR-amplified bacterial 16S and fungal 18S rDNA communities from manure composts at different stages of composting (initial [day 0], thermophilic [day 24], and mature [day 104]). Results showed that the bacterial and fungal community profiles changed over the composting process, with bacterial communities showing a higher diversity compared with the fungal communities. During the thermophilic stage (day 24), the diversity of the bacterial communities increased, while the fungal communities decreased. As the compost reached maturity (day 104), a reverse pattern was observed between the diversity of bacterial and fungal communities. That is, the 18S rDNA T-RFLP-based diversity indices increased, while the 16S rDNA T-RFLP-based diversity decreased. Differences in temperature profiles at different stages of composting impacted the chemical properties and the diversity of the microbial communities. The day 104 compost (mature) had lower water, organic matter and C contents and higher C and OM loss compared with the day 0 (initial) and day 24 (thermophilic) composts, which affected the diversity of the microbial communities. The results presented here demonstrated that distinctive community patterns from manure composts could be rapidly generated using T-RFLP analysis. The succession of peaks in combination of increasing and decreasing peak heights at different stage of composting indicates the high potential of T-RFLP technique to monitor the dynamics of microbial communities, and their variation qualitatively and quantitatively.
93 citations
TL;DR: According to different measuring techniques used in the study, the ferric sulphate coagulation was 10 % more efficient in the overall organic matter removal compared to the aluminium sulphateCoagulation.
Abstract: The removal of natural organic matter by coagulation in the drinking water treatment train was studied for a period of two years. In the middle of the study, the coagulation/flotation process was modified by replacing the aluminium sulphate by ferric sulphate. At the same time, the filtration unit was enhanced by adding a sand filter unit before the activated carbon filtration and by changing new carbons on to the activated carbon filters. A special aim was to compare the efficiency of the aluminium and ferric coagulants in the organic matter removal by several methods, including high-performance size-exclusion chromatography. A comparison of quantity and characteristics of organic matter in treated water before and after treatment process modification provided an insight into process performance. Approximately 95% of high molar mass organic substances were removed in the process with both coagulation agents. The greatest difference between the coagulants occurred in the removal of organic matter having m...
85 citations
TL;DR: A 2(5-1) fractional factorial design was conducted for the biosorption of pentachlorophenol using Aspergillus niger biomass and showed that type of biomass and pH had a larger impact on the removal of PCP.
Abstract: A 2(5-1) fractional factorial design was conducted for the biosorption of pentachlorophenol (PCP) using Aspergillus niger biomass. Effects of several factors on the percentage removal of PCP from aqueous solutions were evaluated. These factors were as follows: type of biomass (autoclaved- chemically modified); pH (3-11); concentration (1-10 mgl−1); temperature (6-32°C); and dissolved oxygen (2.5-20 mgl−1). Time of shaking (equilibrium time), volume of the solution and mass of biomass were kept constant. The results showed that type of biomass and pH had a larger impact on the removal of PCP. Concentration of PCP in the aqueous solution, temperature, and dissolved oxygen only marginally affected the removal efficiency of PCP.
79 citations
TL;DR: A relation between inhibition in shock-load and inhibition in continuous mode can be determined and the procedure herein proposed allows performing off-line bioassays on real biological plants, to assess in real time the inhibiting effect of the incoming wastewater before it reaches the activated sludge reactor.
Abstract: Industrial wastewater often has a high salt content, due to specific factories and to the use of seawater in coastal areas. Once it has reached the activated sludge treatment, saline wastewater may cause biomass inhibition and dramatic loss in purification efficiency. In the present work, the inhibiting effect of saline influent was experimentally evaluated through respirometric tests on samples of the incoming wastewater. Activated sludge was grown in bench-scale continuous flow stirred tank reactor (CFSTR), supplied with synthetic wastewater. Synthetic saline wastewater was prepared using sodium chloride and sodium sulphate at different concentrations. Samples of mixed liquor were drawn from the CFSTR reactor and fed with saline wastewater in shock-load or in continuous mode, then respiration activity and carbon removal yield were evaluated. In batch mode (shock-load), salt/biomass ratios between 0.37 and 30.7 gsalt gvss(-1) gave respiration inhibition between 4% and 84% respectively. The respirometry bioassay required a short response time and the values of respiration inhibition predicted the loss in carbon removal efficiency with a good accuracy. In continuous mode, for salt/biomass ratio of 35.5 gsaltgvss(-1), respiration inhibition of 81% was obtained. This work showed that a relation between inhibition in shock-load and inhibition in continuous mode can be determined, therefore, the procedure herein proposed allows performing offline bioassays on real biological plants, to assess in real time the inhibiting effect of the incoming wastewater before it reaches the activated sludge reactor.
74 citations
TL;DR: To investigate the methanogenic population dynamics during the start-up under gradually increasing free ammonia levels, five mesophilic UASB reactors seeded with different sludges were operated for 140 days and Methanosaeta-related species mainly prevailing in seed sludge were substituted for Methanosarcina as the abundant methanogens although reactor performances were almost comparable and constant.
Abstract: To investigate the methanogenic population dynamics during the start-up under gradually increasing free ammonia levels, five mesophilic UASB reactors seeded with different sludges were operated for 140 days. Changes in the methanogenic community investigated by using 16S rDNA/rRNA based molecular methods such as denaturing gradient gel electrophoresis (DGGE), fluorescent in-situ hybridization (FISH), cloning and DNA sequencing. Free ammonia nitrogen (FAN) in the reactors was gradually increased from 50 to 130 mg l-1 by increasing total ammonia nitrogen (TAN) from 1000 to 2500 mg l-1 in the feed and keeping reactor pH at 7.7 in the active zone. Even at highest FAN level, COD and VFA removal efficiencies above 90 and 98% were obtained, respectively. However, Methanosaeta-related species mainly prevailing in seed sludges were substituted for Methanosarcina as the abundant methanogens although reactor performances were almost comparable and constant.
69 citations
TL;DR: To reduce the suspended solids load to a trickling filter installation, raw swine effluent was pre-treated with ferric chloride and a cationically charged polyacrylamide coagulant resulting in unexpected struvite accumulation downstream of this post-separation process.
Abstract: To reduce the suspended solids load to a trickling filter installation, raw swine effluent was pre-treated with ferric chloride and a cationically charged polyacrylamide coagulant resulting in unexpected struvite accumulation downstream of this post-separation process. Using this pre-treated swine manure, struvite precipitation studies were carried out as a function of pH at laboratory and pilot batch and continuously operated scales. An optimal reaction time of 30 min was established for struvite precipitation in the pre-treated swine wastewater at pH 8.5, minimizing the co-precipitation of interfering minerals. Ferric chloride addition resulted in magnesium solubilization, such that no external additional source of magnesium was required for struvite formation. Aeration alone did not result in significant pH increases, so base addition was required for pH adjustment. X-ray diffraction revealed that the only crystalline phase produced was struvite. Removal of phosphate and ammonium attained 98% and 17% r...
64 citations
TL;DR: The appropriateness of MCA for environmental decision problems can be viewed in the context of a typical decision- making process, making it easier to identify the contribution MCA can make at various decision-making stages.
Abstract: Environmental decision-making occurs in numerous environmental sectors and covers a diverse range of problems. Of the various decision tools available not all of them may be appropriate for any single decision problem, and any particular decision-aid may not be applicable in all decision problems. This article reviews applications of MCA, and considers the appropriateness of Multicriteria Analysis (MCA) in environmental decision-making problems. Due to natural and decision environments being multidimensional, environmental decision-making is characterized by complexity. Consequently MCA has commonly been used in this area. In Environmental Impact Assessment (EIA) the multiple dimensions of the impacts evaluated have been easily represented in MCA as multiple criteria. Waste management and water resource planning problems involving public participation have been facilitated by MCA, through the structuring and articulation of the public's values. MCA has also been applied in water quality problems, allowing the incorporation of incommensurable criteria into evaluations. The appropriateness of MCA for environmental decision problems can be viewed in the context of a typical decision-making process, making it easier to identify the contribution MCA can make at various decision-making stages. MCA can be particularly appropriate when the decision-making context is characterized by multiple objectives and multiple criteria, incommensurable criteria, mixed data and the need for ease of use, and the analysis context is characterized by multiple participants.
61 citations
TL;DR: Methane oxidation patterns were investigated under various environmental conditions including soil moisture content, temperature, and the addition of NH4 + in a sandy landfill cover soil, which seems to be the most important and an efficient means of managing methane oxidation when sandy soils are used in landfill cover.
Abstract: It is advantageous to use coarse soils as landfill cover because they allow better aeration of the biologically active zone. In this study, therefore, patterns of methane oxidation were investigated under various environmental conditions including soil moisture content, temperature, and the addition of NH4+ in a sandy landfill cover soil. The kinetics of CH4 oxidation was also studied at different moisture contents and temperatures. Soil moisture content of 10% (wt/wt) resulted in the maximum CH4 oxidation rate (19.2-22.4 nmol gsoil DW(-1) min(-1)). A Vmax value was not significantly different when the moisture content was more than 10%, but a Km value increased from 5.23 to 75.24 microM as the moisture content increased. The ratio of Vmax to Km was the highest at 10% moisture content. The CH4 oxidation rate increased as the incubation temperature increased, and Q10 values and optimum temperature were determined to be 2.57-2.69 and 30 degrees C, respectively. Both Vmax and Km values decreased at the temperatures below and above 30 degrees C. The addition of various levels of NH4+ resulted in increased or decreased CH4 oxidation rates, however, the initiation of appreciable CH4 oxidation was delayed with increasing amounts of NH4+ application in all samples tested. Among the environmental variables tested, moisture content control seems to be the most important and an efficient means of managing methane oxidation when sandy soils are used in landfill cover.
58 citations
TL;DR: In this article, an experience of P removal by auto nucleation and crystal growth of struvite (MAP) in a demonstrative plant is proposed, located in a municipal wastewater treatment plant in northern Italy.
Abstract: The experience of P removal by auto nucleation and crystal growth of struvite (MAP) in a demonstrative plant is proposed. The demonstrative plant is located in a municipal wastewater treatment plant in northern Italy. The trials are a consequence of previous experimentation carried out using silica sand as seed material. Working in metastable conditions the auto-nucleation process is performed, and allows the control of the precipitation and the growth of MAP inside the FBR reactor. No scaling problems are observed in the collecting pipes. After the treatment of 650m3 of anaerobic supernatants, 0.28 tons of granulated crystalline MAP are produced. The chemical analysis shows its possible use in agriculture as fertilizer. Operative costs analysis confirms the SCP as a cheap way to remove and recover P from anaerobic supernatants.
55 citations
TL;DR: Removal of nickel ions from aqueous solutions containing 1-100 mg l−1, using pine tree materials modified with HCl, was investigated on a laboratory scale and the maximum removal efficiency levels obtained were as follows.
Abstract: Removal of nickel ions from aqueous solutions containing 1-100 mg l−1, using pine tree (Pinus nigra) materials modified with HCl, was investigated on a laboratory scale. For this purpose, two natural adsorbents such as the modified pine bark (MPB) and the modified pine cone (MPC) materials with HCl solution were studied. At first, the required concentration level of the HCl solution for the modification was observed, and then this was followed by the determinations of optimum levels of adsorbent amount, stirring rate, contact time and pH values. Various adsorption isotherms were also obtained by using different concentrations of the heavy metal cations tested in the experiment. As a result, the maximum removal efficiency levels obtained were as follows; 97 % for the modified pine bark at pH 8 and 80 % for the modified pine cone at pH 8.
TL;DR: The development and implementation of a Fuzzy Logic Controller to regulate the aeration in the Taradell Wastewater Treatment Plant and results obtained show that energy savings of more than 10% can be achieved using aeration fuzzy control and at the same time still keeping the good removal levels.
Abstract: Many uncertain factors affect the operation of Wastewater Treatment Plants. Due to the complexity of biological wastewater treatment processes, classical methods show significant difficulties when trying to control them automatically. Consequently soft computing techniques and, specifically, fuzzy logic appears to be a good candidate for controlling these ill-defined, time-varying and non-linear systems. This paper describes the development and implementation of a Fuzzy Logic Controller to regulate the aeration in the Taradell Wastewater Treatment Plant. The main goal of this control process is to save energy without decreasing the quality of the effluent discharged. The fuzzy controller integrates the information coming from two different signals: the Dissolved Oxygen and Oxidation-Reduction Potential values. The simulation results proved that fuzzy logic is a good tool for controlling the aeration of the wastewater treatment plant. The results obtained show that energy savings of more than 10% can be ac...
TL;DR: It is likely that particles and total coliforms are major issues in operating rainwater utilization system, and further studies will be necessary to address the health effect of rainwater in terms of microbial and ecotoxicological measures.
Abstract: Frequent urban floods and insufficient water supply have led to developing technologies for rainwater utilization in order to buffer extreme runoff situations in the watercourses and to provide an ongoing water supply for non-potable use. However, little information is available on the water qualities and runoff properties of collected rainwater in connection with efficient design and maintenance strategies of rainwater utilization systems. In this work, the characteristics of rainwater were investigated in a full-scale rainwater utilization facility in Korea. Samples of runoff rainwater from various catchment surfaces were analyzed for physico-chemical and microbial determinants including metals, nutrients, pH, turbidity, conductivity, and microorganisms. The pollutant concentrations in rainwater storage tank were also monitored to elucidate the impact of input rainwater quality on stored water property. It is likely that particles and total coliforms are major issues in operating rainwater utilization system. However, further studies will be necessary to address the health effect of rainwater in terms of microbial and ecotoxicological measures.
TL;DR: In order to obtain the most effective combination of parameters for TOC removal of phenol solution, experiments were conducted under varied conditions and showed that there is an optimum pH requirement.
Abstract: This study evaluates a new method for chemically destroying organic pollutants in wastewater using spontaneous corrosion of iron metal sheet surfaces in the presence of hydrogen peroxide. Model pollutants (phenol and benzoic acid) were degraded in batch experiments to investigate which parameters affected the process performance. Iron metal sheet surfaces spontaneously corrode under acidic conditions producing iron species (mainly ferrous ions) dissolved in aqueous solution, which react with hydrogen peroxide via the Fenton reaction. In order to optimise the oxidation system, several factors (pH, H2O2 dosage, initial concentration of organic substances) affecting corrosion of the iron metal sheet surface were investigated. Total iron concentration in solution was investigated with different dosages of H2O2 (100 mg l(-1), 1000 mg l(-1) and 1900 mg l(-1)) at different pH values (1.5, 2.5 and 3.0). Iron corrosion increased with the decrease of pH. The addition of H2O2 resulted in a significant increase of iron corrosion. Organic substances also had a marked effect with, for instance, the presence of phenol or benzoic acid resulting in a considerable increase of iron corrosion. In contrast, the absence of either hydrogen peroxide or iron metal brought no change in total organic carbon (TOC). In order to obtain the most effective combination of parameters for TOC removal of phenol solution, experiments were conducted under varied conditions. The experimental results showed that there is an optimum pH requirement (in this work, 2.5). The factors affecting the TOC removal are discussed and the oxidation mechanisms leading to mineralization of organic substances are proposed.
TL;DR: Batch measurements showed that felts exhibited higher adsorption capacities at equilibrium than cloths at high toluene concentrations, whereas this trend may be inverted at low concentrations, and dynamic adsorptive capacities at saturation appeared to be higher than 120 mg g−1 for both cloths and felts, irrespective of relative humidity levels and toLUene concentrations.
Abstract: Due to their bad effects on human health, removing Volatile Organic Compounds from indoor air has become an issue of major interest. In this study, the potential use of six commercial activated carbon felts and cloths for indoor toluene removal was investigated. Both batch and dynamic adsorption studies were performed, at toluene concentrations ranging from 21 to 18160 mg m−3, for an air velocity representative of indoor air treatment (0.37 m s−1). Batch measurements showed that felts exhibited higher adsorption capacities at equilibrium than cloths at high toluene concentrations, whereas this trend may be inverted at low concentrations. Experimental isotherms and kinetics were satisfactorily fitted by the Langmuir-Freundlich model and the Linear Driving Force model respectively. No main differences between the adsorption kinetics of felts and cloths were reported. Dynamic adsorption capacities at saturation appeared to be higher than 120 mg g−1 for both cloths and felts, irrespective of relative humidity...
TL;DR: Ozonation of leachate effluent obtained from a Membrane Bioreactor (MBR) process treating a medium-aged landfill leachates showed reduction in Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) with an increase in five days Biochemical Oxygen demand (BOD5) concentration.
Abstract: Ozonation of leachate effluent obtained from a Membrane Bioreactor (MBR) process treating a medium-aged landfill leachate was investigated. The sequence of ammonia stripping, membrane bioreactor, and ozonation was used in the experiment. Ozonation of the MBR effluent showed reduction in Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) with an increase in five days Biochemical Oxygen Demand (BOD5) concentration. About 73% of COD could be removed at an ozone (O3) dosage of 4.2 mg O3 mg COD(-1). The biodegradability indicated by BOD5/COD ratio increased from 0.03 to 0.08 after ozonation at optimum ozone condition. While analyzing the molecular weight distribution, the fraction of molecular weight (MW) greater than 50 kDa of MBR effluent was transferred to MW 10-50 kDa (38%) at an ozone dosage of 810 mg O3. When O3 dosage was increased to 2,025 mg O3, a rapid change occurred in MW > 50 kDa fraction. This fraction was completely broken down into lower molecular weight fractions. This indicates partial degradation of landfill leachate by ozonation. The colour removal from the leachate was found to be greater than 95%. When the ozonated leachate was recirculated into the MBR system, along with an improvement in the performance of MBR, overall COD removal increased from 78% to 83%. Further, the ozone consumption decreased from 6.1 to 3.4 mg O3 mg COD(-1) removed, thus reducing the ozone requirement.
TL;DR: The shortcut biological nitrogen removal (SBNR) hybrid process is an innovative technology that nitrosofies ammonium to nitrite and then denitrifies nitrite to nitrogen gas and results in a 25% savings of the oxygen needed for nitrification and a 40% savings in carbon source needed for denitrification.
Abstract: The shortcut biological nitrogen removal (SBNR) hybrid (suspended cells combined with attached cells) process is an innovative technology that nitrosofies ammonium to nitrite and then denitrifies nitrite to nitrogen gas. Theoretically, this results in a 25% savings of the oxygen needed for nitrification and a 40% of savings in carbon source needed for denitrification. In this study, the influences of free ammonia (FA) and dissolved oxygen (DO) concentrations on nitrite accumulation were investigated to find the optimal operational factors for stable nitrite accumulation over a long period. The maximum specific utilization rates for ammonium (qa) and nitrite (qn) were determined for suspended and attached cells taken from a bench-scale SBNR reactor and a pilot-scale livestock wastewater treatment plant reactor. For the ammonium and nitrite oxidations in both reactors, the attached cells were more resistant to the FA concentration, but were more significantly influenced by the DO concentration than the susp...
TL;DR: The success of supercritical fluid extraction as a method for removing these contaminants from soils is highlighted and some of the future research needed to develop it as a commercial-scale economic remediation technology are discussed.
Abstract: Considerable effort is being made to remediate soils contaminated with petroleum hydrocarbons, polyaromatic hydrocarbons, polychlorinated biphenyls, dioxins, heavy metals and other organic and inorganic compounds that have resulted from industrial activities, accidental spills and improper waste disposal practices. Current remediation technologies may be limited when treating certain types of contaminated soils and therefore new, efficient and cost effective technologies are being investigated. Supercritical fluid extraction is a potential remediation technology for contaminated soils. It is a simple, fast and selective solvent extraction process that uses a supercritical fluid as the solvent. A commonly used fluid is carbon dioxide at pressures and temperatures greater than 7.4 MPa and 31°C, respectively. In supercritical fluid extraction, the extracted contaminants first dissolve into the supercritical solvent and then these contaminants are separated from the supercritical solvent via a simple change i...
TL;DR: In this study, the removal of Cr6+ in the leather industry wastewater is investigated using MnSO4 that was used easily and economically and could be carried out easily.
Abstract: Chromium (VI) is one of the heavy metals in water and wastewater that has the most toxic characteristic. Consequently, it is dangerous for human and environmental health. Various methods are used for removal of the chromium from wastewater, and new methods have been developed in recent years. Recent studies and investigations on the removal of environmental pollution selected methods that were economical, of optimum efficiently and could be carried out easily. In this study, the removal of Cr6+ in the leather industry wastewater is investigated using MnSO4 that was used easily and economically. Experimental studies are performed in two phases. In the first phase, the optimum MnSO4 dose for removal of Cr6+ was determined. In the second phase, the optimum pH was studied. About 96% removal of chromium was launched with 530 mg l−1 MnSO4 dose at pH value 9 in the wastewater sample.
TL;DR: The capacity of ACFC-supported metal oxides to adsorb both pollutants showed great improvement compared to the virgin adsorbent, and this depended on metal loading as well as on the order of the metal addition and calcination phase.
Abstract: The present investigation attempts to provide mechanisms for the influence of metal catalysts on carbon supports in odorous gas removal. For this purpose, an activated carbon fiber cloth (ACFC) was subjected to successive metal impregnation to modify its surface properties and so increase its treatment capacity. The carbon fiber cloth adsorbent was prepared by classical incipient wetness impregnation followed by calcination in order to obtain metal oxide phases. Different impregnation parameters (type of metal, level of impregnation, calcination temperature) in the removal of hydrogen sulfide and ammonia were studied. Adsorption kinetics and capacities were carried out in a batch reactor at room temperature. It was found that removal activity depended on metal loading as well as on the order of the metal addition and calcination phase. The capacity of ACFC-supported metal oxides to adsorb both pollutants showed great improvement compared to the virgin adsorbent.
TL;DR: The present research revealed that, the application of CaO2 could enhance the degradation of organic-C, organic-N and organic-P during the treatment of polluted sediment.
Abstract: A viable treatment procedure was developed in this research with calcium peroxide (CaO2) as a slow oxygen (O2) release agent for bioremediation of polluted sediments from intensive shrimp farms containing high organic carbon, nitrogen and phosphorus. Experiments with sediment treatment by CaO2 were carried out with, as well as without, biomass seeding at pH ranging from 6.5 to 8.5. The sediment treatment applying CaO2 without seeding yielded a BOD5, organic-C and organic-N removal up to 95%, 17.6% and 75%, respectively compared to the removal of 66%, 8.6% and 57%, respectively in the controlled treatment without CaO, addition. The investigations were also carried out with CaO2 dosage with biomass seeding at different food-to-microorganisms (F/M) ratio between 0.1 and 0.25. The BOD, organic-C and organic-N removal up to 92%, 17.6% and 73%, were achieved for a F/M ratio 0.1. The experimental results indicated complete organic-P removal within 5-7 days of treatment without seeding and within the initial 2 days of treatment with seeding. The present research revealed that, the application of CaO2 could enhance the degradation of organic-C, organic-N and organic-P during the treatment of polluted sediment.
TL;DR: The experimental results showed that K and Mg play an important role in the EBPR process being cotransported with P into and out of bacterial cells, and the proposed ASM2d model extension must be considered in order to accurately simulate the phosphorus removal process.
Abstract: Cations as potassium and magnesium play an important role in maintaining the stability of Enhanced Biological Phosphorus Removal (EBPR) process. In this paper potassium, magnesium and calcium behaviour in EBPR treatment plants has been studied. An ASM2d model extension which takes into account the role of potassium and magnesium in the EBPR process has been developed. Finally, a simulation of the effect on P removal of a shortage of K and Mg was studied. The experimental results showed that K and Mg play an important role in the EBPR process being cotransported with P into and out of bacterial cells. It has been observed that calcium is not involved in P release and uptake. The values of the molar ratios K/P (0.28 mol K mol P−1) and Mg/P (0.36 mol Mg mol P−1) were obtained accomplishing the charge balance, with different K/Mg mass ratios and without phosphorus precipitation. Model predictions accurately reproduced experimental data. The simulations carried out showed the important effect of the K and Mg i...
TL;DR: In order to define an efficient pre-treatment of Olive Oil Mill Wastewater (OOMW) to overcome major obstacles to biological treatment, various organic and mineral coagulants have been tested and lime – AC combination permitted better COD, phenols and colour reduction to respectively, 21, 11 and 11% of the initial values.
Abstract: In order to define an efficient pre-treatment of Olive Oil Mill Wastewater (OOMW) to overcome major obstacles to biological treatment, various organic and mineral coagulants have been tested. In particular, the application of quicklime until a pH around 12 – 12.4 was reached, allowed the reduction of almost 37 % of the initial COD, and approximately 88 % and 71 % of the colour and phenolic content of the waste. Hence, further biological treatments with an adapted aerobic consortium (AC) and a white rot fungus (WRF) strain were improved. The WRF Coriolopsis polyzona was more efficient than AC to reduce colour and polyphenols when the waste was prior diluted or pre-treated; however, it was less effective in COD removal. The combined treatment: lime – AC of OOMW having initial COD of 102 g l−1 led to the elimination of about 77, 91 and 63 %, of the COD, phenols and colour, respectively. Interestingly, the opposite combination AC – lime permitted better COD, phenols and colour reduction to respectively, 21, 1...
TL;DR: Recycle experiments confirmed that the application of the method by recycling acidify sludge to launch subsequent bioleaching is feasible and the optimal recycle rate of acidified sludge for consecutive leaching of Cr from tannery sludge is 2/3.
Abstract: A technologically feasible process called bioleaching was used to remove Cr from tannery sludge with Acidithiobacilli TS6 bacteria in this study. The buffering capacity of tannery sludge and municipal sewage sludge were compared. The effects of initial sulfuric acid addition on bioleaching process and influences of recycle rate of acidified bioleached sludge on subsequent bioleaching reaction were examined. The quantities of initial sulfuric acid addition ranged from 0 to 0.185 ml g−1 dry sludge. Recycle rate(Vbioleached/Vtotal) was controlled at 1/3, 1/2, 3/5 and 2/3. We found that tannery sludge had a higher buffering capacity than sewage sludge. The results showed that there was an increase in the rates of pH reduction and Cr solubilization with the increase of initial sulfuric acid addition. The suitable quantity of sulfuric acid addition was 0.185 ml g−1 dry sludge at the beginning of the first bioleaching process. After 10 days of bioleaching, pH reached 1.5 and almost 100% of Cr could be leached in...
TL;DR: The ability of crab shell to remove copper and cobalt from aqueous solutions was examined in an up-flow packed column and it was indicated that an increase in flow rate decreased the sorption performance of the crab shell.
Abstract: The ability of crab shell to remove copper and cobalt from aqueous solutions was examined in an up-flow packed column. The experiments were conducted to study the effect of important design parameters such as bed height and flow rate. At a bed height of 25 cm, metal uptake capacity of crab shell for copper and cobalt was 52.07 and 20.47 mg g−1 respectively. In addition, the results obtained at different flow rates indicated that an increase in flow rate decreased the sorption performance of the crab shell. The Bed Depth Service Time model and the Thomas model were used to analyze the experimental data and the model parameters were evaluated for copper and cobalt sorption. The column regeneration studies were carried out for five sorption-desorption cycles. Loss of sorption performance was observed as the cycles progressed, indicated by a shortened breakthrough time and a broadened mass transfer zone. However, crab shell maintained a good metal sorption capacity for all the five cycles. The elutant used fo...
TL;DR: Experimental results showed that seeding granules could be successfully maintained in the reactor, and demonstrated for the first time that stored aerobic granules can be used for easy and quick startup of aerobic granular sludge reactor.
Abstract: The startup of a pilot-scale aerobic granular sludge reactor was investigated by seeding with 4-month stored aerobic granules. Two liters of granules were inoculated into the reactor (5.9% of reactor volume), which gave a biomass concentration of 1.03 g l−1. Experimental results showed that seeding granules could be successfully maintained in the reactor. The microbial activity of seeding granules could be fully recovered to that of fresh granules after 2 days of operation, and new granules started to grow after day 5. Newly developed aerobic granules at stable period had similar size and morphology as seeding granules, and a biomass concentration of 6.0 g l−1 was achieved in the reactor. The experiment demonstrated for the first time that stored aerobic granules could be used for easy and quick startup of aerobic granular sludge reactor.
TL;DR: The ideal adsorbed solution theory (IAST) combined with the equivalent background compound (EBC) model can adequately describe the NOM competition and predict the isotherms of MTBE onto the activated carbons.
Abstract: Equilibrium and kinetic adsorption of methyl tert-butyl ether (MTBE) onto three coal-based activated carbons, one coconut-based activated carbon, and two zeolites are elucidated in this study. Natural organic matter (NOM) and MTBE competed for the adsorption of activated carbons to different extents. The ideal adsorbed solution theory (IAST) combined with the equivalent background compound (EBC) model can adequately describe the NOM competition and predict the isotherms of MTBE onto the activated carbons. No competitive adsorption was observed for one of the zeolites, mordenite, due to the molecular effect. Besides, the aperture size, and the SiO2/Al2O3 ratio of the zeolite may also play an important role in the adsorption of MTBE from the aqueous phase. The surface diffusion model accurately simulated the transport of MTBE within the adsorbents employed in different water matrices. For all the activated carbons tested, the surface diffusivity of MTBE in natural water was nearly equal to that in deionized...
TL;DR: Under US or MW irradiation rapid degradation of aromatic halides, halogenated phenols and polychlorinated biphenyls in polluted waters was achieved in the presence of a moderate excess of Fenton's reagent.
Abstract: Microwave (MW) and high-intensity ultrasound (US) have emerged as powerful techniques for the elimination of persistent organic pollutants (POPs) that constitute a major health hazard, whether by direct exposure or through accumulation in biota. In order to achieve decontamination, POPs should be completely mineralized to CO2, H2O and smaller amounts of inorganic ions, or at least converted to less harmful chemical species. Under US or MW irradiation rapid degradation of aromatic halides, halogenated phenols and polychlorinated biphenyls in polluted waters was achieved at neutral pH in the presence of a moderate excess (5-30 eq) of Fenton's reagent. Acidification with acetic acid (pH 2.0-2.3) did not affect the process, but sulphuric acid (pH 1.7-2.0) facilitated complete degradation. Thus, compared to conventional methods, US and MW processes are faster and much more efficient.
TL;DR: Detailed physico-chemical studies on abattoir effluent using lime, alum, ferrous sulphate and an anionic polyelectrolyte resulted in good settling of the sludge and good removals and indicated that lime in combination with alum can also be applied but resultant sludge volume would be more.
Abstract: Detailed physico-chemical studies on abattoir effluent using lime, alum, ferrous sulphate and an anionic polyelectrolyte were tried individually and in combination. Among the coagulants tried, lime resulted in good settling of the sludge. At 400 mg l-1 of lime dose, the Suspended Solids (SS), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) removals were found to be 41.9%, 38.9% and 36.1%, respectively. Best results were obtained with lime and ferrous sulphate in a combination ratio of 400:100 mg l−1, and the COD reduction of 36.1% at 400 mg l−1 of lime, further improved to 56.8%. Lime and alum dose of 400:50 mg l−1 resulted in an increased COD reduction of 42.6% compared to 36.1% at lime dose of 400mg l−1. However, the same lime dose with ferrous sulphate addition of 100 mg l−1 resulted in an increased COD reduction of 56.8% compared to 36.1%. This is a more efficient option for abattoir wastewater treatment and also cost effective. Ferrous sulphate with anionic polyelectrolyte resulted i...
TL;DR: The aim of the study is to identify potential opportunities for reducing fresh water intake and minimising wastewater production by studying the posibility of reuse, recycling and treatment in Morocco.
Abstract: Water is used in most process industries for a wide range of applications. Processes and systems using water today are being subjected to increasingly stringent environmental regulations on effluents and there is growing demand for fresh water. These changes have increased the need for better water management and wastewater minimisation. In Morocco, water use in the food and drink industry is extensive at approximately 24 million m 3 per year including 14 % of drinking water in 1994. This study was conducted in a carbonate soft drink industry plant, during two years, 2001 and 2002. We have investigated the state of consumption and use of fresh water and the generation of the effluent in the factory. The aim of the study is to identify potential opportunities for reducing fresh water intake and minimising wastewater production by studying the posibility of reuse, recycling and treatment.