International Journal of Environmental Science and Technology

Modeling study of the effects of the coagulation kernel with van der Waals forces and turbulence on the particle size distribution

*S. Cho; D. V. Michelangeli

In this study, variations in the size distributions due to different assumptions for the coagulation kernel are investigated. In order to evaluate how the coagulation kernel influences the form of the particle size distribution and to describe the process of the Brownian coagulation, the Brownian coagulation kernel, including the van der Waals forces, is compared with the most frequently used coagulation coefficients. Retardation should be considered for interparticle interactions for particles larger than 1µm radius. However, for particle sizes larger than 0.1 µm, the Brownian kernel is not dominant, so the retardation effect can be ignored. The inclusion of the van der Waals forces in the Brownian coagulation kernel caused a faster coagulation process in the small particle size range. Taking account of the turbulent coagulation kernel, the turbulent coagulation kernel becomes more important when the turbulent intensity is higher. The turbulent coagulation kernel affects the large particle size range and ignoring the turbulent coagulation kernel will lead to overestimation of particle number concentration in model simulation. The results of this study indicate that the inclusion of van der Waals forces or the turbulent coagulation kernel in the total coagulation kernel impacts on the modeled particle size distributions and total particle number concentration.

Pollution reduction and biodegradability index improvement of tannery effluents

1*M. A. Aboulhassan; 1S. Souabi; 2A. Yaacoubi

Al2 (SO4)3, 18H2O, FeCl3 and Ca (OH)2 were used for the treatment of tannery wastewaters. The influences of pH and coagulant dosages were studied. Conditions were optimised according to the pollutant removal efficiencies, the volume of decanted sludge and the biodegradability index improvement. The results indicate that 67-71% of total COD, 76-92% of color and 79-97% of chromium can be removed using the optimum coagulant dosages at the optimum pH range. Al2 (SO4)3, 18H2O and Ca (OH)2 produced better results than FeCl3 in terms of COD, color and chromium removal as well as in terms of biodegradability improvement. Moreover, Al2 (SO4)3, 18H2O and FeCl3 produced the least amount of sludges for a given amounts of COD, color and chromium removed in comparison with Ca (OH)2. Al2 (SO4)3, 18H2O seems to be suitable for yielding high pollutant removals and corresponding low volumes of decanted sludges in addition to improving wastewaters biodegradability index.

Photocatalytic ozonation of 2, 4-dichlorophenoxyacetic acid in water with a new TiO2 fiber

1*R. R. Giri; 2H. Ozaki; 1S. Taniguchi; 1R. Takanami

More effective techniques are required to mineralize the increasing number of recalcitrant organic contaminants at low concentrations in the water environment using advanced oxidation process. Though relatively new, photocatalytic ozonation (O3/UV/TiO2) is considered superior to ozonation (O3) and photocatalysis (UV/TiO2), due to synergistic effects and use of immobilized TiO2 photocatalysts is a milestone in advance oxidation process. This article aimed to elucidate 2, 4-dichlorophenoxyacetic acid (2, 4-D) mineralization characteristics in low aqueous solutions by O3/UV/TiO2 using the world's first high-strength TiO2 fiber catalyst in laboratory experiments. 2, 4-D degradation and TOC removal in O3, UV/TiO2 and O3/UV/TiO2 followed pseudo-first order reaction kinetic. The removal rates for 2, 4-D and TOC in O3/UV/TiO2 were respectively about 1.5 and 2.4-fold larger than the summation of the corresponding values in O3 and UV/TiO2. The O3/UV/TiO2 process was characterized by short-lived few aromatic intermediates, faster degradations of aliphatic intermediates and dechlorination as a major step in 2, 4-D mineralization. The significantly enhanced 2, 4-D mineralization in the process was attributed to increased ozone decomposition and reduced electron-hole recombination on TiO2 surface resulting to a large number of .OH generation. The O3/UV/TiO2 process with the TiO2 fiber catalyst was very promising with respect to the major challenges being faced in AOP involving TiO2, namely separation of powder catalyst in suspension and reduced efficiency of immobilized catalysts (e.g. TiO2 film/fiber).

Saraca indica leaf powder for decontamination of Pb: removal, recovery, adsorbent characterization and equilibrium modeling

P. Goyal; P. Sharma; S. Srivastava; *M. M. Srivastava

The present study explores the effectiveness of Saraca indica leaf powder, a surplus low value agricultural waste, in removing Pb ions from aqueous solution. The influence of pH, biomass dosage, contact time, particle size and metal concentration on the removal process were investigated. Batch studies indicated that maximum biosorption capacity for Pb was 95.37% at the pH 6.5. The sorption process followed the first order rate kinetics. The adsorption equilibrium data fitted best to both Langmuir and Freundlich isotherms. Morphological changes observed in scanning electron micrographs of untreated and metal treated biomass confirmed the phenomenon of biosorption. Fourier transform infrared spectroscopy of native and exhausted leaf powder confirmed lead biomass interactions responsible for sorption. Acid regeneration was tried for several cycles with a view to recover the sorbed metal ion and also to restore the sorbent to its original state. The findings showed that Saraca indica leaf powder can easily be envisaged as a new, vibrant, low cost biosorbent for metal clean up operations.

Wastewater dephosphorization using crude clays

1P. J. M. R. Dable; 1Y. J. Adjoumani; 2B. Yao; 2*G. Ado

The present work aims to establish the possibility of using local clays to treat wastewater. Thus, three clay samples extracted from two localities in the south of Côte d'Ivoire have been studied in their crude state. The qualitative physicochemical study that consisted in measurement of pH variation and argillaceous particles zeta potential showed that the Nieki-Agneby clay and the Beige Anyama clay presented disposal to uptake phosphate ions in solution at pH 5. For each clay, it is shown that the tension accompanying the sorption of a phosphate ion could be estimated to -5 mV. Differences in their composition and in the number of hydrating molecules of water were also accessible. The quantitative study performed with the Nieki-Agneby clay thereafter consisted following the sorption kinetic. The adsorption was found to reach the maximum after 5 h. of exchange, and almost 400 µg phosphate ions in per gram of clay were fixed. Future studies will focus on the modification of these materials in order to increase their sorption capacity.

Environmental management of coastal regions in the Caspian Sea

1J. Nouri; 2*A. R. Karbassi; 1S. Mirkia

Considering rapid population growth and migration, higher accumulation of communities is noticed in coastal areas. This is especially true with the coastal areas of the Caspian Sea. In the present investigation coastal areas between Jouybar to Behshahr region is selected for their special geographical and ecological locations. Further, adverse impacts of human, agriculture and industrial activities was examined along side the above mentioned coasts. It should be pointed out that protected Miankaleh Wildlife zone which is an internationally recognized wetland, falls within area of study. In the present study strengths, weaknesses, opportunities and threats method is used for the evaluation of environmental management status. In this regard, internal and external factors gained 2.28 and 2.58 scores. This is indicative of the abundance of weaknesses over strengths and it also shows that opportunities are more than threats. Subsequently 27 strategies were developed and quantitative strategic planning matrix method was also used to score each strategies. The results of quantitative strategic planning matrix method analysis was programmed in strategic position and action evaluation matrix. The present situation falls within 'competitive' classification. This is indicative of weakness in coordinating development and environmental strategic plans. The result of present investigation strongly emphasis on compilation of strategic environmental plans for the control of population, pollution emission and land use planning changes. The most important strategies include development of environmental regulations and better supervision on enforcement of laws.

Rapid analysis of risk assessment using developed simulation of chemical industrial accidents software package

The environmental consequences are defined as consequences of accidental release of hazardous substances to the natural environment. This release can lead to many hazards depending on the material stored. The consequences of these hazards to the environment are widespread and have significant importance to human communities living in the surroundings. The mathematical models are extremely useful tools to predict the impacts of chemical process accidents. The objective of this paper is to develop a software package for accident simulation and damage potential estimation. The software is coded in visual basic and is compatible with windows working environments. The software is called Simulation of chemical industrial accident. This application is a comprehensive software package which can be integrated with geographical information system to predict and display the consequence of chemical hazards. The software is a user-friendly and effective tool for evaluating the consequences of major chemical accidents, process decision making for land-use planning, namely locating suitable hazardous installations, hazardous waste disposal areas and emergency response plan.

Assessment of Zn, Cu, Pb and Ni contamination in wetland soils and plants in the lake basin

1*G. Nabulo, 2H. Oryem Origa, 3G. W. Nasinyama, 4D. Cole

The impact of waste disposal on trace metal contamination was investigated in eleven wetlands in the Lake Victoria Basin. Samples of soil, water and plants were analysed for total Zn, Cu, Pb and Ni concentrations using flame atomic absorption spectrophotometry. The trace metal concentrations in soil were the highest in Katanga wetland with the highest mean concentrations of 387.5±86.5 mg/kg Zn, 171.5±36.2 mg/kg Pb, 51.20±6.69 mg/kg Cu and 21.33±2.23 mg/kg Ni compared to the lowest levels observed at Butabika (30.7±3.2 mg/kg Zn, 15.3±1.7 mg/kg Pb, 12.77±1.35 mg/kg Cu and 6.97±1.49 mg/kg Ni). Katanga receives waste from multiple industrial sources including a major referral city hospital while Butabika is a former solid waste dumpsite. Wetland soil near a copper smelter had a Cu concentration of 5936.3±56.2 mg/kg. Trace metal concentrations in industrial effluents were above international limits for irrigation water with the highest concentrations of 357,000 ìg/L Cu and 1480 ìg/L Zn at a Cu smelter and 5600 ìg/L Pb at a battery assembling facility compared to the lowest of 50 ìg/L Cu and 50 ìg/L Zn in water discharged from Wakaliga dumpsite. Uptake of trace metals from soil differed from plant to plant and site to site. Higher levels of trace metals accumulated in the root rather than in the rhizome and the least amount was in the leaf. The study identifies industry as a potential source of trace metal contamination of water and the environment pent-up need for policy intervention in industrial waste management .

Production optimization and quality assessment of biodiesel from waste vegetable oil

1*A. A. Refaat; 2N. K. Attia; 1H. A. Sibak; 1S. T. El Sheltawy, 2G. I. ElDiwani

Biodiesel production is worthy of continued study and optimization of production procedures because of its environmentally beneficial attributes and its renewable nature. In Egypt, millions L of oil used for frying foods are discarded each year into sewage systems. Thus, it adds to the cost of treating effluent or pollutes waterways. This study is intended to consider aspects related to the feasibility of the production of biodiesel from waste/recycled oils in an attempt to help reduce the cost of biodiesel and reduce waste and pollution coming from waste oils. The variables affecting the yield and characteristics of the biodiesel produced from used frying oil were studied, the achieved results were analyzed and a set of recommendations was proposed. From the obtained results, the best yield percentage was obtained using a methanol/oil molar ratio of 6:1, potassium hydroxide as catalyst (1%) and 65 'C temperature for one hour. The yield percentage obtained from waste vegetable oil was comparable to that obtained from neat vegetable oil which reached 96.15% under optimum conditions. From the results it was clear that the produced biodiesel fuel, whether from neat vegetable oil or waste vegetable oil, was within the recommended standards of biodiesel fuel.

Adsorption kinetics and intraparticulate diffusivities of Hg, As and Pb ions on unmodified and thiolated coconut fiber

1*J. C. Igwe; 2A. A. Abia; 1C. A. Ibeh

As, Hg and Pb are examples of heavy metals which are present in different types of industrial effluents responsible for environmental pollution. Their removal is traditionally made by chemical precipitation, ion-exchange and so on. However, this is expensive and not completely feasible to reduce their concentrations to the levels as low as required by the environmental legislation. Biosorption is a process in which solids of natural origin are employed for binding the heavy metal. It is a promising alternative method to treat industrial effluents, mainly because of its low cost and high metal binding capacity. The kinetics was studied for biosorption experiments using coconut fiber for As (III), Hg (II) and Pb (II) ions adsorption. The specific surface area and surface charge density of the coconut fiber are 1.186x1025 (m2/g) and 5.39 x1024 (meq/m2), respectively. The maximum adsorption capacity was found to be the highest for Pb (II) followed by Hg (II) and As (III). The modification of the adsorbent by thiolation affected the adsorption capacity. Equilibrium sorption was reached for the metal ions at about 60 min. The equilibrium constant and free energy of the adsorption at 30 ºC were calculated. The mechanism of sorption was found to obey the particle-diffusion model. The kinetic studies showed that the sorption rates could be described by both pseudo first-order and pseudo second-order models. The pseudo second-order model showed a better fit with a rate constant value of 1.16 x 10-4/min. for all three metal ions. Therefore, the results of this study show that coconut fiber, both modified and unmodified, is an efficient adsorbent for the removal of toxic and valuable metals from industrial effluents.

Phosphorus removal in low alkalinity secondary effluent using alum

R. J. Banu; K. U. Do; *I. T. Yeom

The alkalinity plays an important role in phosphorus removal using coagulant. The dosage of coagulant in the low alkalinity wastewater is limited due to rapid pH changes. In the present study, a series of jar test was conducted using low alkalinity wastewater (50 mg/L) to evaluate the optimum pH, dosage and performance parameters (slow mixing and settling time) for the common coagulant alum. From the experiment, it was found that the dosage of coagulant and removal of phosphorus depend upon the pH of the wastewater after adding coagulant. The final optimum pH for efficient P removal was found to be within the range of 5.7-5.9. This range acts as an indicator and it is the maximum tolerable pH range for phosphorus removal for low alkalinity wastewater. The optimum time for slow mix and settling was found to be 20 min. The optimum mole ratio of alum to remove one mole of phosphorous was found to be 2.3. The alum coagulation at pH 7 produced effluent with the total residual phosphorus and reactive phosphorus content of 0.3 and 0.9 mg/L, respectively.

Vermicomposting of domestic waste by using two epigeic earthworms (Perionyx excavatus and Perionyx sansibaricus)

1*S. Suthar; 2S. Singh

The composting potential of two epigeic earthworms (P. excavatus and P. sansibaricus) was studied in 2002 to breakdown the domestic waste under laboratory conditions. The experimental container with P. sansibaricus showed maximum mineralization and decomposition rate than that of P. excavatus. Except for exchangeable K (it was higher (P = 0.004) in a container with P. excavatus), the domestic waste processed by P. sansibaricus showed about 6% more total nitrogen (P = 0.002) and about 7% more available P (P = 0.269) at the end than by P. excavatus. As compared with the initial level organic C content as well as C:N ratio showed a considerable reduction that was noted higher in substrate with P. sansibaricus than those by P. excavatus (organic C, t-test: P = 0.870; C:N ratio, t-test: P = 0.002). The growth (biomass increase) and reproduction parameters such as mean individual live weight, maximum individual growth rate (mg wt./worm/day), number of cocoons and reproduction rate (cocoon/worm/day) were higher in bedding with P. sansibaricus. The maximum earthworm mortality was in vermibed having P. sansibaricus (~50% higher than by P. excavatus) (t-test: P = 0.423), since both species did not show a drastic difference in waste mineralization rate, but comparatively, P. excavatus exhibited better growth and reproduction performance, which further support the suitability of the species for large scale vermiculture operations.

Impact of fertilizer plant effluent on water quality

1O. Obire; 1A. Ogan; 2*R. N. Okigbo

The impact of National Fertilizer Company of Nigeria outfall effluent on the physicochemistry and bacteriology of Okrika creek was investigated during the sampling period from May to December, 1998. The National Fertilizer Company of Nigeria outfall effluent, the Okrika creek water and the Ikpukulubie creek (control) water samples were collected. The physico-chemical parameters analyzed for all the samples included temperature, pH, total chloride, total dissolved solids, dissolved oxygen, conductivity, free ammonia, total phosphate, urea, zinc and iron, while the bacteriological determinations were total culturable aerobic heterotrophic bacteria count and identification of representative isolates. The Okrika creek recorded higher concentrations for all the physico-chemical parameters and bacteria load than the control creek. The higher values of pH, Free NH3, urea, TDS and the conductivity of the National Fertilizer Company of Nigeria outfall effluent above the FEPA standards reflect the poor effluent quality generated by National Fertilizer Company of Nigeria. The bacteria species isolated from the samples include Aerococcus viridans, Alcaligenes faecalis, Bacillus cereus, Citrobacter freundii, Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa, Serratia marcescens and Staphylococcus aureus. In general, the investigation revealed that there was an extremely adverse impact on the physico-chemical and bacteriological water quality characteristics of the Okrika creek as a result of the discharge of poor quality effluent from National Fertilizer Company of Nigeria operations.

Assessment of heavy metal pollution in surface water

1D. Kar; 1P. Sur; 1S. K. Mandal; 2T. Saha; 2*R. K. Kole

A total of 96 surface water samples collected from river Ganga in West Bengal during 2004-05 was analyzed for pH, EC, Fe, Mn, Zn, Cu, Cd, Cr, Pb and Ni. The pH was found in the alkaline range (7.21-8.32), while conductance was obtained in the range of 0.225-0.615 mmhos/cm. Fe, Mn, Zn, Ni, Cr and Pb were detected in more than 92% of the samples in the range of 0.025-5.49, 0.025-2.72, 0.012-0.370, 0.012-0.375, 0.001-0.044 and 0.001-0.250 mg/L, respectively, whereas Cd and Cu were detected only in 20 and 36 samples (0.001-0.003 and 0.003-0.032 mg/L). Overall seasonal variation was significant for Fe, Mn, Cd and Cr. The maximum mean concentration of Fe (1.520 mg/L) was observed in summer, Mn (0.423 mg/L) in monsoon but Cd (0.003 mg/L) and Cr (0.020 mg/L) exhibited their maximum during the winter season. Fe, Mn and Cd concentration also varied with the change of sampling locations. The highest mean concentrations (mg/L) of Fe (1.485), Zn (0.085) and Cu (0.006) were observed at Palta, those for Mn (0.420) and Ni (0.054) at Berhampore, whereas the maximum of Pb (0.024 mg/L) and Cr (0.018 mg/L) was obtained at the downstream station, Uluberia. All in all, the dominance of various heavy metals in the surface water of the river Ganga followed the sequence: Fe > Mn > Ni > Cr > Pb > Zn > Cu > Cd. A significant positive correlation was exhibited for conductivity with Cd and Cr of water but Mn exhibited a negative correlation with conductivity.

Assessment of cement’s dust impact on the soil using principal component analysis and GIS

1*Z. Zerrouqi; 1M. Sbaa; 2M. Oujidi; 1M. Elkharmouz; 2S. Bengamra; 3A. Zerrouqi

To evaluate the impact of the cement's dust emitted by the eastern Moroccan cement factory (Oujda Holcim) and deposited on the soil of the Ain Lahjar commune, 58 samples of soil were collected around the factory on a radius of 3 km approximately. The physicochemical analyses of the upper 3 cm of the soil surface samples correspond to the pH, electrical conductivity, the chlorides and the oxides of Ca, Al, Fe, K, Mn, S and Si which were analyzed by the fluorescence of X-rays. The preliminary results demonstrate that this dust are especially basic and contain a high free lime (43% CaO). The principal component analysis (applied on the 58 samples of soil) allows deducting that the free lime and the sulfur oxide are the tracer elements of this form of pollution. Furthermore, the spatial projection of the factor scores of the principal component analysis using the geographical information system permits to determine the spatial distribution of more polluted areas of soils as well as to estimate their surface (63.3% of the survey zone).

Cross inoculation studies: Response of Vigna mungo to inoculation with rhizobia from tree legumes growing under arid environment

1A. Mahmood; 2*M. Athar

Cross-inoculation experiments were conducted in the greenhouse to test the rhizobia isolated from nodules of seven tree legumes for their effectiveness in Vigna mungo plants. The tree legumes included Albizia lebbeck, Dalbergia sissoo, Leucaena leucocephala, Pithecellobium dulce, Prosopis cineraria, Prosopis glandulosa and Prosopis juliflora, all growing under arid environment. Rhizobia from these legumes formed nodules on the roots of Vigna mungo except isolates from Albizia lebbeck. Dry weight and nitrogen contents of Vigna mungo plants increased significantly (P<0.05) in response to cross inoculation as compared to uninoculated control. Rhizobia from Leucaena leucocephala and Prosopis glandulosa showed significant increase in dry weight (P<0.05) and nitrogen contents (P<0.05) than other inoculated treatments. The natural rhizobia of wild tree legumes growing under arid environment show higher tolerance to prevailing adverse conditions like salt stress, elevated temperatures and drought. These rhizobia may be used to inoculate wild as well as crop legumes cultivated in reclaimed desert lands. These rhizobia may have specific traits that can be transferred to other rhizobia through genetic engineering tools. The cross infection of agriculturally important legumes with isolates from wild legumes may prove a useful means of increasing nitrogen contents within these plants.