Abstract: The present paper describes the study of paste tailings prepared in laboratory using gold tailings, produced in a Finnish gold mine with the incorporation of coal ash. Natural leaching tests were conducted with the original materials (tailings, fly and bottom ashes) and also with paste mixtures that were prepared with different percentages of tailings and ashes. After leaching, the solid wastes were physically and chemically characterized and the results were compared to those selected as blank – the unleached samples. The tailings and the coal ash, as well as the prepared mixtures, were characterized, in addition to the textural parameters, by the following measurements: grain size distribution, chemical composition and pH. Mixtures were also tested in order to characterize their mechanical behavior by measuring the flexural strength, the compressive strength and the consistency. The original tailing samples presented an alkaline pH because during their processing they were previously submitted to pressure oxidation with destruction of the sulfides. Therefore, it was not possible to ascertain the effect of the coal ashes in the acid mine drainage. However, it was possible to verify that the paste reactivity was affected mostly by the bottom ash and that the tailings blended with bottom ash present lower mechanical strength than when blended with a combination of fly and bottom ash. Surface paste disposal offer an attractive alternative to traditional methods in addition to the environmental benefits of incorporating large-volume wastes (e.g. bottom ash). However, a comprehensive characterization of the paste mixtures is crucial to optimize paste design in order to enhance engineer and environmental properties.
Abstract: Conceiving and developing routing protocols for
wireless sensor networks requires considerations on constraints such
as network lifetime and energy consumption. In this paper, we propose
a hybrid hierarchical routing protocol named HHRP combining both
clustering mechanism and multipath optimization taking into account
residual energy and RSSI measures. HHRP consists of classifying
dynamically nodes into clusters where coordinators nodes with extra
privileges are able to manipulate messages, aggregate data and ensure
transmission between nodes according to TDMA and CDMA
schedules. The reconfiguration of the network is carried out
dynamically based on a threshold value which is associated with the
number of nodes belonging to the smallest cluster. To show the
effectiveness of the proposed approach HHRP, a comparative study
with LEACH protocol is illustrated in simulations.
Abstract: A number of toxic chlorophenolic compounds are formed during pulp bleaching. The nature and concentration of these chlorophenolic compounds largely depends upon the amount and nature of bleaching chemicals used. These compounds are highly recalcitrant and difficult to remove but are partially removed by the biochemical treatment processes adopted by the paper industry. Identification and estimation of these chlorophenolic compounds has been carried out in the primary and secondary clarified effluents from the paper mill by GCMS. Twenty-six chorophenolic compounds have been identified and estimated in paper mill waste waters. Electrochemical treatment is an efficient method for oxidation of pollutants and has successfully been used to treat textile and oil waste water. Electrochemical treatment using less expensive anode material, stainless steel electrodes has been tried to study their removal. The electrochemical assembly comprised a DC power supply, a magnetic stirrer and stainless steel (316 L) electrode. The optimization of operating conditions has been carried out and treatment has been performed under optimized treatment conditions. Results indicate that 68.7% and 83.8% of cholorphenolic compounds are removed during 2 h of electrochemical treatment from primary and secondary clarified effluent respectively. Further, there is a reduction of 65.1, 60 and 92.6% of COD, AOX and color, respectively for primary clarified and 83.8%, 75.9% and 96.8% of COD, AOX and color, respectively for secondary clarified effluent. EC treatment has also been found to increase significantly the biodegradability index of wastewater because of conversion of non- biodegradable fraction into biodegradable fraction. Thus, electrochemical treatment is an efficient method for the degradation of cholorophenolic compounds, removal of color, AOX and other recalcitrant organic matter present in paper mill waste water.
Abstract: This paper describes the proficient way of choosing the cluster head based on dominating set algorithm in a wireless sensor network (WSN). The algorithm overcomes the energy deterioration problems by this selection process of cluster heads. Clustering algorithms such as LEACH, EEHC and HEED enhance scalability in WSNs. Dominating set algorithm keeps the first node alive longer than the other protocols previously used. As the dominating set of cluster heads are directly connected to each node, the energy of the network is saved by eliminating the intermediate nodes in WSN. Security and trust is pivotal in network messaging. Cluster head is secured with a unique key. The member can only connect with the cluster head if and only if they are secured too. The secured trust model provides security for data transmission in the dominated set network with the group key. The concept can be extended to add a mobile sink for each or for no of clusters to transmit data or messages between cluster heads and to base station. Data security id preferably high and data loss can be prevented. The simulation demonstrates the concept of choosing cluster heads by dominating set algorithm and trust evaluation using DSTE. The research done is rationalized.
Abstract: Cement is a basic material used for building construction. Chromium as an indelible non-volatile trace element of raw materials occurs in cement clinker in the trivalent or hexavalent form. Hexavalent form of chromium is harmful and allergenic having very high water solubility and thus can easily come into contact with the human skin. The paper is aimed at analyzing the content of total chromium in Portland cements and leaching rate of hexavalent chromium in various leachants: Deionized water, Britton-Robinson buffer, used to simulate the natural environment, and hydrochloric acid (HCl). The concentration of total chromium in Portland cement samples was in a range from 173.2 to 218.5 mg/kg. The content of dissolved hexavalent chromium ranged 0.23-3.19, 2.0-5.78 and 8.88-16.25 mg/kg in deionized water, Britton-Robinson solution and hydrochloric acid, respectively. The calculated leachable fraction of Cr(VI) from cement samples was observed in the range 0.1--7.58 %.
Abstract: Catalytic wet air oxidation (CWAO) is normally carried out at elevated temperature and pressure. This work investigates the potential of NiO-CeO2 nano-catalyst in CWAO of paper industry wastewater under milder operating conditions of 90 °C and 1 atm. The NiO-CeO2 nano-catalysts were synthesized by a simple co-precipitation method and characterized by X-ray diffraction (XRD), before and after use, in order to study any crystallographic change during experiment. The extent of metal-leaching from the catalyst was determined using the inductively coupled plasma optical emission spectrometry (ICP-OES). The catalytic activity of nano-catalysts was studied in terms of total organic carbon (TOC), adsorbable organic halides (AOX) and chlorophenolics (CHPs) removal. Interestingly, mixed oxide catalysts exhibited higher activity than the corresponding single-metal oxides. The maximum removal efficiency was achieved with Ce40Ni60 catalyst. The results indicate that the CWAO process is efficient in removing the priority organic pollutants from wastewater, as it exhibited up to 59% TOC, 55% AOX, and 54 % CHPs removal.
Abstract: Wireless Sensor Networks (WSNs) have many advantages. Their deployment is easier and faster than wired sensor networks or other wireless networks, as they do not need fixed infrastructure. Nodes are partitioned into many small groups named clusters to aggregate data through network organization. WSN clustering guarantees performance achievement of sensor nodes. Sensor nodes energy consumption is reduced by eliminating redundant energy use and balancing energy sensor nodes use over a network. The aim of such clustering protocols is to prolong network life. Low Energy Adaptive Clustering Hierarchy (LEACH) is a popular protocol in WSN. LEACH is a clustering protocol in which the random rotations of local cluster heads are utilized in order to distribute energy load among all sensor nodes in the network. This paper proposes Connected Dominant Set (CDS) based cluster formation. CDS aggregates data in a promising approach for reducing routing overhead since messages are transmitted only within virtual backbone by means of CDS and also data aggregating lowers the ratio of responding hosts to the hosts existing in virtual backbones. CDS tries to increase networks lifetime considering such parameters as sensors lifetime, remaining and consumption energies in order to have an almost optimal data aggregation within networks. Experimental results proved CDS outperformed LEACH regarding number of cluster formations, average packet loss rate, average end to end delay, life computation, and remaining energy computation.
Abstract: The performance of organophosphorus extractants Cyanex 272 and D2EHPA on the purification of concentrate nickel sulfate solutions was evaluated. Batch scale tests were carried out at pH range of 2 to 7 using a laboratory solution simulating concentrate nickel liquors as those typically obtained when sulfate intermediates from nickel laterite are re-leached and treated for the selective removal of cobalt, zinc, manganese and copper with Cyanex 272 ([Ca] = 0.57 g/L, [Mg] = 3.2 g/L, and [Ni] = 88 g/L). The increase on the concentration of D2EHPA favored the calcium extraction. The extraction of magnesium is dependent on the pH and of ratio of extractants D2EHPA and Cyanex 272 in the organic phase. The composition of the investigated organic phase did not affect nickel extraction. The number of stages is dependent on the magnesium extraction. The most favorable operating condition to selectively remove calcium and magnesium was determined.
Abstract: The exploitation of gold ore deposits is highly dependent on efficient mineral processing methods, although actual perspectives based on life-cycle assessment introduce difficulties that were unforeseen in a very recent past. Cyanidation is the most applied gold processing method, but the potential environmental problems derived from the usage of cyanide as leaching reagent led to a demand for alternative methods. Ammoniacal thiosulfate leaching is one of the most important alternatives to cyanidation. In this article, some experimental studies carried out in order to assess the feasibility of thiosulfate as a leaching agent for the ore from the unexploited Portuguese gold mine of Castromil. It became clear that the process depends on the concentrations of ammonia, thiosulfate and copper. Based on this fact, a few leaching tests were performed in order to assess the best reagent prescription, and also the effects of different combination of these concentrations. Higher thiosulfate concentrations cause the decrease of gold dissolution. Lower concentrations of ammonia require higher thiosulfate concentrations, and higher ammonia concentrations require lower thiosulfate concentrations. The addition of copper increases the gold dissolution ratio. Subsequently, some alternative operatory conditions were tested such as variations in temperature and in the solid/liquid ratio as well as the application of a pre-treatment before the leaching stage. Finally, thiosulfate leaching was compared to cyanidation. Thiosulfate leaching showed to be an important alternative, although a pre-treatment is required to increase the yield of the gold dissolution.
Abstract: Nitrogen fertility is an important component for optimum potato yield and quality. Best management practices are necessary in regards to N applications to achieve these goals without applying excess N with may contribute to ground water contamination. Eight potato fields in the Southern San Joaquin Valley were sampled for nitrogen inputs and uptake, tuber and vine dry matter and residual soil nitrate-N. The fields had substantial soil nitrate-N prior to the potato crop. Nitrogen fertilizer was applied prior to planting and in irrigation water as needed based on in-season petiole sampling in accordance with published recommendations. Average total nitrogen uptake was 237 kg ha-1 on 63.5 Mg ha-1 tuber yield and nitrogen use efficiency was very good at 81 percent. Sixty-nine percent of the plant nitrogen was removed in tubers. Soil nitrate-N increased 14 percent from pre-plant to post-harvest averaged across all fields and was generally situated in the upper soil profile. Irrigation timing and amount applied did not move water into the lower profile except for a single location where nitrate also moved into the lower soil profile. Pre-plant soil analysis is important information to be used. Rotation crops having deeper rooting growth would be able to utilize nitrogen that remained in the soil profile.
Abstract: Landfill leachates contain a number of persistent pollutants, including heavy metals. They have the ability to spread in ecosystems and accumulate in fish which most of them are classified as top-consumers of trophic chains. Fish are freely swimming organisms; but perhaps, due to their species-specific ecological and behavioral properties, they often prefer the most suitable biotopes and therefore, did not avoid harmful substances or environments. That is why it is necessary to evaluate the persistent pollutant dispersion in hydroecosystem using fish tissue metal concentration. In hydroecosystems of hybrid type (e.g. river-pond-river) the distance from the pollution source could be a perfect indicator of such a kind of metal distribution. The studies were carried out in the Kairiai landfill neighboring hybrid-type ecosystem which is located 5 km east of the Šiauliai City. Fish tissue (gills, liver, and muscle) metal concentration measurements were performed on two types of ecologically-different fishes according to their feeding characteristics: benthophagous (Gibel carp, roach) and predatory (Northern pike, perch). A number of mathematical models (linear, non-linear, using log and other transformations) have been applied in order to identify the most satisfactorily description of the interdependence between fish tissue metal concentration and the distance from the pollution source. However, the only one log-multiple regression model revealed the pattern that the distance from the pollution source is closely and positively correlated with metal concentration in all predatory fish tissues studied (gills, liver, and muscle).
Abstract: Many cluster based routing protocols have been
proposed in the field of wireless sensor networks, in which a group of
nodes are formed as clusters. A cluster head is selected from one
among those nodes based on residual energy, coverage area, number
of hops and that cluster-head will perform data gathering from
various sensor nodes and forwards aggregated data to the base station
or to a relay node (another cluster-head), which will forward the
packet along with its own data packet to the base station. Here a
Game Theory based Diligent Energy Utilization Algorithm (GTDEA)
for routing is proposed. In GTDEA, the cluster head selection is done
with the help of game theory, a decision making process, that selects
a cluster-head based on three parameters such as residual energy
(RE), Received Signal Strength Index (RSSI) and Packet Reception
Rate (PRR). Finding a feasible path to the destination with minimum
utilization of available energy improves the network lifetime and is
achieved by the proposed approach. In GTDEA, the packets are
forwarded to the base station using inter-cluster routing technique,
which will further forward it to the base station. Simulation results
reveal that GTDEA improves the network performance in terms of
throughput, lifetime, and power consumption.
Abstract: Landfill waste is a common problem as it has an
economic and environmental impact even if it is closed. Landfill
waste contains a high density of various persistent compounds such
as heavy metals, organic and inorganic materials. As persistent
compounds are slowly-degradable or even non-degradable in the
environment, they often produce sublethal or even lethal effects on
aquatic organisms. The aims of the present study were to estimate
sublethal effects of the Kairiai landfill (WGS: 55°55‘46.74“,
23°23‘28.4“) leachate on the locomotor activity of rainbow trout
Oncorhynchus mykiss juveniles using the original system package
developed in our laboratory for automated monitoring, recording and
analysis of aquatic organisms’ activity, and to determine patterns of
fish behavioral response to sublethal effects of leachate. Four
different concentrations of leachate were chosen: 0.125; 0.25; 0.5 and
1.0 mL/L (0.0025; 0.005; 0.01 and 0.002 as part of 96-hour LC50,
respectively). Locomotor activity was measured after 5, 10 and 30
minutes of exposure during 1-minute test-periods of each fish (7 fish
per treatment). The threshold-effect-concentration amounted to 0.18
mL/L (0.0036 parts of 96-hour LC50). This concentration was found
to be even 2.8-fold lower than the concentration generally assumed to
be “safe” for fish. At higher concentrations, the landfill leachate
solution elicited behavioral response of test fish to sublethal levels of
pollutants. The ability of the rainbow trout to detect and avoid
contaminants occurred after 5 minutes of exposure. The intensity of
locomotor activity reached a peak within 10 minutes, evidently
decreasing after 30 minutes. This could be explained by the
physiological and biochemical adaptation of fish to altered
environmental conditions. It has been established that the locomotor
activity of juvenile trout depends on leachate concentration and
exposure duration. Modeling of these parameters showed that the
activity of juveniles increased at higher leachate concentrations, but
slightly decreased with the increasing exposure duration. Experiment
results confirm that the behavior of rainbow trout juveniles is a
sensitive and rapid biomarker that can be used in combination with
the system for fish behavior monitoring, registration and analysis to
determine sublethal concentrations of pollutants in ambient water.
Further research should be focused on software improvement aimed
to include more parameters of aquatic organisms’ behavior and to
investigate the most rapid and appropriate behavioral responses in
different species. In practice, this study could be the basis for the
development and creation of biological early-warning systems
(BEWS).
Abstract: In the present study, feasibility of the selective surface
hydrophilization of polyvinyl chloride (PVC) by microwave treatment
was evaluated to facilitate the separation from automotive shredder
residue (ASR), by the froth flotation. The combination of 60 sec
microwave treatment with PAC, a sharp and significant decrease about
16.5° contact angle of PVC was observed in ASR plastic compared
with other plastics. The microwave treatment with the addition of PAC
resulted in a synergetic effect for the froth flotation, which may be a
result of the 90% selective separation of PVC from ASR plastics, with
82% purity. While, simple mixing with a nanometallic Ca/CaO/PO4
dispersion mixture immobilized 95-100% of heavy metals in ASR
soil/residues. The quantity of heavy metals leached from thermal
residues after treatment by nanometallic Ca/CaO/PO4 was lower than
the Korean standard regulatory limit for hazardous waste landfills.
Microwave treatment can be a simple and effective method for PVC
separation from ASR plastics.
Abstract: Biochar can be produced from the waste matter and its
application has been associated with returning of carbon in large
amounts into the soil. The impacts of this material on physical and
chemical properties of soil have been described. The biggest part of
the research work is dedicated to the hypothesis of this material’s
toxic effects on the soil life regarding its effect on the soil biological
component. At present, it has been worked on methods which could
eliminate these undesirable properties of biochar. One of the
possibilities is to mix biochar with organic material, such as compost,
or focusing on the natural processes acceleration in the soil. In the
experiment has been used as the addition of compost as well as the
elimination of toxic substances by promoting microbial activity in
aerated water environment. Biochar was aerated for 7 days in a
container with a volume of 20 l. This way modified biochar had six
times higher biomass production and reduce mineral nitrogen
leaching. Better results have been achieved by mixing biochar with
compost.
Abstract: Wireless Sensor Network (WSN) routing is complex
due to its dynamic nature, computational overhead, limited battery
life, non-conventional addressing scheme, self-organization, and
sensor nodes limited transmission range. An energy efficient routing
protocol is a major concern in WSN. LEACH is a hierarchical WSN
routing protocol to increase network life. It performs self-organizing
and re-clustering functions for each round. This study proposes a
better sensor networks cluster head selection for efficient data
aggregation. The algorithm is based on Tabu search.
Abstract: The ferrites ZnFe2O4, CdFe2O4 and CuFe2O4 are
synthesized in laboratory conditions using ceramic technology. Their
homogeneity and structure are proven by X-Ray diffraction analysis
and Mössbauer spectroscopy. The synthesized ferrites are subjected
to strong acid and high temperature leaching with solutions of H2SO4,
HCl and HNO3. The results indicate that the highest degree of
leaching of Zn, Cd and Cu from the ferrites is achieved by use of
HCl. The charging of five zinc sulfide concentrates was optimized using
the criterion of minimal amount of zinc ferrite produced when
roasting the concentrates in a fluidized bed. The results obtained are
interpreted in terms of the hydrometallurgical zinc production and
maximum recovery of zinc, copper and cadmium from initial zinc
concentrates after their roasting.
Abstract: Comparative analysis of the properties of melon seed,
coconut fruit and their oil yield were evaluated in this work using
standard analytical technique AOAC. The results of the analysis
carried out revealed that the moisture contents of the samples studied
are 11.15% (melon) and 7.59% (coconut). The crude lipid content are
46.10% (melon) and 55.15% (coconut).The treatment combinations
used (leaching time, leaching temperature and solute: solvent ratio)
showed significant difference (p < 0.05) in yield between the
samples, with melon oil seed flour having a higher percentage range
of oil yield (41.30 – 52.90%) and coconut (36.25 – 49.83%). The
physical characterization of the extracted oil was also carried out.
The values gotten for refractive index are 1.487 (melon seed oil) and
1.361 (coconut oil) and viscosities are 0.008 (melon seed oil) and
0.002 (coconut oil). The chemical analysis of the extracted oils shows
acid value of 1.00mg NaOH/g oil (melon oil), 10.050mg NaOH/g oil
(coconut oil) and saponification value of 187.00mg/KOH (melon oil)
and 183.26mg/KOH (coconut oil). The iodine value of the melon oil
gave 75.00mg I2/g and 81.00mg I2/g for coconut oil. A standard
statistical package Minitab version 16.0 was used in the regression
analysis and analysis of variance (ANOVA). The statistical software
mentioned above was also used to optimize the leaching process.
Both samples gave high oil yield at the same optimal conditions. The
optimal conditions to obtain highest oil yield ≥ 52% (melon seed)
and ≥ 48% (coconut seed) are solute - solvent ratio of 40g/ml,
leaching time of 2hours and leaching temperature of 50oC. The two
samples studied have potential of yielding oil with melon seed giving
the higher yield.
Abstract: In order to obtain efficient pollutants removal in
small-scale wastewater treatment plants, uniform water flow has to be
achieved. The experimental setup, designed for treating high-load
wastewater (leachate), consists of two aerobic biological reactors and
a lamellar settler. Both biological tanks were aerated by using three
different types of aeration systems - perforated pipes, membrane air
diffusers and tube ceramic diffusers. The possibility of homogenizing
the water mass with each of the air diffusion systems was evaluated
comparatively. The oxygen concentration was determined by optical
sensors with data logging. The experimental data was analyzed
comparatively for all three different air dispersion systems aiming to
identify the oxygen concentration variation during different
operational conditions. The Oxygenation Capacity was calculated for
each of the three systems and used as performance and selection
parameter. The global mass transfer coefficients were also evaluated
as important tools in designing the aeration system. Even though
using the tubular porous diffusers leads to higher oxygen
concentration compared to the perforated pipe system (which
provides medium-sized bubbles in the aqueous solution), it doesn’t
achieve the threshold limit of 80% oxygen saturation in less than 30
minutes. The study has shown that the optimal solution for the
studied configuration was the radial air diffusers which ensure an
oxygen saturation of 80% in 20 minutes. An increment of the values
was identified when the air flow was increased.
Abstract: Constructed Wetland (CW) is a reasonable method to
treat wastewater. Current study was carried out to co-treat landfill
leachate and domestic wastewater using a CW system. Typha
domingensis was transplanted to CW, which encloses two substrate
layers of adsorbents named ZELIAC and zeolite. Response surface
methodology and central composite design were employed to
evaluate experimental data. Contact time (h) and leachate-towastewater
mixing ratio (%; v/v) were selected as independent
factors. Phenols and manganese removal were selected as dependent
responses. At optimum contact time (48.7 h) and leachate-towastewater
mixing ratio (20.0%), removal efficiencies of phenols and
manganese removal efficiencies were 90.5%, and 89.4%,
respectively.