Personal Research Database

Full Text: W\Wat Res26, 311.pdf

Abstract: The concentrations of cadmium, copper, lead, the organic compounds of lead and eight polycyclic aromatic hydrocarbons have been measured in surface drainage waters from a major rural highway in north-west England during a number of runoff events. The particulate phase (> 0.45-mu-m) contained > 90% of the inorganic Pb, approximately 70% of the Cu and approximately 56% of the Cd and the particulate-phase metal concentration profiles largely followed those of the suspended sediments. A ‘first-flush’ effect was seen for the dissolved metals. A highly significant correlation was found between the length of the antecedent dry period and the amount of lead and dissolved copper removed during a runoff event but this was not found for the other pollutants. A simple regression model allows the reliable first-order approximation of lead concentrations and removal rates in the runoff waters to be made from the discharge rate and the length of the antecedent dry period. Budget calculations show that approximately 8% of the Pb, 5% of the organic lead and 3% of the PAHs emitted by vehicles are removed in the highway drainage waters.

Keywords: Pollution, Motor Vehicles, Runoff Waters, Drainage Waters, Highway, Lead, Cadmium, Copper, Polycyclic Aromatic Hydrocarbons, Chemical-Composition, Drainage Waters, Metals, Speciation, Lead

Nyholm, N., Jacobsen, B.N., Pedersen, B.M., Poulsen, O., Damborg, A. and Schultz, B. (1992), Removal of organic micropollutants at PPB levels in laboratory activated sludge reactors under various operating conditions: biodegradation. Water Research, 26 (3), 339-353.

Full Text: W\Wat Res26, 339.pdf

Abstract: The biodegradation behaviour of 5 model chemical contaminants, 2,4-dichlorophenoxy acetic acid (2,4-D); 2,4,6-trichlorophenol (TCP); pentachlorophenol (PCP); 4-nitrophenol (4-NP) and lindane, spiked into synthetic peptone sewage to g/l levels (5–1000 g/l) have been studied in laboratory activated sludge reactors under a range of operating conditions (sludge ages of 1–32 days and sludge loadings of 0.09–0.9 mg BOD₅/mg MLSS/d). The reactors were continuously stirred tanks operated under a computer controlled fill and draw cycle of 4 h. Experiments were started with sludge collected from a municipal treatment plant.

In most experiments, a gradual adaptation took place resulting in increases in biodegradation rates by an order of magnitude or more compared to initial biodegradation rates and rates obtained in comparative batch experiments, respectively. Times required for adaptation varied among chemicals and experiments and ranged from 2–5 days for 4-NP to 1–2 months for 2,4-D and lindane. No concentration thresholds for adaptation were observed, and the biodegradation generally followed first-order kinetics. Removals by biodegradation in successfully adapted systems were generally within a range of about 40 to about 95% except for 4-NP, which was degraded to concentration levels below the analytical detection limit. For estimation of the part of the total removal which was due to biodegradation the amounts of PCP, TCP and lindane wasted with the sludge were calculated from sorption isotherms. Volatilization was negligible. The operational parameters influenced the biodegradation differently for the different chemicals. PCP was degraded best at high sludge ages and was not degraded significantly at sludge ages below approx. 8 days. This suggests catabolic degradation by slow growing specific degraders. TCP was consistently degraded at high sludge ages (low sludge loadings) and at random at lower sludge ages, but rate constants were highest at intermediate sludge loadings. A similar pattern was seen for 2,4-D. Lindane was degraded poorly at high sludge ages and to a much greater extent at intermediate and at high sludge loadings. These findings suggest co-oxidation as the dominant degradation mechanism for lindane and as a significant mechanism for TCP and 2,4-D.

Keywords: Biodegradation, Trace Contaminants, Chemical Contaminants, Organic Micropollutants, Xenobiotic Compounds, Activated Sludge, Sewage Treatment Plants, Adaptation

Waara, K.O. (1992), Effects of copper, cadmium, lead and zinc on nitrate reduction in a synthetic water medium and lake water from northern Sweden. Water Research, 26 (3), 355-364.

Full Text: W\Wat Res26, 355.pdf

Abstract: This paper presents laboratory experiments on the effects of heavy metal on nitrate reduction, using natural lake water or a synthetic water medium without complexing agents. A bacteria inoculum consisting of a mixed facultatively heterotrophic bacterial culture, nitrate and glucose were added to tubes, which were filled to capacity, sealed and incubated in the dark at 20-degrees-C. Nitrate reduction was followed in terms of the decrease in added nitrate against time.

For the synthetic water medium, the effects of Cd, Zn and Pb at concentrations of 10-500 µg l^-1 were tested and for Cu at concentrations between 10 and 100 µg l^-1. Nitrate reduction in natural lake water with and without additions of an external bacterial culture was measured. The effect of an addition of 50 µg l^-1 of metal above the natural level was also investigated. In synthetic water, a 50% decrease in nitrate reduction activity was found at about 25 µg Cu l^-1, 85 µg Cd l^-1, 95 µg Pb l^-1 or 200-400 µg Zn l^-1. The order of toxicity was Cu > Cd > = Pb > Zn.

In the lake water, nitrate reduction activity decreased with increasing metal levels. From the experiments involving the addition of metal to lake water the order of toxicity was found to be Cu > Cd > = Pb > Zn.

Keywords: Nitrate Reduction, Copper, Cadmium, Lead, Zinc, Toxicity, Lake Water, Synthetic Water, Microorganisms

Deans, J.R. and Dixon, B.G. (1992), Uptake of Pb²⁺ and Cu²⁺ by novel biopolymers. Water Research, 26 (4), 469-472.

Full Text: W\Wat Res26, 469.pdf

Abstract: A series of different functionalized biopolymers were prepared and their comparative efficiencies for removing lead(II) and copper(II) ions from water at part per million concentrations determined. The biopolymers evaluated included cellulose, alginic acid, chitin, chitosan and carrageenan. Besides the base bipolymers, the carboxymethyl and hydroxamic acid derivatives of these materials were prepared and tested as well. Terephthalic acid and its hydroxamic acid derivative and a state of the art ion exchange resin, Chelex 20TM (Bio-Rad), were also tested as controls. It was found that, generally, the hydroxamic acid derivatives were the most efficient at removing both metals at a number of different starting ion concentrations although no one material was found to be the best under all experimental circumstances.

Keywords: Lead, Copper, Heavy Metals, Biopolymer, Pollution, Cellulose, Alginate, Chitin, Chitosan

Luo, B., Patterson, J.W. and Anderson, P.R. (1992), Kinetics of cadmium hydroxide precipitation. Water Research, 26 (6), 745-751.

Full Text: W\Wat Res26, 745.pdf

Abstract: The kinetics of cadmium hydroxide precipitation in the presence and in the absence of citrate was investigated. Precipitation experiments were conducted in a continuous stirred tank reactor. Experiments were performed with initial cadmium concentrations ranging from 2.0 to 4.0×10^-4 M; a range commonly occurring in electroplating rinsewater.

A population balance model was used to compute the nucleation and particle growth rates and relate these to the supersaturation ratio. Particle growth rates found in the presence of citrate were much lower than that in the absence of citrate. The examination of growth inhibition suggested that the mechanism was surface reaction controlled.

Keywords: Cadmium Hydroxide, Precipitation, Kinetics, Nucleation, Particle Growth, Growth Rate, Population Balance, Growth Inhibition, Citrate

Bhargava, D.S. and Killedar, D.J. (1992), Fluoride adsorption on fishbone charcoal though a moving media adsorber. Water Research, 26 (6), 781-788.

Full Text: W\Wat Res26, 781.pdf

Abstract: Results of studies conducted to investigate the effect of some of the variables viz. sorbent mass input rate, sorbate flow-rate, initial sorbate concentration on the removal of fluoride by adsorption on fishbone charcoal in a moving media adsorption system, are presented. The ratio of attained equilibrium sorbate concentration to the initial sorbate concentration and the fluoride removal capacity of sorbent were found to vary inversely with the sorbent mass input rate whereas they varied directly with the sorbate flow rate and initial sorbate concentration. Empirical relationships have been developed to predict the ratio of attained equilibrium sorbate concentration to the initial sorbate concentration and the fluoride removal capacity of sorbent with respect to the variables investigated for the observed test conditions. The conventional isotherms (Langmuir and Freudlich isotherms) showed no good correlations for the data of the presented study. Correlation equations for the moving media adsorption system have been evolved. The ratio of attained equilibrium sorbate concentration to the initial sorbate concentration was found to be a function of sorbent-sorbate mass input rates ratio. Also, a model between these parameters manifesting a fairly high coefficient of correlation is presented.

Keywords: Adsorption, Fishbone Charcoal, Fluoride Removal, Moving Media Absorber, Isotherm Relationships, Reactor

? Kuo, W.G. (1992), Decolorizing dye wastewater with Fenton’s reagent. Water Research, 26 (7), 881-886.

Full Text: 1992\Wat Res26, 881.pdf

Abstract: Five types of simulated dye wastewater, separately prepared with disperse, reactive, direct, acid and basic dyes, were decolorized with a hydrogen peroxide-ferrous ion system, known as Fenton’s reagent. The results are that the best pH value for decolorization is below 3.5, the average percent removal of chemical oxygen demand (COD) is about 90%, the transparency of wastewater is above 25 cm and the average percent decolorization is above 97%. All the results of treating the dye wastewater of actual dyeing and finishing mills are similar to those in the laboratory. Temperature mainly influences the speed of decolorization, i.e. the lower the temperature, the longer the time for decolorization.

Keywords: Dye Wastewater, Fenton’s Reagent, Decolorization, Transparency, COD, Absorbency

Gagnon, C., Arnac, M. and Brindle, J.R. (1992), Sorption interactions between trace metals (Cd and Ni) and phenolic substances on suspended clay minerals. Water Research, 26 (8), 1067-1072.

Full Text: W\Wat Res26, 1067.pdf

Abstract: The phenomena of pollutant fixation on suspended clay minerals (chlorite, illite and kaolinite) were studied in an estuarine system. Isotherms and the dependence of adsorption on time for Cd, Ni and phenolic compounds (eugenol and vanillic acid) were studied. Clay minerals (as suspended matter) were exposed to trace metals and phenolic compound solutions. It was found that chlorite was a better adsorbent with 71% of Cd and 79% of Ni adsorbed at concentrations of suspended particulate matter of 400 mg l^-1. At pH 8, the quantity of adsorbed phenolic compounds was lower than that of trace metals (up to 23% as compared to up to 79%). After examinations of adsorption capacities, investigation of the interactive effects of these pollutants on the sorption phenomena was studied. Cadmium would compete with nickel for the same adsorption sites. Vanillic acid was less sorbed than eugenol, but phenolic compounds generally enhanced the sorption of metallic cations on studied clay minerals. The presence of metallic cations increased the sorption of phenolic compounds. Investigated phenolic compounds represent the structure of humic substances in the environment, which are considered a predominant form of soluble (or colloidal) organic matter in natural waters.

Keywords: Sorption, Clay Minerals, Metals, Phenolic Compounds, Nickel, Cadmium, Eugenol, Vanillic Acid, Interaction, Atomic-Absorption Spectrometry, St-Lawrence Estuary, Adsorption, Matter, Cadmium, Copper, Oxide, Water

Notes: highly cited

Guibal, E., Roulph, C. and Le Cloirec, P. (1992), Uranium biosorption by a filamentous fungus mucor-miehei pH effect on mechanisms and performances of Uptake. Water Research, 26 (8), 1139-1145.

Full Text: W\Wat Res26, 1139.pdf

Abstract: This study focuses on uranium sorption mechanisms by Mucor miehei, a fungal biomass, used in agro-industries (enzyme synthesis). The pH plays an important part in these phenomena, mainly by its influence on metal or cell wall chemistry. Hydroxylation of uranyl, dependent on the pH and total metal concentration, influences kinetics, via the nature of the limiting phases: diffusion of metal through layers bordering or constituting the biomass, or intramembranar precipitation of uranyl initially adsorbed, and sorption mechanisms. With a moderate pH, sorption of uranylhydroxides modifies extracellular sorbent structures, consequently inducing a multilayer sorption opposed to monolayer adsorption obtained with acid pH. Uptake capacity is characterized by high values obtained even with low metal concentration in solution. Biosorbent could be a technical answer to pollution treatment and valorization of low charge waste streams and leaching solutions obtained in recovery of infra-marginal ores.

Keywords: Adsorption, Complexation, Diffusion, Fungus, Hydrolysis, Isotherms, Kinetics, Leaching, Metal, Microorganisms, pH, Removal, Rhizopus-arrhizus, Sorption, Uranium, Waste, Water

? Kennedy, K.J., Lu, J.H. and Mohn, W.W. (1992), Biosorption of chlorophenols to anaerobic granular sludge. Water Research, 26 (8), 1085-1092.

Full Text: 1992\Wat Res26, 1085.pdf

Abstract: The sorption of chlorophenols by anaerobic sludge granules was studied in order to more completely understand the fate of chlorophenols and their degradation products in upflow anaerobic sludge blanket reactors. Sorption isotherms were determined for pentachlorophenol and most isomers of tri-, di- and monochlorophenols, and the data were fitted to the Freundlich equation. Sorption by the sludge granules was considerable. Most, but not all, chlorophenols had linear sorption isotherms, which were defined by simple distribution coefficients. Those distribution coefficients were only weakly correlated to octanol-water partition coefficients, and there were no obvious relationships between sorption and numbers or positions of chlorine substituents. Sorption of two chlorophenols was highly reversible, but it was not for a third chlorophenol tested. Pentachlorophenol was more strongly sorbed than the lesser-chlorinated phenols, and pentachlorophenol sorption by sludge granules was weaker than its previously reported sorption by other biological materials. The Freundlich model, with empirically determined constants from this study, described the partitioning behaviour of chlorophenols in anaerobic sludge blanket reactors reasonably well.

Keywords: chlorophenols, biosorption, anaerobic, biomass

Moutin, T., Gal, J.Y., El Halouani, H., Picot, B. and Bontoux, J. (1992), Decrease of phosphate concentration in a high rate pond by precipitation of calcium phosphate: Theoretical and experimental results. Water Research, 26 (11), 1445-1450.

Full Text: W\Wat Res26, 1445.pdf

Abstract: The mechanism involved in the decrease of phosphate in a high rate pond (HRP) is investigated. The calcium concentration in the water (1.25-3.75 mM) and the high pH obtained in the reactors (8-10), result in the precipitation of calcium phosphate minerals. Although calcium hydroxyapatite [Ca₅(PO₄)₃OH, pK(s) = 571 is the thermodynamical stable state, the phosphate concentration is determined by the solubility of the amorphous tricalcium phosphate [Ca₃(PO₄)₂, PK(s) = 25.2]. This is confirmed by the calculation of the theoretical predicted solubility as well as various experiments. The relationship between pH and phosphate concentration may be used to optimize the efficiency of this type of reactor to produce a minimum concentration of phosphate in the effluent.

Keywords: Phosphorus Removal, Waste-Water Treatment, High Rate Pond, Calcium, Phosphate, Chemical Precipitation, Hydroxyapatite, pH

Lo, C.K. and Fung, Y.S. (1992), Heavy metal pollution profiles of dated sediment cores from Hebe Haven, Hong Kong. Water Research, 26 (12), 1605-1619.

Full Text: W\Wat Res26, 1605.pdf

Abstract: Eight sediment cores from Hebe Haven were collected and studied for metals including Cd, Cr, Cu, Fe, Ni, Pb, Zn and Ca. Pb-210 and Cs-137 activities were determined to date the time of deposition of the sediment. Hebe Haven is a yacht area and is close to the urbanized coast with several dyeing factories. Except Cd, the greatest enrichment was found at locations closest to the Ho Chung Stream which carried domestic and industrial wastewater to Hebe Haven. Concentrations as high as 0.930, 120, 131, 42.3 and 50.9 mg/kg were found for Cd, Cr, Zn, Cu and Pb, respectively. The corresponding enrichment factors are 13(Cd), 7.0(Cr), 2.9(Zn), 5.2(Cu) and 2.4(Pb). The extent of pollution diminishes from the riverine source. Cr is a typical example because its enrichment was mostly attributed to the nearby dyeing operation. The distribution of Cd appears more complicated. A maximum concentration of 3.60 mg/kg was found at a location far from Ho Chung Stream and with no nearby municipal or industrial activity. No significant Fe and Ni enrichment was found in the area. Ca in all cores decreases towards the sediment-water interface. It is probable that the abundance of shellfish has decreased as a result of excessive exploitation as seafood and pollution. Pb-210 activity and heavy metal concentrations of surficial layers have been ‘diluted’ by excessive deposition of Fe-deficient particles. This likely indicates the rapid deposition of coarser and sandy particles during the construction of a nearby large housing estate. Some Pb-210 activity profiles have periodic low values in deeper layers, which should correspond to events of rapid deposition of erosion during heavy typhoons and rainstorms. Overall, the sedimentation rates calculated were in the range of 0.351-0.561 cm/yr. In one site (Core S4) close to the riverine source and with the best available dating data, the recent anthropogenic fluxes of heavy metals in µg cm^-2 yr^-1 are estimated as: 0.081(Cd), 22(Cr), 20(Zn), 6.4(Cu) and 7.4(Pb).

Keywords: Heavy Metals, Calcium, Pb-210 Dating, Concentration Profiles, Sediment Core, Dyeing Plants, Pollution, River, California, Records

Rav-Achha, Ch. and Rebhun, M. (1992), Binding of organic solutes to dissolved humic substaces and its effects on adsorption and transport in the aquatic environment. Water Research, 26 (12), 1645-1654.

Full Text: W\Wat Res26, 1645.pdf

Abstract: Humic substances constitute a major fraction of dissolved organic matter in natural water and effluents. Their effect on the adsorption of organic contaminants to aquifer material was elucidated, and a model was proposed for the adsorption of organic solutes to aquifer solids in the presence of dissolved humic substances. The model is based on the assumption that organic solute binds to dissolved humic substances in a reversible manner to form a solute humate complex. Following binding, both free and bound fractions of the organic solute are independently adsorbed onto the solid phase. In order to evaluate the validity of the model, the following parameters were determined: (1) the adsorption coefficient of the organic solute to clay; (2) the binding constant of the solute humate complex; and (3) the adsorption of humic acid (HA) to clay, assuming that the solute humate complex is adsorbed similarly to humic acid itself. Using these parameters in the model enabled the effect of dissolved humic substances on adsorption to be evaluated. Experimental results obtained for the adsorption of fluoranthene (a model compound of the PAH group) to clay in the presence of dissolved HA were compared with calculated values derived from the model described above. The sensitivity of the model to various parameters was evaluated and a prediction was made with respect to the effect of dissolved humic substances on the adsorption of a variety of organic solutes. It appears that dissolved humic substances solubilize organic solutes which have higher adsorption coefficients to clay than humic substances, but increase the adsorption of solutes having lower adsorption coefficients relative to humic substances.

Keywords: Sorption, Organic Solutes, Interaction Model, Solubilization, Binding To Humic Substances, Polycyclic Aromatic-Hydrocarbons, Biodegradation, Groundwater, Pollutants, Sorption, Systems, Matter, Water

Delgado, M., Bigeriego, M. and Guardiola, E. (1993), Uptake of Zn, Cr and Cd by water hyacinths. Water Research, 27 (2), 269-272.

Full Text: W\Wat Res27, 269.pdf

Abstract: Studies were conducted in a greenhouse to determine the phytotoxic effect and uptake capacity of Zn, Cr and Cd by the water hyacinth Eichhornia crassipes. Results show that among the three elements tested, Cd was the most phytotoxic, showing up some necrosis in the plant when the concentration was greater than 2.5 ppm. In the case of Cr and Zn, the phytotoxicity produced the appearance of chlorosis in the aerial part of the plant. For the tested rates of Cr (maximum 9 ppm) no reduction of productivity was found, whereas in the case of Zn the concentration of 9 ppm in solution caused a 30% reduction in the weight. As for the heavy metal absorption, it was proved that after 24 days of growth, the heavy metals were totally depleted from the nutritive solution suggesting complete absorption of these metals by the plants.

Keywords: Absorption, Heavy Metals, Chlorosis, Concentration, Growth, Phytotoxic, Necrosis, Water Hyacinth, Pollution, Treatment, Cadmium, Plants, Soils, Corn

Bhargava, D.S. and Sheldarkar, S.B. (1993), Use of TNSAC in phosphate adsorption studies and relationships. Literature, experimental methodology, justification and effects of process variables. Water Research, 27 (2), 303-312.

Full Text: W\Wat Res27, 303.pdf

Abstract: There is a need for developing low cost, easily and abundantly available, yet efficient, adsorbents for the removal of phosphates during the tertiary treatment of wastewaters. The tamarind nut shell activated carbon (TNSAC) prepared on a laboratory scale has been used to evaluate its performance for phosphate adsorption. This paper describes the laboratory production of this adsorbent material in its various forms, and discusses the effects of the TNSAC process variables (the unrinsed and rinsed forms of the TNSAC and the impregnation ratio) on its performance in adsorbing phosphate. The material has been shown to be a good alternative adsorbent. As much as 95% phosphate removal by the unrinsed TNSAC is possible in about 30 min under the test conditions. The phosphate adsorbing capacity is about two times higher for the unrinsed TNSAC in comparison to the rinsed TNSAC. The adsorption rates, however, transit to extremely low rates towards the end when equilibrium conditions could be attained in about 2 h contact time. The phosphate removal mechanics are adsorption and precipitation/ion exchange when unrinsed TNSAC is used, and adsorption alone for the rinsed TNSAC. The maximum phosphate removal is found to take place at an impregnation ratio of 10 for both forms of the TNSAC.

Keywords: Tamarind Nut Shell, Activated Carbon, Phosphate Adsorption, Process Variables, Moving-Media Reactor, Exhausted Activated Carbon, Chemical Regeneration, Water, Diffusion, Sorbent

Bhargava, D.S. and Sheldarkar, S.B. (1993), Use of TNSAC in phosphate adsorption studies and relationships. Effects of adsorption operating variables and related relationships. Water Research, 27 (2), 313-324.

Full Text: W\Wat Res27, 313.pdf

Abstract: The phosphate removal potential of a low cost and abundantly available material, tamarind nut shell activated carbon (TNSAC) was investigated. A previous paper of ours has described the laboratory scale production of this material and the effects of the process variables (unrinsed and rinsed forms of the TNSAC and the impregnation ratio) on its performance in adsorbing phosphates. This paper discusses the effects of operating variables (adsorbent particles size, initial adsorbate concentration, adsorbent dose and contact time duration) on the phosphate adsorption by the TNSAC. Phosphate removal is seen to increase with increasing adsorbent doses, decreasing adsorbent particle size and increasing ratios of initial phosphate concentration to adsorbent dose. The unrinsed TNSAC provides higher phosphate removal in comparison to the rinsed TNSAC. The maximum difference in the effectiveness of the unrinsed and rinsed TNSAC is seen to occur at an adsorbent dose of 2 g l^-1 under the test conditions. The lowest equilibrium phosphate concentration is attained at an impregnation ratio of 1.0. Models for predicting phosphate removal have been evolved. These models also incorporate operational variables such as the adsorbent particle size, initial adsorbate concentration, adsorbent dose, contact time etc., and manifest high values of the correlation coefficients.

Keywords: Tamarind Nut Shell, Activated Carbon, Phosphate Adsorption, Operation Variables

Bhargava, D.S. and Sheldarkar, S.B. (1993), Use of TNSAC in phosphate adsorption studies and relationships. Isotherm relationships and utility in the field. Water Research, 27 (2), 325-335.

Full Text: W\Wat Res27, 325.pdf

Abstract: The studies related to the phosphate removal potential of a laboratory scale produced adsorbent, the tamarind nut shell activated carbon (TNSAC), have been partly reported in two papers by us which described the production of the various TNSAC forms, and the effects of the process variables (unrinsed and rinsed TNSAC forms and the impregnation ratio) and of the operational variables (adsorbent particle size, initial adsorbate concentration, adsorbent dose and contact time duration) on the performance evaluation of the TNSAC in adsorbing phosphates. The performance predictive models were also presented. This paper discusses the adsorption isotherm relationships and models. The applicability of the system to real field situations, and the reuse possibility and removal of the phosphate loaded adsorbent particles, have also been brought out in this paper. The isotherm plots show higher phosphate adsorptive capacity for greater equilibrium concentration values. The highest adsorptive capacity results at an impregnation ratio of 1.0 for both forms of the TNSAC and at all adsorbent doses. The adsorptive capacity is higher for the unrinsed TNSAC in comparison to the rinsed TNSAC, corresponding to the same equilibrium concentration. The rinsed TNSAC yields an isotherm model similar to the Freudlich isotherm. The unrinsed TNSAC does not yield any conventional isotherm forms, yet they have been modelled. Generalized models for predicting the adsorptive capacity have been evolved, and such models also incorporate the impregnation ratio, and the term for the adsorbent particle size. The models have indicated high correlation coefficients. When present in wastewaters, the adsorption of phosphates on the TNSAC is seen to reduce due to the preferential adsorption of other pollutants present in the wastewaters. The spent and phosphate loaded TNSAC particles are seen to be removable. Physical adsorption is seen to be the predominantly likely mechanism of phosphate adsorption on the TNSAC, which suggests the reuse possibility of the TNSAC.

Keywords: Tamarind Nut Shell Activated Carbon, Phosphate Adsorption, Modeling, Isotherm Relationships, Moving-Media Reactor

Ojha, C.S.P. and Graham, N.J.D. (1993), Theoretical estimates of bulk specific deposit in deep bed filters. Water Research, 27 (3), 377-387.

Full Text: W\Wat Res27, 377.pdf

Abstract: The evaluation of bulk specific deposit values forms an integral part of deep bed filtration modelling. As the observations in filtration experiments are generally restricted to the monitoring of headloss and filtrate concentration (in mass units), estimates of only absolute specific deposit values (m/v) are possible. In many previous studies, a term known as the ‘bulk factor’ is incorporated into the modelling of the filtration process such that the product of the bulk factor with the absolute specific deposit (m/v), gives an estimate of the bulk specific deposit (v/v). In these investigations the bulk factor is treated as constant. Alternatively, other authors have obtained the variation of the bulk factor with the absolute specific deposit by using Kozeny’s headloss model. Thus, it can be seen that so far the process of obtaining a particular variation of the bulk factor and its subsequent use in the modelling of a filtration process has not been adequately considered. The present study presents a novel approach based on the development of sequential decision-making algorithms. It is concluded that this approach has the advantages of being computationally more efficient and avoids the need to assume a headloss model.

Keywords: Absolute Specific Deposit, Bulk Factor, Bulk Specific Deposit, Filtration Modeling, Deep Bed Filtration, Headloss, Sequential Algorithms, Filtration

Powelson, D.K., Gerba, C.P. and Yahya, M.T. (1993), Virus transport and removal in wastewater during aquifer recharge. Water Research, 27 (4), 583-590.

Full Text: W\Wat Res27, 583.pdf

Abstract: To assess soil-aquifer treatment of sewage effluent for removal of viruses, studies were conducted at a recharge/recovery site near Tucson, Ariz. Two 13 m2 basins were constructed in coarse sand alluvium, one for secondary-and one for tertiary-treated effluent. Bacterial viruses, MS2 and PRD1, and a chemical tracer, potassium bromide (KBr), were added to effluent applied to these basins. Infiltration rates ranged from 0.2 to 16.8 m/d. Samples of unsaturated flow from depths of 0.30-6.08 m below the basin were taken through porous stainless steel suction-samplers. Bromide and virus results indicated the presence of preferential flow conditions that produced irregular concentration profiles with depth. Virus transport was retarded (R = 1.9) at the beginning of a flooding cycle, but viruses were transported faster than the average water velocity (R = 0.47) when applied after the infiltration rate had declined following 4 days of flooding. Virus specific removal rates (b) during percolation through soil were 2.3-120 times greater than in bottles of effluent or ground water. PRD1 was removed more rapidly during percolation (b = 0.65 h^-1) than MS2 (b = 0.23 h^-1). Effluent type did not significantly affect b for MS2, but the PRD1 rate was nearly 3 times greater with secondary effluent (1.0 h^-1) compared to tertiary effluent (0.35 h^-1). Virus removals at the 4.3 m depth ranged from 37 to 99.7%.

Keywords: Reclamation of Water, Land Disposal, Recharge, Sewage, Effluent, Virus, Bacteriophage, MS2, PRD1, Removal, Transport, Bacteria Removal, Soils, Infiltration, Adsorption, Movement

Auer, M.T. and Niehaus, S.L. (1993), Modeling fecal-coliform bacteria. I. Field and laboratory determination of loss kinetics. Water Research, 27 (4), 693-701.

Full Text: W\Wat Res27, 693.pdf

Abstract: Contamination of surface waters through the discharge of fecal material in surface run-off, combined sewer overflows and point source discharges is an important water quality problem in many urban environments. Field and laboratory studies were conducted to develop and verify the kinetic expressions and attendant coefficients required to simulate the loss of fecal coliform bacteria in lakes due to death [as mediated by irradiance (light) and temperature] and sedimentation. The dark death rate coefficient at 20-degrees-C (k_d = 0.73 d^-1) was established in laboratory experiments utilizing raw sewage diluted with filtered lake water. No consistent relationship was observed between the dark death rate coefficient and temperature (theta = 1). The irradiance-mediated death rate (k_i) was shown to be proportional to irradiance (I) in water column incubations of raw sewage using a dialysis tube technique: k_i = alphaI; alpha = 0.00824 cm² cal^-1. The settling loss rate (1.38 m d^-1) was quantified by determining the association of fecal coliform bacteria with particles of various size classes and measuring the sedimentation rate for those particle classes using sediment traps. Individual loss terms are combined into a single predictive expression which may be used to simulate fecal coliform bacteria dynamics in lakes.

Battistioni, P., Fava, G. and Ruello, M.L. (1993), Heavy metalshock load in activated sludge uptake and toxic effects. Water Research, 27 (5), 821-827.

Full Text: W\Wat Res27, 821.pdf

Abstract: Waste sludge from laboratory units at four different steady-state conditions (5-20 days sludge ages) was employed for studying heavy metal shock load by the jar test system. Metal uptake (Hg, Cd, Ni) and oxygen depletion rates were simultaneously followed. The potential adsorption constants (k(am)) measured reveal a metal affinity sequence Hg > Cd > Ni, in partial contrast to the metal toxicity (MT) one, Hg > Ni > Cd. This suggests different sludge adsorption sites. Hg is preferentially adsorbed on the cell, while Cd is adsorbed on extracellular polymer slimes and Ni on capsular polymers and the cellular wall. Therefore sludge age influences Cd and Ni toxicity, while no effect is observed for Hg.

Keywords: Activated Sludge, Heavy Metals, Adsorption, Bacterial Extracellular Polymers, Mercury Ions, Cadmium Ions, Nickel Ions, Bacterial Extracellular Polymers, Stability-Constants, Removal

? Buitron, G. and Capdeville, B. (1993), Uptake rate and mineralization of hexadecane and naphthalene by a mixed aerobic culture. Water Research, 27 (5), 847-853.

Full Text: 1993\Wat Res27, 847.pdf

Abstract: Biodegradation and mineralization of n-hexadecane and naphthalene by acclimated activated sludge were studied using a batch reactor coupled to a quadripole mass spectrometer. Inital hydrocarbon concentration range was 52-320 mg hexadecane/l and 5-25 mg naphthalene/l, with an S0/X0 ratio between 0.37 and 4.00 mg hydrocarbon/mg MLSS. Mean biomass retention time was 15 days for hexadecane and 20 days for naphthalene. Hydrocarbons were the sole source of carbon utilized. The hydrocarbon degradation rate was modelled by second-order kinetics. The biokinetic coefficients Y(obs) and mu(max)/K(s), and their relation to the S0/X0 ratio were obtained. Total CO₂ production was between 22 and 27% of the initial substrate concentration and the percentage of the metabolic products was between 2.6 and 4.0 for hexadecane and naphthalene, respectively. The rest of the substrate was converted to biomass. Respiratory coefficients for the hydrocarbons studied were calculated.

Keywords: Activated Sludge, Hydrocarbons, Biodegradation, Mineralization, Modeling, Mass Spectrometry, Respirometry, Hexadecane, Naphthalene, Fed-Batch Techniques, Biodegradation Kinetics, Activated-Sludge, Refinery, History, Growth, Model

? Urbain, V., Block, J.C. and Manem, J. (1993), Bioflocculation in activated sludge: An analytic approach. Water Research, 27 (5), 829-838.

Full Text: 1993\Wat Res27, 829.pdf

Abstract: A study on the physico-chemical structure of activated sludge flocs was carried out to get a better insight in its relationship with sludge settleability. For this purpose, 16 sludge samples from different origins were analyzed in order to provide information with regard to their settleability, biomass and exocellular composition, surface characteristics and internal hydrophobicity. The presence of filamentous microorganisms was observed in all samples but was not always associated with poor settleability, supporting to some extent the idea of their role as a backbone in the flocs. Relationships between the measured variables were studied through their linear correlations. A high amount of exocellular polymers (ECP) was associated with poor settling conditions. The DNA fraction and the C/N ratio of the ECP, had also a negative influence on the adsorption of a cationic molecule in the sludge samples. Finally, sludge settleability was described with a mathematical model which shows the opposition between ECP and the internal hydrophobicity of the flocs. From the model, the positive role of hydrophobic interactions should provide a new approach in the understanding of flocculation mechanisms in activated sludge.

Keywords: Activated Sludge, Settleability, SVI, Exocellular Polymers, Hydrophobicity, Model, Surface Charge

Pettersson, C., Håkansson, K., Karlsson, S. and Allard, B. (1993), Metal speciation in a humic surface water system polluted by acidic leachates from a mine deposit in Sweden. Water Research, 27 (5), 863-871.

Full Text: W\Wat Res27, 863.pdf

Abstract: A speciation study of some metals (Al, Fe, Cu, Zn and Cd) was performed in the surface water downstream from a deposit with sulphidic mine waste where acidic leachates were neutralized by mixing with well buffered groundwater and surface run-off. The water was rich in humic and fulvic acids (HFA). The chemical forms of the metals were characterized with respect to their cationic and anionic exchange properties.

In the present pH range (5-8) Al and Fe precipitated as solids that were partly retained by both cation and anion exchangers. Zinc and cadmium were dominated by cationic forms but for cadmium anionic forms were always present in minor amounts under the conditions of the study. Copper was predominantly anionic (as HFA-complex) except at low pH and high concentrations of Al and Fe, which evidently occupied all available complexing sites on the HFA.

Conditional stability constants were estimated for the corresponding metal-HFA complex entirely from field data. The values obtained with this empirical method (logbeta* at pH 7; 4.7 Cu; 3.2 Zn; 4.0 Cd) are in reasonable agreement with measurements in controlled model systems.

Keywords: Aluminum, Cadmium, Copper, Iron, Zinc, Speciation, Anion-Exchangeable, Cation-Exchangeable, Mine Waste, Surface Water, Stability-Constants, Natural-Waters, Organic-Matter, Trace-Metals, Fulvic-Acid, River Water, Adsorption, Complexation, Substances, Extraction

Roy, D., Wang, G.T. and Adrian, D.D. (1993), A simplified solution technique for carbon adsorption model. Water Research, 27 (6), 1033-1040.

Full Text: W\Wat Res27, 1033.pdf

Abstract: A new method of solving the homogeneous surface diffusion model for activated carbon absorption is presented. The method uses Laplace transforms on the equations developed by applying orthogonal collocation. The simultaneous equations developed are nonlinear. Consequently, an iterative method is used in order to calculate, from the batch absorption data, the surface diffusion coefficient and the film transfer coefficient. The model produces a good match between experiment and prediction for laboratory data on an agricultural waste, a dye waste and an aqueous waste stream containing a herbicide. The final form of the equations is presented in a readily usable form for applications to carbon absorption bed practice.

Sharma, D.C. and Forster, C.F. (1993), Removal of hexavalent chromium using sphagnum moss peat. Water Research, 27 (7), 1201-1208.

Full Text: W\Wat Res27, 1201.pdf

Abstract: Batch adsorption studies have shown that sphagnum moss peat, which is essentially oligotrophic, in concentrations ranging from 4 to 40 g/l can be used effectively to remove hexavalent chromium from aqueous solutions. The process is pH dependent, the optimum range being 1.5-3. Treatment of the exhausted peat with 1 M NaOH removed only 50% of the sorbed metal, suggesting that the binding to the peat involved strong chemisorption forces.

Keywords: Peat, Hexavalent Chromium Adsorption, Activated Carbon, Exchange

Alves, M.M., Beca, C.G.G., Decarvalho, R.G., Castanheira, J.M., Pereira, M.C.S. and Vasconcelos, L.A.T. (1993), Chromium removal in tannery wastewaters ‘polishing’ by Pinus sylvestris bark. Water Research, 27 (8), 1333-1338.

Full Text: W\Wat Res27, 1333.pdf

Abstract: The possibility of using ground, dried and classified Pinus sylvestris bark for trivalent chromium removal in tannery wastewater ‘polishing’ was studied. Tests were carried out with synthesized solutions whose chromium concentrations (5 and 20 mg/l) were similar to those found in some effluents of Portuguese tannery industries after physico-chemical treatment. Bark concentrations of 1 and 2 g/l were used (higher concentrations would have no practical value) and chromium removals 90% were achieved in a 4.5–5.0 pH range. Agitation was accomplished by means of both air bubbling and vibrating plate. Slight differences occurred. Bark wetting was achieved either by simple bark/solution contact or vacuum application. No marked differences were observed. From an industrial point of view air bubbling agitation and simple bark/solution contact certainly look more interesting. The presence of other ions decreased the chromium removal though this decrease was never greater than about 20%. Pretreatments of bark were carried out and, in some cases, an increase of about 6–11% in the chromium sorption capacity of bark was observed.

Keywords: Chromium Removal, Pinus Bark, Tannery Wastewater ‘Polishing’, Bark Chromium Adsorption

Saha, S. (1993), Treatment of aqueous effluent for fluoride removal. Water Research, 27 (8), 1347-1350.

Full Text: W\Wat Res27, 1347.pdf

Abstract: Fluoride forms a common aqueous effluent in many chemical industries. Excess of fluoride in the effluent can cause a health hazard. So, effluent containing fluoride needs treatment to reduce its concentration to a disposable value before discharge into public sewage. By conventional methods, the fluoride concentration in the industrial effluent can not be reduced to less than 10-15 mg l^-1 without the help of dilution with fresh water. A method of chemical treatment is discussed here which has been very effective to remove the fluoride ion from effluent to a concentration of 1.5 mg l^-1 or less (which is disposable) by precipitation technique followed by complexation. In this method, precipitation reduces the fluoride ion to a concentration of about 15 mg l^-1 and the balance (1.5 mg l^-1) is complexed to a stable form which being already totally dissociated at that low concentration does not break on further dilution. This improved method has made it possible to save a huge quantity of fresh water which otherwise is needed to dilute the fluoride effluent after conventional treatment in order to meet the statutory requirement.

Keywords: Waste-Water Treatment, Fluoride Concentration, Aqueous Effluent, Chemical Method, Precipitation, Complexation, Fresh-Water Dilution of Effluent

Macchi, G., Pagano, M., Santori, M. and Tiravanti, G. (1993), Battery industry wastewater: Pb removal and produced sludge. Water Research, 27 (10), 1511-1518.

Full Text: W\Wat Res27, 1511.pdf

Abstract: The process of neutralization with NaOH, in the presence of Fe(III) salt, of sulphuric acid battery industry wastewater seems to be more suitable than any other process for Pb removal because at the same time, it allows the exploitation of the scavenger action of Fe(III), which is often present in the same wastewater and precipitates as hydroxides. In order to optimize sludge production, a laboratory research study has been carried out to minimize the quantity of Fe(III) to be added. All aspects concerning the chemistry of wastewater have been taken into consideration step by step and discussed. As a result, a process which requires the addition of Fe(III) so that an Fe/Pb ratio, both expressed as ppm, of the order of 0.5 is achieved. The process has been applied to two artificial solutions, characterized by a content of H2SO4 of 1000 and 5000 ppm, respectively, and by 10 ppm of Pb, as well as to five samples of wastewater. The proposed process takes about 1 h to perform: 30 min for neutralization up to pH 8.5-9.5 and Fe(III) addition and 30 min for correction in the 9-9.5 pH range and for flocculation with the help of a polyelectrolyte. The Pb concentration of the treated effluent is below 0.2 ppm. Conditions for Pb removal using only NaOH or Na₂CO₃ have also been considered.

Keywords: Battery Waste-Water, Treatment, Sludge Production, Pb Removal, Surface Precipitation, Adsorption, Metals, Sorption, Oxides, Model, Lead

Namasivayam, C. and Periasamy, K. (1993), Bicarbonate-treated peanut hull carbon for mercury(II) removal from aqueous solution. Water Research, 27 (11), 1663-1668.

Full Text: W\Wat Res27, 1663.pdf

Abstract: Activated carbon prepared from bicarbonate-treated peanut hulls (BPHC) has been used for the adsorption of Hg(II) over a range of initial metal ion concentrations (10-20 mg dm^-3), agitation time (5-180 min), adsorbent dosage (5-120 mg 100 ml^-1) and pH (1.5-10.0). Adsorption of Hg(II) increased with increase in its initial concentration from 10 to 20 mg dm^-3 and the equilibrium time of adsorption increased from 75 to 90 min for a BPHC dose of 100 mg 100 ml^-1. The process of uptake obeys both the Freundlich and Langmuir isotherms. The applicability of the Lagergren kinetic model has also been investigated. Quantitative removal of 20 mg dm^-3 Hg(II) in 100 ml by 70 mg adsorbent was observed over a pH range of 3.5-10.0. A comparative study with a commercial granular activated carbon (CAC) showed that BPHC is 7 times more effective compared to CAC.

Keywords: Bicarbonate-Treated Peanut Hull Carbon, Hg(II) Adsorption, Adsorption Isotherms, Adsorption Kinetics, pH Effect, Water

Diamadopulos, E., Ioannidis, S. and Sakellaropoulos, G.P. (1993), As(V) removal from aqueous solutions by fly ash. Water Research, 27 (12), 1773-1777.

Full Text: W\Wat Res27, 1773.pdf

Abstract: The present work examines the possible use of fly ash, a by-product of coal power stations, as a means of removing arsenic(V) from water, or equivalently, of restricting its movement in the solid wastes or the soil. Kinetic and equilibrium experiments were performed in order to evaluate the removal efficiency of lignite-based fly ash. Both adsorption and desorption experiments were done at three pH levels, namely 4, 7 and 10. The results indicated that arsenic can be removed from water by fly ash, yet the degree of removal depended markedly on the pH. Removal at pH 4, as demonstrated by the adsorption isotherms, was significantly higher than that at the other two pH values. For 80% removal of arsenic, the solid phase concentration at pH 4 was up to 4 times greater than that at the other two pH levels. During the desorption studies only a small amount of the pre-adsorbed arsenic was released into the water. This amount was practically independent of the initial fly ash loading. This indicates that adsorption of arsenic on fly ash is almost irreversible and, therefore, there are good prospects for arsenic fixation on fly ash in practical applications.

Keywords: Fly Ash, Arsenic, Adsorption, Desorption, Activated Carbon, Natural Waters, Adsorbents, Adsorption, Desorption

Hespanhol, I. and Prost, A.M.E. (1994), Who guidelines and national standards for reuse and water-quality. Water Research, 28 (1), 119-124.

Full Text: W\Wat Res28, 119.pdf

Abstract: Guidelines for reuse and drinking water quality are based on scientific research and epidemiological findings, and as such provide guidance for making risk management decisions related to the protection of public health and the preservation of the environment. Water quality standards are legal impositions enacted by means of laws, regulations or technical procedures, which are established by countries by adapting guidelines to their national priorities and taking in account their technical, economical, social, cultural and political characteristics and constraints. Several examples are presented with the objective of differentiating standards from guidelines, and to show how countries have been adapting WHO guidelines to their situations in order to produce national standards on drinking water quality, and for the use of treated wastewater for crop irrigation.

Zhou, J.L., Rowland, S., Mantoura, R.F.C. and Braven, J. (1994), The formation of humic coatings on mineral particles under simulated estuarine conditions: A mechanistic study. Water Research, 28 (3), 571-579.

Full Text: W\Wat Res28, 571.pdf

Abstract: The adsorption of three humic substances isolated from the River Dodder (Eire) and one commercial humic acid (Aldrich) by six minerals was studied and found to be influenced by mineral type, the nature of the humics and by the solution characteristics. Adsorption was heavily pH-dependent, with lower uptake at higher pH values due to increased ionization of the humic substances. The amount of humic substances adsorbed was in the order: Aldrich humic acid > Dodder humic acid > Dodder fulvic acid > Dodder hydrophilic macromolecular acid corresponding to a decreasing aromatic carbon content and increasing O/C ratio. Desorption experiments showed Aldrich humic acid was the most difficult to be desorbed, followed by Dodder humic acid, Dodder fulvic acid then Dodder hydrophilic macromolecular acid. Humic uptake was found to increase with ionic strength due to the neutralization of charges on both mineral surfaces and humic substances, and more importantly, the compression of diffuse double layers; this also showed that van der Waals attraction is an important part of the interactive forces between humic substances and mineral particles. The amount of humic substances adsorbed varied with mineral type, particle size and surface area, with aluminium oxide having the highest capacity. The effect of temperature on humic adsorption was shown to vary with humic type and two types of reaction mechanism have been proposed responsible for the humic-clay interactions.

Keywords: Humic Coatings, Clay, Oxide, Physical Adsorption, Chemisorption, Desorption, Estuary, Hydrophobic Pollutants, Natural Sediments, Organic-Matter, Iron-Oxides, Adsorption, Sorption, Water, Substances, Aluminum, Carbon

? Qian, Y., Wen, Y.B. and Zhang, H.M. (1994), Efficacy of pretreatment methods in the activated-sludge removal of refractory compounds in coke-plant waste-water. Water Research, 28 (3), 701-707.

Full Text: 1994\Wat Res28, 701.pdf

Abstract: In this study, the possibility and mechanism of anaerobic acidification, ultraviolet radiation, and ozonation as pretreatment methods for improving the biotreatability of coke-plant wastewater have been investigated, a new process-A-A/O system-has been proposed and experiments in lab-scale apparatus and pilot plant have been conducted. It has been concluded that the tested A-A/O system is an efficient and cost-effective way for removing refractory organics from coke-plant wastewater.

Keywords: Anaerobic, Anaerobic Acidification, Anaerobic Pretreatment, Coke Plant, Coke Plant Wastewater, Coke-Plant Waste-Water, Coke-Plant Wastewater, Ozonation, Refractory Organics, Ultraviolet Radiation, Wastewater

Pagga, U. and Taeger, K. (1994), Development of a method for adsorption of dyestuffs on activated sludge. Water Research, 28 (5), 1051-1057.

Full Text: W\Wat Res28, 1051.pdf

Abstract: A simple screening method is suggested to predict the abiotic removal of dyestuffs in wastewater treatment plants by adsorption on activated sludge. Static and dynamic elimination tests with water soluble and poorly water soluble dyestuffs in activated sludge systems were performed. The influence of substance and sludge concentration, water hardness, test duration and analytical methods on the test results was investigated. A detailed description of the method is given.

Keywords: Adsorption, Activated Sludge, Dyestuffs, Abiotic Elimination, Static Elimination Test, Dynamic Elimination Test, Tests

Notes: highly cited

? Ahel, M., Giger, W. and Koch, M. (1994), Behaviour of alkylphenol polyethoxylate surfactants in the aquatic environment. I. Occurrence and transformation in sewage treatment. Water Research, 28 (5), 1131-1142.

Full Text: 1994\Wat Res28, 1131.pdf

Abstract: Specific analytical techniques were used to study the behaviour of alkylphenol polyethoxylate surfactants (APnEO) in several full-scale mechanical-biological sewage treatment plants in the Glatt Valley, Switzerland. Both parent compounds and the major metabolic products were quantified. Untreated sewage and primary effluents contained considerable amounts of surfactant-derived nonylphenolic compounds (3.0–9.6% of the dissolved organic carbon). Parent nonylphenol polyethoxylates (nEO = 3–20) were efficiently eliminated during biological treatment. However, the overall rate of biodegradation was limited due to the formation of biorefractory metabolites, including nonylphenol (NP), nonylphenol mono- and diethoxylate (NP1EO, NP2EO) and nonylphenoxy carboxylic acids (NPEC). The abundance of a particular metabolite was very dependent on the treatment conditions. Studies of the mass flows of nonylphenolic compounds in sewage treatment plants indicated that their fate was determined not only by microbial transformation, but also by physicochemical processes.