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PubMed2001

Adsorption of sodium lauryl sulfate onto arsenic-bearing ferrihydrite.

Ferrihydrite is an excellent adsorbent for binding trace toxic contaminants such as arsenic, and precipitate flotation of the arsenic-bearing ferrihydrite has been studied. Anionic surfactants such as sodium lauryl sulfate (SLS) and sodium oleate (NaOL) are suitable collectors for the flotation. The adsorption of SLS both alone and after the subsequent addition of NaOL on these precipitates at pH 4-5 was measured. It has been shown that the synergistic effect of the two surfactants on flotation is dependent on their addition order. The presence of NaOL before SLS in the conditioning stage can prevent the adsorption of SLS because of the electrostatic shielding of adsorption sites on the precipitates. The post addition of NaOL to the SLS-bearing precipitates can promote the flocculation of the precipitates and enhance entrainment of SLS for better flotation. The SLS adsorption data fit better with the modified Frumkin isotherm than the Langmuir isotherm. Thermodynamic parameters (-delta Gads0,delta Hads0, and delta Sads0) have been derived from the analysis of the adsorption isotherms. The results suggest that the adsorption of SLS on AFH is physical and exothermic.

Adsorption↗

PubMed2001

The treatment and reuse of wastewater in the textile industry by means of ozonation and electroflocculation.

Two different oxidation treatments, ozonation and electroflocculation, were experimented on a pilot scale to test their efficiency in removing polluting substances from wastewaters of textile industries. Both pilot plants used reproduced very closely a full-scale treatment in order to obtain indications about the feasibility of a transfer on industrial scale. By means of ozone treatment very high colour removal (95-99%) was achieved and treated waters were reused satisfactorily in dyeing even with light colours. This evidence despite the fact that the chemical oxygen demand of treated waters was still in a range (75-120 mg/l, a decrease up to 60%) that was usually considered to be too high for recycling purposes, especially for dyeing light colours. Treating plants working at the above-mentioned conditions should guarantee low operating costs. A biological pre-treatment and a sand filtration are absolutely essential. The transfer on industrial scale of the treatment is currently under development under an already financed European project. Electrochemical treatment showed to be very efficient in removing colour (80-100%) and chemical oxygen demand (70-90%). Moreover, a sensible decrease of chloride and sulphate ions was detected. Removal of flocculated material (post-treatment) must be, however, perfected in order to establish a correct costs-to-benefits ratio and therefore, propose an implementation of the technique on an industrial scale.

Color↗

PubMed2001

Polar nitrogen compounds and their behaviour in the drinking water treatment process.

Aliphatic and alicyclic amines as well as ethanolamines are extremely polar compounds, frequently found in the environment, and some of them have high toxicity. To address the contamination of selected German surface waters examined and the importance of bank filtration in Eastern Germany, investigations on the behaviour of polar organic nitrogen compounds during water treatment were carried out. Test conditions were designed appropriately for drinking water treatment conditions, and the tests were carried out using model water as well as bank filtrate. Test filter studies of microbial degradation of selected compounds demonstrated the following order of biodegradability: ethanolamine > dimethylamine > pyrrolidine > ethylenediamine. piperidine > diethylamine > morpholine > piperazine > cyclohexylamine. Flocculation tests using iron salts as well as aluminium salts as coagulants showed very low removal rates for the amines. The best results for the removal of the polar organic nitrogen compounds from the water were obtained using ozonation. Based on the reaction-rate constants, the order of degradation by ozone is: piperazine > morpholine > ethylenediamine > piperidine, cyclohexylamine > dimethylamine > ethanolamine > pyrrolidine > diethylamine. Disinfection by chlorine-containing agents under drinking water treatment conditions did not give effective elimination of the selected polar nitrogen compounds.

Amines↗

PubMed2001

Errors in bound water measurements using centrifugal settling method.

Centrifugal settling method (CSM) is commonly used to estimate the bound water content in sludges. The sludge sediment matrix should be purely plastic for accurate measurements to the bound water content. This communication, however, addressed for the first time that, owing to the inhibited elasticity of the sludge matrix, sediment height rebound was commonly observed for the flocculated sludge. Also, different sludges could have distinct elastic responses after centrifugation. There existed no simple correlation to incorporate the elastic rebound of sludge sediment in bound water measurement. The possible errors incorporated into CSM for measuring bound water contents were highlighted.

Centrifugation↗

PubMed2002

Prevalence of Cryptosporidium oocysts and giardia cysts in the drinking water supply in Japan.

A one-year monitoring of Cryptosporidium oocysts and Giardia cysts was conducted at a water purification plant. A total of 13 samples of 50 L river source water and 26 samples of 2,000 L-filtered water, treated by coagulation flocculation, sedimentation and rapid filtration, were tested. Prior to conducting a survey of a water purification plant, we developed a method for concentrating Cryptosporidium oocysts from a large volume of raw or filtered water using a hollow fiber ultrafiltration (UF) membrane, and this procedure was adapted to survey a water purification plant. Cryptosporidium oocysts were detected in all of the 13 raw water samples. The geometric mean concentration was 40 oocysts 100 L. Giardia cysts were detected in 12 of 13 raw water samples (92%) and the geometric mean concentration was 17 cysts/100 L. Probability distributions of both Cryptosporidium oocyst and Giardia cyst concentration in raw water were nearly lognormal. In filtered water samples, Cryptosporidium oocysts were detected in 9 of the 26 samples (35%) with the geometric mean concentration of 1.2 oocysts /1,000 L and Giardia cysts in 3 samples (12%) with 0.8 cysts/1,000 L. The estimated log10 removal efficiency of Cryptosporidium oocysts and Giardia cysts by rapid-sand filtration was 2.47 and 2.53, respectively. Empty particles were removed at a higher log10 than intact oocysts and cysts. The efficiency of particle removal in the rapid sand filtration process tends to be reduced under cold-water conditions. Close management is necessary in the winter when the water temperature is low.

Animals↗

PubMed2002

Quantitative assessment of trihalomethane formation using simulations of reaction kinetics.

A modelling procedure with a time discretisation of 1 min is developed in order to study and simulate the kinetics of formation of total trihalomethanes (TTHM) in water treatment plants. This methodology was applied on two significant processing units of Athens (Galatsi Treatment Plant-GTP, Menidi Treatment Plant-MTP). The fundamental concept of the model was based on the representation of the water treatment plant as a mixed flow reactor, where the formation of TTHM was predicated on a generalised reaction of total halogens with an organic precursor. Differential rates of reactants and products were expressed in terms of the reaction stoichiometry. Volatilisation, flocculation, coagulation and sedimentation processes were also incorporated in the model in order to assess their distinct role. The most appropriate coefficient set was sought and it was found that a stoichiometric ratio of 0.5 for total halogen, 0.6 for organic substrate and 0.2 for TTHM (or 2.5:3:1) resulted in the best fit between simulated and experimental data. The present modelling approach should be considered as a promising methodological basis towards the realistic reproduction of the dynamics of water treatment plants and the development of reliable numerical tools for the accurate prediction of THM formation.

Disinfectants↗

PubMed2002

Use of bituminous coal for concentration of enteroviruses from sewage and effluent.

A method has been developed for concentration of enteroviruses from untreated and treated domestic wastewater using bituminous coal bed as a virus adsorbent. A bed made from 1.5 g of 120 mesh coal powder was used for concentrating enteroviruses from 100 ml of clarified sewage at different pH values with and without addition of AlCl3. To enhance the adsorption of viruses, requisite quantities of aluminium chloride were added so that a final concentration of 0.0005 M could be achieved. At pH 3.0 maximum adsorption (82.8%) of poliovirus type 1 from artificially contaminated clarified sewage was observed without addition of AlCl3. However, at pH 5.0 maximum virus adsorption of 98.7% was achieved after addition of aluminium chloride. An average recovery of 86.9% of adsorbed viruses at pH 5.0 was achieved from coal bed with 3% flocculating beef extract at pH 9.5. This method for concentration of enteroviruses incorporating use of coal was compared with that of Millipore membrane filter method applied to raw sewage and clarified sewage. The results obtained from the methodology using coal as adsorbent was subjected to Student's "t" test and it was observed that its efficiency is confirmed for recovery of enteroviruses from raw and nonclarified sewage. These results are also comparable with that obtained with MF method. The results presented in this paper are indicative of the potential of this method for both treated and raw sewage.

Adsorption↗

PubMed2003

Pre-treatment optimisation studies for secondary effluent reclamation with reverse osmosis.

Physical-chemical pre-treatment was used for the reverse osmosis unit for reclamation of secondary effluents. The pilot plant was equipped with a variety of tertiary treatment units to prevent fouling and biofouling of the cellulose-acetate reverse osmosis membranes used. The optimisation of pre-treatment involved application of various concentrations of lime to raise the pH to 10.3-12.1, and to stabilise the sludge generated, as well as different dosages of ferric chloride (15, 20, and 25 mg/L) for the coagulation and solid-liquid separation. Sodium hypochlorite (8 mg/L) and UV disinfection are used for microbiological control. The water quality obtained, under the optimum conditions (pH=10.5; FeCl(3): 25 mg/L; anionic flocculant: 0.5 mg/L; sodium hypochlorite: 8 mg/L) was high, showing an average conductivity of 66 microS/cm and low COD values 4 mg O(2)/L. The product water is suitable for injection into a groundwater aquifer to counteract seawater intrusion.

Biocompatible Materials↗

PubMed2003

Test for assessing shear sensitivity of activated sludge flocs: a feasibility study.

Sludge deflocculation can cause, like excessive growth of filamentous bacteria, activated sludge wastewater treatment failure. Yet, unlike the latter cause, there exists no widely accepted tool to assess the flocculation level of activated sludge and to predict sludge deflocculation. In this study, a test procedure is proposed to assess the sensitivity of activated sludge flocs to shear. The test consists in subjecting sludge sample to a shear treatment followed by a sludge volume measurement (SV(30)), with reference to a control. The ratio (%) obtained by dividing the SV(30) of the sheared sample by the SV(30) of the control is used to express the shear sensitivity. In a first series of experiments using two types of sludge, the test was shown to be able of ranging sludge samples in a correct order of shear sensitivity. Applying this so-called shear-SV test procedure to a series of sludge samples allowed to distinguish amorphous sludges (SV(30) ratio> or =100%) from normal sludges (SV(30) ratio<100%). The test was shown to be repeatable and simple. It requires only basic laboratory equipment and implies minimum cost. It can be used as framework for the assessment of activated sludge shear sensitivity in practice.

Feasibility Studies↗

PubMed2003

Modeling of chlorine effect on floc forming and filamentous micro-organisms of activated sludges.

Chlorination is the most economical, non-specific method to control the excessive growth of filamentous micro-organisms causing bulking in activated sludge systems in the treatment of food industrial wastewaters; it was one of the first methods used to control filamentous bulking and is still widely employed. Considering that chlorination affects both floc-forming and filamentous micro-organisms and leaves undesirable disinfection by-products, it is necessary to define the adequate doses to control bulking, minimizing the effect on floc-forming bacteria. In the present work the effect of biomass concentration and type of micro-organism on chlorine decay kinetics was evaluated; the inactivation of either a filamentous (Sphaerotilus natans) or a floc-forming (Acinetobacter anitratus) micro-organism due to chlorination was also analyzed. For chlorine decay assays, the samples were treated in a batch system with sodium hypochlorite ranging between 9.8 and 56.6 mg Cl(2) (gVSS)(-1). Respirometric assays were used to evaluate the effect of chlorine on micro-organisms respiratory activity; in these cases, sodium hypochlorite doses ranged between 2.5 and 18 mgCl(2) (gVSS)(-1).A model that allowed to predict simultaneously chlorine consumption and respiratory activity decay for both micro-organisms as a function of time was proposed. The model includes three coupled differential equations corresponding to respiratory inhibition, readily organic matter oxidation by chlorine and chlorine decay. The rate of chlorine decay depended on both, type and concentration of the micro-organisms in the system. Chlorine consumption rate due to S. natans was 2-4 times faster than A. anitratus. Using the proposed model initial critical chlorine doses (the lowest initial dose that leads to a total inhibition of the respiratory activity) were calculated for both micro-organisms and values of 11.9 mgCl(2) (gVSS)(-1) for S. natans and 4.5 mgCl(2) (gVSS)(-1) for A. anitratus were obtained. These critical doses indicated that in non flocculated pure cultures, floc-former bacteria A. anitratus was more susceptible to chlorine action than S. natans.

Acinetobacter↗

PubMed2003

Floc morphology and size distributions of cohesive sediment in steady-state flow.

Fractal dimensions of particle populations of cohesive sediment were examined during deposition experiments in an annular flume at four conditions of steady-state flow (0.058, 0.123, 0.212 and 0.323Pa). Light microscopy and an image analysis system were used to determine area, longest axis and perimeter of suspended solids. Four fractal dimensions (D, D(1), D(2), D(k)) were calculated from the slopes of regression lines of the relevant variables on double log plots. The fractal dimension D, which relates the projected area (A) to the perimeter (P) of the particle (P proportional, variant A(D/2)), increased from 1.25+/-0.005 at a shear stress of 0.058Pa to a maximum of 1.36+/-0.003 at 0.121Pa then decreased to 1.34+/-0.001 at 0.323Pa. The change in D indicated that particle boundaries became more convoluted and the shape of larger particles was more irregular at higher levels of shear stress. At the highest shear stress, the observed decrease in D resulted from floc breakage due to increased particle collisions. The fractal dimension D(1), which relates the longest axis (l) to the perimeter of the particle (P proportional to l(D1)), increased from 1.00+/-0.006 at a shear stress of 0.058Pa to a maximum of 1.25+/-0.003 at 0.325Pa. The fractal dimension D(2), which relates the longest axis with the projected area of the particle (A proportional to l(D(2)), increased from 1.35+/-0.014 at a shear stress of 0.058Pa to a maximum of 1.81+/-0.005 at 0.323Pa. The observed increases in D(1) and D(2) indicate that particles became more elongated with increasing shear stress. Values of the fractal dimension D(k), resulting from the Korcak's empirical law for particle population, decreased from 3.68+/-0.002 at a shear stress of 0.058Pa to 1.33+/-0.001 at 0.323Pa and indicate that the particle size distribution changed from a population of similar sized particles at low shear to larger flocculated particles at higher levels of shear. The results show that small particle clusters (micro-flocs) are the formational units of larger flocs in the water column and the stability of larger flocs is a function of the shear stress at steady state.

Environmental Monitoring↗

PubMed2000

Effect of short-term sunlight irradiation on absorbance spectra of chromophoric organic matter dissolved in coastal and riverine water.

Samples of riverine and coastal, filtered (filter pore size 0.2 microm) water were exposed to short-term sunlight irradiation which reduced their absorbance in the UV and visible regions. Absorbance losses in coastal chromophoric dissolved organic matter (CDOM) were up to 10-fold smaller than those in riverine CDOM. Accompanying changes of absorbance spectra shapes (increased slope parameter) were, probably, a result of decrease of the mean molecular size of light absorbing organic matter. The potential of coastal CDOM to photodegradation was smaller and was exhausted during the course of a day-long experiment. A distinctive feature of spectral changes after sunlight exposure was a maximum absorbance decrease which appeared at approximately 300 nm in riverine and at approximately 280 nm in coastal water. That selective absorbance loss has been ascribed in both cases to the disappearance of chromophores of terrestrial origin which, in coastal water, had a lower mean molecular size (due to flocculation and/or prior photodegradation) but, nevertheless, retained their molecular properties.

Environmental Monitoring↗

PubMed2002

Removal of NOM in the different stages of the water treatment process.

Natural organic matter (NOM) is abundant in natural waters in Finland and in many ways affects the unit operations in water purification. In this study, the organic matter content in water in different stages of a full-scale treatment process over 1 year was measured. The full-scale treatment sequence, studied at the Rusko water treatment plant in Tampere, Finland, consisted of coagulation, flocculation, clarification by sedimentation or flotation, activated carbon (AC) filtration, and disinfection. High-performance size exclusion chromatography (HPSEC) was used for separation to determine changes in the humic substances content during the purification process. In addition, total organic carbon (TOC), KMnO4-number, and UV-absorbance at wavelength 254 nm (UV254) were measured. High molecular weight (HMW) matter was clearly easier to remove in coagulation and clarification than low molecular weight (LMW) matter. Furthermore, depending on the regeneration of the activated carbon filters, activated carbon filtration was effective to a degree but did not remove most of the lowest molecular weight compounds. Significant correlation was established among HPSEC, KMnO4, UV254 absorbance, and TOC. HPSEC proved to be a fast and relatively easy method to estimate NOM content in water and, in fact, gave more information than traditional methods on the type of NOM in a water sample. It also helped the process performance follow-up.

Absorption↗

PubMed1994

Recognition ability and cytotoxicity of some oligosaccharidyl substituted beta-cyclodextrins.

This paper reports a chemico-enzymatic synthesis of beta-CD derivatives. The recognition properties of these derivatives were tested using flocculating yeast and isolated lectins. It was observed that the substitution of beta-cyclodextrins with galactose end arms induces the better recognition by a cell-linked galactose-specific lectin. The physicochemical effects of the beta-CD derivatives on membranes were estimated using red blood cells and the effects on the viability of yeast and human rectal tumor cells were appreciated by measuring the mitochondrial deshydrogenase activity. The substitutions of the beta-CD ring by sugar antennae decrease the negative physicochemical effects of the beta-CD, ie their hemolytic properties. However, these substitutions induce significant modifications of the biological properties of the molecules, particularly the cytotoxicity and the growth of eukaryotic cells.

Animals↗

PubMed2003

Polyacrylamide + Al2(SO4)3 and polyacrylamide + CaO remove coliform bacteria and nutrients from swine wastewater.

Animal wastes are a major contributor of nutrients and enteric microorganisms to surface water and ground water. Polyacrylamide (PAM) mixtures are an effective flocculent, and we hypothesized that they would reduce transport of microorganisms in flowing water. After waste water running at 60.0 1 min(-1) flowed over PAM + Al2(SO4)3, or PAM + CaO in furrows, total coliform bacteria (TC) and fecal coliform bacteria (FC) were reduced by 30-50% at 1 and 50 m downstream of the treatments compared to the control. In a column study, PAM + Al2(SO4)3, and PAM + CaO applied to sandy, sandy loam, loam, and clay soils reduced NH4+ and ortho-P concentrations in leachate compared to the source waste water and the control. PAM + Al2(SO4)3 and PAM + CaO applied to sandy, sandy loam and loam soils reduced both total and ortho-P, concentrations in leachate compared to he source wastewater and control treatment. In a field study, PAM + Al2(SO4)3, or PAM + CaO treatments did not consistently reduce NH4+, NO3-, ortho-P, and total P concentrations in wastewater flowing over any soil compared to inflow wastewater or the control treatment. With proper application PAM + Al2(SO4)3 and PAM + CaO may be able to reduce the numbers of enteric bacteria in slowly flowing wastewater running off animal confinement areas, reducing the amount of pollutants entering surface water and groundwater.

Acrylic Resins↗

PubMed1999

Preparation and in vitro characterization of HSA-mPEG nanoparticles.

Surface modified human serum albumin (HSA) nanoparticles with a size of approximately 150 nm in diameter were prepared from a PEG-HSA conjugate, methoxy-polyethylene glycol modified human serum albumin (HSA-mPEG) using a coacervation method and crosslinked with glutaraldehyde. The zeta-potential of the surface modified nanoparticles was significantly lower than that of unmodified HSA nanoparticles. The existence of a hydrated steric barrier surrounding the nanoparticles was confirmed by electrolyte and pH induced flocculation tests. The surface modified nanoparticles showed a reduced plasma protein adsorption on the particle surface compared with unmodified particles.

Animals↗

PubMed2001

Effect of aluminum sulfate and cationic polyelectrolytes on the destabilization of emulsified wastes.

Emulsified oil in wastewater constitutes a severe problem in the different treatment stages. Aluminum salts have been traditionally used as coagulants in wastewater treatments. Polyelectrolytes are used to coagulate and flocculate colloidal systems. The performance of aluminum sulfate in comparison to polyelectrolytes (chitosan and polyacrylamide) as conditioning chemicals for an emulsion waste was tested, and the predominant mechanisms acting in each case were analyzed. Turbidimetry, jar test, colloidal titration and microscopy were used to test emulsion destabilization. Both charge neutralization and bridge formation were identified and confirmed as mechanisms of interaction of polyelectrolytes with waste constitutents. Charge neutralization would be more important for chitosan than for polyacrylamide treatment. A coincidence between the doses necessary to reach zero colloidal charge and minimum turbidity was observed for polyelectrolytes. The time necessary to produce system clarification was larger for aluminum sulfate than for polyelectrolytes; this time was shortened for higher aluminum sulfate concentration. The pH showed a marked effect on aluminum sulfate performance with the optimum at pH 6; polyelectrolyte action was practically not affected by pH. Polyelectrolyte addition produced the minimum turbidity for the same doses that zero colloidal charge; at higher doses, emulsion was restabilized and became turbid again. However, aluminum sulfate treatment did not produce emulsion restabilization.

Acrylic Resins↗

PubMed2001

The production of poly-(gamma-glutamic acid) from microorganisms and its various applications.

This review article deals with the chemistry and biosynthesis of poly-(gamma-glutamic acid) (gamma-PGA) produced by various strains of Bacillus. Potential applications of gamma-PGA as thickener, cryoprotectant, humectant, drug carrier, biological adhesive, flocculant, or heavy metal absorbent, etc. with biodegradability in the fields of food, cosmetics, medicine and water treatments are also reviewed.

Absorption↗