Aerobic digestibility of waste aerobic granular sludge (AGS) assessed by respirometry, physical-chemical analyses, modeling and 16S rRNA gene sequencing

Research has evolved on aerobic granular sludge (AGS) process, but still there are very few studies on the treatment of excess AGS sludge, with almost none considering its aerobic digestion. Here therefore, the aerobic digestibility of typical AGS sludge was assessed. Granules were produced from acetate-based synthetic wastewater (WW) and were subjected to aerobic digestion for 64 d. The stabilization process was monitored over time through physical-chemical parameters, oxygen uptake rates (OUR) and 16S rRNA gene sequencing. The microbial analyses revealed that the cultivated granules were dominated by slow-growing bacteria, mainly ordinary heterotrophic organisms with potential for polyhydroxyalkanoates (PHA) aerobic storage (PHA-OHOs), polyphosphate and glycogen accumulating organisms (PAOs and GAOs), fermentative anaerobes and nitrifiers (AOB and NOB). Differential abundance analysis of the bacterial data (before versus after digestion) discriminated between the most vulnerable microbiome genera and those most resistant to aerobic digestion. Furthermore, modeling of the stabilization process determined that the endogenous decay rate constant (bH) for the heterotrophs present in the granules was notably low; bH = 0.05 d-1 (average), four times less than for common activated sludge (AS), which is rated at 0.2 d-1. For first time, the research reveals another important feature of AGS sludge, i.e. the slow-decaying character of its bacteria (along with their known slow-growing character). This results in slower stabilization, need of bigger digesters and reconsideration of the specific OUR limits in biosolids regulations (SOUR limit of 1.5 mg/gTSS.h), for waste AGS compared to conventional waste AS. The study suggests that aerobic digestion of waste AGS (fully-granulated) could differ from that of conventional AS. Future work is needed on aerobic digestibility of real AGS sludges from municipal and industrial WWs, compared to synthetic WWs.

Erythrocyte fatty acids and desaturase indices in early pregnancy are associated with risk of preeclampsia

Preeclampsia (PE) is a pregnancy disorder that may be associated with inadequate maternal nutrition. Fatty acids are vital for placental and fetal growth. Fatty acid desaturases, key enzymes influencing the metabolism of polyunsaturated fatty acids, are reported to be associated with cardiometabolic risk. Any imbalance in the levels of omega-3 and omega-6 fatty acids can result in increased inflammatory response. The current study reports the levels of erythrocyte fatty acids and desaturase index across gestation in women who develop PE (n = 108) and compares them with non-PE women (n = 216). Maternal erythrocyte fatty acids were measured at 4 time points during pregnancy (i.e., 11-14, 18-22, 26-28 weeks and at delivery) using gas chromatography. Maternal total erythrocyte saturated fatty acids and omega-6/omega-3 fatty acid ratio was higher in the PE group as compared to the non-PE group at 11-14 weeks and 18-22 weeks respectively. Maternal Δ5 desaturase index was lower while Δ6 desaturase index was higher in the PE group at 11-14 and 18-22 weeks. Maternal stearoyl CoA desaturase-18 (SCD-18) index was lower at 11-14 weeks and at delivery. These changes were mainly observed in the early onset PE (EOP) group. Δ6 desaturase index at 11-14 weeks predicted the risk of EOP. Imbalance in fatty acid levels and desaturase indices predate the clinical diagnosis of PE, indicating their role in its pathophysiology. Measurement of fatty acids and desaturase indices in early pregnancy merits evaluation as predictors of risk of PE.

Mechanisms of persistence and impact of ordinary heterotrophic organisms in aerobic granular sludge

The stability of granules, contaminant removal and microbial structure of an aerobic granular sludge (AGS) process were investigated with a focus on ordinary heterotrophic organisms (OHOs). Long-term stable granules and high removals of COD (97 %), NH₄⁺ (98 %), P (85 %) and total N (77 %) were achieved. Sequencing analyses identified 6.6 % of phosphorus-accumulating organisms in the sludge, concordant with the observed bio-P removal capacity. However, OHOs were the most abundant bacteria in the sludge (70-93 %) without resulting in unstable aggregates. Under current dogmas of microbial competition in activated sludge, it seemed contradictory that OHOs could persist in the long term in the AGS where COD was depleted beginning in the anaerobic phase. Microbial analyses showed that OHOs could survive in granules by micropredation, proteolysis, fermentation and EPS consumption. Heterotrophic-nitrification/ aerobic-denitrification was an active pathway in the AGS. These findings contribute to a better understanding of microbial competition in AGS and its stability.

Ordinary heterotrophic organisms with aerobic storage capacity provide stable aerobic granular sludge for C and N removal

The study investigated the mechanisms and microbial communities underlying the long-term stability and removal performances shown by aerobic granular sludge (AGS) reactor involving polyhydroxyalkanoates (PHA) aerobic-storing bacteria. The characteristics of the sludge, removal performances and bacterial community structure were determined. The prevailing metabolic phenotype was similar in the parent conventional activated sludge (CAS) reactor and its upgraded AGS version, showing high COD and NH₄ uptake, versus low P and N reduction. Polyphosphate and glycogen accumulating organisms, PAO and GAO, were not enriched in the reactors despite initial targeting of anaerobic-aerobic cycle. Instead, PHA-aerobic storing bacteria (Thauera and Paracoccus) were dominant, but revealing a stable AGS system for BOD and N removal. The PAO/GAO failed selection and Thauera overgrowth were analyzed for beneficial use in developing alternative AGS technology for BOD and N removal applications.

Microbial mortality behavior promoted by silver (Ag+/Ago)-modified zeolite-rich tuffs for water disinfection

BACKGROUND

In developing countries, death due to diseases caused by fecal-oral ingestion can be avoided by taking action on drinking water issues. Adequate access to water treatment systems to reduce infections is a critical cause. Silver has been used as an antibacterial product, including biomedical applications. Therefore, in this paper, the effect of the chemical speciation of silver from silver-modified zeolite-rich tuffs on the mortality of Escherichia coli (E. coli), Streptococcus faecalis (S. faecalis) and Candida albicans (C. albicans) suspended in aqueous solution was investigated for disinfection purposes.

METHODS

The following aspects were considered to develop the investigation: a) the technique to prepare the modified zeolitic materials, either with ionic silver or silver nanoparticles, which were obtained in two ways: one, with grapefruit extract and the second, by using non-thermal plasma generated in a dielectric barrier discharge reactor of parallel plates; b) the response of the prokaryotes (bacteria) and eukaryote (yeast) microorganisms to disinfectant agents in batch systems; c) the disinfection processes as a function of time to obtain kinetics parameters; and d) the kinetics of the silver release from the silver-modified zeolite-rich tuffs, considering the models of Higuchi and Korsmeyer. The zeolitic materials were characterized by low-vacuum scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).

RESULTS

The non-thermal plasma reduced ionic silver is more efficient at generating silver compounds with several oxidation states, which are essential during the microbial inhibition process. For the bacterial (E. coli and S. faecalis), the materials with nanoparticles were efficient to inactivate them. However, the yeast (C. albicans) reaches the total inactivation when the zeolitic material contains ionic silver in the crystalline network.

CONCLUSION

The E. coli, S. faecalis and C. albicans survival behavior suspended in aqueous solutions after contact with Ag-modified natural zeolites depends on the chemical speciation of the silver present in these materials, Ag⁺¹ in the case of OAg_iZ or nanoparticles of Ag^o promoted by the grapefruit extract (OAg_npTZ), as well as by non-thermal plasma generated in a dielectric barrier discharge reactor of parallel plates (OAg_npPZ). In general, the concentration of silver in the aqueous solution after the disinfection process cannot exceed the recommended levels established for international organizations. The OAg_npPZ is a potential microbicide agent against E. coli and C. albicans, and the OAg_{n pT}Z for F. faecalis.Graphical abstractARTWORK.

Anaerobic treatment of chocolate-processing industry wastewater at different organic loading rates and temperatures

The objective of the present study was to determine the optimum operating temperature of laboratory-scale upflow anaerobic sludge blanket (UASB) reactors during the treatment of a chocolate-processing industry wastewater at medium applied organic loading rates (OLR_appl). Four UASB reactors were operated at different temperature (15, 20, 25 and 30 °C) and three OLR_appl (2, 4 and 6 kg soluble chemical oxygen demand (COD_s)/(m³ d)). The flowrate and the hydraulic retention time were constant (11.5 L/d and 6 h, respectively). The monitored parameters were pH, temperature, COD_s, and total and volatile suspended solids. The COD_s removal efficiency (RE) and biogas production rate (BPR) were calculated. The 15 °C UASB reactor had the lowest RE (39 to 78%) due to the low operating temperature. Regardless of the OLR_appl, the RE of the 20, 25 and 30 °C reactors was high and similar to each other (between 88 and 94%). The BPR of the four UASB reactors had the same behaviour as the RE (BPR of 15 °C: 0.3 to 0.5 L_biogas/(L_reactor d) (L_b/(L_r d)) and BPR of 20, 25 and 30 °C: 0.5 to 1.9 L_b/(L_r d)).

Special Appreciations Are Given to Top Five Peer-Reviewers of Journal of Food Quality and Hazards Control in 2018

The article's abstract is no available.

Sludge reduction by ozone: Insights and modeling of the dose-response effects

Applying ozone to the return flow in an activated sludge (AS) process is a way for reducing the residual solids production. To be able to extend the activated sludge models to the ozone-AS process, adequate prediction of the tri-atoms effects on the particulate COD fractions is needed. In this study, the biomass inactivation, COD mineralization, and solids dissolution were quantified in batch tests and dose-response models were developed as a function of the reacted ozone doses (ROD). Three kinds of model-sludge were used. S1 was a lab-cultivated synthetic sludge with two components (heterotrophs X_H and X_P). S2 was a digestate of S1 almost made by the endogenous residues, X_P. S3 was from a municipal activated sludge plant. The specific ozone uptake rate (SO₃UR, mgO₃/gCOD.h) was determined as a tool for characterizing the reactivity of the sludges. SO₃UR increased with the X_H fraction and decreased with more X_P. Biomass inactivation was exponential (e^-β.ROD) as a function of the ROD doses. The percentage of solids reduction was predictable through a linear model (C_Miner + Y_sol ROD), with a fixed part due to mineralization (C_Miner) and a variable part from the solubilization process. The parameters of the models, i.e. the inactivation and the dissolution yields (β, 0.008-0.029 (mgO₃/mgCOD_ini)^-1 vs Y_sol, 0.5-2.8 mg COD_sol/mgO₃) varied in magnitude, depending on the intensity of the scavenging reactions and potentially the compactness of the flocs for each sludge.

Bacterial inactivation and regrowth in ozonated activated sludges

Ozonation of the return activated sludge (AS) flow is an emerging option for excess-sludge reduction. This study aimed to evaluate the potential changes suffered by some kinetic parameters of the activated sludge models (ASMs) in the combined ozone-AS process. The heterotrophic maximum specific growth rate (μ_Hmax) was determined by respirometry in three model-sludges (S1 to S3) treated in batch with different O₃ doses. S1 was a fresh synthetic biosolid composed by only two particulate fractions. S2 was a digestate of S1 almost made by the endogenous residues. S3 was from a municipal wastewater treatment plant. μ_Hmax increased significantly from 3.5 d^-1 originally, to more than 10 d^-1 in the ozonated sludges. Ozonation promoted the selection of fast-growing bacteria in the activated sludges, after transitory inactivation and long lag times. Some microorganisms survived to 3 months of digestion and subsequent ozonation, and then regrow faster than before, once fed again with acetate. The research is of interest from the point of view of the application of the ASM models to the ozone-AS process, but also for wastewater disinfection in general.

Activated sludge mass reduction and biodegradability of the endogenous residues by digestion under different aerobic to anaerobic conditions: Comparison and modeling

This study was performed to identify suitable conditions for the in-situ reduction of excess sludge production by intercalated digesters in recycle-activated sludge (RAS) flow. The objective was to compare and model biological sludge mass reduction and the biodegradation of endogenous residues (XP) by digestion under hypoxic, aerobic, anaerobic, and five intermittent-aeration conditions. A mathematical model based on the heterotrophic endogenous decay constant (bH) and including the biodegradation of XP was used to fit the long-term data from the digesters to identify and estimate the parameters. Both the bH constant (0.02-0.05 d(-1)) and the endogenous residue biodegradation constant (bP, 0.001-0.004 d(-1)) were determined across the different mediums. The digesters with intermittent aeration cycles of 12 h-12 h and 5 min-3 h (ON/OFF) were the fastest, compared to the aerobic reactor. The study provides a basis for rating RAS-digester volumes to avoid the accumulation of XP in aeration tanks.

An in silico model to demonstrate the effects of Maspin on cancer cell dynamics

Most cancer treatments efficacy depends on tumor metastasis suppression, where tumor suppressor genes play an important role. Maspin (Mammary Serine Protease Inhibitor), an non-inhibitory serpin has been reported as a potential tumor suppressor to influence cell migration, adhesion, proliferation and apoptosis in in vitro and in vivo experiments in last two decades. Lack of computational investigations hinders its ability to go through clinical trials. Previously, we reported first computational model for maspin effects on tumor growth using artificial neural network and cellular automata paradigm with in vitro data support. This paper extends the previous in silico model by encompassing how maspin influences cell migration and the cell-extracellular matrix interaction in subcellular level. A feedforward neural network was used to define each cell behavior (proliferation, quiescence, apoptosis) which followed a cell-cycle algorithm to show the microenvironment impacts over tumor growth. Furthermore, the model concentrates how the in silico experiments results can further confirm the fact that maspin reduces cell migration using specific in vitro data verification method. The data collected from in vitro and in silico experiments formulates an unsupervised learning problem which can be solved by using different clustering algorithms. A density based clustering technique was developed to measure the similarity between two datasets based on the number of links between instances. Our proposed clustering algorithm first finds the nearest neighbors of each instance, and then redefines the similarity between pairs of instances in terms of how many nearest neighbors share the two instances. The number of links between two instances is defined as the number of common neighbors they have. The results showed significant resemblances with in vitro experimental data. The results also offer a new insight into the dynamics of maspin and establish as a metastasis suppressor gene for further molecular research.

Comparison of Fe-Al-modified natural materials by an electrochemical method and chemical precipitation for the adsorption of F- and As(V)

The adsorption of fluoride and arsenic ions by modified natural materials may have an impact on the removal of F- and As(V) from waters. In this work, a zeolitic material and pozzolan (commonly known as pumicite) were modified with aluminium an iron by an electrochemical method and chemical precipitation, respectively. The adsorbents were characterized by X-ray diffraction, scanning electron microscopy with energy X-ray disperse spectroscopy analysis and the point of zero charge (pHzpc). F- and As(V) adsorption properties of both materials were investigated. Adsorption kinetic data were best fitted to pseudo-second-order model and equilibrium data to the Langmuir isotherm model. The highest F- and As(V) sorption capacities were obtained for modified zeolitic (0.866 mg/g) and pozzolan (3.35 mg/g) materials, respectively, with initial F- or As(V) concentrations of 10 mg/L. It was found that the unmodified materials did not show either adsorption of F- ions or As(V), which indicated that Al and Fe in the adsorbents are responsible for the adsorption of these ions. In general, both modified materials show similar capacities for the adsorption of F- and As(V).

The levels of antibodies to Panton-Valentine leukocidin (PVL) vary with PVL prevalence along a north-to-south gradient

Recent research on Staphylococcus aureus vaccine development has focused on active immunization against Panton-Valentine leukocidin (PVL), a potent leukotoxin associated with both superficial and severe deep-seated infections. PVL prevalence is highly variable worldwide, but it is unknown to what extent immunity to PVL varies between patients from geographic areas with different PVL-positive S. aureus prevalences. We conducted a retrospective multicentric study of anti-PVL and anti-alpha-toxin (Hla) antibody levels in uninfected adult patients from France (low PVL prevalence; n = 200), Algeria (moderate prevalence; n = 143), and Senegal (high prevalence; n = 228). The antibody levels were quantified by an enzyme-linked immunosorbent assay (ELISA) procedure. Because Hla is present in virtually all S. aureus strains, its corresponding antibody levels were considered to reflect population exposure to S. aureus. Compared with French participants, the average anti-PVL antibody levels were 2.5-fold and 8.2-fold higher in Algerian and Senegalese participants, respectively (p < 0.001). Conversely, anti-Hla antibody levels did not differ between participants from the three countries, suggesting that the observed differences in anti-PVL antibody levels were not biased by variations in population exposure to S. aureus. Hence, anti-PVL antibody levels in the general populations of France, Algeria, and Senegal vary widely and match variations in PVL-positive S. aureus strain prevalence, with an increasing north-to-south gradient. To conclude, immunity to PVL in a given population correlates with local PVL prevalence. This finding can help to inform PVL vaccine strategies.

Modeling and parameter estimation of two-phase endogenous respirograms and COD measurements during aerobic digestion of biological sludge

Long-term aerobic digestion batch tests were performed on a sludge that contained mainly two fractions, a heterotrophic biomass XH and its endogenous residues XP, which were cultivated in conditions known to favor bio-storage (XSto). The objective was to model the stabilization of the sludge and determine the parameters of the endogenous decay processes, based on simultaneous measurements of the chemical oxygen demand (COD) and oxygen uptake rates (OUR). The respirograms were shown to have a two-phase structure that was describable with activated sludge model 3 (ASM3), but not with ASM1. Comparing the information from the COD and OUR data suggested the presence of two different groups of heterotrophs (XHa and XHb), one that decays with oxygen consumption and another without using O2. A modified ASM3 model was proposed, which was able to fit the OUR and COD data from the digesters, as well as cases from the literature.

Aerobic stabilization of biological sludge characterized by an extremely low decay rate: modeling, identifiability analysis and parameter estimation

Aerobic digestion batch tests were run on a sludge model that contained only two fractions, the heterotrophic biomass (XH) and its endogenous residue (XP). The objective was to describe the stabilization of the sludge and estimate the endogenous decay parameters. Modeling was performed with Aquasim, based on long-term data of volatile suspended solids and chemical oxygen demand (VSS, COD). Sensitivity analyses were carried out to determine the conditions for unique identifiability of the parameters. Importantly, it was found that the COD/VSS ratio of the endogenous residues (1.06) was significantly lower than for the active biomass fraction (1.48). The decay rate constant of the studied sludge (low bH, 0.025 d(-1)) was one-tenth that usually observed (0.2d(-1)), which has two main practical significances. Digestion time required is much more long; also the oxygen uptake rate might be <1.5 mg O₂/gTSSh (biosolids standards), without there being significant decline in the biomass.

Staphylococcus aureus nasal and pharyngeal carriage in Senegal

Nasal and pharyngeal swabs were collected from 132 patients admitted to the Principal Hospital in Dakar (Senegal), in January and February 2012. The prevalence of Staphylococcus aureus carriage was 56.1% (n = 74): 40.2% for pharyngeal samples and 36.4% for nasal samples. None of the isolates was methicillin-resistant. Carriage was independently associated with being female (p <0.01) and large households (≥15 members) (p 0.04). The luk-PV genes encoding Panton-Valentine leukocidin (PVL) were present in 26.2% of the isolates. These data highlight the importance of the oropharynx as a site of colonization, and the high prevalence of PVL-positive isolates in Senegal as compared with industrialized countries.

Using SWAT, Bacteroidales microbial source tracking markers, and fecal indicator bacteria to predict waterborne pathogen occurrence in an agricultural watershed

Developing the capability to predict pathogens in surface water is important for reducing the risk that such organisms pose to human health. In this study, three primary data source scenarios (measured stream flow and water quality, modelled stream flow and water quality, and host-associated Bacteroidales) are investigated within a Classification and Regression Tree Analysis (CART) framework for classifying pathogen (Escherichia coli 0157:H7, Salmonella, Campylobacter, Cryptosporidium, and Giardia) presence and absence (P/A) for a 178 km(2) agricultural watershed. To provide modelled data, a Soil Water Assessment Tool (SWAT) model was developed to predict stream flow, total suspended solids (TSS), total N and total P, and fecal indicator bacteria loads; however, the model was only successful for flow and total N and total P simulations, and did not accurately simulate TSS and indicator bacteria transport. Also, the SWAT model was not sensitive to an observed reduction in the cattle population within the watershed that may have resulted in significant reduction in E. coli concentrations and Salmonella detections. Results show that when combined with air temperature and precipitation, SWAT modelled stream flow and total P concentrations were useful for classifying pathogen P/A using CART methodology. From a suite of host-associated Bacteroidales markers used as independent variables in CART analysis, the ruminant marker was found to be the best initial classifier of pathogen P/A. Of the measured sources of independent variables, air temperature, precipitation, stream flow, and total P were found to be the most important variables for classifying pathogen P/A. Results indicate a close relationship between cattle pollution and pathogen occurrence in this watershed, and an especially strong link between the cattle population and Salmonella detections.

As(III) and As(V) sorption on iron-modified non-pyrolyzed and pyrolyzed biomass from Petroselinum crispum (parsley)

The sorption of As(III) and As(V) from aqueous solutions onto iron-modified Petroselinum crispum (PCFe) and iron-modified carbonaceous material from the pyrolysis of P. crispum (PCTTFe) was investigated. The modified sorbents were characterized with scanning electron microscopy. The sorbent elemental composition was determined with energy-dispersive X-ray spectroscopy (EDS). The principal functional groups from the sorbents were determined with FT-IR. The specific surfaces and points of zero charge (pzc) of the materials were also determined. As(III) and As(V) sorption onto the modified sorbents were performed in a batch system. After the sorption process, the As content in the liquid and solid phases was determined with atomic absorption and neutron activation analyses, respectively. After the arsenic sorption processes, the desorption of Fe from PCFe and PCTTFe was verified with atomic absorption spectrometry. The morphology of PC changed after iron modification. The specific area and pzc differed significantly between the iron-modified non-pyrolyzed and pyrolyzed P. crispum. The kinetics of the arsenite and arsenate sorption processes were described with a pseudo-second-order model. The Langmuir-Freundlich model provided the isotherms with the best fit. Less than 0.02% of the Fe was desorbed from the PCFe and PCTTFe after the As(III) and As(V) sorption processes.

Treatment of a chocolate industry wastewater in a pilot-scale low-temperature UASB reactor operated at short hydraulic and sludge retention time

The aim of this work was to evaluate the performance of a 244-L pilot-scale upflow anaerobic sludge blanket (UASB) reactor during the treatment of chocolate-processing industry wastewater under low-temperature conditions (18 ± 0.6 °C) for approximately 250 d. The applied organic loading rate (OLR) was varied between 4 and 7 kg/m(3)/d by varying the influent soluble chemical oxygen demand (CODsol), while keeping the hydraulic retention time constant (6.4 ± 0.3 h). The CODsol removal efficiency was low (59-78%). The measured biogas production increased from 240 ± 54 to 431 ± 61 L/d during the experiments. A significant linear correlation between the measured biogas production and removed OLR indicated that 81.69 L of biogas were produced per kg/m(3) of CODsol removed. Low average reactor volatile suspended solids (VSS) (2,700-4,800 mg/L) and high effluent VSS (177-313 mg/L) were derived in a short sludge retention time (SRT) (4.9 d). The calculated SRT was shorter than those reported in the literature, but did not affect the reactor's performance. Average sludge yield was 0.20 kg-VSS/kg-CODsol. The low-temperature anaerobic treatment was a good option for the pre-treatment of chocolate-processing industry wastewater.

COD fractionation and biological treatability of mixed industrial wastewaters

This study was conducted at a centralized wastewater treatment plant that receives discharges from nearly 160 industries. The chemical oxygen demand (COD) was fractionated for two objectives: delineation of the limits of the activated sludge process being used at the plant, and evaluation of the potential environmental impact of the treated effluent. Physico-chemical analyses, respirometric and biodegradation tests, as well as COD fractionation were carried out. Molasses-wastewaters were determined to be the major contribution to the plant. The influent was dark brown in color, with a relatively high content of both organics (2503 mg/L COD) and salts (5459 μS/cm conductivity), but a low biochemical oxygen demand (568 mg/L BOD(5)) and BOD(5)/COD ratio (0.24). The degradability of the organics was limited by the high content of inert soluble COD (S(I)). The COD fractionation pattern was 40-20-40% for S(I), X(I) (inerts) and S(H) (soluble hydrolyzable), respectively. More than 90% BOD(5) removal was obtained, which was sufficient for the plant to meet the national Standards. However, the effluent discharged into the river was intensely colored and polluted (>1000 mg/L COD, >5000 μS/cm), emphasizing the need for legislation regulating COD, color and salinity, and for upgraded treatment methods worldwide for molasses wastewaters.

Initial-rate based method for estimating the maximum heterotrophic growth rate parameter (μHmax)

Currently, the method most used for measuring the maximum specific growth rate (μ(Hmax)) of heterotrophic biomass is by respirometry, using growth batch tests performed at high food/microorganism ratio. No other technique has been suggested, although the former approach was criticized for providing kinetic constants that could be unrepresentative of the original biomass. An alternative method (seed-increments) is proposed, which relies on measuring the initial rates of respiration (r(O2)(_ini)) at different seeding levels, in a single batch, and in the presence of excess readily biodegradable substrate (S(S)). The ASM1-based underlying equations were developed, which showed that μ(Hmax) could be estimated through the slope of the linear function of r(O2)(_ini)·(V(WW)+v(ML)) vs v(ML) (volume of mixed liquor inoculum); V(WW) represent the wastewater volume added. The procedure was tested, being easy to apply; the postulated linearity was constantly observed and the method is claimed to measure the characteristics of the biomass of interest.

Adsorption of cadmium by Na and Fe modified zeolitic tuffs and carbonaceous material from pyrolyzed sewage sludge

In the present study the process of adsorption of cadmium from aqueous solutions using Na-zeolitic tuff, Fe-zeolitic tuff and carbonaceous material from pyrolyzed sewage sludge treated with HCl was investigated. The cadmium removal efficiency was studied as a function of contact time, adsorbate concentration, pH and adsorbent dose. The results showed that removal of cadmium was best described by the Langmuir-Freundlich isotherm. The kinetic experimental results were best described by the pseudo-first order model. The results indicate that the adsorption mechanism is physical and chemical sorption on heterogeneous materials. The maximum retention of cadmium was at pH around 6.0 for the materials. In kinetic studies, the Na and Fe modified zeolitic tuffs showed similar sorption capacities for cadmium and they were higher than the capacity found for carbonaceous material.

Spectrometric characterization of effluent organic matter of a sequencing batch reactor operated at three sludge retention times

Effluent organic matter (EfOM) from activated sludge systems is composed primarily of influent refractory compounds, residual degradable substrate, intermediate products and soluble microbial products (SMPs). Depending on operational conditions (hydraulic and sludge retention time (SRT)), the quantity and quality of EfOM significantly changes. The main objective of this research was to quantify and characterize the EfOM of a lab-scale activated sludge sequencing batch reactor (SBR), which was operated at three SRTs and fed glucose, an easily biodegradable substrate. EfOM was followed with two direct-quantification methods (chemical oxygen demand (COD) and dissolved organic carbon (DOC)), three spectrometric methods (ultraviolet absorbance at 254 nm (UVA(254)), excitation-emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC)) and three organic matter (OM) indices (specific UVA(254) (SUVA), SUVA-COD, COD/DOC ratio). The significant increment of UVA(254) and OM indices after treatment indicated an accumulation of refractory high-molecular-weight humic-like compounds in the EfOM, which demonstrated that EfOM was composed mainly by SMPs and not glucose. On the other hand, as the SRT increased, the amount of EfOM decreased, but SUVA, SUVA-COD and fluorescence intensity increased; these trends indicated the accumulation of SMPs of increased molecular weight and aromaticity. Increasing SRT in the SBRs reduced the amount of EfOM, but increased its aromaticity and reactivity. Visual analysis of EfOM EEMs showed two protein- and one humic-like peak, which were attributed to SMPs generated within the SBRs. PARAFAC determined that a two-component model best represented EfOM EEMs. The two-components from PARAFAC were mathematically correlated to the visually identified protein- and humic-like SMPs peaks.

Stepwise calibration of the activated sludge model no. 1 at a partially denitrifying large wastewater treatment plant

Activated sludge modeling technology is maturing; however, currently, there exists a great need to increase its use in daily engineering practice worldwide. A good way for building the capacities of the practitioners is to promote good modeling practices and standardize the protocols. In this study, a systematic procedure was proposed to calibrate the Activated Sludge Model No. 1 (ASM1) at a large wastewater treatment plant, by which the model adequately predicted the quality of the effluent and the sludge quantities. A hydraulics model was set up and validated through a tracer test. The Vesilind settling constants were measured and combined with the default value of the flocculent zone settling parameter, to calibrate the clarifiers. A virtual anoxic tank was installed in the return activated sludge to mimic the denitrification occurring in the settlers. In ASM1, the calibrated parameters were only two influent chemical oxygen demand fractions and one kinetic constant (oxygen half-saturation coefficient).

Clinical relevance of cagA and vacA gene polymorphisms in Helicobacter pylori isolates from Senegalese patients

The molecular epidemiology of Helicobacter pylori in Africa is poorly documented. From January 2007 to December 2008, we investigated 187 patients with gastric symptoms in one of the main tertiary hospitals in Dakar, Senegal. One hundred and seventeen patients were culture-positive for H. pylori. Polymorphisms in vacA and cagA status were investigated by PCR; the 3'-region of cagA was sequenced, and EPIYA motifs were identified. Bacterial heterogeneity within individuals was extensively assessed by using an approach based on vacA and cagA heterogeneity. Fourteen per cent of H. pylori-positive patients displayed evidence of mixed infection, which may affect disease outcome. Patients with multiple vacA alleles were excluded from subsequent analyses. Among the final study population of 105 patients, 29 had gastritis only, 61 had ulcerated lesions, and 15 had suspicion of neoplasia based on endoscopic findings. All cases of suspected neoplasia were histologically confirmed as gastric cancer (GC). The cagA gene was present in 73.3% of isolates. CagA proteins contained zero (3.7%), one (93.9%) or two (2.4%) EPIYA-C segments, and all were western CagA. Most of the isolates possessed presumed high-vacuolization isotypes (s1i1m1 (57.1%) or s1i1m2 (21.9%)). Despite the small number of cases, GC was associated with cagA (p 0.03), two EPIYA-C segments in the C-terminal region of CagA (p 0.03), and the s1 vacA allele (p 0.002). Multiple EPIYA-C segments were less frequent than reported in other countries, possibly contributing to the low incidence of GC in Senegal.

Divergence between respirometry and physicochemical methods in the fractionation of the chemical oxygen demand in municipal wastewater

For activated sludge modeling purposes, the methods used to evaluate the readily biodegradable chemical oxygen demand (RBCOD) in the influents are by biological or via physicochemical assays. However, there has not been sufficient wide comparison between these methods. The main goal of this study was to investigate the performance of the main chemical oxygen demand (COD) fractionation protocols, considering a representative wastewater in the context of tropical and developing countries. Different physicochemical characterization procedures, respirometric tests, and chemical analyses were performed. The fate of the soluble COD in the aeration tanks was studied. The results of the study showed that a marked difference may exist, in municipal wastewaters, between the estimates of the RBCOD fractions measured by respirometry and by any of the physicochemical methods. The evaluated influent showed a rather large fraction of COD that was passing the filters without being rapidly biodegradable, but which was removed quickly by enmeshment in the bioflocs. The consequences of such divergences and behavior are discussed.

[Helicobacter pylori and gastroduodenal lesions in Dakar, Senegal]

INTRODUCTION

The bacteriological characteristics of Helicobacter pylori (HP) vary in function of time and place. The aim of this study was to update histological and bacteriological feature of HP infection in patients presenting gastroduodenal lesions in Dakar, Senegal.

PATIENTS AND METHOD

This prospective study included patients with gastroduodenal lesions managed over a 6-month period in a digestive endoscopy center in Dakar. In all cases gastric biopsy was performed to obtain specimens for histological diagnosis according Sydney modified classification and HP culture with antibiogram.

RESULTS

A total of 158 patients were included. Mean patient age was 48.7 years and the sex-ratio was 1.2. Endoscopic lesions were ulcer in 88 cases, gastritis in 54 cases and tumors in 16. Histological examination demonstrated chronic gastritis in 100% of cases, inflammatory activity in 79.1%, metaplasia in 78.5%, gastric atrophy in 41.1%, adenocarcinoma in 7.6%, dysplasia in 5.7%, and MALT lymphoma in 2.5% with presence of HP in 72.8% of cases. Cultures were positive for HP in 65.8% of cases. Antibiograms indicated that HP was sensitive to amoxicilline in 100% of cases, clarithromycine in 96.6%, ciprofloxacine in 84.1%, and métronidazole in 29.5%.

CONCLUSION

Chronic gastritis is a constant feature of gastroduodenal lesions in Dakar. Histology combined with culture showed HP infection in 78.5% of cases. The antibiotic sensitivity of HP in Dakar has changed over the past decade.

Comparison of Cd-Pb adsorption on commercial activated carbon and carbonaceous material from pyrolysed sewage sludge in column system

The sorption behaviour of Cd and Pb from aqueous solutions in columns, using both commercial activated carbon and a carbonaceous material from pyrolysis of sewage sludge, was determined. The breakthrough data obtained for Cd and Pb sorption could be described by the linear form of the Thomas adsorption model. The breakthrough capacities found from column studies were different for each metal and the data reflect the order of metal affinity for the adsorbents materials. The adsorption capacity of the carbonaceous material was higher for cadmium than for lead in a single system and in binary systems, and, for activated carbon, the sorption capacities of lead and cadmium were similar in the binary system. The results indicated that the carbonaceous material from pyrolysis of sewage sludge is a better adsorbent than activated carbon of cadmium and lead.

Full activated sludge model no. 1 calibration experience at a medium-size WWTP in Mexico

As part of the efforts done to introduce the practice of modeling in Latin America, this research carried out at the North-East WWTP of Monterrey represents the first comprehensive modeling case in Mexico. The main objective was to reproduce the organic carbon removal and sludge production rates of the plant, based on ASM1. Different intermediate studies were performed prior to the calibration of the model: influent characterization, tracer tests and hydraulics modeling, sludge settling tests and respirometry. Two fractionation methods (STOWA protocol and Influent-advisor) were compared, showing no equivalent patterns. A stepwise sequence of calibration was developed and successfully applied. The hydraulics of the reactors at the plant was reproduced by use of a series of 3 to 5 CSTRs. The waste and return activated sludge flowrates (Q(WAS) and Q(RAS)) were corrected based on the inorganic and total suspended solids mass balances. The Vesilind settling constants were measured (V(o) and r(hind)), while the flocculent zone settling parameter (r(floc)) was adjusted to calibrate the secondary clarifier. In ASM1, the adjusted parameters were the COD soluble inert fraction (frS(I)) and the particulate substrate fraction (FrX(S)). All other ASM1 parameters were kept at their default values. The steady-state calibrated model (in GPS-X) adequately described the quality of the effluent (carbon and nitrogen) as well as the sludge composition (M. Liquor and WAS). This case study provides voluntarily detailed data to allow its wide use for training and teaching purposes.

Pollutant removal from oily wastewater discharged from car washes through sedimentation-coagulation

Wastewater from car washes represents a potential problem for the sewer system due to its emulsified oils and suspended material. Treatment of wastewater discharged from four car washes was investigated by sedimentation and coagulation. The effect of the coagulants Servical P (aluminium hydroxychloride), Servican 50 (poly(diallyldimethylammonium chloride)), aluminium sulfate and ferric chloride was evaluated. The achieved removal using sedimentation was of 82%, 88% 73% and 51% for oils, total suspended solids, COD, and turbidity, respectively. In the treatment by coagulation we achieved average efficiencies nearly to 74% for COD removal, greater than 88% in the case of total suspended solids removal and 92% in the case of turbidity and except the performance of Servican 50 greater than 90% in oil removal. We concluded that the oil residual concentration and COD in the treated water allows pouring it in the sewer system complying with the limits of the Mexican rule NOM-002-ECOL-1996 and it is possible even its reuse, at least in the case of the chassis washing of cars.

[HIV/AIDS prevalence among the attendees at the Center for Voluntary Anonymous Detection and Support in Pikine/Guediawaye, Senegal]

Within the framework of HIV/AIDS epidemic control, a Center for Voluntary Anonymous Detection and Support (CDVAA) was opened in March 2003 in Pikine/Guediawaye, Senegal. The purpose of this study was to analyze the prevalence of the HIV infection among attendees at the center over a one-year period as a basis for targeting the services of the CDVAA towards improving public health. This retrospective epidemiological study based on analysis of CDVAA attendee records was carried out from April 8, 2003 to April 7, 2004. The CDVAA in Pikine/Guediawaye shares premises with the Departmental Center for Popular and Sports Education. Sampling was exhaustive with inclusion of all people that attended the CDVAA during the study period. Study variables were age, sex, family status, educational level, ethnic group, religion, reason for detection, knowledge about HIV/AIDS prevention methods, results of the test, and, in case of infection, acceptance/refusal of referral to an appropriate management facility. Data were computed and analyzed using EpiInfo 6.04d software. The most common reason for detection was curiosity to know serologic status (69%). Test results were positive in 3% of cases. Infection was due to HIV1 in 65% of cases, HIV2 in 24%, and both (HIV1-HIV2 co-infection) in 11%. Ninety-one percent of attendees that underwent testing returned to pick-up their results. Sixty-eight percent of attendees that tested positive accepted referral to an appropriate management facility. HIV infection was significantly more frequent in attendees who were 24 years old, married, or illiterate and in attendees reporting risky behavior. To further encouraging progress already achieved, the CDVAA must improve the quality of its services and promote its activities as a means of familiarizing the target population on prevention of sexual transmitted diseases and HIV/AIDS, with a particular focus on safe behavior.

[Assisted reproductive technoloy: indications and perceptions among couples presenting for infertility at Dakar University Hospital]

AIMS

To identify, among the cases of sterility, the indications for assisted reproductive technology to analyze the knowledge, attitudes and perceptions regarding ART among patients consulted for infertility

PATIENTS AND METHODS

A retrospective analysis of 1718 files of infertile patients, selecting the cases likely to recover from ART completed by an individual and anonymous survey assessing knowledge regarding ART techniques among 209 patients seeking infertility consultation.

RESULTS

Among women, cervico-vaginal (26.7%) and tubal (20.9%) etiological factors were the predominating causes of infertility. Among men, azoospermatozoa was the predominant cause of infertility (24.5%). The indications for ART were estimated at 98.8% of cases: 3.14% indicated for artificial insemination, 95.7% for in-vitro fertilization. Around 18.21% of couples could have conceived with the assistance of these methods, compared to 3.8% of pregnancies obtained without ART. Among interviewed couples, a favorabl, perception of ART was found: although the majority of patients (78.9%) were ready to resort to ART, only 24.9% of interviewed women were in a position to mobilize required resources.

CONCLUSION

Advocacy for the feasibility of ART in the public hospital setting should be supported by the potential indications of modern technology demonstrated in this study.

Design of a tracer test experience and dynamic calibration of the hydraulic model for a full-scale wastewater treatment plant by use of AQUASIM

The setup of the hydraulic model structure of wastewater treatment plants (WWTPs) is an important step in the calibration of activated sludge models. The hydrodynamics of a full-scale municipal WWTP (Monterrey, Mexico) has been studied by means of the use of tracer tests and of a commercial simulator. A presimulation approach allowed the authors to quantify the appropriate rhodamine mass, set up a sampling plan, and evaluate the anticipated visual effect of the tracer test in the receiving river. The hydraulic behavior of the aeration tank for the first treatment line, a 7-cell plug-flow reactor, was shown to be best represented by 5 virtual mixed-tanks-in-series. The second treatment line, which included a vertical loop reactor (VLR), was best modeled as 3 tanks-in-series. The VLR, alone, was shown to be similar to a continuously stirred tank reactor, and not a circuit of tanks, as generally used to represent oxidation ditch reactors.

Design of a monitoring network and assessment of the pollution on the Lerma river and its tributaries by wastewaters disposal

While the 2005 progress report of the United Nations Millennium Development Goals stresses out the need of a dramatic increase in investment to meet the sanitation target in the third world, it is important to anticipate about some parallel negative impacts that may have this optimistic programme (extension of sewer networks without sufficient treatment works). Research was initiated on Lerma River (Mexico), subjected to many rejects disposal, to design a monitoring network and evaluate the impact of wastewaters on its water quality. The discharges was inventorized, geo-positioned with a GPS and mapped, while the physico-chemical characteristics of the river water, its tributaries and main rejects were evaluated. Microtox system was used as an additional screening tool. Along the 60 km of the High Course of Lerma River (HCLR), 51 discharges, with a diameter or width larger than 0.3 m (including 7 small tributaries) were identified. Based on the inventory, a monitoring network of 21 sampling stations in the river and 13 in the important discharges (>2 m) was proposed. A great similitude was found between the average characteristics of the discharges and the river itself, in both the wet and dry seasons. Oxygen was found exhausted (<0.5 mg/L) almost all along the high course of the river, with COD and TDS average levels of 390 and 1980 mg/L in the dry season, against 150 and 400 mg/L in the wet season. In the dry season, almost all the sites along the river revealed some toxicity to the bacteria test species (2.9 to 150 TU, with an average of 27 TU). Same septic conditions and toxicity levels were observed in many of the discharges. Four of the six evaluated tributaries, as well as the lagoon (origin of the river), were relatively in better conditions (2 to 8 mg/L D.O., TU<1) than for the Lerma, acting as diluents and renewal of the HCLR flow rate. The river was shown to be quite a main sewer collector. The high surface water contamination by untreated wastewaters that is depicted in this research should be taken into account in the Millennium Goals strategies, by promoting treatment plan works simultaneously, when sewer networks in the third world would extend.

[Economic contribution of gynecological and obstetrical ultrasound in an advanced strategy for the Zinguinchor region]

Aiming to strengthen the accessibility of ultrasound technology to rural populations, an advanced strategy ultrasound programme was implemented in the health districts of Sedhiou, Oussouye, Bignona and Ziguinchor all located within Casamance in Senegal. Within the first year of activity (January 1, 2001-December 31, 2001), the team from the regional health centre (RHC) was dispatched 56 times. Ultrasound scans were performed in the homes of 1,273 patients among which 192 were referred to the RHC for specialised follow-up and treatment. The financial benefit for the RHC totaled 3,120,000 francs; 2,612,500 francs for the district hospital; and 3,561,300 francs for the population at large. The advanced strategy for performing ultrasound scans has therefore been economically profitable at the community level as much as at the level of health structures. Through supporting the activities of the district hospitals, the RHC contributed technical support and increased the potential, not solely for the treatment of disease but for the health services overall. The revenue generated has given managers a greater possibility to improve health care and services. The decentralisation programme and reduction in the cost have decreased the unsatisfied needs in ultrasound services by making the technology more financially and geographically accessible. Thus, by saving input costs in terms of time, transportation and capital, the practice of ultrasound scans in district hospitals has been strengthened and has improved the capacity to provide care and treat the population's health problems. The continuation of this programme is advantageous, but necessitates two complementary actions: enhancing of the technical level and capacity of the district hospitals with the installation of ultrasound technology and equipment, and raising the level of knowledge by training staff in administering ultrasound scans.

[Impact of the number of antenatal consultations on the morbidity and mortality of children and women in the health district of Ziguinchor]

In order to assess the impact of the number of antenatal consultations (CPN) on the foetal and maternal morbidity and mortality, a prospective survey has been carried out in 1999, in the health district of Ziguinchor, Senegal. The investigation was led in seven health facilities which offered obstetrical cares, from January 1 to march 31, over a sample of 862 delivered women and 870 newborns. The number of antenatal consultations was zero in 26 cases (3%), one in 130 cases (15%), two in 198 cases (23%), three in 302 cases, and more than three in 206 cases (24%). Three elements of the mothers' profile have a statistically significant influence on the number of antenatal consultations: the delivery facilities, the ethnic groups, and the caesarean antecedent. For the other elements, the test is not significant. The number of antenatal consultations has a statistically significant link with: eclampsia, abruptio placentae, distich and maternal death. Some elements of the mothers' profile seem to be a cause of morbidity and mortality of children and women. In fact, we have notice: a statistically significant link between the health facilities and the dystocy; and between ethnic groups and abruptio placentae; an impossibility of drawing conclusion for the other cases. In short, the eclampsia and the maternal death are the only elements which seem to be improved by an increasing number of CPN without any influence of external factors.

[Outcome of early pregnancies at the Gynecological and Obstetrical Service of the Regional Hospital Center of Ziguinchor]

In order to evaluate the evolution and the issue of pregnancies among women who are less than 20 years old, a retrospective inquiry has been made in the gynecological and obstetrical service at the regional hospital center of Ziguinchor, in Senegal. It covered a period of three years from January 1st 1997 to December 31st 1999. It concerned 477 cases of patients received at the end of their pregnancy. The risks of morbidity and mortality were globally higher in the group of 13-17 than that of 18-19. The Khi2 test has confirmed a statistically significant difference (p < 0.05) for evacuation, hospitalizations, abortions and dead-born frequencies. For the study of the other parameters (causes of evacuations, length of stay in hospital, evolutive term, way of delivery, maternal death frequency and theircauses, and the types of dead-born), the frequencies haven't been significantly different. So, the risk of morbidity and mortality is higher with the pregnancy of adolescents who are less than 18 years old. Hence the interest of doing every thing to prevent pregnancies among adolescents by an appropriate contraceptive method and to look with priority after any pregnancy occurring among this age group.

[A new decision support tool in the campaign against maternal mortality: the Dystocia Risk Score]

At Ziguinchor Regional Hospital (ZRH) in Senegal, 80% of maternal deaths are associated with late referral of dystocia cases. The gynecology and obstetrics team of the ZRH, in collaboration with the teaching staff of the Institute of Health and Development (ISED), tried to find ways to combat maternal mortality and stillbirth, based on double-entry contigency tables and a logical framework. We developed a tool more elaborate than a simple decision tree: the dystocial risk score. This tool has three components: A column provides a list of eight characteristics to check for in the woman: history of cesarean section, limping, less than 150 cm in height, no living child, less than 18 years old, more than 35 years old, other risk factors, no risk factors. A horizontal section provides a checklist of possible outcomes of the pregnancy itself: obstacle praevia, precedence, noncephalic presentation, uterine length of over 35 cm, loss of amniotic fluid over 12 hours or more, other abnormalities, no abnormalities. A rectangular grid indicates the prognosis. This grid consists of three zones: a large blue zone (dangerous), a medium-sized grey zone (doubtful) and a small blue zone (hopeful). A positive DRS is obtained if there is at least one cross in the dangerous zone and/or at least two crosses in the doubtful zone. If these conditions are not fulfilled, the DRS is negative. A positive DRS indicates that the woman should be referred to a center specialized in obstetric emergency care. This tool was validated in a study of 376 pregnant women carried out over a period of six months. It was found to have a sensitivity of 83.6%, a specificity of 90.1%, a positive predictive value of 72.3% and a negative predictive value of 94.1%. The DRS is a simple, easy-to-use decision-making tool. The large-scale use of this tool (by midwives, chief nurses and health workers) would accelerate the identification of pregnant women with a high risk of dystocia. The timely referral of these women to specialized emergency obstetrics centers would increase the efficacy of care and would reduce the levels of maternal mortality and stillbirth.

Generalized model of pentachlorophenol distribution in amended soil-water systems

This paper describes laboratory experiments and subsequent statistical data analysis performed to reevaluate the overall effect of soil characteristics and liquid-phase composition on the extent of pentachlorophenol (PCP) adsorption in complex soil-water systems. The PCP adsorption isotherms were first generated for eight soils of varying physical and chemical properties. Binding tests were then performed in the presence of different additives (surfactant, oil, etc.) and conditions (temperature and pH) based on a fractional factorial design. Statistical analysis of data showed strong interdependencies among several of the soil parameters, but confirmed that organic carbon content (foc) and pH of the soils were the best predictors of the adsorption constant of PCP (Kd) for nonamended soil-water systems. It was determined that the effect on Kd of a 0.2 unit decrease in soil pH was approximately the same as increasing foc by 1%. From studying the effect of the amendments, two interactions (surfactant-pH and surfactant-oil) and two primary effects (surfactant and oil) have been detected. The effectiveness of the surfactant in decreasing Kd varied depending on the pH and oil content of the soil. A generalized nonlinear model expressing Kd as a function of pH, foc, oil content of soil, and surfactant dose was developed for the range of conditions studied. The proposed model and modeling approach can be adapted to other types of contaminants or variables for specific natural and engineered systems.

[An innovative training experience in public health at the Cheikh Anta Diop University of Dakar]

The Institute for Health and Development (ISED) at the University of Dakar, was created in 1987. Its mission is to fulfill the public health training needs of Senegalese health care professionals. ISED is responsible for a training program entitled "Certificat d'études Spéciales" (CES), the equivalent of a Masters of Public Health degree. The "CES" is a two-year program comprised of six modules, which last four months each. The ISED training approach stresses trainee responsibility above all. It is based on the trainee's professional tasks and is oriented toward the problems identified by the trainees themselves. In this sense it is highly adaptive and flexible. Each module is implemented in the same way; initially there is a 15 day residential phase for intensive theoretical courses, followed by an application period of 75 days in the trainee's work place, and then a final residential phase of 15 days for writing and presenting a technical report on the work in the field. This model allows trainees to bring together the theoretical and the practical. The trainers directly supervise each of these three phases. The two residential phases are conducted in the ISED training center, located in Mbour, 80 Km south of Dakar. 103 trainees are enrolled in the program in seven different classes. Of these trainees, 93 are health care specialists (85 physicians 7 pharmacists, 1 dentist). Ninety percent of previous graduates have been civil servants who work for the Ministry of Health in Senegal and the remaining 10% were from Burkina Faso and Togo. The training program is considered by all stockholders, beneficiaries, and relevant financial institutions, to be appropriate, beneficial and successful.