Drinking water provision and quality at the Sahrawi refugee camps in Tindouf (Algeria) from 2006 to 2016.

Drinking water provision has been a constant challenge in the Sahrawi refugee camps, located in the desert near Tindouf (Algeria). The drinking water supply system is itself divided in three zones which pump groundwater from different deep aquifers. It is equipped with reverse osmosis plants and chlorination systems for treating water. The allocation of water supplied to the Saharawi refugees for human consumption in 2016 has been estimated at between 14 and 17 L/person/day on average. This supplied water volume is below recommended standards, and also below the strategic objective of the Sahrawi government (20 L/person/day). Yet the local groundwater resources are huge in comparison with estimated consumption, and hence there is great potential for increasing the supplied volume through effecting improvements in the supply system. The physico-chemical quality of the raw and supplied water between 2006 and 2016 has been assessed according to Algerian standards for human consumption. The raw water of two zones of the supply system presents a very high conductivity and high concentrations of chloride, nitrate, fluoride, sulfate, sodium, calcium, potassium and iodide concentrations of natural origin, which may entail health risks. The treatment of water in a reverse osmosis plant greatly improves its quality and osmosed water met the standards. However, the supply of osmosed and raw water needs to be combined in Zone 1, to avoid an excessive reduction in water volume, and the supplied raw water poses a risk to the health of the refugees. The present study provides an example of a drinking water supply system under extreme drought conditions and in the political and social conditions of a refugee camp. Furthermore, it establishes a reference for supplied water allocation and quality in the Sahrawi refugee camps.

New insights to study the accumulation and erosion processes of fine-grained organic sediments in combined sewer systems from a laboratory scale model.

The deposition and resuspension of sediments are issues of considerable concern in combined sewer systems management. Sediments can produce the loss of hydraulic capacity and odour generation in sewers, and are also considered the main source of pollution due to their occasional uncontrolled discharges into the environment via Combined Sewer Overflows (CSO). Sewer sediments contain granular and cohesive organic fractions that can have a significant influence on bed resistance. In order to address the relationship between sewer sediment composition and its erodibility, accumulation and erosion experiments were performed in a flume test facility fed with wastewater. The flume was placed in a Wastewater Treatment Plant (WWTP), in which different circular pipe geometries were set. Wastewater flow inlet conditions and bed structures were monitored during the experiments. The photogrammetric technique Structure from Motion (SfM) was applied to record the bed deposit structures, providing accurate measurements of the accumulation rates. The SfM was also used to assess sediment transport and the characteristics of the bed forms after the erosion tests. In addition, velocity distributions and shear stress profiles were measured during the erosion tests to characterize flow resistance and sediment erosion. During both accumulation and erosion tests, sediments were sampled in order to analyse their physicochemical properties, thus highlighting the study of the biodegradability of the organic matter. Different deposition periods showed biological transformations in the bed deposit structure, which were seen to affect its cohesion, and in consequence, its erosion threshold. Tests with significant erosion rates agreed in broad terms with dimensionless sediment transport models derived from previous experimental studies performed with partly cohesive and organic materials in sewer pipes.

Hydraulic, wash-off and sediment transport experiments in a full-scale urban drainage physical model.

This paper presents a dataset obtained from hydraulic and sediment transport experiments performed in a full-scale urban drainage physical model of 36 m2. The study seeks to accurately measure sediment mobilization through the different parts of the model (surface, gully pots and pipe system), also obtaining a precise characterization of water flow and using realistic rainfall simulator to ensure the transferability of the results. Three different rain intensities and five sediment granulometries were tested in 6 hydraulic and 23 wash-off and sediment transport experiments. The following experimental data were produced: surface elevations and 2D runoff velocities measured by visualization techniques; surface and in-pipe water depths; flow discharges, total suspended solids concentrations and particle size distribution at the entrance of the gully pots and at the pipe system outlet; and sediment mass balances. This data is optimal for developing and validating wash-off and sediment transport formulations in urban drainage models, towards better treatment and management techniques for minimizing the impact of urban surface pollutants on the environments of towns and cities.

Experimental study of pollutant washoff on a full-scale street section physical model.

This study analyses the mobilization of total suspended solids (TSS) for different spatial distributions of sediment load located over the roadway surface of a full-scale street section physical model. At the sewer network outlet, flow discharges were measured and TSS pollutographs were determined with manual grab samples and inferred from turbidity records. In all the tests, the rain duration was 5 min and its averaged intensity was 101 mm/h. In addition, solids that were not washed off at the end of the experiments were collected from the street surface, gully pots and pipes and the mass balance error was checked. The experiments were configured to assess the influence of the initial load, spatial distribution method, distance from gully pot and distribution area dimensions on the TSS washoff. The study showed that sediment initial load and distribution cannot explain completely pollutant washoff processes because other variables such as the spatial rainfall distribution or the runoff depth also affect to the outlet pollutographs and system mass balances.

Monitoring accumulation sediment characteristics in full scale sewer physical model with urban wastewater.

A series of experiments were carried out with real wastewater in a pilot flume located at A Coruña wastewater treatment plant (WWTP) (Spain). A full scale model was developed to test a circular (300 mm inner diameter) and an equivalent area egg-shaped plastic pipe under controlled experimental conditions (pipe slope 2-5‰, averaged discharge Q = 4 L/s). Velocity profiles and sediment accumulation in the pipe invert was daily measured. Within the 7-11 days, the average sediment accumulation rate found in the circular pipe was between 1.4 and 3.8 mm/d. The sediment height depended on the input wastewater sediment distribution and organic content. The egg-shaped pipe presented no sediment deposit for the same downstream boundary conditions, although biofilms were attached to the walls of both pipes. Besides, wastewater quality was monitored continuously and sediment composition was studied at the end of experiments. Two types of sediment were recorded: a granular bed deposit (ρ = 1,460 kg/m3, d50 = 202 µm) and wall biofilms (ρ = 1,190 kg/m3, d50 = 76 µm).

Characterisation of sediments during transport of solids in circular sewer pipes.

This research is focused in the monitoring of sediments in circular sewer pipes with different diameters at a flume facility fed with urban wastewater. For this purpose, sediment physical and chemical characteristics, and sediment mobility were recorded. The Structure from Motion photogrammetric technique was used for the measurement of sediment bed evolution. In addition, sediment properties were determined in order to study the cohesiveness of the bed deposits. In particular, the chemical oxygen demand and the oxygen uptake rate of the sediment samples were analysed after different accumulation periods on the pipe inverts, resulting in a relation between these parameters and the mobility processes of solids.

Assessing wastewater micropollutant loads with approximate Bayesian computations.

Wastewater production, like many other engineered and environmental processes, is inherent stochastic in nature and requires the use of complex stochastic models, for example, to predict realistic patterns of down-the-drain chemicals or pharmaceuticals and personal care products. Up until now, a formal method of statistical inference has been lacking for many of those models, where explicit likelihood functions were intractable. In this Article, we investigate Approximate Bayesian Computation (ABC) methods to infer important parameters of stochastic environmental models. ABC methods have been recently suggested to perform model-based inference in a Bayesian setting when model likelihoods are analytically or computationally intractable and have not been applied to environmental systems analysis or water quality modeling before. In a case study, we investigate the performance of three different algorithms to infer the number of wastewater pulses contained in three high-resolution data series of benzotriazole and total nitrogen loads in sewers. We find that all algorithms perform well and that the uncertainty in the inferred number of corresponding wastewater pulses varies between 6% and 28%. In our case, the results are more sensitive to substance characteristics than to catchment properties. Although the application of ABC methods requires careful tuning and attention to detail, they have a great general potential to update stochastic model parameters with monitoring data and improve their predictive capabilities.

Altered dipeptidyl peptidase IV and prolyl endopeptidase activities in chronic tonsillitis, tonsillar hyperplasia and adenoid hyperplasia.

OBJECTIVE: To analyse peptidase activities in the removed tonsils and adenoids from patients with chronic tonsillitis, tonsillar hyperplasia and adenoid hyperplasia. METHODS: We have analyzed 48 tissue samples from patients undergoing tonsillectomy and adenoidectomy for chronic tonsillitis, tonsillar hyperplasia or adenoid hyperplasia. Tonsillectomy and adenoidectomy samples were collected and frozen for later enzyme analysis. The catalytic activity of a pool of peptidases (dipeptidyl peptidase IV, prolyl endopeptidase, aminopeptidase A, aminopeptidase N, aspartyl aminopeptidase, aminopeptidase B, neutral endopeptidase, pyroglutamyl peptidase I, puromycin-sensitive aminopeptidase and cystinyl aminopeptidase) was measured fluorometrically. RESULTS: The activity of prolyl endopeptidase was higher in tonsillar hyperplasia and adenoid hyperplasia than in chronic tonsillitis. On the contrary, dipeptidyl peptidase IV activity was higher in chronic tonsillitis than in hypertrophic tissues. When data were stratified by age and gender, dipeptidyl peptidase IV was also found to be more active in adult and male chronic tonsillitis tissues. Inversely, dipeptidyl peptidase IV activity was higher in tissues of females with tonsillar hyperplasia. CONCLUSIONS: These data indicate the involvement of dipeptidyl peptidase IV and prolyl endopeptidase in the mechanisms underlying chronic tonsillitis, tonsillar hyperplasia and adenoid hyperplasia.

Estudio comparativo in vitro de la filtración entre composite y dentina al polimerizar con luz halógena Vs con luz de plasma / In vitro comparative study of filtration between composite resin and dentin after polymerizing with halogen and plasma arc light

Introducción: Justificación y objetivos: existen estudios de polimerización realizados con lámparas de luz halógena en los que se valoran negativamente las altas intensidades de luz por la contracción rápida de la resina que podría provocar despegamientos. Según la información proporcionada por el fabricante de las lámparas de polimerización plasmática rápida, el curado con éstas origina una mayor rigidez del material que limita la contracción al evitar la redistribución cómoda de la estructura molecular. Material y método: se adhirieron 30 cilindros de composite a superficies dentarias lisas; 15 se polimerizaron con lámparas de luz halógena y 15 con lámparas de polimerización plasmática rápida, se sumergieron en azul de metileno y se midió la filtración con estereomicroscopio. Resultados: en el análisis de la varianza se obtuvo un grado de libertad que corresponde a una suma de cuadrados de 112,15, F=0,1403 y P=0,7113. No se han encontrado diferencias en cuanto a la filtración en función de que la polimerización se haya realizado con lámparas de luz halógena o con las de polimerización plasmática rápida (AU)