Variations saisonnières des formes de phosphores dans une station de traitement des eaux usées par lagunage, sous climat aride de Marrakech (Maroc)

L'objectif de ce travail est d'étudier dans un premier temps la dynamique du phosphore dans un système de traitement d 'eaux usées par lagunage facultatif, en relation avec les compartiments biologiques: phytoplancton, zooplancton et bactéries, dans un deuxième temps, d'évaluer, sous les conditions du climat aride, les performances épuratoires de ce système en ce qui concerne les formes du phosphore. Un intérêt particulier est porté au phénomène du relargage du phosphore par les sédiments. Les résultats montrent qu'il y a une évolution saisonnière et cyclique du phosphore dans les bassins de lagunage, en étroite corrélation avec le phytoplancton et le zooplancton. Le phytoplancton représente la part importante des formes organiques du phosphore particulaire. Les meilleures performances d'élimination du phosphore sont notées au printemps (77% pour les PO4 et 64 % pour le phosphore total). La période la moins performante est la période automne-hiver où les rendements moyens ne dépassent pas 38%. Le phosphore éliminé est stocké dans les sédiments. En période estivale, des phénomènes de relargage du phosphore à partir des sédiments ont été mis en évidence, favorisés par une zonation verticale des eaux à cette période. Des essais aulaboratoire ont montré la grande aptitude des sédiments de la station de lagunage étudiée à relarguer le phosphore, avec intervention de l'activité biologique du sédiment.Assimilation, sedimentation and release are the principal mechanisms controlling the behavior of phosphorus in aquatic ecosystems. There are numerous investigations of the phosphorus cycle in lakes and rivers in relation to the eutrophication process. There are, however, few studies about phosphorus cycling in waste stabilization ponds and most of these have discussed phosphorus removal. The aims of this paper were: 1) to study phosphorus dynamics in relation to the biomass compartment (zooplancton, phytoplancton and bacteria); and 2) to evaluate the phosphorus removal efficiency of the treatment plant under arid climatic conditions. Of particular interest was the remobilization of phosphorus from the pond sediment, both under laboratory conditions and in the field. The experimental installation consisted of two ponds receiving domestic wastewater (mean flow=120.4+5.8 m3.day-1 and specific organic load=56 kgBOD.ha-1. day-1; pond area=0.5 ha and depth=1.5 m). Samples were taken twice monthly from the surface, B1(S) and B2(S), and from the 1.5 m layers, B1(F) and B2(F). Composite (24 h) samples were taken from the inflow and the outflowof the plant to determine the removal efficiencies. In each sample, soluble reactive phosphorus (PO4), total phosphorus (PT) and total soluble phosphorus (PTD) were determined. Particulate phosphorus (PTP) was calculated as (PT-PTD) and soluble organic phosphorus (POD) as (PTD-PO4). Phosphorus release was measured in a plexiglas flask containing sediment (collected by corer from the pond bottom) overlaid with distilled water. Over 15 days, daily measurements were made of PO4 and total phosphorus. Sediment dry weight (%), volatile matter, organic carbon (%) and total phosphorus were measured before and after each test. Phosphorus contents of the phytoplankton, zooplankton and bacteria were estimated using the methods of BOUGIS (1974).The results show that cyclical and seasonal variations of phosphorus content were closely correlated with variations in the biological components. Significant correlation coefficients were noted between chlorophyll-a and particulate organic phosphorus. Organic phosphorus in algal cells was the more important form of particulate organic phosphorus. Under the arid climate, the waste stabilization ponds were more efficient at phosphate removal during the spring-summer period (77% of PO4 and 64% of total phosphorus in spring). The first pond may play the major role in phosphate removal. Phosphorus is only eliminated from stabilization ponds through accumulation in the sediment. However, part of the phosphorus which accumulates in pond sediments remains potentially mobile. During the summer period, phosphorus release from the sediment, observed in situ, was favored by stratification of the overlying water. The same phenomenon was noted during the autumn, particularly the release of POD. Laboratory studies have shown that phosphorus release may amount to 55 mg P m-2d-1. Biological activity may play a significant role in this mobilization

Multidisciplinary intensive functional restoration versus outpatient active physiotherapy in chronic low back pain: a randomized controlled trial.

STUDY DESIGN: Randomized parallel group comparative trial with a 1-year follow-up period. OBJECTIVE: To compare in a population of patients with chronic low back pain, the effectiveness of a functional restoration program (FRP), including intensive physical training and a multidisciplinary approach, with an outpatient active physiotherapy program at 1-year follow-up. SUMMARY OF BACKGROUND DATA: Controlled studies conducted in the United States and in Northern Europe showed a benefit of FRPs, especially on return to work. Randomized studies have compared these programs with standard care. A previously reported study presented the effectiveness at 6 months of both functional restoration and active physiotherapy, with a significantly greater reduction of sick-leave days for functional restoration. METHODS: A total of 132 patients with low back pain were randomized to either FRP (68 patients) or active individual therapy (64 patients). One patient did not complete the FRP; 19 patients were lost to follow-up (4 in the FRP group and 15 in the active individual treatment group). The number of sick-leave days in 2 years before the program was similar in both groups (180 ± 135.1 days in active individual treatment vs. 185 ± 149.8 days in FRP, P = 0.847). RESULTS: In both groups, at 1-year follow-up, intensity of pain, flexibility, trunk muscle endurance, Dallas daily activities and work and leisure scores, and number of sick-leave days were significantly improved compared with baseline. The number of sick-leave days was significantly lower in the FRP group. CONCLUSION: Both programs are efficient in reducing disability and sick-leave days. The FRP is significantly more effective in reducing sick-leave days. Further analysis is required to determine if this overweighs the difference in costs of both programs

Microgenomic Analysis in Skeletal Muscle: Expression Signatures of Individual Fast and Slow Myofibers

BACKGROUND: Skeletal muscle is a complex, versatile tissue composed of a variety of functionally diverse fiber types. Although the biochemical, structural and functional properties of myofibers have been the subject of intense investigation for the last decades, understanding molecular processes regulating fiber type diversity is still complicated by the heterogeneity of cell types present in the whole muscle organ. METHODOLOGY/PRINCIPAL FINDINGS: We have produced a first catalogue of genes expressed in mouse slow-oxidative (type 1) and fast-glycolytic (type 2B) fibers through transcriptome analysis at the single fiber level (microgenomics). Individual fibers were obtained from murine soleus and EDL muscles and initially classified by myosin heavy chain isoform content. Gene expression profiling on high density DNA oligonucleotide microarrays showed that both qualitative and quantitative improvements were achieved, compared to results with standard muscle homogenate. First, myofiber profiles were virtually free from non-muscle transcriptional activity. Second, thousands of muscle-specific genes were identified, leading to a better definition of gene signatures in the two fiber types as well as the detection of metabolic and signaling pathways that are differentially activated in specific fiber types. Several regulatory proteins showed preferential expression in slow myofibers. Discriminant analysis revealed novel genes that could be useful for fiber type functional classification. CONCLUSIONS/SIGNIFICANCE: As gene expression analyses at the single fiber level significantly increased the resolution power, this innovative approach would allow a better understanding of the adaptive transcriptomic transitions occurring in myofibers under physiological and pathological condition

Microfluidic device for robust generation of two-component liquid-in-air slugs with individually controlled composition

Using liquid slugs as microreactors and microvessels enable precise control over the conditions of their contents on short-time scales for a wide variety of applications. Particularly for screening applications, there is a need for control of slug parameters such as size and composition. We describe a new microfluidic approach for creating slugs in air, each comprising a size and composition that can be selected individually for each slug. Two-component slugs are formed by first metering the desired volume of each reagent, merging the two volumes into an end-to-end slug, and propelling the slug to induce mixing. Volume control is achieved by a novel mechanism: two closed chambers on the chip are initially filled with air, and a valve in each is briefly opened to admit one of the reagents. The pressure of each reagent can be individually selected and determines the amount of air compression, and thus the amount of liquid that is admitted into each chamber. We describe the theory of operation, characterize the slug generation chip, and demonstrate the creation of slugs of different compositions. The use of microvalves in this approach enables robust operation with different liquids, and also enables one to work with extremely small samples, even down to a few slug volumes. The latter is important for applications involving precious reagents such as optimizing the reaction conditions for radiolabeling biological molecules as tracers for positron emission tomography

Normal and cystic follicular development in the cow

International audienc

Développement folliculaire terminal et kystes folliculaires chez la vache

National audienc