| Environnement, ingénierie & développement |  |
N°65 - Novembre 2013
1. Influence du pH sur la libération du phosphore accumulé dans les boues de surface d'un filtre planté de roseaux recevant des eaux usées traitées avec du FeCl3
Constructed wetlands (CW) provide good removal of organic matter and nitrogen (Hammer, 1989; Kadlec et al, 2000. Molle et al, 2005), but their performance for phosphorus removal are the subject of debate (Vymazal et al, 1998. Brix et al, 2001.). However, phosphorus is a factor in eutrophication of surface waters, and it is therefore necessary to limit discharges into the natural environment. In order to improve denitrification and phosphorus removal as compared to classical vertical flow constructed wetlands (VFCWs), the French company SCIRPE has developed a process called Azoé® patented in 2007 (Michel, 2007). The process includes a pre-treatment on a biological trickling filter to partly degrade the organic load, followed by two vertical stages of partially saturated constructed wetlands for the removal of nitrogen by nitrification and denitrification. The reduction of phosphorus in the Azoé® system is achieved through the addition of FeCl3 as a coagulant, followed by filtration through the VFCWs. Phosphorus thus precipitated is thereby accumulated in the form of a sludge layer mostly at the surface of the 1st filter. Over time, the sludge layer progressively grows and may eventually release part of the accumulated phosphorus depending on the biophysicochemical conditions (Kim et al., 2013). The objective of this study was to determine the influence of pH on the solubilization of phosphorus from sludge material sampled from a plant in operation. Results showed that the […]
2. Éditorial n°65 Déchets Sciences et Techniques
Après les 3 précédents numéros qui nous ont conduits à Agadir (Maroc) puis à Rouyn-Noranda (Québec, Canada) par la publication d’articles ayant fait l’objet de communications orales à des colloques scientifiques organisés dans ces villes sur des problématiques environnementales d’intérêt pour DST, nous revenons dans ce numéro à un sommaire plus classique.
3. Diagnostic du système de collecte des excreta et eaux usees domestiques dans les milieux inondables de la ville de Lomé : cas du quartier Zogbédji
Surveys were conducted in 180 concessions of Zogbédji, one neighborhood of Lomé, capital of Togo. In this work, the results show that more than 78% of concessions have a system for collecting excreta. The different types of pits are encountered septic tanks (50.7%), traditional (38.7%), the LCM (8.4%) and tubs (2.1%). Emptying sanitation is provided largely by the diggers (49.64%) against 30.2% achieved by vacuum trucks. Wastewater can be found practically in the street.There is no network of potable water and91.1% of concessions use well water for various household and 96.1% to supply water to the periphery of TDE for drinking water. Disease respondents found to have suffered from diarrhea (20.5%), frequent abdominal pain (16.1%) of parasites (36.7%), and malaria in all seasons.
4. Valorisation du verre à bouteille comme addition fine dans les bétons autoplaçants
In the region of Annaba (Algeria), the colored glass bottles are not sorted or recycled. It should be noted that in some countries like Canada, the recycling of colored glass bottles is not currently viable; the storage would be cheaper [Oxford Brookes University, 2004]. But, the valorization of glass bottles in the concrete could constitute an interesting ecological and economical alternative, allowing the removal of bulky waste and pollutants and their qualification as a new source of building materials. Technically, glass bottles contain significant amounts of alkalis that can cause detrimental effects to concrete in relation to alkali-silica or alkali-aggregate reaction if the glass is used in coarse form. In the other hand, many authors [Chen et al, 2006] agree that the glass causes a beneficial behaviour associated with the pozzolanic reaction when used in powder form. Indeed, our work is a contribution to the valorization of powder glass bottles for substituting the limestone filler traditionally used as an addition in self compacting concrete (SCC). The results obtained show a beneficial behaviour of glass powder on the characteristics, of fresh and hardened self-compacting concrete to a dosage of 30 to 60% compared to the mass of cement.
5. Essai de compostage comme voie de valorisation des déchets ménagers solides dans la ville de Bukavu au sud-Kivu (RD Congo)
The identification of fly-tipping and the quantification of waste found conducted from 4th October 2010 in Bukavu town (DR Congo) for the waste recovery has shown an unequal distribution of waste fly-tipping according to the commune and a big heterogeneity of waste found ; unequal distribution and heterogeneity in relation with the number of residents of each quarter, the location of quarter due to down town and type of activities done in different quarters of different communes.The results of quantification of waste produced in Ibanda commune has shown that the average of 2.7 kg of waste are produced per day and per resident in this commune. And the composting proposed and checked within 8 weeks as mode of waste recovery of domestic solid waste majority biodegradable proven to be able to reduce 92.5 % of volume of waste produced in four weeks.
6. Étude de l’efficacité de traitement d’eaux usées industrielles
This study aims to evaluate the effectiveness of treatment of the purification plant of the industrial effluents of company CBGN (Company of Fizzy drinks of the North of Fez).The study of purification performance of the station was carried out at various operating parameters of the STEP namely: pH, flow and temperature. And at bioreactor to evaluate the reports BOD5 and COD, suspended matter (SM) and the nutritive matters, nitrogen, phosphorus,…. for the growth of the micro-organisms.The results obtained show an effectiveness of treatment as of SM with an output which can reach 90 %.
7. Élaboration d’une pouzzolane de synthèse à partir des sédiments de barrage
Precipitations, in the showers, cause the fast erosion of the slopes. The fine solid particles which are transported by the rivers arrive up to the levels of the stoppings where they settle. Thus, after continuous downpours the dam silts up ; which decreases its lifespan. One of the solutions adopted at summer was unsilting, but in front of the great quantity of product rejected simply downstream from the stopping, the problems of environment appeared. The use of this recovered mud in the manufacture of pozzolanic cement, contributes in the resolution of these problems. The study shows that the addition of 30 % of calcined mud with cement (CPA) makes it possible to obtain pozzolanic cement. Indeed, the quantity of added artificial pozzolana creates a chemical reaction with the lime released during the hydration of cement to form a calcium silicate hydrate probably the tobermorite and gehlenite.