Hydrologie : recherche actuelle

Physical methods like ultrasound, ultraviolet and nanoparticles are very useful in wastewater purification and recycling. The ultrasound irradiation in a liquid leads to the acoustic cavitation phenomenon, which can affect a number of mechanical, acoustic, chemical and biological changes in waste analysis. In present study, ultrasonic irradiation treatment technique was used to treat the sewage sludge effluent, which was collected from Delhi and another sample of pure E-coli strain was processed. Samples were treated in ultrasonic bath at 35 and 130 kHz of irradiation for different time periods of 5 min, 10 min, 20 min and 30 min including control (untreated). Treated samples were tested for different parameters, viz. bacterial cell count, chemical oxygen demand (COD), degree of disintegration COD (DDCOD), scanning electron microscope (SEM), optimum density (OD) of cells and reactive oxygen species (ROS). Result shows significant disintegration in ultrasonic treated sewage sludge and E-coli samples as compared with untreated (control). We observed an increased level of ROS and decreased bacterial population in treated samples with 35 kHz and 130 kHz of frequency. Result suggests that the ultrasonic treatment was more effective by increasing time and frequency. Study concludes that low-frequency ultrasonic bath at 130 kHz is more effective as compared to 35 kHz.

The paper presents the study carried out in a peri urban settlement of Nairobi Kenya and involved treatment of raw grey water generated from bathroom, kitchen and laundry for flushing toilet and laundry work. The study utilized both chemical and physical treatment. The chemical treatment involved alum addition in the raw grey water and pH adjustment using bicarbonate salts. The physical treatment involved filtration using Quartz sand and filtration of pH adjusted treated grey water using filter paper. The major ions studied were ions which could interfere with lathering of soaps or could cause stains on clothes and toilet fixtures or could be potentially health hazardous. These ions were Fe, Mn, Ca, Mg, Pb and Hg. The levels of these ions in raw grey water and in treated grey water were determined using atomic absorption spectroscopy. The results for the levels of these ions before treatment were compared to the set standards for potable water by Kenya Bureau of Standards [1]. The levels of these ions in the treated grey water after adjusting the pH were found to be within the Maximum Contaminant Limits (MCL) set by KEBS [1]. Thus the overall treatment of the raw grey water produced water of good quality which complied with the set standards for potable water by KEBS [1]. The results of this treatment could contribute immensely in the fulfillment of the millennium development goals.

Direct current is applied to olive mill wastewater effluent which is held between two electrodes in a vertical mode. Wastewater with a total dissolved solid and COD of about 39,300 and 120,000 mg/l, respectively, is used. The effect of pH, voltage, current, and bed height on the dewatering process is investigated. The results, under certain conditions, showed that EOD is an energy saving process for water removal and can be used for treatment of olive mill wastewater. The process revealed high efficiency in reducing COD and total dissolved solid (TDS). Water medium converted from acidic to basic upon application of direct current. Increasing the voltage or the current enhanced the EOD process. Use of additives at certain level also enhanced the dewatering process; addition of alum or electrolyte at certain concentration enhanced the removal rate. Sodium chloride is the most effective electrolyte in EOD process. The on/off test, although saves energy, but did not perform better in the term of percentage water removal compared to that of the continuous process, without on/off test.

This study investigated the removal of RR-2 and RB-4 dyes from aqueous solutions by adsorption using poppy bagasse, sugar beet bagasse, aluminium hydroxide sludge, phosphogypsum, ferrochromium plant waste, and orange peel. Aluminium hydroxide sludge had the highest adsorption capacity for both dyes. The equilibrium time was 2 days. The effects on adsorption of pH, adsorbent concentration, and stirring rate were investigated. The highest removal percentage was 80.75% and 99.74% for RR-2 and RB-4, respectively. Adsorption of RR-2 was expressed better with a Freundlich adsorption equation, while adsorption of RB-4 was expressed better with a Langmuir adsorption equation. Adsorption of RR-2 agreed with the pseudo-first-order rate equation and adsorption of RB-4 followed the pseudo-second-order rate equation. Moreover, both removal processes are endothermic. Various thermodynamic parameters, such as ?G°, ?HG°, and ?SG°, were calculated.