The removal of contaminants in slow sand filters occurs mainly in the colmation layer or schmutzdecke a biologically active layer consisting of algae, bacteria, diatoms and zooplankton. A ripening period of 6 8 weeks is required for this layer to form, during which time filter performance is sub-optimal. In the current study, an environmental scanning electron microscope was used to visualise t...

The prevalence of colloid deposition at grain-to-grain contacts in two porous media (spherical glass beads and angular quartz sand, 710-850 microm) was examined using X-ray microtomography (XMT) under conditions where the colloid-grain surface interaction was solely attractive (lacking an energy barrier to deposition), and under fluid velocity conditions representative of engineered filtration ...

In Ethiopia, the most common method of disposal of waste water is by land spreading. This treatment method has numerous problems, namely high labor requirements and the potential for eutrophication of surface and ground waters. Constructed wetlands are commonly used for treatment of secondary municipal wastewaters and they have been gaining popularity for treatment of agricultural wastewaters i...

The structures of every kind rest on the soil under laying them. The stability of these structures depends upon the load carrying capacity of the soil. The bearing capacity of soil also depends upon the quantum of coarser particles presents in it. The plate load test is used for the design of footing. Therefore, in the present investigation, the plate load tests were conducted to study the sand...

A new method to correlate intrinsic reactivity and treatability efficiency of metallic iron (Fe) was evaluated. A 2.0 mg L methylene blue (MB) solution was used in gravity fed column experiments. The intrinsic reactivity of nine Fe materials (ten samples) was characterized using the EDTA test. Three commercial Fe materials ZVI1 (0.40 0.80 mm), ZVI9 (0.50 mm) and ZVI10 (0.45 0.55 mm) were tested...

The frequency of recovery of atypical mycobacteria was estimated in two treatment plants providing drinking water to Paris, France, at some intermediate stages of treatment. The two plants use two different filtration processes, rapid and slow sand filtration. Our results suggest that slow sand filtration is more efficient for removing mycobacteria than rapid sand filtration. In addition, our r...