Anomalous Seepage Flows and Piping in Oje-Owode earthdam: Granular filter-drain media as controlling measure

There was loss of water at Oje-Owode dam embankment through seepage. Evidence of some degrees of fracturing and seepage at the dam toe been reported. Previous results showed that the dam embankment was permeable and anomalous seepage occurred at the toe. This study, therefore attempted the application of locally sourced granular filters, precisely, stone dust from quarry, to model the control of seepage and piping at the toe of the dam embankment. Coarse soil samples were collected from quarry site as selected granular filters. Granite stones of sizes ½ - ¾ inch were selected as the drain samples. These were subjected to particle size analysis, compaction tests, specific gravity; and constant head permeability test. Numerical analyses were also carried out to generate flow lines, seepage rates and velocity vectors of the dam. The results of the simulated flow net showed a seepage value of 3.8066 x 10-8 m3/s per width, while total seepage at maximum phreatic level and at full length (896m) of dam axis was 3.4107 x 10-5 m3/s. This indicated loss of water from dam toe through seepage. The velocity vector contours showed flow directions and maximum velocity magnitude of 3.6 x 10-8m/s in the direction of decreasing heads. The modelled filter-drain installed at dam toe controlled the anomalous seepage water and prevented piping as though it were a horizontal drain. The flow lines were controlled at coordinate points (36.25m, 0.56m) and remained horizontal through the filter media, until it exited the dam at the toe at coordinate points (41.88m, 0.59m), which is relatively a save point for collection. The modelled filter-drain media installed at dam toe controlled the anomalous seepage water and prevented piping. Keywords: Oje- Owode dam, Piping, Granular Sand filter, Numerical analyses, Seepage

Effects of Detention Period and Sand-Based Surface Flow Constructed Wetland in Kitchen Wastewater Treatment using Phragmites Australis (Common Reed) as Macrophyte

A greenhouse laboratory-scale experiment was conducted at the Department of Civil Engineering, Ladoke Akintola University of Technology (LAUTECH) Ogbomoso, Nigeria in May 2013 to demonstrate the performance of free water surface-flow sand- based constructed wetland, prepared with locally available plants, specifically common reed (Phragmites australis), as a viable low-cost efficient treatment option for domestic wastewater from kitchen. The nutrient removal and performance evaluation of the constructed wetland in treatment of kitchen wastewater was investigated. Treatment efficiency was evaluated during the 10-day retention period, and results indicated that the nutrients reduction corresponds to a longer retention time in wetland beds. There is a remarkable reduction in B.O.D (38.2-100%), hardness (100%), turbidity (55.2-77.2%), Nitrate (66.7-100%), zinc, ORP (45.0-79.1%), Sulphite (24-100%) sulphate (100%), TSS (55.2-82.3%) and little reduction in TDS (6.93-40%) and also there was increase in pH (31.7-45.6%), Magnessium (16.7-50%), Iron (50-75%), calcium ( 16.7-50%) The final effluent was found to be suitable for non-drinking purposes like crop irrigation, keeping aquatic animals and direct discharge into a receiving water body as the concentrations were well below allowable limits.The treatment system was found to be economical, as the cost of construction only was involved and maintenance cost very minimal. It was environmentally friendly as it was free from offensive odour and insect invasion. A pilot scale constructed wetland is recommended for further research works. Keywords: Constructed wetland, Kitchen wastewater, Nutrient removal, Retention period, Phragmites australi

Performance Evaluation of Sand-based Surface flow Constructed wetland in Domestic Wastewater Treatment using Typha Orientalis as Macrophyte

A laboratory-scale free water surface-flow constructed wetland was set up at the Department of Civil Engineering; Ladoke Akintola University of Technology (LAUTECH) Ogbomoso, Nigeria in May 2013 to demonstrate the performance of sand- based constructed wetland, using Typha Orientalis as a viable low-cost efficient treatment option for domestic wastewater from kitchen. The nutrient removal and performance evaluation of the constructed wetland in treatment of kitchen wastewater against retention period of ten days was investigated. During the 10-day retention period, the sand- based constructed wetland set up with Typha Orientalis had improved the wastewater quality significantly as it had reduced 94.9% of Turbidity, BOD5 by 79.0%, NO-3 by 66.7%, 87.9% of SO-4 , 70.24% of Cl-, Conductivity by 70.8% and Magnesium by 80.62%. The pH value and Dissolve Oxygen increased by 28.3% and 64.01% respectively and the initial offensive odour of the raw water was no more noticeable. The final effluent was found to be suitable for non-drinking purposes like crop irrigation and keeping aquatic animals. However, it was noted that a 7- day detention time was optimal for the treatment of domestic wastewater from kitchen. The treatment system was found to be economical, as the cost of construction only was involved and maintenance cost very minimal. It was environmentally friendly as it was free from offensive odour and insect invasion. The prototype scale is recommended for in-situ use, especially for wastewater from kitchen. Keywords: Constructed wetland, Domestic wastewater, Nutrient removal, Retention period, Typha Orientalis