Paula K. M. M. Freire

Application of a simulated annealing optimization to a physically based erosion model

A major risk concerning the calibration of physically based erosion models has been partly attributable to the lack of robust optimization tools. This paper presents the essential concepts and application to optimize the erosion parameters of an erosion model using data collected in an experimental basin, with a global optimization method known as simulated annealing (SA) which is suitable for solving optimization problems of large scales. The physically based erosion model that was chosen to be optimized here is the Watershed Erosion Simulation Program (WESP), which was developed for small basins to generate the hydrograph and the respective sedigraph. The field data were collected in an experimental basin located in a semiarid region of Brazil. On the basis of these results, the following erosion parameters were optimized: the soil moisture-tension parameter (N(s)) that depends also on the initial moisture content, the channel erosion parameter (a), the soil detachability factor (K(R)), and the sediment entrainment parameter by rainfall impact (K(I)), whose values could serve as initial estimates for semiarid regions within northeastern Brazil.

CUCKOO SEARCH VIA LÉVY FLIGHTS FOR OPTIMIZATION OF A PHYSICALLY-BASED RUNOFF-EROSION MODEL (doi: 10.4090/juee.2012.v6n2.123131)

During animal waste agricultural applications, the major concern is the pathogen spreading, which may contaminate groundwater. Colloid release and pathogen transport during irrigation were evaluated in intact agricultural soil columns in this research using Escherichia coli as a model strain. In order to be easily identified and quantified, E. coli was incorporated with green fluorescent protein genes. The experiments were conducted at a water flow rate of 100 ml/min and the elution was collected and analized for colloid release and E. coli transport. Colloid release and E. coli transport were simulated using an implicit, finite-difference scheme with colloid release rate coefficient and E. coli deposition rate coefficient as constant, linear and exponential functions of the soil depth, respectively. It seemed that exponential functions had the best fit against the colloid release and E. coli transport observations.Niger Delta Estuary Nigeria is influenced by tidal currents due to its proximity to the Atlantic Ocean. Tides in the region are mostly semidiurnal, having two high and low water levels each day, with tidal prism ranging from 0.4 to 1.5m. The effects of tidal current reduces with distance inland and are strongest at the inlets with velocity varying from 2.0 to 5.0m/sec. The depth of the Estuary Rivers is controlled by the strength of the tidal currents; areas very close to ocean with stronger tidal effect are very deep; while shallow rivers predominates the hub of the estuary. Tidal current provides the steady supply of energy that moves sediments in and out of the estuaries from the seashore thus determing river bathymetric shapes through modification of existing morphology by eroding or depositing of sediments along the river course, while further sediment deposition is curtailed at the bottom as the estuary gets shallower due to the increasing stirring by waves. Despite all the sediment coming into the estuaries, many canals in the region have remained as open-water bodies, even after some thousand years. This suggests that, the interaction between the tide and the shape of the canal floor helps to regulate long-term sedimentation. However, the Dredged Canals in the Niger Delta estuaries have suffered high siltation rates because of excessive supply of sediments generated by storm/flood waters from upland and disposal of spoils from dredging activities into the water bodies, which causes some imbalance in the estuarine self-cleaning mechanism. Sediment loads entering the mangrove swamp environment are essentially polycentric; suspended fines enter the system both from the sea and the rivers. A mathematical model was formulated to predict and study the behavior of the sea bed levels, tidal heights and currents, in other to understand how they interact with each other. The model was calibrated using data obtained from local field observations and measurements. The model results compares favorably with the field results, with average correlation coefficient of 0.9 (see figures 2-13).The result showed that Niger Delta estuaries erode, accrete, or remain stable, depending on the rate at which sediment is supplied or removed from them by flood waters and tidal currents.Domestic sewage treatment experiments were conducted in trickling filters in laboratory pilot plants in which the peeled dehydrated fruits of Luffa cyllindrica were used as a support medium for microbiological growth, in order to verify its capacity to remove organic matter, measured in terms of Biochemical Oxygen Demand (BOD5,20) and Chemical Oxygen Demand (COD). Other parameters such as suspended and settleable solids were also measured. The results obtained, when compared to results from similar pilot plant using stones as supporting medium, and with the removals predicted by classic formulas used for trickling filters design, indicated that this support medium may substitute with advantages, under specific conditions, the traditional support media. Further studies are recommended.The wastewater treatment station (WWTS) by wetlands consists of a physic-biological system with part of the filtering formed by plants and projected according to the filtering soil principle. The elements that constitute the medium, in this case the soil, microorganisms and plants, are responsible for the organic matter and the sewage odor compounds degradation. This study employed the static and dynamic olfactometry methodologies to evaluate the treated effluents odor removal in two stations by root-zone wetlands in rural communities in Irati (PR). Olfactometry results were compared to the effluents physic-chemical analysis, and parameters such as dissolved oxygen (DO), chemical oxygen demand (COD) and pH were taken into account. Results revealed DO increase and COD removal in the treated effluents. Olfactometric analyses pointed to noticeable levels of odor in the treated effluents; however, there was significant reduction in the odor intensity of exit effluents in relation to the entrance ones. In general, the wastewater treatment station through wetlands showed efficient to the removal of odor compounds, as well as the removal or organic matter from the medium.