ABSTRACT Objectives: A good knowledge of water quality can guide policy makers for improved access to drinking water in a context of galloping demography and rapid urbanization. The aim of this study ...was to characterize the physico-chemical parameters of drinking water from boreholes and wells in Ferkessédougou, Côte d'Ivoire. Methodology and Results: Wells and boreholes were chosen based on their location and relative importance. Water was collected during the rainy season from 7 wells and 3 boreholes and analysed. Physical parameters (pH, conductivity, turbidity, STD) were measured in situ using multi-parameter probes. Chemical parameters (NO3-, NO2-, NH4+, PO43, Fe2+, Absorbance at 410 nm, Na+, Ca2+, Mg2+, K+, SO32-) were analysed using a molecular absorption spectrophotometer. Overall, the results indicated that boreholes and wells water were acidic (average pH < 7) and slightly mineralized (EC < 500 µS/cm). Moreover, water from wells and boreholes were not statistically different based on their quality. Conclusions and application of finding: Concentration values for cations (NH4+, Fe2+, Mg2+, Ca2+, Na+ and K+) and anions (NO3-, NO2- and PO43-) in wells and boreholes water in this study area complied with the WHO guidelines. It is deduced that the quality of groundwater in Ferkessédougou is acceptable based on its physico-chemical characteristics, although nitrates concentrations in the two drinking water sources remain at critical levels for the population health. Such results can serve as a basis for improved control of boreholes and wells water quality in Ferkessédougou. They can also help define better policies and strategies of access to drinking water in urban areas in Côte d'Ivoire. Keywords: Water quality; Drinking water; Groundwater; Water resources.
Settling is one of the processes occurring in waste stabilization ponds (WSP). Part of suspended solids (SS) is removed by sedimentation but very often the efficiency of WSP is presented without ...making a difference between settling and biological processes. In this way the WSP is seen as a black box process. This work presents an experimental approach to the study of the removal of wastewater suspended solids in a test column in order to improve our knowledge of the settling process in ponds. These results show that the settling test in columns can be used to estimate the half removal time (t50) for the study of settling characteristics of suspended solids in wastewater stabilization ponds. The aim of this study was to determine the half removal time (t50) in anaerobic, facultative and maturation ponds, and in the influent to these ponds, at the experimental wastewater treatment plant of CERTE (Recycling and Treatment Center of Wastewater in Tunisia), by a column settling test. The experiments lasted between 15 and 120 min. The column was 2 m high with sampling systems at various depths: 40, 80, 120, 160 and 200 cm. Half-removal suspended solids time t50 was defined as the time at which 50% of SS was removed. Models derived from the scientific literature were used to interpret the experimental data. The experimental results demonstrated that higher suspended solids concentrations in the influent led to shorter t50 values and better settling. Key words: half removal time, settling column, suspended solids, stabilization ponds, anaerobic ponds
ne varie pas significativement (p > 0,05) d'une saison a l'autre. Une gestion efficace de ces déchets doit associer les actions « prevention », « valorisation » et « stockage » avec un maximum de ...pré-collecte.
Dry composting toilets are increasingly being used as practical sanitation systems in areas with inadequate sewage disposal and inefficient (or inexistent) hydraulic network. In Côte d’Ivoire, the ...by-products from such systems are progressively used in peri-urban agriculture as organic fertilizer, most of the times regardless of any hygienic quality assessment; constituting thereby a major health risk. The main objective of this study was to assess the inactivation rates of key microbiological parameters i.e., total coliforms (TC), fecal coliforms (FC), fecal streptococci (FS) and Ascaris lumbricoides (AL) during the composting process of fecal matters from dry composting toilets. Feces from dry composting toilets pits located at Abobo- Sabgé, Abidjan, Côte d’Ivoire, were collected every two weeks from February to June 2017 and their microbiological contents, along with two physico-chemical characteristics (moisture content and pH) were analyzed. Results revealed noticeable concentration decreases for all the microbiological parameters, except AL. The concentrations dropped from 7.72 to 3.93, 7.61 to 2.70, and 7.10 to 3.11 (log FCU/g) for TC, FC and FS, respectively, during the monitoring period. Regarding AL, there was an increase during the first 29 days, then a decrease in their concentrations over the last 3 months. Furthermore, the study revealed that all fecal bacteria followed a first-order kinetic with the inactivation rates being 0.31, 0.24, and 0.21 d-1 for FC, TC and FS, respectively. The amount of fecal bacteria in the composts suggests that an additional time is required for maturation before any uses of such material as fertilizer.
Given the environmental concerns and public health risks that could arise, the use of composting toilets by-products requires compliance with quality standards beforehand. However, such quality ...assessment is often lacking for those by-products in rapidly urbanizing sub-Saharan cities. This study examines the kinetics of major mineral nutrients i.e., nitrogen (N), phosphorus (P), and potassium (K), which are among the key indicators of a compost’s stability during a composting process of fecal matters from composting toilets. The monitoring was carried out at Abobo-Sagbé, Abidjan, Côte d’Ivoire over a 4.5-month period. Feces-based compost data collected on 6 different dates (i.e., on the 28th , 48th , 62nd , 76th , 90th , and 133nd day from the start of the composting process) were analyzed, and screened for their contents in total N, total P and K. Results showed a rapid decrease of the content of all three elements during the first 29 days, followed by a sharp increase, especially for P and K, and then a quite stable variation during the last 2 months of the monitoring. Variations of C/N ratio during the study were similar to those reported previously. Although the proportions of P and K were satisfactory at the end of the monitoring period, the final C/N ratio was relatively high compared to suitable ratios characterizing mature composts, suggesting therefore additional time may be required before any use of the compost as fertilizer in agriculture.
Recovery of microalgae is one of the main technological and economic concerns in a High Rate Algal Pond because of the small size, the negative surface charges and the low density of these ...microalgae. Usual recovery techniques (e.g. centrifugation) carry prohibitive energy costs with respect to the final value of products. Moreover, efficient recovery techniques (i.e., those that are natural, sustainable and low cost) are of great interest in waste water treatment processes. In this article, a literature review is conducted in order to identify the theories and mechanisms of three methods used for microalgae recovery (i.e. auto-flocculation, bio-flocculation and co-flocculation), and the characterization of physico-chemical conditions necessary for their implementation. This review could advance the current knowledge regarding some of the processes discussed in the literature and provide a basis for the optimal management of reactors in order to achieve efficient results using these methods.
Recovery of microalgae is one of the main technological and economic concerns in a High Rate Algal Pond because of the small size, the negative surface charges and the low density of these ...microalgae. Usual recovery techniques (e.g. centrifugation) carry prohibitive energy costs with respect to the final value of products. Moreover, efficient recovery techniques (i.e., those that are natural, sustainable and low cost) are of great interest in waste water treatment processes. In this article, a literature review is conducted in order to identify the theories and mechanisms of three methods used for microalgae recovery (i.e. auto-flocculation, bio-flocculation and co-flocculation), and the characterization of physico-chemical conditions necessary for their implementation. This review could advance the current knowledge regarding some of the processes discussed in the literature and provide a basis for the optimal management of reactors in order to achieve efficient results using these methods. PUBLICATION ABSTRACT
Sediment accumulation and evaluation of sludge production in wastewater stabilization ponds under a Mediterranean climate: Case study of Tunisia This project studied a stabilization pond system in ...Tunisia composed of four ponds (one anaerobic, one facultative and two maturation) under a Mediterranean climate. The objectives of this work were to determine the sludge characteristics and to study sediment accumulation and spatial distribution in the various ponds. This work was carried out in a pilot-scale stabilization pond system treating domestic wastewater for 282 person-equivalents (PE). The anaerobic pond was 96 m super(3) in volume, 3.25 m in depth. The facultative and two maturation ponds were respectively 180, 164 and 147 m super(3) in volume with mean organic loading rates of 7.6, 4.1 and 3.3 kg BOD5 times d super(-1) respectively. The characteristics of the influent and effluent (including: suspended solids (SS); volatile suspended solids (VSS); chemical oxygen demand (COD) and biochemical oxygen demand (BOD)) were determined twice-monthly during two months of year 2005. A database of previous studies was used to determine the characteristics of the influent and effluent corresponding to the period 1998-2005. The sludge accumulation rates and distribution were determined by measuring the thickness of the sludge layer at 90 to 105 locations throughout each pond. Considering the total volume of sludge determined for the four ponds, the sediment accumulation rate was 0.029 m super(3) per person-equivalent per year, corresponding to an accumulation of 4.14 kg dry matter per person-equivalent per year. In the three ponds, the distribution of sludge is uneven, with greater accumulation near the inlet. To study the horizontal variation in the sludge characteristics, two samples with five replicates were collected in the inlet and in the outlet of the facultative pond, whereas, for the vertical variation, sludge cores were collected, then sectioned into slices. Several parameters such as total carbon (CT), total nitrogen (NT), total phosphorus (PT), dry matter (DM) and volatile matter (VM) were measured on these sub-samples. The results show that (DM) content in the deepest layer is higher than that near the surface, whereas CT, NT, PT, VM decrease with depth. Key words: sludge accumulation rate, wastewater stabilization ponds, sludge distribution, nutrient
Water soils erosion has not been studied enough in the region of Bonoua south-eastern Côte d'Ivoire where major economic activity remains the agriculture. Consequently, control methods are necessary ...in order to ensure sustainable management of soils and to secure agricultural productions. The objective of this study is to supply tools for mapping multifactorial vulnerability to water soil erosion. The method involves an analysis of the main factors of erosion: rainfall erosivity, soil erodibility, slope and land use. Obtained maps are integrated in Geographic Information System (GIS) throughout an additive combinaison to establish a vulnerability water soils erosion map. This map is validated after ground observations. Three classes of multifactorial vulnerability to water erosion have been distinguished: areas with low vulnerability (29 per cent); areas with middle vulnerability (34 per cent) and areas with high vulnerability (37 per cent). Thus, in the region of Bonoua, classes with a middle or high multifactorial vulnerability represent 71 per cent of the study area. This first map is a tool that would help decision makers in attribution of areas for agricultural activities and for socio-economic substructures.
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