Assessment of pathogenic bacteria in water and sediment from a water reservoir under tropical conditions (Lake Ma Vallée), Kinshasa Democratic Republic of Congo

This study was conducted to assess potential human health risks presented by pathogenic bacteria in a protected multi-use lake-reservoir (Lake Ma Vallée) located in west of Kinshasa, Democratic Republic of Congo (DRC). Water and surface sediments from several points of the Lake were collected during summer. Microbial analysis was performed for Escherichia coli, Enterococcus (ENT), Pseudomonas species and heterotrophic plate counts. PCR amplification was performed for the confirmation of E. coli, ENT, Pseudomonas spp. and Pseudomonas aeruginosa isolated from samples. The results reveal low concentration of bacteria in water column of the lake, the bacterial quantification results observed in this study for the water column were below the recommended limits, according to WHO and the European Directive 2006/7/CE, for bathing water. However, high concentration of bacteria was observed in the sediment samples; the values of 2.65 × 103, 6.35 × 103, 3.27 × 103 and 3.60 × 108 CFU g−1 of dry sediment for E. coli, ENT, Pseudomonas spp. and heterotrophic plate counts, respectively. The results of this study indicate that sediments of the Lake Ma Vallée can constitute a reservoir of pathogenic microorganisms which can persist in the lake. Possible resuspension of faecal indicator bacteria and pathogens would affect water quality and may increase health risks to the population during recreational activities. Our results indicate that the microbial sediment analysis provides complementary and important information for assessing sanitary quality of surface water under tropical conditions

Trace metal distributions in the sediments from river-reservoir systems: case of the Congo River and Lake Ma Vallée, Kinshasa (Democratic Republic of Congo)

The contamination of drinking water resources by toxic metals is a major problem in many parts of the world, particularly in dense populated areas of developing countries that lack wastewater treatment facilities. The present study characterizes the recent evolution with time of some contaminants deposited in the Congo River and Lake Ma Vallée, both located in the vicinity of the large city of Kinshasa, capital of Democratic Republic of Congo (DRC). Physicochemical parameters including grain size distribution, organic matter and trace element concentrations were measured in sediment cores sampled from Congo River (n = 3) and Lake Ma Vallée (n = 2). The maximum concentration of trace elements in sediment profiles was found in the samples from the sites of Pool Malebo, with the values of 107.2, 111.7, 88.6, 39.3, 15.4, 6.1 and 4.7mgkg−1 for Cr, Ni, Zn, Cu, Pb, As and Hg, respectively. This site, which is characterized by intense human activities, is especially well known for the construction of numerous boats that are used for regular navigation on Congo River. Concerning Lake Ma Vallée, the concentration of all metals are generally low, with maximum values of 26.3, 53.6, 16.1, 15.3, 6.5 and 1.8mgkg−1 for Cr, Ni, Zn, Cu, Pb and As, respectively. However, the comparison of the metal profiles retrieved from the different sampled cores also reveals specific variations. The results of this study point out the sediment pollution by toxic metals in the Congo River Basin. This research presents useful tools for the evaluation of sediment contamination of river-reservoir systems

Trace metal distributions in the sediments from river-reservoir systems: case of the Congo River and Lake Ma Vallée, Kinshasa (Democratic Republic of Congo)

The contamination of drinking water resources by toxic metals is a major problem in many parts of the world, particularly in dense populated areas of developing countries that lack wastewater treatment facilities. The present study characterizes the recent evolution with time of some contaminants deposited in the Congo River and Lake Ma Vallée, both located in the vicinity of the large city of Kinshasa, capital of Democratic Republic of Congo (DRC). Physicochemical parameters including grain size distribution, organic matter and trace element concentrations were measured in sediment cores sampled from Congo River (n = 3) and Lake Ma Vallée (n = 2). The maximum concentration of trace elements in sediment profiles was found in the samples from the sites of Pool Malebo, with the values of 107.2, 111.7, 88.6, 39.3, 15.4, 6.1 and 4.7 mg kg−1 for Cr, Ni, Zn, Cu, Pb, As and Hg, respectively. This site, which is characterized by intense human activities, is especially well known for the construction of numerous boats that are used for regular navigation on Congo River. Concerning Lake Ma Vallée, the concentration of all metals are generally low, with maximum values of 26.3, 53.6, 16.1, 15.3, 6.5 and 1.8 mg kg−1 for Cr, Ni, Zn, Cu, Pb and As, respectively. However, the comparison of the metal profiles retrieved from the different sampled cores also reveals specific variations. The results of this study point out the sediment pollution by toxic metals in the Congo River Basin. This research presents useful tools for the evaluation of sediment contamination of river–reservoir systems

Assessment of pathogenic bacteria in water and sediment from a water reservoir under tropical conditions (Lake Ma Vallée), Kinshasa Democratic Republic of Congo

This study was conducted to assess potential human health risks presented by pathogenic bacteria in a protected multi-use lake-reservoir (Lake Ma Vallée) located in west of Kinshasa, Democratic Republic of Congo (DRC). Water and surface sediments from several points of the Lake were collected during summer. Microbial analysis was performed for Escherichia coli, Enterococcus (ENT), Pseudomonas species and heterotrophic plate counts. PCR amplification was performed for the confirmation of E. coli, ENT, Pseudomonas spp. and Pseudomonas aeruginosa isolated from samples. The results reveal low concentration of bacteria in water column of the lake, the bacterial quantification results observed in this study for the water column were below the recommended limits, according to WHO and the European Directive 2006/7/CE, for bathing water. However, high concentration of bacteria was observed in the sediment samples; the values of 2.65 × 103, 6.35 × 103, 3.27 × 103 and 3.60 × 108 CFU g−1 of dry sediment for E. coli, ENT, Pseudomonas spp. and heterotrophic plate counts, respectively. The results of this study indicate that sediments of the Lake Ma Vallée can constitute a reservoir of pathogenic microorganisms which can persist in the lake. Possible resuspension of faecal indicator bacteria and pathogens would affect water quality and may increase health risks to the population during recreational activities. Our results indicate that the microbial sediment analysis provides complementary and important information for assessing sanitary quality of surface water under tropical conditions

Trace metals and persistent organic pollutants in sediments from river-reservoir systems in Democratic Republic of Congo (DRC): Spatial distribution and potential ecotoxicological effects

This paper discusses the occurrence and spatial distribution of metals and persistent organic pollutants (POPs: including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), Polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs) in sediments from a river-reservoir system. Surface sediments were sampled from thirteen sites of the Congo River Basin and Lake Ma Vallée, both situated in the vicinity of the capital city Kinshasa (Congo Democratic Republic). Sediment qualities were evaluated using toxicity test based on exposing Ostracods to the sediment samples. The highest metal concentrations were observed in sediments subjected to anthropogenic influences, urban runoff and domestic and industrial wastewaters, discharge into the Congo River basin. Ostracods exposed to the sediments resulted in 100% mortality rates after 6 d of incubation, indicating the ultimate toxicity of these sediments as well as potential environmental risks. The POPs and PAHs levels in all sediment samples were low, with maximum concentration found in the sediments (area of pool Malebo): OCP value ranged from 0.02 to 2.50 with POCPs: 3.3 lg kg_1; PCB ranged from 0.07 to 0.99 with Total PCBs (P7 _ 4.3): 15.31 lg kg_1; PAH value ranged from 0.12 to 9.39 with PPAHs: 63.89 lg kg_1. Our results indicate that the deterioration of urban river-reservoir water quality result mainly from urban stormwater runoff, untreated industrial effluents which discharge into the river-reservoirs, human activities and uncontrolled urbanization. This study represents useful tools incorporated to evaluate sediment quality in river-reservoir systems which can be applied to similar aquatic environments