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The radioactivity associated with artisanal and small-scale gold mining activities (ASM) carried out along the Ulindi River, in the eastern Democratic Republic of the Congo, was evaluated by gamma-ray spectrometry and inductively coupled plasma–mass spectrometry of soil and sediment samples. The results revealed that activity concentrations of 238U (up to 3127 ± 98 Bq kg−1), 226Ra (up to 2710 ± 89 Bq kg−1) and 232Th (up to 2142 ± 162 Bq kg−1) were 71- to 89-fold higher than the worldwide average concentrations reported by UNSCEAR in soils. Primordial radionuclides are, thus, present in high concentrations in deposits of gold in that region and the average ambient effective radiation dose rate was determined at 8.4 mSv y−1 (range 0.5 to 40 mSv y−1). This area may be classified as a natural high background radiation area (HBRA). The radiation risk for artisanal miners and population members manipulating those geological materials were assessed through radiological parameters. such as the radium equivalent activity index (RaEq), outdoor gamma absorbed dose rate (ODRA), annual effective dose equivalent (AEDE), and excess lifetime cancer risk (ELCR). The mean values of these parameters were significantly elevated in comparison to the world average levels and indicated the existence of significant radiation risks for gold miners and members of the local population. A radiation safety policy seems needed to protect workers and the local population in this region.

The concentrations and distribution of naturally occurring radionuclides (238U, 235U, 234U, 230Th, 226Ra, 210Pb, 232Th, 228Ra, and 40K) were determined by alpha and gamma spectrometry in soil and sediments collected from Luilu and Dilala rivers located in the mining district of Kolwezi (Lualaba Province) of the Democratic Republic of the Congo. The average concentrations of 238U and 226Ra in the analyzed samples were 5 - 10 times higher than the world average values for soil provided by the United Nations Scientific Committee on the Effects of Atomic Radiation. However, the average concentrations of 232Th were found similar to the world average. In both river basins, artisanal mining activities and mineral washing sites displayed the higher concentration values of radionuclides. The mean values of health risk indices calculated for those sites were found significantly higher compared to world average levels. Radiation protection measures seem needed to ensure the radiation safety of local populations. Graphical Abstract

The objective of this research is to determine the concentration and potential health risks of toxic metals in six most consumed freshwater fish species (Auchenoglanis occidentalis, Bagrus ubangensi, Citharinus gibbosus, Distichondus fasciolatus, Marcusenius moorii and Schilbe mystus). A total of 126 samples of these fish species were collected from seven sites of Congo River in the vicinity of Kinshasa City, Democratic Republic of the Congo. Toxic metals (Cr, Co, Ni, Zn, Se, Ag, Cd, Sn, Sb and Pb) levels in fish muscle tissues were determined using Inductively Coupled Plasma Mass Spectrometry whereas Hg analysis was carried out using atomic absorption spectrophotometry. The maximum metal concentration (mg kg-1 wet weight) of Zn (59.72), Sb (5.98) and Pb (4.96) was detected in muscle tissues of Marcusenius moorii, Citharinus gibbosus and Distichondus fasciolatus respectively. Pb, Zn, and Hg values in many fish samples exceeded the permissible levels set by Food and Agriculture Organization and World Health Organization for human consumption. Given the concentrations of Pb in all fish species and Zn in Marcusenius moorii, human health implications are likely to occur on continuous consumption. Addition, the evaluation of potential health risks for fish consumers indicates that there may or not be adverse effects.

The aim of this review was to summarise the available HBM data in DRC in order to provide recommendations for developing the HBM field. We performed a systematic search of PubMed/MedLine, EMBASE, and ISI Web of Science for papers on exposure levels to chemicals in DR C (2009-2019). A total of 12 papers were found: 9 in Kinshasa (75.0%) and 3 in Katanga (25.0%). Globally, the results reveal concern about exposure levels to environmental chemicals, mostly heavy metals. Some studies connected HBM data to negative health effects (preeclampsia, birth defects, children's temperament difficulties, holoprosencephaly) demonstrating the importance of regulation in occupational and environmental settings. The recommendations of this review include expanding HBM studies as well as the number of environmental chemicals; and establishment of a national HBM laboratory for developing and/or enhancing the capacity of DRC to undertake a national policy-related HBM.

In many suburban municipalities of developing countries, the household drinking water comes mainly from groundwater including, wells, streams and springs. These sources are vulnerable because poor hygienic conditions and sanitation prevail causing persistence and recurrent waterborne diseases. In this research, a survey study on water resource use and an epidemiological survey of waterborne diseases were conducted among users of water points and medical institutions in suburban communes of Selembao and Kimbanseke (Kinshasa, the Democratic Republic of the Congo). In addition, physicochemical (temperature, pH, O2, electrical conductivity, and soluble ions: Na+, K+, PO43−, SO42−, NO3−, NO2−) and bacteriological (FIB: faecal indicator bacteria) analyses of water from 21 wells and springs were performed according to the seasonal variations. FIB included Escherichia coli (E. coli), Enterococcus and Total Coliforms. The survey results indicate that more than 75% of the patients admitted to local medical institutions between 2016 and 2019 are affected by waterborne diseases, including typhoid fever, amoebic dysentery, diarrhoea, gastroenteritis disorders and cholera. Except for NO3− in some sites, the water physicochemical parameter values are within WHO permissible limits for drinking/domestic water quality. On the contrary, the results revealed high FIB levels in water from unmanaged wells and springs during rainy and dry seasons. The microbiological pollution was significantly higher in the rainy season compared to the dry season. Interestingly, no FIB contamination was observed in water samples from managed/developed wells. The results from this study will guide local government decisions on improving water quality to prevent recurrent waterborne diseases.

The contamination of water resource and food chain by persistent organic pollutants (POPs) constitutes a major environmental and human health concern worldwide. The aim of this study was to investigate the levels of POPs in irrigation water, soil and in Amaranthus viridis (A. viridis) from different gardening sites in Kinshasa to evaluate the potential environmental and human health risks. A survey study for the use of pesticides and fertilizers was carried out with 740 market gardeners. The levels of POPs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs)) were analyzed in irrigation water and 144 vegetable samples collected from different gardening sites. The assessment of potential human health risk was estimated by calculating daily intake and toxic equivalency to quantify the carcinogenicity. The results show highest PAH levels in A. viridis from all studied sites. The concentrations of the sum of seven PCBs (Σ7PCBS) congeners in analyzed plants ranged between 15.89 and 401.36 ng g−1. The distributions of OCPs in both water and A. viridis were congener specific, chlorpyrifos-ethyl and p,p′-DDE were predominantly detected. Among PBDEs, only BDE47 was quantified with noticeable concentration in A. viridis, while no PBDEs were detected in irrigation water. Higher estimated daily intake values indicate that consuming leafy vegetables might associate with increased human health risks. However, calculated incremental lifetime cancer risk values indicates no potential carcinogenic risk for the local population. The results of this study provide important information on A. viridis contamination by POPs and strongly recommend implementing the appropriate measures to control the use of chemicals used in studied gardening areas. Thus in Kinshasa, urban agriculture control programs for POPs and fertilizers is very important in order to protect the public health through direct and dietary exposure pathways., Graphical abstract Unlabelled Image, Highlights • Survey study was performed for the use of pesticides and fertilizers. • Persistence Organic Pollutants (POPs) in soil, water and A. viridis were investigated. • Highest PAH levels were observed in soil, water and A. viridis from all studied sites. • Estimated daily intake indicates potential health risks associated to leafy vegetables consumption. • Incremental lifetime cancer risk values indicate no potential carcinogenic.

Abandoned mines and mining activities constitute important sources of toxic metals and Rare Earth Elements (REEs) affecting surrounding environmental compartments and biota. This study investigates the contamination degree and distribution of toxic metals and REEs in contrasting sediment, soil and plant samples surrounding rivers in the African copperbelt area characterized by the presence of numerous abandoned mines, artisanal and industrial mining activities. ICP-MS results highlighted the highest concentration of Cu, Co and Pb in sediments reaching values of 146,801, 18,434 and 899 mg kg−1, respectively. In soil, the values of 175,859, 21,134 and 1164 mg kg−1 were found for Cu, Co and Pb, respectively. These values are much higher than the sediment guidelines for the protection of aquatic life and international soil clean-up standards. Enrichment factor and geoaccumulation index results indicated important contribution of mining activities to the study sites pollution in addition to natural background. Highest metal accumulation in leaves of Phalaris arundinacea L., was observed, reaching values of 34,061, 5050 and 230 mg kg−1 for Cu, Co, and Pb, respectively. The ∑REE concentration reached values of 2306, 733, 2796 mg kg−1 in sediment, soil and plant samples, respectively. The above results were combined with geographical information including satellite imagery, hydrography and mining concessions. Maps were produced to present the results in a comprehensive and compelling visual format. The results will be disseminated through an innovative mapping online platform to simplify access to data and to facilitate dialogue between stakeholders.

Water resource contamination is still a major concern in several regions of developing countries especially in sub-Saharan countries in which polluted waters pose serious risks to human health and the environment. The seasonal variation of the physicochemical parameters including pH, temperature (T), electrical conductivity (EC), dissolved oxygen (O2), dissolved organic carbon (DOC), total organic carbon (TOC), and trace metals were assessed in water samples collected from wells (n=3) and two rivers which were the River Lukemi (RLK, n=3) and River Luini (RLN, n=2) located in the City of Kikwit (Province of Kwilu, Democratic Republic of the Congo). Samples were collected during the dry and wet seasons. The concentration of trace metals (Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Cd, Sn, Sb, and Pb) in water was measured using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and soluble ions (Na+, K+, NH4+, SO42-, NO3-, and Cl-) analysis was performed using Ion Chromatography. The results indicate the seasonal difference in the physicochemical composition of water e.g., the pH was lower in the wet compared to the dry season. pH values during the wet season ranged from 4.12 to 5.60 in wells and from 5.55 to 6.31 in rivers while the dry season values ranged from 6.27 to 6.98 in wells and from 7.09 to 7.44 in rivers. The concentrations of soluble ions and other physicochemical parameters (O2, DOC and TOC) also varied with the seasons, being higher in the wet and lower in the dry season. With the exception of Mn, the average concentrations of other trace metals measured in water samples from wells and rivers met the World Health Organization (WHO) guidelines for drinking/domestic water quality. Mn concentration in water samples analysed ranged between 634 to 812 and 1352–1741 µg L−1 during the dry and wet seasons, respectively. These results imply that the high concentration of Mn in the water samples may be explained by the geological origin and result of natural weathering processes. In general, according to the parameters analysed, the water samples taken from the sites studied in both seasons appear to meet drinking water standards according to the WHO guidelines but with the two exceptions of the pH and Mn. This study is important for the present situation and can be applied in similar environmental compartments in the future to assess the availability of safe drinking water in developing countries.

Microbial populations which are resistant to antibiotics are an emerging environmental concern with potentially serious implications for public health. Thus, there is a growing concern in exploring the occurrence of antibiotic resistance in the environment with no limitations to the factors that contribute to their emergence. The aquatic environment is considered to be a hot-spot for the acquisition and spread of antibiotic resistance due to pollution with emerging contaminants derived from anthropogenic activities. In this study, we report on the isolation and characterization of 141 Pseudomonas spp. from aquatic sediments receiving partially (un)treated hospital and communal effluents from three distinct geographical locations: Democratic Republic of the Congo (DRC), India (IN), and Switzerland (CH). P. putida (42%) and P. aeruginosa (39%) were the dominant Pseudomonas species. The highest frequency of antibiotic resistance against eight anti-pseudomonas agents was found among IN isolates (35–60%), followed by DRC (18–50%) and CH (12–54%). CTX-M was the most frequent β-lactamase found in CH (47% of isolates), while VIM-1 was dominant in isolates from DRC (61%) and IN (29%). NDM-1 was found in 29% of the total IN isolates and surprisingly also in 6% of CH isolates. Chromosomally-encoded efflux mechanisms were overexpressed in P. aeruginosa isolates from all three geographic locations. In vitro conjugative transfers of antibiotic resistance plasmids occurred more frequently under tropical temperatures (30 and 37 °C) than under temperate conditions (10 °C). The presence of Extended Spectrum β-lactamases (ESBLs) and Metallo β-lactamases (MBLs) in the isolates from environmental samples has important implications for humans who depend on public water supply and sanitation facilities. To our knowledge, this is the first study to demonstrate a comparison between treated/untreated effluents from urban and hospital settings as a source of microbial resistance by evaluating the aquatic ecosystems sediments from tropical and temperate climate conditions. Taken together, our findings demonstrate a widespread occurrence of antibiotic resistance in aquatic ecosystems sediments receiving untreated/treated wastewater and how these contemporary sources of contamination, contribute to the spread of microbial resistance in the aquatic environment. This research presents also useful tools to evaluate sediment quality in the receiving river/reservoir systems which can be applied to similar environments.

The objective of the present research was to evaluate the contamination level and potential risks at a part of a large and important river in Central Africa, the Congo River. Surface sediments were collected from seven stations located in Maluku-Kinsuka section, at the vicinity of Kinshasa, capital city of Democratic Republic of the Congo. The concentration of toxic metals (Cr, Co, Ni, Cu, Zn, As, Cd and Pb) in sediment samples were determined using Inductive Coupled Plasma-Mass Spectroscopy (ICP-MS). The Hg analysis was carried out using Advanced Mercury Analyzer (AMA). The evaluation of the pollution degree was based on Sediment Quality Guidelines (SQGs), Enrichment Factor (EF), Geoaccumulation Index (Igeo), and using toxicity test based on exposing Ostracods to the sediment samples. The result revealed high metal concentrations in sediments from the 4 densely populated areas (Kinkole, Kauka fishermen, Demoulin, Chanic), reaching the values (mg kg−1) of of 95.5, 14.3, 37.1, 139.9, 281.5, 4.8, 6.6, 200.9 and 4.9 mg kg−1 for Cr, Co, Ni, Cu, Zn, As, Cd, Pb and Hg, respectively. These values are above SQGs and probable effect levels. In these sites, Igeo and EF values showed heavily to extremely polluted and severe enrichment to extremely severe enrichment for analysed metals. Additionally, Ostracods exposed to sediments resulted in 100% mortality rates after 6 days of incubation, demonstrating the sediment toxicity as well as potential risks for aquatic living organisms. The pollution in these sites may be explained by local intense human activities with various commercial, presence of uncontrolled landfills in riverbank and industrial settlements, as well as by the construction of boats for the regular navigation along the river. This research presents useful tools for evaluating sediments quality and risk, which can be applied to similar environments.

The occurrence and dissemination of antibiotic resistant genes (ARGs) that are associated with clinical pathogens and the evaluation of associated risks are still little investigated in developing countries under tropical conditions. In this context, cultivable and molecular approaches were performed to assess the dissemination of bacteria and their antibiotic resistance genes in aquatic environment in Kinshasa, Democratic Republic of the Congo. Cultivable approach quantified β-lactam, carbapenem resistant, and total Escherichia coli (E. coli) and Enterbacteriaceae (Ent) in river sediments and surface waters that receive raw hospital effluents. The molecular approach utilized Quantitative Polymerase Chain Reaction (qPCR) to quantify the total bacteria and the richness of relevant bacteria (Escherichia coli (E. coli), Enterococcus, and Pseudomonas (P. spp)), and antibiotic resistance genes (ARGs: blaOXA-48, blaCTX-M, blaIMP, blaTEM) in sediment samples. Statistical analysis (ANOVA method, principle component analysis, and correlation matrix) were used to explore the significance of hospital contribution and seasonal variation of bacteria and ARGs into explored aquatic ecosystems in suburban municipalities of Kinshasa, Democratic Republic of the Congo. The contribution of hospitals to antibiotic resistance proliferation is higher in the dry season than during the wet season (P value

An epidemiological survey conducted among users of water points and medical institutions in the N'djili Kilambu neighborhood of Kinshasa in Democratic Republic of the Congo, indicates that waterborne diseases have already affected more than 60% of the patients admitted to local clinics between 2013 and 2017. In order to raise public and political awareness about this hazardous health issue resulting from the lack of safely managed sanitation systems, this study investigates the microbial quality of drinking water from local water resources. Water samples were collected from nine wells and streams used as drinking sources, and analyzed for Fecal Indicator Bacteria (FIB), including Escherichia coli, Enterococcus, and Total Coliforms. Physicochemical parameters (pH, electrical conductivity, O2, and soluble ions (Na+, K+, PO43-, SO42-, NO3-, NO2-) were also analyzed. Except for NO3- and NO2-, the average concentrations of the physicochemical parameters and dissolved ions generally meet the guidelines for drinking/domestic water quality. By contrast, the results reveal high levels of FIB in the water samples collected during both dry and wet seasons. The contamination is significantly higher during the wet season compared to dry season, due to increased runoff, open defecation practices, and more frequent overflow of onsite sanitation systems and septic tanks.

The management of hospital waste is a high-risk practice in the hospitals of Kinshasa, the largest city of the Democratic Republic of the Congo, from the point of view of public health and the environment. A multi-criteria study carried out in 4 hospitals assessed the situation and put forward solutions.

This study is a part of the research methods for sustainable management of sandy soils of the province of Kinshasa (DRC).The intended aim is to characterize the soil sites with high agricultural activity in Kinshasa and to identify the main constraints to productivity. The diagnosis revealed that soils of three sites investigated studied are sandy and characterized by low retention capacity in the field ( tot (≤ 0.1 %), P ass ( −1 ), inexchangeable bases and are saturated to more than 60 % Al. Microbiological characteristics are weak in terms of microbial carbon, basal and induced respiration, and enzymatic activities. These characteristics are influenced by the organic matter and are the limitations on the productivity of these soils.

The contamination of freshwater resources with various organic and inorganic contaminants is still a major problem in many parts of the world, especially in developing countries in which the poor water quality continues to pose a serious threat to human health. In this study, the assessment of groundwater quality was performed in the municipality of Bumbu (Kinshasa, Democratic Republic of the Congo) according to the seasonal variation. Water physicochemical parameters [pH, electrical conductivity (EC), dissolved oxygen and soluble ions (Na+, K+, PO4 3−, SO4 2−, NO3 −, NO2 −)] and faecal indicator bacteria (FIB) including Escherichia coli (E. coli), Enterococcus (ENT) and Total coliforms (TC) were analysed. Except for EC and NO3 −, the results revealed low concentration of other water physicochemical parameters, which are below the recommended limits, according to World Health Organization guideline for drinking water. Additionally, the result showed high concentration of FIB reaching the values of 1.6 × 104, 1.5 × 104 and 9.0 × 105 CFU 100 mL−1 for E. coli, ENT and TC, respectively. The pollution was substantial in wet season compared to dry season. PCR amplification for human-Bacteroides indicated that more than 90 % of bacteria were from human origin. Our results highlight the potential human risk associated with the exposure to water contamination from wells due to the high level of NO3 −, EC, E. coli and ENT in both dry and wet seasons. The approach developed in this study helps provide a better understanding of the physicochemical and microbiological pollution of wells in large cities characterized with lack of wastewater and sanitation facilities.

The objective of the present study was to assess the status of surface sediments from Funa River. Sediment samples were characterized for physicochemical parameters including grain size, organic matter and toxic metals. The result revealed high metal concentrations in river sediments, reaching values of 154.19, 186.00, 1105.34, 3.69, 548.02 and 5.45 mg kg-1 for Cr, Cu, Zn, Cd, Pb and Hg, respectively. A strong correlation was observed between analyzed metals and organic matter suggesting that these contaminants could have originated from common sources with a similar transport pathway. Based on the Sediment Quality Guidelines for the Protection of Aquatic Life (SQGs), Funa River is considered as highly polluted with toxic metals indicating the potential environmental and human health risk. The results of this research represent a useful tool to assess the sediment quality of urban river receiving system which can be applied to similar environment.

The present study aims to determine the levels of heavy metals in edible nine different commonly consumed fish species (Pseudotolithus elongatus, Pseudotolithus senegalensis, Cynoglossus senegalensis, Trichiurus lepturus, Galeoides decadactylus, Pentanemus quinquarius, Chrysichthys nigrodigitatus, Mugil curema, and Arius latiscutatus). Fishes were collected during August 2016 from five sites of West Atlantic Ocean Coast of the Democratic Republic of the Congo. Heavy metals (Cr, Cu, Zn, Ni, Sb, Cd, Pb, and Se) levels in fish muscle tissues were determined using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) whereas Hg analysis was carried out using atomic absorption spectrophotometry (AAS). Metal concentrations varied considerably among sampling sites and fish species (P

In many urban and peri-urban areas of developing countries, shallow wells and untreated water from urban rivers are used for domestic purposes, including drinking water supply, population bathing and irrigation for urban agriculture. The evaluation and monitoring of water quality are therefore necessary for preventing potential human risk associated with the exposure to contaminated water. In this study, physicochemical and bacteriological parameters were assessed in an urban river (named Kokolo Canal/Jerusalem River) draining the municipality of Lingwala (City of Kinshasa, Democratic Republic of the Congo) and in two shallow wells used as drinking water supplies, during the wet and dry seasons in order to estimate the seasonal variation of contamination. The faecal indicator bacteria (FIB) isolated strains (Escherichia coli (E. coli) and Enterococcus (ENT)) from water and surface sediment, were characterized for human-specific bacteroides by molecular approach. The results revealed very high faecal contamination of water from the shallow wells, and of water and sediments from the river, during both wet and dry seasons. During the wet season, E. coli reached the values of 18.6x105 and 4.9x105 CFU 100 mL-1 in Kokolo Canal and shallow wells, respectively; and Enterococcus reached the values of 7.4x104 and 2.7x104 CFU 100 mL-1. Strong mutually positive correlation was observed between E. coli and ENT, with the range of R-value being 0.93 < r < 0.97 (p-value < 0.001, n=15). The PCR assays for human-specific Bacteroides indicated that more than 98% of 500 isolated FIB strains were of human origin, pointing out the effect of poor household sanitation practices on surface water but also on groundwater contamination. The water samples from the shallow wells and Kokolo Canal were highly polluted with faecal matter in both seasons. However, the pollution level was significantly higher during the wet season compared to the dry season. Physicochemical analysis revealed also very high water electrical conductivity, with values much higher than the recommended limits of the World Health Organization guideline for drinking water. These results highlight the potential human health risk associated with the exposure to water contamination from shallow wells and Kokolo Canal, due to the very high level of human FIB. Rapid, unplanned and uncontrolled population growth in the city of Kinshasa is increasing considerably the water demand, whereas there is a dramatic lack of appropriate sanitation and wastewater facilities, as well as of faecal sludge (and solid waste) management and treatment. The lack of hygiene and the practice of open defecation is leading to the degradation of water quality, consequently the persistence of waterborne diseases in the neighbourhoods of sub-rural municipalities, and there is a growing threat to the sustainability to water resources and water quality. The results of this study should encourage municipality policy and strategy on increasing the access to safely managed sanitation services; in order to better protect surface water and groundwater sources, and limit the proliferation of epidemics touching regularly the city.

La possibilité d’éliminer la turbidité et les coliformes, en utilisant un système de filtration lente sur sable à plusieurs étapes, a été étudiée à l’échelle du laboratoire. Le but de l’étude était de montrer que cette technologie constitue une solution de traitement efficace de l’eau en milieu rural et dans de petites agglomérations des pays en voie de développement. Dans cette étude, un système a été monté et testé. Ce système était constitué de deux filtres lents à sable en série, lesquels sont précédés de deux filtres à granulométrie grossière à flux ascendant. L’efficacité de cette technologie a été évaluée par la mesure de la turbidité et le dénombrement des coliformes totaux et thermotolérants. Les résultats obtenus ont montré : (i) d’excellents abattements de la turbidité malgré le niveau élevé de celle de l’eau brute (de 20 unités de turbidité néphélométrique (NTU) à plus de 100 NTU); (ii) une bonne élimination des coliformes, en fonction de la maturité biologique des filtres utilisés; (iii) de plus, il a été constaté que la turbidité de l’effluent à la sortie du second filtre lent à sable était largement en dessous de la norme de l’Organisation Mondiale de la Santé (OMS) concernant l’eau potable.Globalement, chaque étape individuelle du système de filtration à plusieurs étapes joue un rôle important dans le processus global de réduction de la turbidité, ainsi que du nombre de coliformes. Il a été remarqué que le filtre à granulométrie grossière, en plus de son rôle protecteur de filtre lent à sable contre les matières en suspension, constitue aussi une barrière importante de traitement dans la diminution du nombre de coliformes. L’addition d’un second filtre lent à sable en série a apporté une efficacité supplémentaire au processus de traitement, en ramenant la turbidité d’effluent proche de 1 NTU et en permettant d’obtenir des abattements additionnels de coliformes., The ability to remove turbidity and coliforms, using a multistage filtration system, was studied in the laboratory. The aim of the study was to show that this technology constitutes an effective solution for water treatment in rural regions and small communities in developing countries. In this study, a system was assembled and tested. The system comprised two slow sand filters in series, which were preceded by two coarse upflow filters. The effectiveness of this technology was evaluated by measuring the turbidity and the number of total and thermotolerant coliforms. The results showed excellent removals of turbidity despite the high level of turbidity in the raw water (from 20 nephelometric turbidity units (NTU) to more than 100 NTU). The turbidity of the effluent from the final slow filtration system was well below the World Health Organization (WHO) standard for drinking water. There was a good removal of the total and thermotolerant coliforms, which was a function of the biological maturity of the filters used.Each individual stage of the multistage system was an important treatment barrier in the overall process of turbidity and coliform removal. The coarse filter was not only important for protecting the slow sand filter from solids loading and thus increasing its run length, but was also a significant contributor to coliform removal. The second slow sand filter in series provided additional capacity to the process by reducing the effluent turbidity to close to 1 NTU and it also provided additional removal of coliforms under challenging operations.

The availability of safe drinking water in sub-Saharan countries remains a major challenge because poor sanitation has been the cause of various outbreaks of waterborne disease due to the poor microbiological quality of water used for domestic purposes. The faecal indicator bacteria (FIB) used in the present study included Escherichia coli (E. coli) and Enterococcus (ENT). FIB and aerobic mesophilic bacteria (AMB) were quantified during July 2015 (dry season) and November 2015 (rainy season) in order to assess the quality of drinking water from wells (n = 3; P1, P2, and P3), and two rivers, the River Lukemi (RLK, n=3) and River Luini (RLN, n=2) in the city of Kikwit, which is located in the province of Kwilu in the Democratic Republic of the Congo. Kikwit is well known for its outbreaks of persistent and recurrent waterborne diseases including Entamoeba, Shigella, typhoid fever, cholera, and Ebola Viral Hemorrhagic Fever. Consequently, E. coli, ENT, and AMB were quantified in water samples according to the standard international methods for water quality determination using the membrane filtration method. The FIB characterization was performed for human-specific Bacteroides by PCR using specific primers. The results obtained revealed high FIB concentrations in river samples collected during both seasons. For example, E. coli respectively reached 4.3x104 and 9.2x104 CFU 100 mL-1 in the dry season and the wet season. ENT reached 5.3x103 CFU 100 mL-1 during the dry season and 9.8x103 CFU 100 mL-1 in the wet season. The pollution was significantly worse in the wet season compared to the dry season. Surprisingly, no faecal contamination was observed in well water samples collected in the dry season while E. coli and ENT were detected in all wells in the wet season with values of 6, 7, and 11 CFU mL-1for E. coli in wells P1, P2, P3, respectively and 3, 5, 9 CFU mL-1for ENT in the same wells. Interestingly, the PCR assays for human-specific Bacteroides HF183/HF134 indicated that 97-100 % captured in all analyses of isolated FIB were of human origin. The results indicate that contamination of E. coli, ENT, and AMB in the studied water resources increases during the wet season. This study improves understanding of the microbiological pollution of rivers and wells under tropical conditions and will guide future municipal/local government decisions on improving water quality in this region which is characterised by persistent and recurrent waterborne diseases. Although the epidemiology can be geographically localised, the effects of cross border transmission can be global. Therefore, the research results presented in this article form recommendations to municipalities/local authorities and the approach and procedures can be carried out in a similar environment.

The increasing contamination of fresh water resource by toxic metals and Persistence Organic Pollutants (POPs) is a major environmental concern globally. In the present investigation, surface sediments collected from three main rivers named, Makelele, Kalamu and Nsanga, draining through the city of Kinshasa, Democratic Republic of the Congo, were characterized for grain size, organic matter, toxic metals, POPs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), poly- brominated diphenyl ethers (PBDEs)), and polycyclic aromatic hydrocarbons (PAHs). Furthermore, enrichment factor (EF) and geoaccumulation index (Igeo) were performed to determine metal source and pollution status. The results highlighted high concentration of toxic metals in all sediment samples, reaching the values (mg kg-1) of 325 (Cu), 549 (Zn), 165 (Pb) and 1.5 (Cd). High values of PCBs and OCPs were detected in sediment samples, e.g. in Makelele river, PCB values ranged from 0.9 to 10.9 with total PCBs (∑7 PCBs x 4.3): 169.3 mg kg-1; OCPs from 21.6 to 146.8 with ∑OCPs: 270.6 mg kg-1. The PBDEs concentrations were higher in investigated rivers comparatively with values detected in many rivers from Sub-Saharan Africa. The SPAHs value ranged from 22.6 to 1011.9 mg kg-1. River contamination may be explained by local intense domestic activities, urban and agricultural runoff, industrial and hospital wastewaters discharge into the rivers without prior treatment. This research provides not only a first baseline information on the extent of contamination in this tropical ecosystem but also represents useful tools incorporated to evaluate sediment quality in the river receiving systems which can be applied to similar aquatic environments.

In DRC, hospital waste correspond to a mixture of the waste similar to household waste (DAOM) and waste of Infectious clinical activities (HCW). As part related to hospital hygiene, our study focuses on the impact of clinical waste in the workplace and the environment.For the workstation, on 20 selected people, more than 70% suffered from chest tightness, organic dust syndrome, dryness of the throat and nose, fungi and actinomycetes. About 40% have suffered from gastrointestinal disorders in the handling of hospital waste (from collection to treatment / disposal).From an environmental perspective, the physicochemical characterization of the outgoing storm water litter deposits from four selected hospitals (CUK, HGRK, HGRN, and HGK) show high levels for most of the parameters studied. For the first campaign carried out in 2006, the ratio of BOD5 / COD is 0.08 leachate. Based on available data, the pollution load is composed of chloride (5529 mg / l), COD (890 mg / l) and Cd (20 1 g / l). The electrical conductivity is 25,80 µS cm-1, the pH is basic (9 07) and the average is T ° (27 03° C). For the 2011 campaign, the ratio of BOD5/ COD has a higher value of 0.46; the chloride concentration was 177.17 mg / l and the MEST reach the value of 231.40 mg / l. The value of AOX concentration is 0.89 mg / l.These results indicate the existence of toxic substances in the leachate that may impact on the environment. This finding is reinforced by the analyzes in the river waters that receive leachate., En RDC, les déchets hospitaliers correspondent à un mélange des déchets assimilés aux ordures ménagères (DAOM) et des déchets d’activités de soins à risques infectieux(DASRI). Dans le cadre lié à l’hygiène hospitalière, notre étude s’intéresse à l’impact de ces déchets hospitaliers sur le poste de travail et l’environnement.Pour le poste de travail, sur 20 personnes choisies, plus de 70 % ont souffert de la sensation d’oppression thoracique, du syndrome de poussières organiques, de la sécheresse de la gorge et du nez, des moisissures et des actinomycètes. Environ 40 % ont souffert d’affections gastro-intestinales lors de la manipulation des déchets hospitaliers (de la collecte au traitement/élimination).Du point de vue environnemental, la caractérisation physico-chimique des eaux de ruissellement sortant des dépôts de déchets sauvages des quatre hôpitaux choisis (CUK, HGRK, HGRN, HGK)1 montrent des concentrations élevées pour la plupart des paramètres étudiés. Pour la première campagne réalisée réalisé en 2006, le rapport DBO5/DCO est de 0,08 pour les lixiviats. Sur la base des données disponibles, la charge polluante est composée des chlorures (5529 mg/l), de la DCO (890 mg/l) et du Cd (20,1 µg/l). La conductivité électrique est de 25,80 µS/cm-1, le pH est basique (9,07) et la T° est moyenne (27,03 °C). Pour la campagne de 2010, le rapport DBO5/DCO a une valeur plus élevée de 0,46 ; la concentration en chlorures est de 177,17 mg/l et les MEST atteignent la valeur de 231,40 mg/l. La valeur de la concentration en AOX est de 0,89 mg/l. Ces résultats indiquent l’existence de substances toxiques dans ces lixiviats qui peuvent avoir un impact sur l’environnement. Cette constatation est consolidée par les analyses effectuées dans les eaux de rivière qui réceptionnent les lixiviats.

Data concerning the occurrence of emerging biological contaminants such as antibiotic resistance genes (ARGs) and fecal indicator bacteria (FIB) in aquatic environments in Sub-Saharan African countries is limited. On the other hand, antibiotic resistance remains a worldwide problem which may pose serious potential risks to human and animal health. Consequently, there is a growing number of reports concerning the prevalence and dissemination of these contaminants into various environmental compartments. Sediments provide the opportunity to reconstruct the pollution history and evaluate impacts so this study investigates the abundance and distribution of toxic metals, FIB, and ARGs released from hospital effluent wastewaters and their presence in river sediments receiving systems. ARGs (blaTEM, blaCTX-M, blaSHV, and aadA), total bacterial load, and selected bacterial species FIB [Escherichia coli, Enterococcus (ENT)] and species (Psd) were quantified by targeting species specific genes using quantitative PCR (qPCR) in total DNA extracted from the sediments recovered from 4 hospital outlet pipes (HOP) and their river receiving systems in the City of Kinshasa in the Democratic Republic of the Congo. The results highlight the great concentration of toxic metals in HOP, reaching the values (in mg kg−1) of 47.9 (Cr), 213.6 (Cu), 1434.4 (Zn), 2.6 (Cd), 281.5 (Pb), and 13.6 (Hg). The results also highlight the highest (P < 0.05) values of 16S rRNA, FIB, and ARGs copy numbers in all sampling sites including upstream (control site), discharge point, and downstream of receiving rivers, indicating that the hospital effluent water is not an exclusive source of the biological contaminants entering the urban rivers. Significant correlation were observed between (i) all analyzed ARGs and total bacterial load (16S rRNA) 0.51 to 0.72 (p < 0.001, n = 65); (ii) ARGs (except blaTEM) and FIB and Psd 0.57 < r < 0.82 (p < 0.001, n = 65); and (iii) ARGs (except blaTEM) and toxic metals (Cd, Cr, Cu, and Zn) 0.44 to 0.72, (p < 0.001, n = 65). These findings demonstrate that several sources including hospital and urban wastewaters contribute to the spread of toxic metals and biological emerging contaminants in aquatic ecosystems.

Although the United Nations General Assembly recognized in 2010 the right to safe and clean drinking water and sanitation as a human right that is essential to the full enjoyment of life and all other human rights, the contamination of water supplies with faecal pathogens is still a major and unsolved problem in many parts of the world. In this study, faecal indicator bacteria (FIB), including Escherichia coli (E. coli) and Enterococcus (ENT), were quantified over the period of June/July 2014 and June/July 2015 to assess the quality of hospital effluents (n = 3: H1, H2 and H3) and of rivers receiving wastewaters from the city of Kinshasa, Democratic Republic of Congo. The water and sediment samples from the river-receiving systems were collected in, upstream and downstream of the hospital outlet pipe (HOP) discharge. The analysis of E. coli and ENT in water and sediment suspension was performed using the cultural membrane filter method. The FIB characterization was performed for general E. coli, Enterococcus faecalis(E. faecalis) and human-specific Bacteroides by PCR using specific primers. The results revealed very high FIB concentration in the hospital effluent waters, with E. coli reaching the values of 4.2 × 10(5), 16.1 × 10(5) and 5.9 × 10(5) CFU 100 mL(-1), for the hospital effluents from H1, H2, and H3, respectively; and Enterococcus reaching the values of 2.3 × 10(4), 10.9 × 10(4) and 4.1 × 10(4) CFU 100 mL(-1), respectively. Interestingly, the FIB levels in the water and sediment samples from river-receiving systems are spatially and temporally highly variable and present in some samples with higher values than the hospital effluents. The PCR assays for human-specific Bacteroides HF183/HF134 further indicate that more than 98% of bacteria were from human origin. The results of this research therefore confirm the hypothesis of our previous studies, indicating that in developing countries (e.g., Democratic Republic of Congo and South India), the hospital effluent waters can be a significant source of the deterioration of the bacteriological quality for urban rivers. The approach used in this investigation can be further used to decipher the pollution of water resources by human faecal contamination. The results of this research will help to better understand the microbiological pollution problems in river-receiving systems and will guide municipality decisions on improving the urban water quality.

Active and abandoned mine activities constitute the sources of deterioration of water and soil quality in many parts of the world, particularly in the African Copperbelt regions. The accumulation in soils and the release of toxic substances into the aquatic ecosystem can lead to water resources pollution and may place aquatic organisms and human health at risk. In this study, the impact of past mining activity (i.e., abandoned mine) on aquatic ecosystems has been studied using ICP-MS analysis for trace metals and Rare Earth Elements (REE) in sediment samples from Lubumbashi River (RL) and Tshamilemba Canal (CT), Katanga, Democratic Republic of the Congo (DRC). Soil samples from surrounding CT were collected to evaluate trace metal and REE concentrations and their spatial distribution. The extent of trace metal contamination compared to the background area was assessed by Enrichment Factor (EF) and Geoaccumulation Index (Igeo). Additionally, the trace metal concentrations probable effect levels (PELs) for their potential environmental impact was achieved by comparing the trace metal concentrations in the sediment/soil samples with the Sediment Quality Guidelines (SQGs). Spearman's Rank-order correlation was used to identify the source and origin of contaminants. The results highlighted high concentrations of trace metals in surface sediments of CT reaching the values of 40152, 15586, 610, 10322, 60704 and 15152 mg kg−1 for Cu, Co, Zn, Pb, Fe and Mn, respectively. In the RL, the concentrations reached the values of 24093, 2046, 5463, 3340, 68290 and 769 mg kg−1 for Cu, Co, Zn, Pb, Fe and Mn, respectively. The ΣREE varied from 66 to 218 and 142–331 mg kg−1 for CT and RL, respectively. The soil samples are characterized by variable levels of trace metals. The EF analysis showed “extremely severe enrichment” for Cu and Co. However, no enrichment was observed for REE. Except for Mo, Th, U, Eu, Mo, Ho and Tm for which Igeo is classified as “moderately polluted and/or unpolluted”, all elements in different sites are classified in the class 6, “extremely polluted”. The trace metal concentrations in all sampling sites largely exceeded the SQGs and the PELs for the Protection of Aquatic Life recommendation. Cu and Co had positive correlation coefficient values (r = 0.741, P < 0.05, n = 14). This research presents useful tools for the evaluation of water contamination in abandoned and active mining areas.

Management of municipal solid wastes in many countries consists of waste disposal into landfill without treatment or selective collection of solid waste fractions including plastics, paper, glass, metals, electronic waste, and organic fraction leading to the unsolved problem of contamination of numerous ecosystems such as air, soil, surface, and ground water. Knowledge of leachate composition is critical in risk assessment of long-term impact of landfills on human health and the environment as well as for prevention of negative outcomes. The research presented in this paper investigates the seasonal variation of draining leachate composition and resulting toxicity as well as the contamination status of soil/sediment from lagoon basins receiving leachates from landfill in Mpasa, a suburb of Kinshasa in the Democratic Republic of the Congo. Samples were collected during the dry and rainy seasons and analyzed for pH, electrical conductivity, dissolved oxygen, soluble ions, toxic metals, and were then subjected to toxicity tests. Results highlight the significant seasonal difference in leachate physicochemical composition. Affected soil/sediment showed higher values for toxic metals than leachates, indicating the possibility of using lagoon system for the purification of landfill leachates, especially for organic matter and heavy metal sedimentation. However, the ecotoxicity tests demonstrated that leachates are still a significant source of toxicity for terrestrial and benthic organisms. Therefore, landfill leachates should not be discarded into the environment (soil or surface water) without prior treatment. Interest in the use of macrophytes in lagoon system is growing and toxic metal retention in lagoon basin receiving systems needs to be fully investigated in the future. This study presents useful tools for evaluating landfill leachate quality and risk in lagoon systems which can be applied to similar environmental compartments.

The occurrence of emerging biological contaminants including antibiotic resistance genes (ARGs) and Faecal Indicator Bacteria (FIB) is still little investigated in developing countries under tropical conditions. In this study, the total bacterial load, the abundance of FIB (E. coli and Enterococcus spp. (ENT)), Pseudomonas spp. and ARGs (blaTEM, blaCTX-M, blaSHV, blaNDM and aadA) were quantified using quantitative PCR in the total DNA extracted from the sediments recovered from hospital outlet pipes (HOP) and the Cauvery River Basin (CRB), Tiruchirappalli, Tamil Nadu, India. The abundance of bacterial marker genes were 120, 104 and 89 fold higher for the E. coli, Enterococcus spp. and Pseudomonas spp., respectively at HOP when compared with CRB. The ARGs aadA and blaTEM were most frequently detected in higher concentration than other ARGs at all the sampling sites. The ARGs blaSHV and blaNDM were identified in CRB sediments contaminated by hospital and urban wastewaters. The ARGs abundance strongly correlated (r ≥ 0.36, p < 0.05, n = 45) with total bacterial load and E. coli in the sediments, indicating a common origin and extant source of contamination. Tropical aquatic ecosystems receiving wastewaters can act as reservoir of ARGs, which could potentially be transferred to susceptible bacterial pathogens at these sites.

The emergence of new infectious agents is a potential risk associated with genetic manipulation and field cultivation of genetically modified organisms and constitutes a new challenge in molecular epidemiology. The main objective of the current study was to synthesize silver nanoparticles and evaluate the antibacterial activity of these nanoparticles. E. coli and Enterococcus sp. were isolated from wastewater samples collected from Kalamu River. The preliminary characterization of silver nanoparticles was carried out using UV-visible spectrophotometer. Noble metals, such as silver nanoparticles, exhibit unique and adjustable optical properties due to their external plasmon resonance. The reduction of silver ions was monitored by measuring the UV-visible spectrum of the solutions after dilution of a small aliquot (0.2 mL) of the aqueous component. The antibiotic susceptibility test results confirmed the inactivity of these antibiotics tested against the wild strain of Enterococcus sp. The synthesized silver nanoparticles displayed a good antibacterial activity against Enterococcus sp. The synthesis of silver nanoparticles is designed precisely to alleviate this situation; and these results provide a strong evidence that silver nanoparticles can be used to fight antibiotic-resistant bacteria.

The pollution assessment and the evaluation of potential risks in the Atlantic Coastal Region of the Democratic Republic of the Congo are still very limited. Consequently, the present study investigates for the first time the concentrations of heavy metals and persistent organic pollutants (organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs)) in river, estuary, and marine sediments from this area. The results highlighted high concentrations of Cr, Zn, As, and Pb exceeding the probable effect level (PEL) on aquatic life. Zn was the most dominant element detected at a range of 180–480 mg kg−1 in marine sediment, 132–382 mg kg−1 in estuary sediment, and 121–687 mg kg−1 in river sediment. Total PCBs (∑7 × 4.3) ranged from 1995 to 20,156 μg kg−1, 2013–12,058 μg kg−1, and 1861–36,417 μg kg−1 in marine, estuary, and river sediments, respectively. Total PCBs (∑7 × 4.3) were above PEL for all sediments, suggesting potential adverse effects on benthic organisms. The OCP, PBDE, and PAH levels were low to moderate for all sediments. Taking into consideration, the concentrations of Zn, Pb, PCBs, and DDTs, probable environmental risks, are present.