The impact of hospital and urban wastewaters on the bacteriological contamination of the water resources in Kinshasa, Democratic Republic of Congo

ABSTRACT

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 × 10⁵, 16.1 × 10⁵ and 5.9 × 10⁵ CFU 100 mL⁻¹, for the hospital effluents from H1, H2, and H3, respectively; and Enterococcus reaching the values of 2.3 × 10⁴, 10.9 × 10⁴ and 4.1 × 10⁴ 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.

KEYWORDS:

• faecal indicator bacteria
• hospital effluent
• human-specific Bacteroides
• human health risk
• tropical condition
• water pollution

Compliance with ethical standards

Sediment samples were collected from public areas and facilities. We confirm that the field studies did not involve endangered and protected species. The funder had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

Conflict of interest

The authors declare no conflict of interest.

Funding

We are grateful to the financial sources of the Swiss National Science Foundation (grant n° 31003A_150163/1). This result presents the collaboration between the University of Geneva (Institute F. A. Forel), the University of Kinshasa and the Pedagogic National University of Congo (Democratic Republic of Congo)