Chlorine Tolerant Bacteria

Assessment of chlorine tolerant bacteria recovered from wastewater effluent in Eastern Cape Province, South Africa

Mojisola C. Owoseni 1,2,3*  and Anthony I. Okoh 2,3

 1 – Department of Microbiology, Federal University Lafia, PMB 146, Nasarawa State, Nigeria.

2 – SAMRC Microbial Water Quality Monitoring Centre, University of Fort Hare Alice, 5700 South Africa.

3 – Applied and Environmental Microbiology Research Group, Department of Biochemistry and Microbiology, University of Fort Hare, Alice 5700, South Africa.

*Corresponding author’s email: moji.owoseni@gmail.com; telephone: +2349034509990



The transmission of chlorine tolerant pathogens to waterbodies via discharge of inadequately treated wastewater effluents can contribute to outbreak of infectious diseases. This study investigated the chlorine tolerance of some bacterial pathogens recovered from final effluents of  two wastewater treatment plants in the Eastern Cape, South Africa. Secondary effluent samples were collected from the clarifier of two wastewater treatment plants in Eastern Cape Province.

The bacterial survival (n=20) at the recommended chlorine dosage (0.5 ml), lethal dose (n=3) and inactivation kinetics (n=3) at lethal doses were examined. Bacterial isolates (n=20) were confirmed by PCR assay and isolates (n=3) which showed the highest chlorine tolerance were further identified using the 16S rRNA gene sequence. Nucleotide sequences were compared to known sequences in the GenBank and submitted to the Basic Local Alignment Search tools (BLAST) search engine at the NCBI GenBank.

 Data was analysed using Analysis of variance (ANOVA) and linear regression. Bacterial isolates (n=20) screened at the recommended dose of 0.5 mg/l were inactivated within a range of 4.71 – 6.02 log at chlorine residuals of 0.04 – 0.42 mg/l after 30 min. The bacterial isolates with the highest survival were identified as Klebsiella sp., Bacillus sp. and Staphylococcus sp. Higher chlorine doses (0.75 – 1.5mg/l) showed a marked reduction (p < 0.05) in the viability of bacterial isolates from 0.67 to 1 log. Inactivation kinetics showed a high rate of bacterial kill (R = 0.85 – 0.98) in 30 min contact time at 0.75 – 1.5 mg/l chlorine dose.

Disinfection at 0.5 mg/l chlorine indicates a poor removal efficiency of bacterial isolates while increasing the disinfection dose to 0.75 – 1.5 mg/l increased the inactivation rate. Data obtained suggests a need to review 2 current chlorine standards for wastewater treatment especially in resource-poor countries dependent on cost-effective disinfectant for wastewater treatment.

Keywords: Bacterial pathogens; wastewater effluent; chlorine tolerance; lethal dose;inactivation kinetics. 








Africa is mankind’s ancestral home and the store of its greatest wealth of genetic diversity as well as an equally rich social and cultural heritage. Recent advances in genomics offer new and powerful tools and techniques which allow us to dissect and analyze the genetic structure of individuals, families and populations at unprecedented levels of detail and with nearly global coverage of the variation they contain and affords us new avenues to interpret this variation in the context of biology, history and environment, furthering our understanding of all of these and their relation to the health and wellbeing of individuals and populations worldwide. The application of these tools and technologies to African populations offers unique challenges and opportunities which must be met if their full potential for improving the lives and livelihoods of Africans across the continent is to be realized. Sudan is a microcosm of the diversity of the African continent, neighboring regions and beyond and is fully representative of these challenges and opportunities. As a step towards addressing them, we propose a series of events under the theme of “Genomics and Human Health in Africa” , bringing together relevant stakeholders including scientific and research communities , health care providers and policy makers from across the continent together with international partners and collaborators.