Assessment of the water sources for potential channels of faecal contamination within Vhembe District Municipality using sanitary inspections and hydrogen sulphide test.

Numerous human activities and poor sanitation management cause public health concern, particularly in rural communities without reliable water supply systems and resources for the monitoring of the quality of their water sources. This study assessed the relationship between observed sanitary risks and hydrogen sulphide (H2S) strip test results in the identification of faecal contamination of various water sources used at household level in rural areas of the Vhembe District Municipality. The highest percentage sanitary risk scores ranging from 50 to 100% were recorded for both river and dam water commonly used by the households for multiple purposes, including drinking. All the surface water samples (100%) also tested positive for H2S production, which is linked to the contamination of water sources by bacteria of faecal origin. The overall results showed a significant and positive correlation (r = 0.623, p = 0.003 in the wet season and r = 0.504, p = 0.017 in the dry season) between sanitary risk scores and H2S strip test results. In low resource settings, the use of sanitary inspections combined with the inexpensive and easy-to-use H2S strip tests can be effective as drinking water quality management tools to raise an awareness among community members of the faecal contamination of their water sources.

Impacts of cerium oxide nanoparticles on bacterial community in activated sludge.

Rapidly developing industry raises concerns about the environmental impacts of nanoparticles, but the effects of inorganic nanoparticles on bacterial community in wastewater treatment remain unclear. The present research assessed the impact of cerium oxide nanoparticles (nCeO) on the microbiome of activated sludge system. The results showed that 18,330 over 28,201 reads generated from control samples were assigned to Proteobacteria while 5527 reads (19.6%), 3260 reads (11.567%), and 719 reads (2.55%) were assigned to unclassified_Bacteria, Firmicutes and Actinobacteria, respectively. When stressed with nCeO2 NPs, a decrease on reads was noted with 53, 48, 27.7 and 24% assigned to Proteobacteria. Gammaproteobacteria (80.57%) was found to be the most predominant Proteobacteria. The impact of nCeO2 NPs was also observed on pollutants removal as only 1.83 and 35.15% of phosphate and nitrate could be removed in the bioreactor stressed with 40 mg-nCeO2-NPs/L. This was confirmed by a drastic reduction of activities for enzymes catalysing denitrification (NaR and NiR) and degradation of polyphosphate (ADK and PPK). ADK appeared to be the most affected enzyme with activity decrease reaching over 90% when stressed with 10 mg-nCeO2/L. Furthermore, bacterial diversity was not significantly different whereas their species richness showed significant difference between control and treated samples. A large number of reads from control samples could not be classified down to the lower taxonomic level "genera" suggesting hitherto vast untapped microbial diversity. The denitrification related genera including Trichococcus and Acinetobacter were found to alternatively dominating treated samples highlighting those nCeO2 NPs could enhance the growth of some bacterial species while inhibiting those of others. Nevertheless, the study indicates that nCeO2 NPs in wastewater at very high concentrations may have some adverse effects on activated sludge process as they inhibit the removal of phosphate.

The impact of zinc oxide nanoparticles on the bacterial microbiome of activated sludge systems.

The expected growth in nanomaterial applications could result in increased amounts of nanoparticles entering municipal sewer systems, eventually ending up in wastewater treatment plants and therefore negatively affecting microbial populations and biological nutrient removal. The aim of this study was to ascertain the impact of zinc oxide nanoparticles (nZnO) on the bacterial microbiome of an activated sludge system. A metagenomic approach combined with the latest generation Illumina MiSeq platform and RDP pipeline tools were used to identify and classify the bacterial microbiome of the sludge. Results revealed a drastic decrease in the number of operational taxonomic units (OTUs) from 27 737 recovered in the nZnO-free sample to 23 743, 17 733, and 13 324 OTUs in wastewater samples exposed to various concentrations of nZnO (5, 10 and 100 mg/L nZnO, respectively). These represented 12 phyla, 21 classes, 30 orders, 54 families and 51 genera, completely identified at each taxonomic level in the control samples; 7-15-25-28-20 for wastewater samples exposed to 5 mg/L nZnO; 9-15-24-31-23 for those exposed to 10 mg/L and 7-11-19-26-17 for those exposed 100 mg/L nZnO. A large number of sequences could not be assigned to specific taxa, suggesting a possibility of novel species to be discovered.

Microbial profiling of South African acid mine water samples using next generation sequencing platform.

This study monitored changes in bacterial and fungal structure in a mine water in a monthly basis over 4 months. Over the 4-month study period, mine water samples contained more bacteria (91.06 %) compared to fungi (8.94 %). For bacteria, mine water samples were dominated by Proteobacteria (39.14 to 65.06 %) followed by Firmicutes (26.34 to 28.9 %) in summer, and Cyanobacteria (27.05 %) in winter. In the collected samples, 18 % of bacteria could not be assigned to a phylum and remained unclassified suggesting hitherto vast untapped microbial diversity especially during winter. The fungal domain was the sole eukaryotic microorganism found in the mine water samples with unclassified fungi (68.2 to 91 %) as the predominant group, followed by Basidiomycota (6.9 to 27.8 %). The time of collection, which was linked to the weather, had higher impact on bacterial community than fungal community. The bacterial operational taxonomic units (OTUs) ranged from 865 to 4052 over the 4-month sampling period, while fungal OTUs varied from 73 to 249. The diversity indices suggested that the bacterial community inhabiting the mine water samples were more diverse than the fungal community. The canonical correspondence analysis (CCA) results highlighted that the bacterial community variance had the strongest relationship with water temperature, conductivity, pH, and dissolved oxygen (DO) content, as compared to fungi and water characteristics, had the greatest contribution to both bacterial and fungal community variance. The results provided the relationships between microbial community and environmental variables in the studied mining sites.

Seasonal variation of nutrient loads in treated wastewater effluents and receiving water bodies in Sedibeng and Soshanguve, South Africa.

The discharge of inadequately treated wastewater effluent presents a major threat to the aquatic environment and public health worldwide. As a water-scarce country, South Africa is facing an alarming situation since most of its wastewater discharges are not meeting the permissible limit. The aim of this study was to assess the physicochemical quality of treated wastewater effluents and their impact on receiving water bodies. During the study period, pH, temperature, free chlorine residue (Cl(-)), dissolved oxygen (DO), nitrate (NO3 (-1)), orthophosphate (PO4 (-3)) and chemical oxygen demand (COD) were measured in order to ascertain whether the selected wastewater systems in Sedibeng and Soshanguve complied with the South African and World Health Organization standards during wet and dry seasons. These parameters were analysed for samples collected from raw wastewater influent, treated wastewater effluent and receiving water bodies. The study was carried out between August 2011 and May 2012, and samples were collected on a weekly basis during both seasons. The physicochemical quality of effluents did not comply with the regulatory limits set by South Africa in terms of pH in Meyerton, Rietgat and Sandspruit (pH 7.6 to 8.1); free chlorine in Sandspruit (0.27 ± 0.05 mg/L); nitrate in Leeuwkuil and Rietgat (2.1 and 3.8 mg/L, respectively) during the wet season; orthophosphate in Meyerton during the wet season and in Sandspruit during the dry season (1.3 mg PO4 (-3) as P/L and 1.1 mg PO4 (-3) as P/L, respectively); and chemical oxygen demand in Rietgat during the dry season and in Sandspruit during the wet season (75.5 and 35 mg/L, respectively). Furthermore, the quality of the receiving water bodies did not comply with the South African standards recommended for pH, chemical oxygen demand and orthophosphate and DO (5 mg/L) in Rietgat during the wet season. The geometric mean of the water quality index values ranged between 32.4 and 36.9 for the effluent samples and between 38.1 and 65.7 for the receiving water bodies. These findings revealed that the receiving water bodies were classified as having "poor" quality status, except Leeuwkuil receiving water body (Vaal River) and Sandspruit upstream (Sandspruit stream). The dry season showed a relatively lower water quality index. This situation might be attributed to the higher amount of organic matter and lower microbial activities in the receiving water bodies. This study suggests that wastewater effluents and receiving water systems should be monitored regularly to ensure best practices with regard to nutrient treatment and discharge of wastewater.

Population Growth and Its Impact on the Design Capacity and Performance of the Wastewater Treatment Plants in Sedibeng and Soshanguve, South Africa.

This study investigated the effects of population growth on the performance of the targeted wastewater treatment plants in Sedibeng District and Soshanguve peri-urban area, South Africa. The impact of population growth was assessed in terms of plant design, operational capacity (flow rate) and other treatment process constraints. Between 2001 and 2007, the number of households connected to the public sewerage service increased by 15.5, 17.2 and 37.8% in Emfuleni, Lesedi and Midvaal Local Municipalities, respectively. Soshanguve revealed a 50% increment in the number of households connected to the sewerage system between 1996 and 2001. Except for Sandspruit (-393.8%), the rate of influent flows received by Meyerton increased by 6.8 ML/day (67.8%) and 4.7 ML/day (46.8%) during the dry and wet seasons, respectively. The flow rate appeared to increase during the wet season by 6.8 ML/day (19.1%) in Leeuwkuil and during the dry season by 0.8 ML/day (3.9%) in Rietgat. Underperformance of the existing wastewater treatment plants suggests that the rapid population growth in urban and peri-urban areas (hydraulic overloading of the wastewater treatment plants) and operational constraints (overflow rate, retention time, oxygen supply capacity of the plants and chlorine contact time) resulted in the production of poor quality effluents in both selected areas. This investigation showed that the inefficiency of Meyerton Wastewater Treatment Plant was attributed to the population growth (higher volumes of wastewater generated) and operational constraints, while the cause of underperformance in the other three treatment plants was clearly technical (operational).

Prevalence of enteropathogenic bacteria in treated effluents and receiving water bodies and their potential health risks.

The failure of wastewater treatment plants to produce effluents of a high microbiological quality is a matter of great concern in terms of water resource pollution. A more serious concern is that this water source is used by communities in developing countries for multiple purposes, which include drinking, recreation and agriculture. The current study investigated the prevalence and potential health risks of enteropathogenic bacteria (Salmonella typhimurium, Shigella dysenteriae and Vibrio cholerae) in the treated effluents of three selected South African Wastewater Treatment Works as well as their receiving water bodies. Culture-based and polymerase chain reaction techniques were used to detect and identify the pathogenic bacteria. The conventional methods revealed that of the 272 water samples collected, 236 samples (86.8%) tested presumptively positive for Salmonella spp., 220 samples (80.9%) for Shigella spp. and 253 samples (93.0%) for V. cholerae. Molecular test results indicated that out of the randomly selected presumptive positive samples (145), zero to 60% of samples were positive for S. typhimurium and S. dysenteriae and 20% to 60% for V. cholerae. For the health risk assessment, the daily combined risk of S. typhimurium, S. dysenteriae and V. cholerae infection was above the lowest acceptable risk limit of 10(-4) as estimated by the World Health Organization for drinking water. This study showed that the target treated wastewater effluents and their receiving water bodies could pose a potential health risk to the surrounding communities.

Comparing the tolerance limits of selected bacterial and protozoan species to nickel in wastewater systems.

Heavy-metal resistant microorganisms play a significant role in the treatment of industrial wastewater. The detoxifying ability of these resistant microorganisms can be manipulated for bioremediation of heavy metals in wastewater systems. This study aimed at comparing the tolerance limit of selected wastewater protozoan species (Aspidisca sp., Trachelophyllum sp. and Peranema sp.) against Ni(2+) with that of selected bacterial species (Bacillus licheniformis-ATCC12759, Brevibacillus laterosporus-ATCC64 and Pseudomonas putida-ATCC31483) commonly found in wastewater systems. The isolates were exposed to various concentrations of Ni(2+) in mixed liquor and their tolerance to Ni(2+) assessed at different temperatures (25°C, 30°C, 35°C and 40°C) and pHs (4, 6, 7, 8 and 10). The physicochemical parameters such as chemical oxygen demand (COD) and dissolved oxygen (DO) of the media and the growth rates of the isolates were measured using standard methods. In terms of their minimum inhibitory concentrations (MIC), the results revealed that the isolates could tolerate Ni(2+) at concentrations ranging between 32 and 52ppm for protozoa and between 52 and 84ppm for bacteria. B. licheniformis-ATCC12759 was the most tolerant bacterial species (MIC: 84ppm-Ni(2+)) while Peranema sp. was the most tolerant protozoan species (MIC: 52ppm-Ni(2+)). At 10 and/or 20ppm-Ni(2+) the growth of B. licheniformis-ATCC12759 (6.30 days(-1) for 10 and 5.73 days(-1) for 20ppm-Ni(2+)), P. putida-ATCC31483 (6.02 days(-1) for 10 and 5.31 days(-1) for 20ppm-Ni(2+)) and Peranema sp. (2.15 days(-1) for 10ppm-Ni(2+)) was stimulated after one day of incubation. Statistical evidence showed significant differences (p=0.0065) between the MIC of the six isolates and positive correlations between COD and the growth rates of isolates (r=0.8999/0.8810 for bacteria/protozoa). The tolerance limit of all isolates was significantly dependent on the pH and the temperature. The study suggests that these isolates can be used for the bioremediation of nickel in industrial wastewater systems.