Assessment of physicochemical parameters and prevalence of virulent and multiple-antibiotic-resistant <Emphasis Type="Italic">Escherichia coli</Emphasis> in treated effluent of two wastewater treatment plants and receiving aquatic <Emphasis Type="Italic">milieu</Emphasis> in Durban,South Africa

The poor operational status of some wastewater treatment plants often result in the discharge of inadequately treated effluent into receiving surface waters. This is of significant public health concern as there are many informal settlement dwellers (ISDs) that rely on these surface waters for their domestic use. This study investigated the treatment efficiency of two independent wastewater treatment plants (WWTPs) in Durban, South Africa and determined the impact of treated effluent discharge on the physicochemical and microbial quality of the receiving water bodies over a 6-month period. Presumptive Escherichia coli isolates were identified using biochemical tests and detection of the mdh gene via PCR. Six major virulence genes namely eae, hly, fliC, stx1, stx2, and rfbE were also detected via PCR while antibiotic resistance profiles of the isolates were determined using Kirby-Bauer disc diffusion assay. The physicochemical parameters of the wastewater samples ranged variously between 9 and 313.33 mg/L, 1.52 and 76.43 NTUs, and 6.30 and 7.87 for COD, turbidity, and pH respectively, while the E. coli counts ranged between 0 and 31.2?×?10³ CFU/ml. Of the 200 selected E. coli isolates, the hly gene was found in 28 %, fliC in 20 %, stx2 in 17 %, eae in 14 %, with stx1 and rfbE in only 4 % of the isolates. Notable resistance was observed toward trimethoprim (97 %), tetracycline (56 %), and ampicillin (52.5 %). These results further highlight the poor operational status of these WWTPs and outline the need for improved water quality monitoring and enforcement of stringent guidelines.     

Environmental justice in Nigeria: A narration of residents’ experience in Ile-Ife

The sharing of environmental cost by residents in various residential areas in the developing world is perceived to be unfair. This study therefore assessed residents’ experiences of environmental justice in Ile-Ife, Nigeria. Three residential areas were identified in the study area and samples were selected using systematic sampling. Using availability and condition of urban infrastructure, severity of environmental problems and residents’ involvement in environmental issues, the study examined environmental justice in the study area. The study established a variation in environmental issues across identified residential areas. The severity of environmental problem measured through an index tagged Severity of Environmental Problem (SEPI) revealed that environmental problems was most severe in the core (SEPI = 4.00), followed by the peripheral area (SEPI = 3.71) and least in the transition area (SEPI = 3.56). On the condition of available environmental infrastructure, the study revealed that the conditions of infrastructure were most improved in the peripheral area (ICI = 3.07), followed by the core (ICI = 2.67) and the least in the transition area (ICI = 2.42). The study concluded that residents’ experiences of environmental justice differ significantly across the different residential zones as reflected by residents’ socio-economic characteristics. Furthermore, it established that age, gender, educational status, and number of years spent in the area can be used to explain the differences in residents’ experience of environmental justice in the study area. To enhance the liveability, the study recommends adequate provision of environmental amenities needed by each category of people in the city.     

Aerobic dechlorination of cis- and trans-dichloroethenes by some indigenous bacteria isolated from contaminated sites in Africa

IntroductionChlorinatedethenesareamongthemostcommoncontaminantsobservedingroundwatersystems (Bouwer,1994;McCarty,1994) .Thesecompoundsvaryinnumberofchlorinesubstituents,fromthemostchlorinated,terachloroethene (PCE ) ,tothemonochlorinatedvinylchloride (VC …     

Aerobic dehalogenation potentials of four bacterial species isolated from soil and sewage sludge

In Polar regions subject to acid precipitation, the spring flood period is swift and can be divided into three phases. In phase one, dilution and anion substitution by SO4 controls episodic acidification. Phase two is characterized by interaction of snowmelt water with the catchment. A combination of several factors contributes to declines in pH and ANC. In forest and wetland ecosystems, organic acids greatly contribute to the pH depression in the streams. In the coastal tundra and forest-tundra zones, "salt-effect" acidification predominantes. The increase in toxic forms of trace (Ni, Cu) and rare (Fe, Al, Mn) elements during pH depressions may create stress conditions for the fauna of polar fresh waters during a flood period.     

Aerobic biodegradation of dichloroethenes by indigenous bacteria isolated from contaminated sites in Africa

The widespread use of tetrachloroethene (PCE) and trichloroethene (TCE) as dry cleaning solvents and degreasing agents for military and industrial applications has resulted in significant environmental contamination worldwide. Anaerobic biotransformation of PCE and TCE through reductive dechlorination frequently lead to the accumulation of dichloroethenes (DCEs), thus limiting the use of reductive dechlorination for the biotransformation of the compounds. In this study, seven bacteria indigenous to contaminated sites in Africa were characterized for DCE degradation under aerobic conditions. The specific growth rate constants of the bacterial isolates ranged between 0.346-0.552d(-1) and 0.461-0.667d(-1) in cis-DCE and trans-DCE, respectively. Gas chromatographic analysis revealed that up to 75% of the compounds were degraded within seven days with the degradation rate constants ranging between 0.167 and 0.198d(-1). The two compounds were also observed to be significantly degraded, simultaneously, rather than sequentially, when present as a mixture. Phylogenetic analysis of the 16S rRNA gene sequences of the bacterial isolates revealed their identity as well as their relation to other environmentally-important bacteria. The observed biodegradation of DCEs may contribute to PCE and TCE removal at the aerobic fringe of groundwater plumes undergoing reductive dechlorination in contaminated sites.     

Haloalkane and haloacid dehalogenases from aerobic bacterial isolates indigenous to contaminated sites in Africa demonstrate diverse substrate specificities

Five bacteria were isolated from contaminated sites in Nigeria and South Africa using the culture enrichment technique. They were subjected to standard cultural, biochemical and microbiological techniques and identified to be species of Bacillus, Burkholderia, Corynebacterium, Micrococcus and Pseudomonas. Axenic cultures of the bacterial isolates utilized 1,2-dichloroethane (1,2-DCE) as the sole carbon source up to a final substrate concentration of 10 mM. Their mean generation time in 1,2-DCE ranged significantly (P<0.05) from 9.77 to 15.72 h with the maximum chloride release ranging between 59% and 86%. All the bacterial isolates produced two different dehalogenases, viz. one which is heat labile and specific for halogenated alkanes with optimum activity at a pH of 7.5 and the other which is more heat stable with a higher pH optimum of 9.0 and specific for halogenated alkanoic acids. However, the two enzyme types when tested demonstrated wide substrate specificities. It is therefore adjudged that these organisms may play a vital role in the bioremediation of sites polluted with chlorinated hydrocarbons.     

Whole-cell bacterial biosensors for rapid and effective monitoring of heavy metals and inorganic pollutants in wastewater

The increasing number of potentially harmful pollutants in the wastewater effluent discharge necessitates the need for the development of fast and cost effective analytical techniques for extensive monitoring programmes to assess the effectiveness of the treatment process. This study compared the use of bacterial biosensors to the conventional Daphnia magna assay, Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) tests as well as chemical analysis, for monitoring the toxicity of wastewater. The bacterial biosensors constructed in this study, using S. sonnei and E. coli, were found to be sensitive to the toxicity of the wastewater effluents. A linear increase in bioluminescence with increasing concentration of heavy metals and inorganic pollutants in water was observed, with a correlation coefficient (r(2)) as high as 0.995 and 0.997, respectively. No notable correlation between biosensor toxicity and BOD and COD test results was observed. These bacterial biosensors could provide appropriate alternatives for a rapid, sensitive and cost effective detection of wastewater quality. However, the differences in sensitivity obtained for the different systems suggest that the use of a battery of toxicity assays may be required to provide a real ecotoxicological assessment of wastewater samples.     

Understanding the patterns and processes underlying water quality and pollution risk in West–Africa River using self-organizing maps and multivariate analyses

Environmental Science and Pollution Research - Rivers are dynamic systems in complex interactions with their surrounding environments. Reliable and fast interpretation of water quality is therefore...     

Chlorophenols and other related derivatives of environmental concern: properties, distribution and microbial degradation processes

Chlorophenols are chlorinated aromatic compound structures and are commonly found in pesticide preparations as well as industrial wastes. They are recalcitrant to biodegradation and consequently persistent in the environment. A variety of chlorophenols derivatives compounds are highly toxic, mutagenic and carcinogenic for living organisms. Biological transformation by microorganisms is one of the key remediation options that can be exploited to solve environmental pollution problems caused by these notorious compounds. The key enzymes in the microbial degradation of chlorophenols are the oxygenases and dioxygenases. These enzymes can be engineered for enhanced degradation of highly chlorinated aromatic compounds through directed evolution methods. This review underscores the mechanisms of chlorophenols biodegradation with the view to understanding how bioremediation processes can be optimized for cleaning up chloroaromatic contaminated environments.     

Perceived causes, exposures and adjustments to seasonal heat in different residential areas in Ibadan, Nigeria

Local perception can be an important resource for assessing and managing climate-related extremes and identifying adjustment strategies unique to specific settings. The objectives of the study are two-fold. Firstly, it examined the perceived causes, exposures and adjustments to seasonal heat events using different residential density areas of Ibadan, Nigeria, as spatial units of analysis. Secondly, it investigated the relationship between heat exposure, built environment, socio-economic and cultural factors. Results show that intense heat from the sun, climate change and absence of rains, among others, was identified as perceived causes. Number of electricity hours, distance from water supply points and the number of neighborhood trees were listed as the three most important factors affecting heat exposure. In addition, there were considerable variations in the perceived causes (F?=?4.86, p?<?0.05), in exposures (F?=?3.61, p?<?0.05), and in adjustments to seasonal heat (F?=?8.75, p?<?0.05) across different residential density areas in Ibadan, Nigeria. The study demonstrates that local knowledge based on the perceptions, exposures and adjustments to seasonal heat waves has the potential in some cases to provide valid inputs into vulnerability and adaptation assessments.