Effect of some physicochemical parameters on the decay rate of enteric bacteria isolated from a surface water

Abstract

Abstract Water is essential to life, the public health significance of water quality cannot be over emphasized. In Nigeria, majority of people living along the course of water bodies still source and drink from the rivers and streams. There is, therefore, the need to determine the load of contamination and effect of pH and salinity on the decay rate of enteric bacteria in water samples from River Owena, Owena, Nigeria in order to develop adequate water quality management. Water samples from River Owena were collected from three representative monitoring points (inflow, middle course and the outflow) in Owena, Nigeria. The load of enteric bacteria in the water samples were determined using membrane filtration technique. The physicochemical characteristics of the water samples were determined using standard methods. The incidence and prevalence of gastroenteritis in the community around River Owena was determined using a structured questionnaire. Microcosm studies were used to evaluate the decay rate of enteric bacteria at varying salinity and pH. Canonical correlation analysis was used to determine the relationship between the load of enteric bacteria and the incidence and prevalence of gastroenteritis in the community around River Owena. The incidence and prevalence of gastroenteritis in the community around River Owena were estimated to be 0.75 and 0.51 respectively. Escherichia coli had positive relationships with incidence (r=0.76) and prevalence (r=0.65). Similarly, faecal coliforms had positive relationships with incidence (r=0.82) and prevalence of gastroenteritis (r=0.67), while enterococci showed positive relationship with incidence (r=0.59) and prevalence of gastroenteritis (r=0.87). Increase in pH and salinity increased the decay rate of enteric bacteria thereby reducing the growth of enteric bacteria, the optimum pH for the growth and survival of enteric bacteria ranged between pH 5.0 and pH 7.0. The optimum salinity for the growth of enteric bacteria isolated in water samples from River Owena ranged between 10% and 50% salinity. Findings revealed high levels of faecal contamination at the different representative monitoring points on River Owena, pH and salinity influenced the load and decay rate of enteric bacteria in water from River Owena essential in water safety plans and water management practices.