Effects of treated agro-industrial effluents on physical and chemical characteristics of the receiving stream Wawa in south-eastern Côte d'Ivoire

Abstract

In this research we examined the impact of effluents from an agro-industrial plant on River Wawa. Water quality was assessed by monitoring monthly during a year. Eleven parameters were retained: temperature, conductivity, dissolved oxygen, turbidity, pH, chemical oxygen demand, nitrates, nitrites, ammonia, orthophosphates and organic pollution index. Except temperature and ammonia which didn't differ among sites, chemical oxygen demand and organic pollution index were significantly (p < 0.00001) higher at reference sites upstream the discharge point of effluents than sites located downstream. On the contrary, values of the other variables were significantly (p < 0.05) higher at sites receiving the effluents. These results certainly support the hypothesis that the rejected effluents have a negative influence on the water quality downstream the discharge point. However, results suggest a decrease of the parameters content at the second site more distant from the discharge point, maybe due to the self-purifier capacity of the receiving stream. Ecological impacts not being all immediate, this wastewater could have a negative impact on the species living in the receiving stream in long term, either by bio-accumulation or by bio-magnification. It would be interesting to undertake complementary studies of bio-accumulation or bio-magnification on fauna.

Assessing the Organic Pollution and Aquaculture Activity of Surface water at Shatt-Al-Arab Estuary Southern of Iraq

“…Also, significant differences (P<0.01) were found among stations , the highest mean value (3.52 µg.L -1 ) was recorded at station 4, while the lowest mean value (1.25 µg.L -1 ) was recorded at station 1. Orthophosphate lowest concentrations characterize the station 1 that does not receive municipal wastewater discharges, which is more distant from the discharge points of effluents, or may be due to the self-purifier capacity of the receiving stream at this station, this conclusion was in agreement with Kouame et al (2012). Whereas the highest levels were recorded at station 4 due to the waste water discharges loaded with organic matter received at this station.…”

“…High levels of phosphates and other nutrients encourage eutrophication which could further deplete the dissolved oxygen levels of the estuary (Kouame et al, 2012). In addition, nutrients (nitrites and phosphates) may be diluted as they are washed downstream by current.…”

“…Evaluation of dissolved oxygen is crucial to the survival of aquatic organisms (Kouame et al, 2012). Water flow of the estuary is causing oxygen dissolve in water.…”