Potential Impacts of Kirinya Wetland in Treating Secondary Municipal Effluent from Jinja Stabilisation Ponds
Abstract/
Kirinya West wetland is located on the Northern shores of Lake Victoria in Jinja- Uganda The wetland receives secondary treated effluent from the stabilisation ponds owned and operated by the National Water and Sewerage Corporation. The effluent finally enters Lake Victoria at the Napoleon Gulf. In this paper, we report the baseline water quality before the bio-mauipu-lation of tbe wetland and demonstrate the impact of Kirinya West wetland in treating secondary municipal effluent from the existing waste stabilisation ponds. The bio-manipulation of the wetland will entail spreading the effluent from the stabilisation ponds over the northern edges of the wetland so as to increase the treatment area of the wetland and its treatment efficiency. Bio-manipulation will increase tbe current treatment efficiency of the wetland, as the contact between plants and the wastewater will increase. The baseline data indicate that there was significant improvement of water quality as the wastewater flowed through the ponds (61% decrease in NH4-N, 46.9% in PO...p and 98% in faecal colifonns). There was a further reduction in the concentration of pollutants (80% for NH4-N and 98% for faecal coli forms) as the wastewater flowed through the wetland before reaching Lake Victoria at the Napoleon Gulf. However, channelised flow allowed wastewater to flow at the western edge of the wetland and this is associated to the effluent from the stabilisation pond that discharge at the northwestern edge of the wetland.
Notes
CONCLUSION: The values of conductivity and concentrations of nutrients and faecal coliforms measured in this study, clearly demonstrate that the wastewater from the stabilisation ponds is channelled in Kirinya West wetland. Most of it flows on the western edge of the wetland in the same location where the effluent from the ponds is discharged. Low values of most variables at the swamp-lake interface of Napoleon Gulf, Lake Victoria, provide evidence that the Kirinya wetland, still provides some tertiary treatment, as the concentration and values of most variables decrease through the swamp towards the lake. Ammonium nitrogen from the last maturation pond further decreased by 80% and faecal coliforms by 98%. Overall the values in the effluent (nutrients and -faecal coliforms) from the ponds were still bigher than those recommended by NEMA for effluent discharge into water or on land (NEMA, 1999) Hopefully, the wetland will provide more effluent treatment (up to tertiary level) after it bas been bio-manipulated and the wastewater distributed over a large expanse of the wetland.