Parasitological Profile of Raw Wastewater and the Efficacy of Biosand Filter in Reduction of Parasite Ova and Cysts

Abstract

The disposal of wastewater in water bodies has a negative impact in the
environment and the health of people who use such water bodies for either irrigation or drinking purposes. In this study, we evaluated the  parasitological profile of wastewater from the Ahmadu Bello University Teaching Hospital sewage treatment plant, Zaria, Nigeria using the magnesium sulphate floatation method. The parasite removal efficiency
of biosand filter was also tested in comparison with the sewage treatment plant. A total of 960 L of wastewater was examined and a significant level of parasite eggs, cysts and oocysts were detected. In all, 1,648 parasites eggs, cysts and oocysts per litre were counted. Ova of Ascaris spp showed the highest count/litre of 307 (18.63%) followed by ova of Taenia spp (n=287; 17.42%). The least count per litre was exhibited by cysts of Giardia spp (n=58; 3.52%). The analysis revealed that 52.61% of the parasite eggs, cysts and oocysts was removed by the sewage treatment plant while egg removal efficiency of the biosand filter was 97.45%. Further comparison of mean parasite eggs/litre in the effluents of biosand filter and the sewage treatment plant using Wilcoxon’s Signed Ranks Test indicated a significant difference (p < 0.05) with biosand filter having lower  counts per litre. The results obtained therefore demonstrate that the raw wastewater was laden with parasite eggs, cysts and oocysts and hence pose public health threat to the users of the effluent downstream. The biosand filter was more efficient than the sewage treatment plant; its effluent contains insufficient level of the ova, cysts and oocysts of parasites well below the less than one (<1) helminth ova/protozoa cysts as  recommended by WHO.