Survey of algae in water reservoir tanks of some selected sachet water in Kano metropolis, Nigeria

Abstract

The physico-chemical and algal properties of eight different sachet water factories (reservoir tanks), in  urban, Kano were evaluated monthly for a period of six months to ascertain compliance with recommended standard of World Health Organization (WHO) and National Agency for Food and Drug Administration and Control (NAFDAC). Parameters like temperature, pH, and electrical
conductivity were determined using instrumental methods. Turbidity, nitrate, phosphate and chloride were determined using spectrophotometric methods. Dissolve oxygen and biochemical oxygen demand were determined using standard titrimetric methods. The study revealed that, the levels of temperature (27-29°C) and concentration of nitrate (0.4-1.0mg/l), phosphate (0.1-0.7mg/l), chloride (2.0-4.6mg/l), electrical conductivity (67.0-128.0µs/cm), dissolved oxygen (4.0-6.0mg/l) and biochemical oxygen demand (2.0-3.0mg/l), pH (7.0-7.3),were within WHO standards (also adopted by NAFDAC). The levels of turbidity were found to be high in some factories. Thirteen algal species were identified which belong to four families of algae, Bacilariophyceae 23% (Navicula sp., Fragilaria
sp., and Synedra sp.), Cyanophyceae 23% (Agmenellum sp., Oscillatoria sp., Geleocapsa sp.), Euglenophyceae 8% (Euglena viridis), Chlophyceae 46% (Chlorella sp., Chlorococcus sp., Selenastrum sp., Spirogyra sp., Zyganema sp.). A positive relationship exists between algal species and turbidity, nitrate and temperature indicating that these parameters favored the distribution of algal species. The presence of Cyanophyceae is a matter of concern since this family of algae release toxic substances in water, and their presence indicates water pollution. There is a need to assess and monitor algal growth in water reservoir tanks of sachet water factories to ascertain the species and estimated density of algae which is important to reduce impact of toxigenic algae in water reservoir
tanks.