Objective To examine algae densities and their associations with selected physiochemical and sensory in dicators in source water and water samples at different treatment processes, and to provide basis for control and prevention of algae pollution in centralized water supply.
Methods Algae density, pH, temperature, nitrate nitrogen, ammonia nitrogen, orthophosphate, turbidity, and chromaticity in source water were measured, and the algae densities in water at two treatment processes (water collecting sump and after filtration) were also measured to calculate the removal rates of various pollutants in a water treatment plant from April to May 2013. Pearson correlation analyses were performed.
Results The selected indicators evaluated for the source water were (5.47& #177;1.69)& #215;106/L for algae density, (7.33& #177;0.23)NTU for turbidity, 18.24& #177;0.22 for chromaticity, (0.16& #177;0.04)mg/L for ammonia nitrogen, (0.46& #177;0.13)mg/L for nitrate nitrogen, (0.02& #177;0.01)mg/L for orthophosphate, 7.48 for pH, and 26.8℃ for temperature. The algae density in the water collecting sump, the filtrated water, and the finished water was (1.15& #177;0.95)& #215;106/L, (0.81& #177;0.06)& #215;106/L, and 1.10& #215;105/L, respectively. The removal rates were 85.2% for algae density, 83.2% for turbidity, and 75.4% for chromaticity, respectively. The algae density in source water was positively associated with chromaticity and temperature (P<0.05), and negatively with orthophosphate (P<0.05). The density of cyanophyceae and nitrate nitrogen were positively associated (P<0.05).
Conclusion The algae density is high in the source water of the selected water plant, and is positively associated with chromaticity and temperature. Moreover, the density of cyanophyceae and nitrate nitrogen is also positively correlated. Effects of nitrate nitrogen pollution on the growth of toxic algae should be a concern.
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