Efficiency assessment of drinking water treatment processes in the removal of phytoplankton at Damietta – Egypt

Document Type : Original articles

Authors

Botany Department, Faculty of Science, Damietta University, Egypt.

Abstract

The present study intended to evaluate the efficiency of removal of phytoplankton of four different techniques used in the drinking water treatment plants (DWTPs) at Damietta. Water was monthly sampled throughout one year from April 2013 to March 2014. The pH of water as well as the concentrations of ammonia, nitrite, silica, orthophosphate and heavy metals were within the allowable limits and decreased towards the output in the four DWTPs. By contrast, the levels of dissolved oxygen (DO) and aluminium (Al) increased towards the output. Only in one of the four DWTPs examined, turbidity exceeded the allowable limits.  Out of the 96 phytoplankton taxa encountered, 48 belong to Chlorophyta, 23 to Bacillariophyta and 11 to Cyanobacteria. The water treatment processes resulted relatively efficient removal of Cyanobacteria which were replaced by Chlorophyta. The efficiency of DWTPs in removal of phytoplankton depended on the technique used; where the most effective technique was the rapid rate gravity sand filter with 94.3% removal, followed by the roughing gravel filter technique with 89.5% removal and the clariflocculator technique with 73% removal, while the least effective one was the plate settler technique with 69.5% removal. In fact, the excessive growth of Cyanobacteria at intakes of all DWTPs needs a preliminary physical removal to avoid cell lysis and cyanotoxin release during chemical treatment.

Keywords

Scientific Journal for Damietta Faculty of Science
Volume 5, Issue 1
Special Volume, Conference
December 2015
Pages 48-61

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