Using of particle counter as a monitoring tool for giardia and cryptosporidium in a water purification plant

ABSTRACT

Drinking water plays a major role in the spread of intestinal protozoa pathogenic for human, namely Giardia Iamblia and Cryptosporidium parvum. Surface water is contaminated with Giardia or Cryptosporidium in two major ways wastewater treatment plants may discharge effluent with cysts or by fecal pollution by various animals that live on the watersheds. So, they are of great concern to the water treatment industry because they are known to have caused a number of waterborne outbreaks of diseases. Since, -the identifying of Giardia cysts and Cryptosporidium oocysts require, special technique and lab personnel specially trained in microbiology. Particle counting is another physical technique for enumeration of Giardia cysts and Cryptosporidium oocysts by instrument depending on their size distribution. This study aims at evaluating the use of particle counter as a monitoring tool for particle removal in a conventional pilot water treatment plant. The results revealed that coagulation, sedimentation, and filtration removed the most percentage of both parasites. The average removals of both parasites by coagulation and sedimentation were 76% and 71%, while filtration process only removed about >/=99.5%. On the other hand, the average removal of turbidity was 90.7% by coagulation and sedimentation and 95.2% by filtration. The average over-all removals of turbidity, Giardia, and Cryptosporidium were 99.53%, 99.95%, and 99.89%, respectively. While, the average log removal of parasites and turbidity were 3.3 log for Giardia, 3.02 log for Cryptosporidium, and 2.38 log for turbidity. A significant strong correlation was found between total particle removal and cyst and oocyst sizes removals, while a significant correlation between turbidity and parasites removal were observed. So, particle counter and turbidimeter can be used as surrogate indicator of Giardia and Cryptosporidium removal. The study recommended reducing the risk of raw water infection by Giardia and Cryptosporidium through the multiple barrier approach to treatment, including watershed protection, optimization of chemical pretreatment, filtration, disinfection, and a properly operated and maintained distribution system. It should be installed on-line instruments - particle counting and turbiditimeter monitoring - at various stages of the water treatment process to evaluate water purification plant performance for Giardia and Cryptosporidium removal and enable the operator to develop optimal operations conditions to achieve maximum particulates removal