EFFECTS OF FILTRATION TEMPERATURE, HUMIC ACID AND DOSING ON CRYPTOSPORIDIUM SIZED PARTICLES BREAKTHROUGH

摘要

Filtration is an essential and vital process in drinking water treatment. Recent Cryptosporidium outbreaks have highlighted concerns about filter efficiency and in particular particle breakthrough. Understanding the causes of breakthrough is essential worldwide, as the parasite cannot be destroyed by conventional disinfection with chlorine. The breakthrough of particles links many factors. This research aims to investigate particle breakthrough related to changes in temperature, humic acid and chemical dosing Experiments were conducted using a laboratory filter column to establish the relationship between temperature, humic acid and chemical dosing changes to floc strength and particle breakthrough. The temperature was set at a series range as 5 ℃ 15 ℃ and 25 ℃; humic acid concentration was 5mg/l. Each was combined with a series of Al dose changes. A laser particle counter was installed to assess the particle breakthrough online. ? potential, Turbidity and UV_(254) absorption were measured before (after coagulation) and after filtration. The results show that particle breakthrough is influenced significantly by temperature, humic acid and dosing. Particle breakthrough rapidly at lower temperatures but higher temperatures reduced at the same coagulant dose. With coagulants, even at low doses, particle breakthrough is significantly reduced. With humic acid concentration at 5mg/l, particle breakthrough is faster and the amount is much bigger than those without humic acid even in high temperature. There is an optimal dose in filtration; the optimal dose gives a ? potential equal to about zero.