The effects of filtration temperature and alum dosing on Cryptosporidium sized particle breakthrough

Understanding the causes of breakthrough in filtration is essential worldwide. Breakthrough links many factors, such as filtration flow rate and flow rate changes, temperature, chemical dosing, raw water quality, etc. These factors can affect floc strength, which has been recognized as one of the most important factors in filter efficiency and particle breakthrough, related to Cryptosporidium outbreaks. This research aims to investigate particle breakthrough related to temperature and chemical dosing. Experiments were conducted to establish the relationship between temperature and chemical dosing changes to floc strength and particle breakthrough. The temperature was set at a series range as 5 °C, 15 °C and 25 °C. Each was combined with a series of Al dose changes. A laser particle counter was installed to assess the particle breakthrough online. ζ potential and turbidity were measured before (after coagulation) and after filtration. The results show particle breakthrough is influenced significantly by temperature and dosing. Particle breakthrough increased rapidly at lower temperatures but at higher temperatures it reduced at the same coagulant dose. With coagulants, even at low doses, particle breakthrough reduced significantly. There is an optimal dose in filtration; the optimal dose gives a ζ potential equal to about zero.