Coupled chemically-assisted filtration (CCAF) approaches for increasing filter resilience and performance during drinking water treatment

Abstract

The paramount objective of drinking water treatment is the prevention of acute waterborne disease. Filtration remains a critical barrier for ensuring that Cryptosporidium spp. and Giardia are removed during drinking water treatment. During periods of source water quality change is when water treatment systems have the highest likelihood of process upsets that can result in pathogen transport through the water treatment systems. The goal of this research was to develop an approach for rapid detection of filter performance degradation and methods to assist with prediction of coagulant dosages for increased filter resilience. Four objectives were studied to achieve this goal. Full-scale water treatment plant filtration data were analyzed to determine periods of process deviations leading to upset conditions. Filter performance dashboards were developed to summarize water quality parameters on a monthly basis to identify emerging or chronic issues impacting filtration performance. Real-time filter performance control charts were developed to detect filter breakthrough prior to reaching filter run termination criteria. Zeta potential was assessed as a potential critical control element through investigations on a direct-filtration pilot plant. The study found that development of filter performance dashboards can be used to detect underlying conditions that can lead to filter upset conditions, such as early breakthrough or other correctable process oscillations that lead to reduced operational resilience to upset. Real-time control charts were found to be capable of detecting filter breakthrough well before exceedance of internal alarm limits for filter run termination. Finally, measurement of online zeta potential was found to be a promising tool to assess and to control coagulation chemistry to meet water quality needs, and to prevent chemical over- or under-dosing conditions that can lead to pathogen transport through the filtration process. Data driven analytics and the addition of online zeta potential monitoring is recommended as tools to improve water treatment plant resilience against pathogen breakthrough under changing water quality conditions.