Design, Operation, and Analysis of a Biological Sand Filter Using Copper as a Disinfectant

Aqua Clara International (ACI) is a nonprofit organization that uses biological sand filters (BSFs) to provide economical, clean water to families in developing countries. ACI often recommends loading 20 L/d in BSFs in which a brass alloy is included as a disinfectant. A bench-scale study was conducted to investigate the effectiveness of using copper as the disinfectant. Five filters were constructed to compare different arrangements and amounts of copper shavings to a control, column 1. The control was modeled after ACI design specifications but no metallic disinfectant was included. Columns 2 - 5 were also scaled according to ACI recommendations. Columns 2 and 3 each contained 4.7 g of copper, and Columns 4 and 5 each contained 2.35 g. In columns 2 and 4, copper was placed in a single layer; while in columns 3 and 5, the copper was dispersed throughout the fine sand. After 31 days of testing, the average removal efficiency for total coliforms in columns 1 - 5 was 96.5%, 93.9%, 97.4%, 95.4%, and 97.5% respectively. A single, 20 L/d BSF was constructed with 94 g of copper dispersed throughout the fine sand layer. The average removal efficiency for fecal coliforms and turbidity was 97.3% and 65.7%, respectively.