# Practical Algal Control in Lower Yangtze Reservoirs Using Composite Microfiltration Physical Enclosure

## TL;DR

A new physical enclosure system using microfiltration effectively reduces microalgae in Yangtze River reservoirs, improving water quality and reducing treatment costs.

## Contribution

A composite microfiltration physical enclosure system is introduced to efficiently remove microalgae from reservoirs.

## Key findings

- The composite membrane reduced algae density in filtered water by over 80%.
- The system effectively filters multiple algae species, lowering the risk for downstream treatment plants.
- It reduces the burden on traditional water treatment processes and lowers operating costs.

## Abstract

Source water reservoirs in the lower reaches of the Yangtze River are increasingly threatened by algal contamination, driven by fluctuations in upstream water quality. To ensure stable reservoir operation and protect downstream drinking water sources, physical enclosures are widely used. However, most algal pollution in reservoirs consists of microalgae (diameters < 100 μm), and conventional algae barriers are effective primarily against visible algal blooms but perform poorly against microscopic algal clusters. To address this limitation, we developed a composite microfiltration physical enclosure system by integrating a microfiltration membrane, supported by a mechanical layer, onto physical enclosures. The algal removal performance of this system was evaluated from lab-scale tests to field-scale applications. Results demonstrated that the composite membrane exhibited excellent interception efficiency against algal aggregates, with algae density in the filtered water reduced by over 80%. The composite enclosure effectively filters multiple algae species, significantly reducing the risk of algae entering downstream water treatment plants, thereby alleviating the burden of traditional processes and reducing operating costs.