backspolning

Backspolning, or backwashing, is a cleaning procedure used in filtration systems to remove accumulated solids from the filter media. In normal filtration, liquid flows through the media in the forward direction, trapping particles and contaminants. Backspolning reverses the flow, lifting and dislodging trapped material and carrying it to a waste line, thereby restoring the filter’s permeability and efficiency.

The process is common in sand and multimedia filters used in drinking water treatment, swimming pools, wastewater treatment, and various industrial filtration setups. A typical backspolning cycle includes reversing flow for a set period, sometimes accompanied by an air scour to enhance debris removal. After the backwash, a rinse or re-normalization step is performed to settle the media back into its proper bed. In filters that use diatomaceous earth (DE) or surface-filter media, backspolning may involve flushing out debris and refreshing the coating or layer to maintain filtration performance.

Control of backspolning is usually automated in modern plants. Systems monitor differential pressure, turbidity of the effluent, or both to determine when the filter is no longer performing adequately and must be backwashed. The duration and frequency of backspolning are adjusted to balance filtration effectiveness with water and energy use.

Considerations include water and energy costs, generation of backwash wastewater, and the need for proper drainage and environmental compliance. When properly managed, backspolning restores filtration efficiency, prolongs media life, and maintains target water quality across a range of applications.