Backwashchemische

Backwashchemische denotes chemical additives used during the backwash phase of granular-media filtration. Backwashing reverses flow to remove accumulated solids, and chemicals may be added to improve cleaning, sanitize the filter, control biofouling, or prevent scale formation. The term appears in some European technical sources and is less common in general water-treatment literature.

Common agents include oxidants (such as chlorine or hydrogen peroxide) for disinfection, pH adjusters, surfactants to reduce surface tension, dispersants or chelating agents to prevent scaling, and polymers that aid in flocculation and sludge removal. Dosing is carefully controlled by process automation and adjusted to water quality, flow rate, and filter media type; compatibility with media and corrosion considerations are important.

Backwash chemical dosing is typically timed with backwash cycles and may follow a low-dose residual disinfection. Spent backwash water is collected for treatment, neutralization, or compliant discharge. Operators monitor indicators such as differential pressure, backwash duration, and effluent turbidity to assess effectiveness and to optimize chemical use.

In some systems, chemical usage during backwashing is minimized or avoided through alternatives such as enhanced air-scour, pulsed backwashing, or steam cleaning. Regulatory and safety considerations include proper chemical storage, handling, and worker protection, as well as treatment or neutralization of spent backwash streams to meet environmental and drinking-water standards.