A modified river water die-away test is developed for controlling the biodegradability of anionic surfactants (AS) and non-ionic surfactants (NS) of detergent powders. The tested powder undergoes a procedure replicating the washing process. An aliquot of the final solution is introduced into river water exhibiting good biodegradative ability. Primary biodegradation of both types of surfactant is monitored over 20 days and the MBAS method used for determining AS and the indirect tensammetric method for NS.
Twelve detergent powders purchased in Polish supermarkets in 1995 are analysed. AS in all tested powders exhibit a relatively fast and complete biodegradation. NS are very diverse in terms of biodegradability: two powders had NS not satisfying the 80% biodegradability limit.