The behaviour of the s-triazine herbicides, atrazine and simazine, during primary and secondary biological waste water treatment

Abstract

The behaviour of the s-triazine herbicides atrazine and simazine, and their degradation products, desethylatrazine and desisopropylatrazine during bench-scale primary and secondary waste water treatment processes were investigated. Adsorption of the four compounds onto raw waste water solids during primary treatment was minimal and there was no significant increase in removal over time or with increasing suspended solids concentration. When in contact with biologically active mixed liquor suspended solids for up to 18 h, all four triazine compounds exhibited a low but significant loss (9.5 – 39.1%) from the aqueous phase. Comparable removals also occurred in live and dead mixed liquors, whereas negligible loss of these herbicides was apparent when solids had been eliminated from the mixed liquor, therefore physical adsorption onto the mixed liquor solids was concluded to be the dominant process. There was no observed increase in adsorption over time, however, greater removals tended to be associated with higher mixed liquor suspended solid concentrations.