Changes of the quality of activated sludge during the biological treatment of landfill leachate

The effect of chemically pretreated landfill leachate on the properties of activated sludge has been investigated. The leachate was pretreated by a two-stage method consisting of coagulation and oxidation. The mixture of pretreated leachate (from 2.5 to 15 wt. %) and municipal wastewater was fed into a bioreactor. Results of the studies showed that the pretreated leachate contributed to the dispersion of the activated sludge floes. As a result, a very low value of volume index (30 cm'/gTs) and a significant turbidity of supernatant liquid were observed at the same time. The dispersion phenomenon was also confirmed by floe size distribution. An increase of the amount of small and very small floes was observed.