Table 1.

Total solid composition of the digesters sludge and feed sludge

	Control (M1, M2)	M3	M4
TS composition of the digester
Fraction of LFUS-pretreated TSAS in the digester sludge	0%	6%	9%
TPS (g/l) of the digester:	478	478	478
TSAS (g/l) without LFUS pretreatment	522	459	430
LFUS-pretreated TSAS (g/l)	0	63	92
TS composition of the feed sludge
Fraction of LFUS-pretreated TSAS in feed sludge	0%	23%	33%
TSAS (g/l) without LFUS pretreatment	278	215	186
LFUS-pretreated TSAS (g/l)	0	63	92

TS total solid, TSAS thickened secondary activated sludge, TPS thickened primary sludge, LFUS low-frequency ultrasound