Gravity drainage of activated sludge: from laboratory experiments to industrial process

Abstract

Gravity belt thickening is commonly used for dewatering activated sludge. However, only a few results concerning this process, and the mathematical description of the drainage of residual sludges, have been published. Laboratory drainage experiments were carried out on several activated sludges to compare different published modelling approaches. Data showed a linear relationship between the infinite mass of the cake (M C ) and the total mass of the dry solids in the initial sludge sample (DS):so, an empirical equation was modified to predict the evolution of the cake dry solids content-over time:Two sets of empirical coefficients were derived according to the range of the initial dry solids content of the sludge (C b < 2% or C b > 2%). These coefficients were not significantly influenced by the origin of the activated sludge and thus can be considered as constants. Simulation results using the chosen model accord will with experiments carried out on an industrial gravity belt thickener working under field conditions.

Dewatering of drinking water treatment sludge by vacuum electro-osmosis

“…The other three groups of samples were raw sludge to which we added different amounts of either HCl or NaOH solution to give each a different initial pH. Prior to the experiment, we adjusted the A c c e p t e d M a n u s c r i p t 5 moisture content of DWTS to 90% by gravity drainage [19]. In each experiment we placed 4500 ml of DWTS into the sludge tank of the dewatering apparatus (Fig.…”

Electro-dewatering of wastewater sludge: An investigation of the relationship between filtrate flow rate and electric current

“…The conditioner dose was fixed from preliminary gravity drainage tests (Olivier et al, 2004;Ginisty et al, 2012).…”

“…Next, the stirring speed was reduced to 20 rpm for a 30 s period in order to promote flocs growth. After the conditioning stage the sludge was filtered using a laboratory batch drainage apparatus (Olivier et al, 2004;Vaxelaire et Olivier, 2006) and then diluted to a suitable dry solids content (2.5e3.2% (wt%)) with an appropriated amount of supernatant (filtrate). A series of electro-dewatering runs were performed at different electric currents (100, 160, 200, 300, 320 and 500 mA) or at different applied voltages (30, 40, and 50 V) with different amounts of dry solids (5, 9, 10, and 15 g DS ) with an applied pressure of 5 bar.…”

Activated Sludge and Other Aerobic Suspended Culture Processes

“…The alum sludge was more compacted than the sludge produced from the addition of the organic polymer. Laboratory studies were conducted to compare different published modeling approaches for the gravity drainage of sludge (Olivier et al, 2004). The results showed a linear relationship between the infinite mass of cake and the total mass of the dry solids in the initial sludge sample.…”