A review on the dewaterability of bio-sludge and ultrasound pretreatment

Abstract

Bio-sludge, which contains large quantities of water, biomass and extracellular polymeric substances (EPS), is difficult to be dewatered as a "super-compactable" sludge [Water Res. 35 (5) (2001) 1358]. Reported water content in bio-sludge was commonly about 80-90% wt after dewatering process. The EPS and the form of water in sludge influences the structure of sludge. Adding cationic fluctuations can change the form of water in sludge and increase the velocity of dewatering process, but has little influence on the final water content. According to Bien's work [Water Sci. Technol. 36 (4) (1997) 287], a combination of ultrasound or other method could agglomerate the sludge, improve the activities of biomass [Ultrasonics 38 (2000) 711; Ultrasonics 40 (2002) 25], enhance anaerobic process [Water Sci. Technol. 36 (11) (1997) 155; Water Sci. Technol. 36 (11) (1997) 121; Water Res. 35 (8) (2001) 2003; Water Sci. Technol. 36 (12) (1997) 117] and decrease over 10% final water content of sludge. The mechanisms of ultrasonic influence on sludge are not very clear, but the application of ultrasound to industrial process is relatively easy and possible.

Separation of Microparticles from Suspension Utilizing Ultrasonic Standing Waves in a Piezoelectric Cylinder Actuator

“…Some years ago, power ultrasound was considered too expensive for water treatment in the industry [20]. De-watering of bio-sludge (consisting of water, biomass and extracellular polymeric substances) is a complicated process [21]. Ultrafiltration, microfiltration, high performance tangential flow filtration, membrane chromatography and an electrophoretic membrane contactor have become extremely important when dealing with biotechnological products and their separation and purification [22].…”

Effect of hydrothermal treatment temperature on the properties of sewage sludge derived solid fuel

“…However, the high contents of moisture and heavy metal are still present as the key challenges on sludge-to-energy conversion (Neyens & Baeyens 2003;Yin et al 2004). For the purposes of energy recovery or low-cost disposal, dewatering and/or drying are commonly applied as preliminary processes.…”

“…Therefore, a pre-treatment process that involves the modification of sludge structure might be required for reaching low moisture content in sludge. Several methods were investigated to improve the dewaterability including thermal method (Neyens & Baeyens 2003), chemical treatment (Ruiz-Hernando et al 2013), mechanical disintegration (Yin et al 2004), freezing and others.…”

Adaptive neuro-fuzzy modelling of anaerobic digestion of primary sedimentation sludge

“…Anaerobic digestion is the most often applied process for stabilization of sewage sludge at medium and large wastewater treatment plants [1][2][3]. Anaerobic process must be monitored and controlled due to its instability in circumstance conditions.…”