Membrane bioreactors sludge: From production to disposal

Waste in the Treatment of Textile Wastewater by Pressure-Driven Membrane Processes

“…These coupled systems deal with sludge development due to the growth/decay of microorganisms, which is unavoidable in both processes. Apart from the different operating conditions of the two systems (MBR has higher sludge retention time (SRT)), there are also differences in the quality of the resulting sludge at the end of wastewater treatment [13,49]. Massé et al and Fenu et al compared sludge morphology in CAS and MBR systems and showed that the larger size CAS flocs aggregation forms (≈200 μm) consisted of more filamentous bacteria than in MBR, which consisted of smaller flocs (≈50 μm) with more non-flocculating bacteria [50,51].…”

“…Massé et al and Fenu et al compared sludge morphology in CAS and MBR systems and showed that the larger size CAS flocs aggregation forms (≈200 μm) consisted of more filamentous bacteria than in MBR, which consisted of smaller flocs (≈50 μm) with more non-flocculating bacteria [50,51]. Floc aggregation is related to extracellular polymeric substances (EPS), which are the third component between water and the cells most present in the sludge [13]. EPS is the product of bacteria and can account for about 80% of the total mass of the sludge and is responsible for the structural and functional integrity of the flocks [52].…”

“…Uronic acid in the EPS composition can form hydrogels and interact with the interstitial water in the presence of polyuronate molecules. Polyuronates may hinder flocculation, resulting in a reduction of sludge volume [13].…”

“…In addition, it has been found that a higher energy requirement is needed to achieve water removal from sludges with lower water content. Usually, pretreatments affect the metabolism of microorganisms and cell lysis-cryptic growth, leading to the release of intracellular and extracellular substances [13]. Biological methods are more attractive because they are less expensive and more environmentally friendly than chemical methods.…”

“…It is necessary to treat the retentate before disposal because it has disastrous consequences for the environment [11,12]. In membrane bioreactors (MBRs), a certain amount of sludge is produced due to the growth and decay of the bacteria contained in them [13]. In this case, treatment and disposal is required to avoid negative impacts on the environment.…”