Characterization of a hybrid powdered activated carbon-dynamic membrane bioreactor (PAC-DMBR) process with high flux by gravity flow: Operational performance and sludge properties

Abstract

Three PAC-DMBRs were developed for wastewater treatment under different PAC dosages with biomass concentrations averaged at 2.5, 3.5 and 5.0g/L. The DMBRs could be continuously operated at 40-100L/mh, while higher fluxes were obtained within the PAC-DMBRs with hydraulic retention times varying in 4-10h. A dose of 1g/L PAC brought about obvious improvement in the sludge particle size distribution, settling, flocculating and dewatering properties due to the formation of biological PAC, and the sludge properties were further improved at a higher PAC dose (3g/L). The addition of PAC notably shortened the DM formation time after air backwashing and enhanced pollutant removal. Moreover, under a long solid retention time (approximately 150d), the concentrations of both soluble and bound extracellular polymeric substances (EPS) decreased substantially because of the adsorption and biodegradation effects of the biological PAC. No obvious impact on biomass activity was observed with PAC addition.

Effects of powdered activated carbon addition on filtration performance and dynamic membrane layer properties in a hybrid DMBR process

“…Except for the sludge morphology and PSD, other properties (such as sludge flocculation, settling, and dewatering abilities) were also found to be enhanced to some extent, as reported in other references and in our previous study [7,10,13]. Moreover, the characteristics of biopolymers such as EPS and soluble microbial products (e.g., their quantity and quality related to the production, biodegradation, and accumulation process in the bioreactor) was an important concern affecting both effluent quality and DM layer filterability.…”

“…It has been recognized that biodegradation is the main mechanism for pollu-tant removal and that the retention effect of the DM layer could enhance their removal [5,6]. In this study, more efficient pollutant removal (especially of organic substances) in the PAC-DMBR was attributed to improvement in the physicochemical and biological effects by PAC due to enhanced adsorption, biodegradation, and also the retention effect of the DM layer, as noted in previous studies conducted on DMBRs as well as MBRs [6,10,28,29].…”

“…In addition, previous studies reported that the EPS concentrations were lower after PAC addition, which was considered to be related to the adsorption and biodegradation effects of the biological PAC [10,16]. Moreover, researchers claimed that the two mechanisms played different roles in organics adsorption related to the adsorption capacity of PAC.…”

“…Turbidity was measured with a turbidity meter (ET266020, Lovibond Corporation, Germany), and the filtration flux of the DM with the volumetric method. The total filtration resistance (R t ) was calculated based on Darcy law using the varied flux during filtration cycles and constant water head or trans-membrane pressure (TMP) according to the previous study [10].…”

“…Hybrid DMBRs developed by adding various additives were verified to be effective in improving treatment performance, modifying sludge properties and enhancing the permeability of the DM layer [10][11][12][13][14]. A previous DMBR study reported that sludge properties, including flocculating, settling and dewatering abilities, were enhanced after PAC addition, and were accompanied by better DM layer permeability [10]. In a bio-diatomite enhanced DMBR, good permeability of the DM layer was attributed to the homogeneous, semi-compressibility, and highly porous structure of the cake layer [11].…”