Effects of salinity on the characteristics of biomass and membrane fouling in membrane bioreactors

Abstract

This study investigated the effects of high salinity on the performance and membrane fouling of membrane bioreactor (MBR) with saline wastewater. Synthetic wastewaters containing 5 to 20 g/L salts (NaCl) were treated in identical lab-scale (7 L) MBRs monitoring removals of dissolved organic carbon (DOC) and ammonia. Increase in salt concentrations did not significantly change the removal efficiency of DOC in the MBRs. However, the ammonia removals decreased from 87% to 46 % with increasing salt concentrations. PCR-DGGE analysis indicated changes in the microbial communities' composition due to high salinity; and the changes in microbial composition in turn have affected the performance of the MBRs. Membrane fouling was accelerated by the increased pore blocking resistance at higher salt concentrations. Analysis results of physicochemical and biological characteristics of biomass (EPS, floc size, zeta potential) verified the impacts of high salinity on the increased membrane fouling.

Performance of membrane bioreactor (MBR) systems for the treatment of shipboard slops: Assessment of hydrocarbon biodegradation and biomass activity under salinity variation

“…According to previous experiences [32], the gradual increase of salinity can aid to better sustain nitrification. Indeed, previous experiences [60] revealed that for a shock load from 0 to 20 g NaCl L −1 the removal efficiency of ammonia was recovered after 30-40 days of operation, whereas in the present study the nitrification ability was recovered in almost one week. However, in Phase II a slight decrease of nitrification efficiency was observed, likely due to the increasing percentage of slops that could exert a stress effect on the nitrifying population.…”

“…Conversely, the use of biological treatments is becoming increasingly popular in the field of saline wastewater characterised by high organic content and petroleum hydrocarbons [5,[10][11][12][13][14][15], even if the presence of high concentrations of a separate oily phase usually requires proper pre-treatment [16]. In recent years, membrane bioreactors (MBRs) have been applied for saline wastewater treatment [17][18][19][20]. Indeed, MBRs feature high-quality effluent, small footprint and low sludge production rates [21].…”

“…However, one of the major challenges of the MBR process hindering its extended application is still represented by fouling phenomena [21,[25][26][27][28]. This situation might be exacerbated when treating shipboard slops because high levels of salinity and petroleum hydrocarbons can exert significant stress on the bacterial consortium, providing a worsening of mixed liquor characteristics in terms of viscosity, amount of filamentous bacteria, extracellular polymeric substances (EPSs) and soluble microbial products (SMPs), producing substantial membrane fouling [19,20,29]. In recent years it has been suggested to combine membranes with biofilm systems with the aim of improving the performance of the whole system, in terms of pollutant removal and membrane filtration.…”

Nitrous oxide emissions in a membrane bioreactor treating saline wastewater contaminated by hydrocarbons

“…2b). In particular, during the period at 14 and 17 gNaCl L À1 the COD removal efficiency was higher than 96% (as average), confirming the effectiveness of the membrane process despite the high salinity (Jang et al, 2013). However, with the increase of the salinity, the reduction of the biological efficiency entailed the total COD decrease (till to 75%) (Fig.…”

NF-RO Membrane Performance for Treating the Effluent of an Organized Industrial Zone Wastewater Treatment Plant: Effect of Different UF Types

“…Conductivity is the key parameter in Turkish irrigation water standards [29] since salinity related parameters like total dissolved solids (TDS), Na, Cl, and sodium adsorption rate (SAR) are in relation with the EC value. Recent studies have focused on the rejection and effects of salinity in membrane operations especially in membrane bioreactors (MBR) [30,31]. Average flux values of NF and RO membranes after UF filtration are shown in Figure 5.…”