Influence of operating pH on biodegradation performance and fouling propensity in membrane bioreactors for landfill leachate treatment

Abstract

This research has investigated the effects of varying mixed liquor pH (i.e. 5.5, 6.5, 7.5, 8.5) on the landfill leachate biodegradability and fouling behavior in two submerged membrane bioreactors (MBR) for a 150-day period. In the experiments, variations in organic removal and dissolved organic matters (DOM) transformation, microbial community and mixed liquor properties as well as the fouling behavior were monitored and systematically analyzed. The findings indicated that the organic removal in both MBRs was insignificantly different for the entire experimental pH range and that the pH levels influenced the DOM transformation. In the analysis of microbial community, PCR-DGGE revealed considerable structural changes, pointing to an effect of pH on the dynamic shift in bacterial species. In addition, clone library analysis showed that Proteobacteria was the dominant phylum in the MBRs and that the dominant bacterial community belonged to the classes Betaproteobacteria and Gammaproteobacteria, both of which were more abundant at pH 8.5 than at pH 5.5. The experiment also showed that the mixed liquor properties were affected by the pH variations. The extracellular polymeric substance (EPS) formation in the mixed liquor at pH 5.5 significantly contributed to membrane fouling while hindering the inorganic and humic substances fouling. Nevertheless, the organic fouling under the low pH condition could be effectively removed by membrane chemical cleaning. It is expected that the experimental results could be applied to enhance the biodegradability and mitigate the fouling in the MBR process.

Novel and Conventional Technologies for Landfill Leachates Treatment: A Review

“…However, membrane fouling is considered the main drawback, due to the interaction between the membrane and fouling agents, leading to the membrane's efficiency deterioration [66,67]. Moreover, membrane fouling was found to be most severe at pH 5.5, followed by at pH 8.5, while the fouling at pH 6.5 and 7.5 was quite similar and less severe than that at pH 5.5 and 8.5 [68], identifying MBR technology as an expensive and dangerous technical choice for leachate treatment.…”

Comparison between mixed liquors of two side-stream membrane bioreactors treating wastewaters from waste management plants with high and low solids anaerobic digestion

“…This fact can be mainly due to the higher stress of the biomass in MBR-HS, caused by accumulation of non-biodegradable solids (Hao et al, 2010) and high salinity (40.13 ± 4.65 mS/cm) (Jang et al, 2013) that can lead to bacteria stress. MBRs treating landfill leachates, it can be mentioned that Sanguanpak et al, (2015) reported concentrations lower than the SMP obtained in MBR-LS. In fact, the SMPp concentrations measured in MBR-LS are around twice higher than those reported by these authors.…”

“…Therefore, these bacteria are able to degrade carbohydrates, increasing the relationship between proteins and carbohydrates concentration. by Sanguanpak et al (2015), the measured eEPS concentrations were lower. It is probably due to the low organic matter concentration available for the microorganisms in MBR-LS and MBR-HS.…”

Membrane bioreactor technology for leachate treatment at solid waste landfills

“…While there is no clear definition of the exact fouling phenomena occurring during filtration, extracellular polymeric substances (EPS) have been widely reported to play a key role in this regard. More specifically, several studies have shown that the biomass supernatant ''Soluble Microbial Product'' (SMP) and its carbohydrate fraction are the main determinants affecting fouling (Sanguanpak et al 2015c;Rosenberger et al 2005;Dvořák et al 2011;Chang et al 2002). The complex interaction of hydrodynamics, mass transfer, biological degradation, and existing compounds makes it difficult to isolate all the parameters that could help in predicting membrane fouling , although the most Defrance and Jaffrin 1999;Vyas et al 2002), the filtration time (short-term vs. long-term; Yang et al 2006;Zhang et al 2006), the operating conditions and cleaning procedures (Sanguanpak et al 2015a;Trussell et al 2006;Cui et al 2003), the setup configuration (external vs. submerged; Xue et al 2015) and the initial stage of the membrane (new vs. cleaned; Le Clech et al 2003).…”