Abstract
Phenolic industrial wastewater, such as those from coal gasification, are considered a challenge for conventional anaerobic wastewater treatment systems because of its extreme characteristics such as presence of recalcitrant compounds, high toxicity, and salinity. However, anaerobic membrane bioreactors (AnMBRs) are considered of potential interest since they retain all micro-organism that are required for conversion of the complex organics. In this study, the degradation of phenol as main carbon and energy source (CES) in AnMBRs at high salinity (8.0 g Na+⋅L–1) was evaluated, as well as the effect of acetate and an acetate-butyrate mixture as additional CES on the specific phenol conversion rate and microbial community structure. Three different experiments in two lab-scale (6.5 L) AnMBRs (35°C) were conducted. The first reactor (R1) was fed with phenol as the main CES, the second reactor was fed with phenol and either acetate [2 g COD⋅L–1], or a 2:1 acetate-butyrate [2 g COD⋅L–1] mixture as additional CES. Results showed that phenol conversion could not be sustained when phenol was the sole CES. In contrast, when the reactor was fed with acetate or an acetate-butyrate mixture, specific phenol conversion rates of 115 and 210 mgPh⋅gVSS–1 d–1, were found, respectively. The syntrophic phenol degrader Syntrophorhabdus sp. and the acetoclastic methanogen Methanosaeta sp. were the dominant bacteria and archaea, respectively, with corresponding relative abundances of up to 63 and 26%. The findings showed that dosage of additional CES allowed the development of a highly active phenol-degrading biomass, potentially improving the treatment of industrial and chemical wastewaters.
Highlights
Rapid industrialization has generated many industrial effluents that constitute a major source of pollution (Lin et al, 2013)
Batch tests with initial phenol concentrations of 50, 200, and 500 mg·L−1 were performed to determine a possible inhibition by phenol on the acetoclastic specific methanogenic activity (SMA) of the anaerobic membrane bioreactors (AnMBRs) biomass (Figure 2)
The present study showed the feasibility of using AnMBR for the treatment of phenolic wastewater at high sodium concentrations
Summary
Rapid industrialization has generated many industrial effluents that constitute a major source of pollution (Lin et al, 2013). Wastewater characteristics that are considered extreme, such as high organic pollutant concentration, presence of recalcitrant or refractory as well as toxic or inhibitory compounds, and high salinity, reduce the performance of conventional anaerobic systems, which leads to process imbalance or reactor failure (Dereli et al, 2012). Chemical and petrochemical wastewater, such as coal gasification, is an example of an industrial effluent with toxic phenolics as the major organic pollutants (Li et al, 2017) Other compounds such as acetate or butyrate, which could be used by microorganisms as carbon and energy sources (CES), are present in coal gasification wastewater as common contaminants (Singer et al, 1978; Blum et al, 1986; Ji et al, 2016). Under closed-water-loops, increasing salinity in the wastewater is expected
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