Bioaugmentation for treatment of full-scale diethylene glycol monobutyl ether (DGBE) wastewater by Serratia sp. BDG-2

https://doi.org/10.1016/j.jhazmat.2016.01.076Get rights and content

Highlights

  • BDG-2 grew well at 30 °C, pH 9 and 2000 mg L−1 of initial DGBE concentration.

  • It could obtain 96.92% of COD (generated by DGBE) removal efficiency in 39.9 h.

  • The technological matching was made based on the characteristics of DGBE wastewater and BDG-2.

  • Stable operation of bio-augmentation treatment facilities was finally accomplished.

Abstract

A novel bacterial strain BDG-2 was isolated and used to augment the treatment of silicon plate manufacturing wastewater that primarily contains diethylene glycol monobutyl ether (DGBE). BDG-2 was identified as a Serratia sp. Under the optimal conditions of 30 °C, pH 9 and DGBE concentration of 2000 mg L−1, the bioaugmented system achieved 96.92% COD removal after 39.9 h. Laboratory-scale technological matching results indicated that, in a biofilm process with the addition of 100 mg L−1 ammonia and 5 mg L−1 total phosphorus (TP), 70.61% COD removal efficiency could be obtained in 46 h. Addition of polyaluminium chloride (PAC) to the reactors during the suspension process enhanced the settleability of the BDG-2 culture. Subsequently, successful start-up and stable operation of a full-scale bioaugmented treatment facilities were accomplished, and the volumetric organic load in the plug-flow aeration tank was 2.17 ± 0.81 kg m−3 d−1. The effluent COD of the facilities was stable and always below 100 mg L−1.

Introduction

Diethylene glycol monobutyl ether (DGBE) is widely used as an solvent for industrial production of materials such as latex paint and ink and as a degreasing agent in manufacturing. With their long-term and still increasing industrial use and the biotoxic and biorefractory properties (the BOD5/COD is 0.12 in wastewater), large amount of DGBE enter and accumulate in the environment, causing great environmental risks [18], [15], [4].

Some microorganisms have the ability to use ethers as the sole carbon and energy sources under anaerobic and aerobic conditions. These microorganisms have been exclusively examined through the route of the enrichment, isolation, and identification of the microbial characteristics followed by assessment of their degradation performances and metabolic products. However, knowledge concerning the bioaugmentation for treatment of actual ether wastewater is limited [25], [26], [16].

Bioaugmentation is the process of adding desirable and selected strains or mixed cultures into bioreactors to improve the performance of pollutants degradation [11], [9], especially applied in the refractory contaminant treatment [19], [30], [8]. Many screened strains or acclimated microbial consortia are shown significant abilities of degradating recalcitrant or toxic organics in laboratory [28], [13], [27], but have to face up to the risk of failure inducing by inhospitable actual conditions in full-scale facilities.

The previous studies of ether degradation have concentrated on methyl-tert-butyl ether (MTBE), a commonly used chemical to replace the toxic compounds in gasoline and to increase the octane number and combustion efficiency [3], [26], [1], and polybrominated diphenyl ethers (PBDEs), a class of common flame-retardant chemicals that are used in diverse commercial products. The bioaugmented degradation of DGBE wastewater has not yet been investigated in depth [29], [12]. Due to the increasing prevalence of DGBE worldwide, its slow degradation rate in natural environments, low removal efficiency and the high-concentration inhibition [4], method for improving the biodegradation of DGBE are needed [3], [20].

At the background of existing wastewater treatment construction, to provide an efficient strain for the bioaugmented treatment of DGBE wastewater, a bacterium capable of degrading high concentrations of DGBE was isolated in the present study. Moreover, laboratory-scale technological matching was conducted, and after start-up based on the obtained matching parameters the treatment performances of full-scale facilities was evaluated. These results can help to promote ether biodegradation and provide useful information for the bioaugmented treatment of actual ether wastewater.

Section snippets

DGBE wastewater

The actual DGBE wastewater in this study was obtained from a silicon plate manufacturer in China. The wastewater had high pH and COD concentration and showed significant fluctuations in water quality and quantity. The COD concentration was 5934.91 ± 1518.58 mg L−1, the pH ranged from 8.5 to 9, and the average treatment capacity of the treatment plant was 575.5 m3 d−1.

Treatment process

The process for bioaugmented treatment of DGBE wastewater was performed as illustrated in Fig. 1. The influent flew into a regulating

Identification of the BDG-2 strain

A DGBE-degrading bacterium was screened and named BDG-2. The BDG-2 colony on the plate of MS medium was white, moist and smooth. The results of sequencing and homology searches using BLAST indicated that the strain BDG-2 (1423 bp, accession number KR052192) was a member of the genus Serratia and exhibited 99.4% sequence similarity with the 16S rRNA of Serratia marcescens (accession number AB272352).

Optimal conditions for Serratia sp. BDG-2

As shown in Fig. 2(A), BDG-2 demonstrated relatively high COD removal efficiencies at pHs of 8 and

Conclusions

This research was a systemic work consisting from strain screening to lab-scale technical matching and final full-scale filed implementation. In the present study, BDG-2 was isolated, which exhibited the best DGBE removal performance at 30 °C, pH 9 and an initial substrate concentration of 2000 mg L−1. In the laboratory-scale technological matching test, BDG-2 achieved higher DGBE removal when the biofilm process was used. This process involved the addition of 100 mg L−1 ammonia and 5 mg L−1 TP.

Acknowledgments

This study was supported by the Science and Technology Service Network Initiative of the Chinese Academy of Science (KFJ-EW-STS-121), the Ministry of Science and Technology of China for International Science and Technology Cooperation and Exchanges (No. 2013DFG92600) and the West Light Foundation of the Chinese Academy of Sciences.

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