Abstract
Biological processes have high removal efficiencies and low operational costs, but the secondary effluent of coking wastewater (CWW), even at a low concentration, is difficult for microorganisms to degrade directly. In this study, glucose was used as a carbon source and co-metabolic substrate for microbial acclimation in order to enhance the advanced treatment of coking wastewater (CWW). The removal performance of the pollutants, especially recalcitrant compounds, was studied and the changes in the microbial community structure after activated sludge acclimation were analyzed. The effect of glucose addition on the secondary biochemical effluent of coking wastewater (SBECW) treatment by the acclimated sludge was further studied by a comparison between the performance of two parallel reactors seeded with the acclimated sludge. Our results showed that the concentrations of chemical oxygen demand (COD), total organic carbon (TOC), and UV absorption at 254 nm (UV254) of the wastewater decreased in the acclimation process. Refractory organic matter, such as polycyclic aromatic hydrocarbons and nitrogen-containing heterocyclics, in the SBECW was effectively degraded by the acclimated sludge. High-throughput sequencing revealed that microbes with a strong ability to degrade recalcitrant compounds were enriched after acclimation, such as Thauera (8.91%), Pseudomonas (3.35%), and Blastocatella (10.76%). Seeded with the acclimated sludge, the reactor with the glucose addition showed higher COD removal efficiencies than the control system without glucose addition (p < 0.05). Collectively, glucose addition enhanced the advanced treatment of coking wastewater (CWW).
Highlights
Coking wastewater (CWW) is a typical high concentration, organic wastewater generated in the coal refining, gas purification, chemical product recovery, and refining processes, that contains a variety of recalcitrant compounds [1,2]
The scientific questions we addressed are: (1) how effective is the performance of acclimated sludge in the removal of recalcitrant organic matter; (2) how the diversity of the microbial communities differs before and after domestication; (3) whether the addition of glucose enhances the performance of the advanced treatment of secondary biochemical effluent of coking wastewater (SBECW)
When the proportion of SBECW in the influent reached 100% (Figure 1b), the intensity of the UV-Vis spectra in the wavelength range of 220–230 nm displayed an obvious decrease after treatment, suggesting that the concentration of benzene series significantly decreased after treatment
Summary
Coking wastewater (CWW) is a typical high concentration, organic wastewater generated in the coal refining, gas purification, chemical product recovery, and refining processes, that contains a variety of recalcitrant compounds [1,2]. Effective methods should be adopted to perform an advanced treatment on recalcitrant compounds after the secondary biochemical process for CWW. Liu and colleagues demonstrated that low concentration polyether wastewater could be effectively treated by acclimated activated sludge when sodium acetate was added as the carbon source [14]. Wang and colleagues found that when glucose was added as the carbon source to acclimated activated sludge for 180 days, the cyclohexane carboxylic acid could be steadily degraded by over 90% [15]. Sun and colleagues showed that adding glucose as a co-metabolic substrate to domesticate activated sludge in sequencing batch reactors (SBRs) could achieve the effective degradation of 2-chlorophenol at a concentration of 40 mg/L [16]. Adding biodegradable substrates/cosubstrates to domesticate activated sludge can allow for the degradation of recalcitrant compounds in wastewater. The effect of the addition of an biodegradable substrate/co-substrate on the bacterial community structure has rarely been reported
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