Peili Lu

Simultaneous removal of organic matter and iron from hydraulic fracturing flowback water through sulfur cycling in a microbial fuel cell

The high volume of flowback water (FW) generated during shale gas exploitation is highly saline, and contains complex organics, iron, heavy metals, and sulfate, thereby posing a significant challenge for the environmental management of the unconventional natural gas industry. Herein, the treatment of FW in a sulfur-cycle-mediated microbial fuel cell (MFC) is reported. Simultaneous removal efficiency for chemical oxygen demand (COD) and total iron from a synthetic FW was achieved, at 72 ± 7% and 90.6 ± 8.7%, respectively, with power generation of 2667 ± 529 mW/m3 in a closed-circuit MFC (CC-MFC). However, much lower iron removal (38.5 ± 4.5%) occurred in the open-circuit MFC (OC-MFC), where the generated FeS fine did not precipitate because of sulfide supersaturation. Enrichment of both sulfur-oxidizing bacteria (SOB), namely Helicobacteraceae in the anolyte and the electricity-producing bacteria, namely Desulfuromonadales on the anode likely accelerated the sulfur cycle through the biological and bioelectrochemical oxidation of sulfide in the anodic chamber, and effectively increased the molar ratio of total iron to sulfide, thus alleviating sulfide supersaturation in the closed circuitry. Enrichment of SOB in the anolyte might be attributed to the formation of FeS electricity wire and likely contributed to the stable high power generation. Bacteroidetes, Firmicutes, Proteobacteria, and Chloroflexi enriched in the anodic chamber were responsible for degrading complex organics in the FW. The treatment of real FW in the sulfur-cycle-mediated MFC also achieved high efficiency. This research provides a promising approach for the treatment of wastewater containing organic matters, heavy metals, and sulfate by using a sulfur-cycle-mediated MFC.

Practical Identifiability Analysis and Optimal Experimental Design for the Parameter Estimation of the ASM2d-Based EBPR Anaerobic Submodel

Identifiability analysis is a precondition for reliable parameter estimation. Building on previous work on structural identifiability, this paper focuses on the practical identifiability and optimal experimental design (OED) of the EBPR anaerobic submodel. The nonnegative determinant of the Fisher informationmatrix (FIM) found in this study clearly demonstrates that the parametersYPO4, KA, qPHA, and XPAO in the submodel are practically identifiable using SA and SPO4 as the measured variables and fixing KPP as the default value. Furthermore, fixing KPP to study the practical identifiability of the other parameters and to estimate their values is shown to be valid. Subsequently, a modeling-based procedure for the OED for parameter estimation was proposed and applied successfully to anaerobic phosphorus release experiments. According to the FIM D-criterion, the optimal experimental condition was determined to be an initial SA concentration of 300mg/L. Under the optimal experimental condition, errors in the values of YPO4,KA, qPHA, andXPAO are all below 20%, and the estimated values were 0.35 ± 0.02mg P/mg COD, 3.88 ± 0.41mg COD/L, 3.35 ± 0.27mg P/(mg COD ∗ d−1), and 1500 ± 72mg COD/L, respectively. Compared to the results from the nonoptimal experimental condition, the practical identifiability and the estimation precision of the four parameters were improved.

The treatment of flowback water in a sequencing batch reactor with aerobic granular sludge: Performance and microbial community structure

The extensive application of hydraulic fracturing technology has significantly promoted the large-scale development of shale gas. However, it is a great challenge for shale gas extraction to effectively manage large-volume flowback water (FW) with high salinity and complex organic substances. Here, we report an aerobic granular sludge (AGS) tolerable to high salinity, and suited to the treatment of FW. The performance of a sequencing batch reactor (SBR) with the AGS for the treatment of the synthetic FW and the microbial community structure at different salinity levels were investigated. The AGS fed with synthetic FW possessed a larger average particle size and a higher settling rate (50 m h-1). When NaCl concentration increased to 50.0 g L-1, the removal efficiency of total organic carbon (TOC) increased to 79 ± 1%, and the removal rate of polyacrylamide (PAM) raised up to 42.7 ± 0.7 g m-3 d-1. Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Sphingobacteriia dominated in the microbial community of AGS. Cellvibrionaceae, Rhodocyclaceae, Enterobacteriaceae, Moraxellaceae, Pseudomonadaceae, and Halomonadaceae belonging to Betaproteobacteria and Gammaproteobacteria played important role in degrading PAM, polycyclic aromatic hydrocarbons (PAH), and some other organics in FW at high salinity. These results suggest that an AGS-based SBR is a promising technology for the treatment of FW.

A Mini-Review on Toxicity of Triclosan in Aquatic Environment

Triclosan (TCS) is a synthetic broad spectrum antimicrobial agent that has been added in amounts of personal care products and household products. Its widespread use and resistant to degradation resulted in the inevitably release into aquatic environment and thus its potential toxicity towards aquatic organisms is of concern. To understand the risk associated with TCS in aquatic ecosystems, a min review of available literature on its acute and chronic toxicity towards aquatic organisms was conducted in this study. The acute toxicity data showed that TCS always would not show lethal effects at realistic concentration and the LC50 of TCS towards different trophic species spanned more than six orders of magnitude in concentration. Among the tested organisms, algae are the most sensitive species. The chronic toxicity data of TCS on aquatic microorganisms, microalgae, aquatic macrophytes, invertebrates and fishes were systematically collected. TCS show endocrine disruption, cytotoxic, and genotoxic effects on tested organisms, and its toxicity would be enhanced or reduced while coexisting with other pollutants or environmental parameters. Its selection and spread of multidrug resistance, microorganisms should be of concern and the potential combination effects of heavy mental and TCS on cross-resistance of microorganisms might be explored in the future due to their same selective function on multidrug resistance. Daphnia and rotifer are two major components of aquatic invertebrates; more comprehensive researches have been conduct to reveal the response of Daphnia to TCS exposure while just three studies were conducted to assess its toxicity on rotifer. Considering limited ecotoxicological information and significant TCS LC50/EC50 variations to aquatic species, further studies on potential consequences of long-term TCS exposure to more abundant and ecologically relevant species are critically need to better regulate its utilization, and the effects of environmental parameters should be taken into consideration while investigating TCS toxicity towards target species due to their significant effects.