Estrogen toxicity reduction of industrial biochemical tailwater by electrolysis biofilters with ceramsite­sulfur-siderite fillers.

Biochemical tailwater of the industrial park wastewater treatment plant is facing the growing demand of advanced treatment and toxicity reduction. However, existing information on toxicity reduction of real industrial biochemical tailwater is still limited so far. Herein, the water quality of biochemical tailwater from an integrated industrial park in Taihu Lake Basin, China, was systematically investigated, and typical endocrine disrupting chemicals (EDCs) and estrogen toxicity were detected. Estrogen toxicity reduction by previously proposed electrolysis biofilters with ceramsite­sulfur-siderite fillers was further verified. Results showed that total nitrogen (TN) and estrogen toxicity removal increased by 41.0 % and 30.3 % respectively under the optimal voltage of 4 V and electric loading of 24 h/d, and significantly positive correlation between estrogen toxicity reduction and TN removal (p < 0.05) was observed. The lowest effluent estrogen toxicity was 0.79-0.95 ngE2/L (in estradiol equivalent concentration) by the biofilter with ceramsite­sulfur-siderite fillers, which was lower than the estrogen disruption effects mass concentration threshold of 1 ng/L. Electrical stimulation promoted the increase of the abundance of denitrifying bacteria Thauera and electroactive bacteria Hydrogenophaga, thus enhancing the removal of TN, furthermore, the abundance of Thiobacillus and Sulfuritalea were significantly correlated with the reduction of estrogen toxicity. The study highlights the potential of electrolysis biofilter in realizing the synergy of estrogen toxicity reduction and autotrophic denitrification of industrial biochemical tailwater, and paves the way for the application of electrolysis biofilter in the advanced purification of industrial biochemical tailwater.

Patent analysis of chemical treatment technology for wastewater: Status and future trends.

In order to reveal the status and trends of chemical treatment for wastewater, the patents analysis from both structured and unstructured data was performed in this study. 35,838 patents recorded in the Derwent Innovation Index database were adopted. The results showed that China was the country with the largest number of patents in the field, and the United States was the main exporter of international technology flows. Chemical processes combined with biological and physical processes was the mainstream, and ozonation and electrochemical treatment were the major single technologies. Technology evolution path generally showed the transition from biological process-combined chemical treatment to electrochemical treatment and finally to physical process-combined chemical treatment. Furthermore, future trends were revealed from both patents and papers. It demonstrated that efficient removal of ammonia nitrogen, green water treatment agents and resourcezation of wastewater were the key innovation directions, and technologies with regard to efficient use of energy (including photocatalytic technology and microbial fuel cell) were the main research hotspots. Overall, this study provided a comprehensive understanding for the research and application of chemical treatment for wastewater technologies.

Does electrolysis facilitate simultaneous nitrogen removal and toxicity reduction of low C/N dyeing wastewater by sulfur-based denitrification biofilter?

The concern about wastewater effluent toxicity has motivated the innovation of enhancement technologies on sulfur-based denitrification biofilter in recent years. Electrolysis is a common technology to reduce or remove toxic pollutants. However, the effect of electrolysis on simultaneous total nitrogen (TN) removal and toxicity reduction in sulfur-based denitrification biofilter has not been reported yet. Herein, for the first time, this study investigated the synergistic effects of electrolysis-induced TN removal and toxicity reduction of secondary effluent of dyeing wastewater containing 20 µg/L of nonylphenol (NP), at different carbon to nitrogen ratios (C/N) in several sulfur-based denitrification biofilters. All of the biofilters achieved the denitrification rate of 300.15 g∙N/m3∙d during the stabilization period at C/N = 5. The CSAHD (ceramisite and sulfur as filters) biofilter had highest TN removal rate to achieve the denitrification rate of 257.46 g∙N/m3·d at C/N = 2. Siderite and dolomite both facilitated TN removal efficiency by 9.3%-12.6% under low C/N ratio and acted as the buffer agent in biofilters. Toxicity characteristic leaching procedure (TCLP) test showed that the amount of leached heavy metals was lower than the concentration limit standard of USEPA. Electrolysis did not promote the removal of TN, however, it could reduce NP concentration and increase the biotoxicity relative inhibition rate of effluent by 12.5%-167%, and affect the functional microbial community structure. Our work clarified some misunderstandings about the application of electrolysis-based strengthening technology and enlightened the future development of simultaneous TN removal and toxicity reduction of dyeing wastewater.

Electrochemical removal of nitrate by Cu/Ti electrode coupled with copper-modified activated carbon particles at a low current density.

Electrochemical reduction is currently one of promising methods for nitrate removal from water, yet most treatment approaches have problems of high cost and energy consumption. In this work, a low current density was applied in electrochemical reduction of nitrate. Copper-modified titanium (Cu/Ti) electrodes with optimal electrochemical activity and fastest kinetics were firstly screened. Thirty minutes of electrodeposition time and neutral pH were found to have the greatest nitrate reduction rate of 83.14%. To further improve the removal of nitrate, activated carbon (AC) and copper-modified activated carbon (Cu/AC) particles were applied to construct three-dimensional reaction systems, with removal rates of nitrate of 88.72% and 96.05%, respectively. The average conversion rates of nitrate to ammonia nitrogen increased from 15.28% to 42.68% and 62.64% in AC- and Cu/AC-based reaction systems, respectively. Oxidation of Cu(0) on surfaces of Cu/Ti cathode and Cu/AC particles to Cu(I) was revealed by X-ray photoelectron spectroscopy (XPS) and Cu LMM spectra analysis. Besides, results of water chemistry characteristics indicated the conversion of AC to carbonate ion. It could be concluded that enhanced nitrate reduction of Cu/Ti-based reaction system was attributed by Cu particle- and AC-mediated electron transfer. This study provided a reference for low-cost electrochemical reduction of nitrate.