Influence of COD/sulfate ratios on the integrated reactor system for simultaneous removal of carbon, sulfur and nitrogen.

An integrated reactor system was developed for the simultaneous removal of carbon, sulfur and nitrogen from sulfate-laden wastewater and for elemental sulfur (S°) reclamation. The system mainly consisted of an expanded granular sludge bed (EGSB) for sulfate reduction and organic carbon removal (SR-CR), an EGSB for denitrifying sulfide removal (DSR), a biological aerated filter for nitrification and a sedimentation tank for sulfur reclamation. This work investigated the influence of chemical oxygen demand (COD)/sulfate ratios on the performance of the system. Influent sulfate and ammonium were fixed to the level of 600 mg SO(4)(2-) L⁻¹ and 120 mg NH(4)(+) L⁻¹, respectively. Lactate was introduced to generate COD/SO(4)(2-) = 0.5:1, 1:1, 1.5:1, 2:1, 3:1, 3.5:1 and 4:1. The experimental results indicated that sulfate could be efficiently reduced in the SR-CR unit when the COD/SO(4)(2-) ratio was between 1:1 and 3:1, and sulfate reduction was inhibited by the growth of methanogenic bacteria when the COD/SO(4)(2-) ratio was between 3.5:1 and 4:1. Meanwhile, the Org-C/S²â»/NO(3)(-) ratios affected the S(0) reclamation efficiency in the DSR unit. When the influent COD/SO(4)(2-) ratio was between 1:1 and 3:1, appropriate Org-C/S²â»/NO(3)(-) ratios could be achieved to obtain a maximum S° recovery in the DSR unit. For the microbial community of the SR-CR unit at different COD/SO(4)(2-) ratios, 16S rRNA gene-based high throughput Illumina MiSeq sequencing was used to analyze the diversity and potential function of the dominant species.

Simultaneous analysis of photosystem responses of Microcystis aeruginoga under chromium stress.

Chromium (Cr) is a toxic metal that poses a great threat to aquatic ecosystems. Information is limited on coinstantaneous responses of photosystems I (PSI) and II (PSII) to Cr(VI) stress due to lack of instruments that can simultaneously measure PSI and PSII activities. In the present study, responses of quantum yields of energy conversion and electron transport rates of PSI and PSII in Microcystis aeruginosa cells to Cr(VI) stress were simultaneously analyzed by a DUAL-PAM-100 system. Quantum yield of cyclic electron flow (CEF) under Cr(VI) stress and its physiological role in alleviating toxicity of Cr(VI) were also analyzed. At 5 mg L(-1) Cr(VI), quantum yield and electron transport rate of PSII decreased significantly, and light-induced non-photochemical fluorescence quenching lost. Cr(VI) also inhibited efficiency of PSII to use energy under high light more than of PSI. PSII showed lower maximal electron transport rate and light adaptability than PSI. Electron transport rate of PSI was higher and decreased less than that of PSII, implying less sensitivity of PSI to high light and Cr(VI). Energy dissipation through non-light-induced non-photochemical fluorescence quenching increased with increasing Cr(VI) concentration. CEF was stimulated under Cr(VI) treatment and made a significant contribution to quantum yield and electron transport of PSI, which was essential for protection of PSI from stresses of Cr(VI) and high light.

Biosorption of Cu(II) by powdered anaerobic granular sludge from aqueous medium.

Copper(II) biosorption processes by two pre-treated powdered anaerobic granular sludges (PAGS) (original sludges were methanogenic anaerobic granules and denitrifying sulfide removal (DSR) anaerobic granules) were investigated through batch tests. Factors affecting the biosorption process, such as pH, temperature and initial copper concentrations, were examined. Also, the physico-chemical characteristics of the anaerobic sludge were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy image, surface area and elemental analysis. A second-order kinetic model was applied to describe the biosorption process, and the model could fit the biosorption process. The Freundlich model was used for describing the adsorption equilibrium data and could fit the equilibrium data well. It was found that the methanogenic PAGS was more effective in Copper(II) biosorption process than the DSR PAGS, whose maximum biosorption capacity was 39.6% lower. The mechanisms of the biosorption capacities for different PAGS were discussed, and the conclusion suggested that the environment and biochemical reactions during the growth of biomass may have affected the structure of the PAGS. The methanogenic PAGS had larger specific surface area and more biosorption capacity than the DSR PAGS.