The effect of low temperature and low light intensity on nutrient removal from municipal wastewater by purple phototrophic bacteria (PPB)

There has been increased interest in alternative wastewater treatment systems to improve nutrient recovery while achieving acceptable TCOD, TN, and TP discharge limits. Purple phototrophic bacteria (PPB) have a high potential for simultaneous nutrient removal and recovery from wastewater. This study evaluated the PPB performance and its growth at different operating conditions with a focus on HRT and light optimization using a continuous-flow membrane photobioreactor (PHB). Furthermore, the effect of low temperature on PPB performance was assessed to evaluate the PPB’s application in cold-climate regions. In order to evaluate PPB performance, TCOD, TN, and TP removal efficiencies and Monod kinetic parameters were analyzed at different HRTs (36, 18, and 9 h), at temperatures of 22°C and 11°C and infrared (IR) light intensities of 50, 3, and 1.4 Wm-2. The results indicated that low temperature had no detrimental impact on PPB’s performance. The photobioreactor (PHB) with cold-enriched PPB has a high potential to treat municipal wastewater with effluent concentrations below target limits (TCOD˂ 50mgL-1, TN˂10 mgL-1, and TP˂1 mgL-1). Monod kinetic parameters Ks, K, Y, and Kd were estimated at 20-29 mgCODL-1, 1.6-1.9 mgCOD(mgVSS.d)-1, 0.47 mgVSS mgCOD-1, and 0.07-0.08 d-1 at temperatures of 11°C-22°C respectively. The results of the steady-state mass balances showed TCOD, TN, and TP recoveries of 80%-86%, which reflected PPB’s substrate and nutrient assimilation. Previous studies utilized high light intensities (˃ 50 Wm-2) to provide PPB with the maximum energy required for its growth. In order to enable the PPB technology as a practical approach in municipal wastewater treatment, light intensity must be optimized. Based on the literature, there is no study on PPB performance at low light intensities using a continuous-flow membrane photobioreactor. The effect of low light intensities of 3, and 1.4 Wm-2 on PPB performance was addressed in this study. The results indicated that PPB at a light intensity as low as 1.4 Wm-2 were able to treat municipal wastewater with effluent concentrations below above-mentioned target limits. Light intensity (1-50 Wm-2) had no detrimental impact on PPB performance and Monod kinetic parameters. This study showed that the optimized light intensity required for municipal wastewater treatment with PPB is significantly lower than previously indicated in the literature. The energy consumptions attributed to PHB’s illumination of 3, and 1.4 Wm-2 were determined to be 1.44, and 0.67 kWh/m3 which is significantly lower than previous studies (˃ 24 kWh/m3)

Selenium-bridged clusters - synthesis and structural characterization of cp2mo2fe2(mu(4)-se)(mu(3)-se)2(co)6

Thermolysis of Fe2(CO)6{mu-SeC(Ph)=C(H)Se} (1) and Cp2Mo2(CO)6 (2) yields the new cluster Cp2Mo2Fe2(mu4-Se)(mu3-Se)2(CO)6 (3) and Cp2Mo2(CO)4(PhCCH) (4). Structural characterization of 3 shows an unusual mu4-Se ligand bridging the two wing-tip Fe atoms and the two hinge Mo atoms of the Mo2Fe2 butterfly-tetrahedron core

HEPTACARBONYLBIS(TRIPHENYLPHOSPHINE)-BIS(MU(3)-TELLURIUM)-TRIIRON

The heptacarbonyl-1kappa3C,2kappa2C,3kappa2C-bis(mu3-tellurido)-bis(triphenylphosphine)-2kappaP,3kappaP-triiron, (PPh3)2-Fe3(CO)7(mu3-Te)2, structure is a distorted square-pyramid motif with three Fe and two Te atoms at the vertices; Fe(1), Fe(2), Te(1) and Te(2) form the base of the pyramid with Fe(1)-Te(1) = 2.531 (1), Fe(1)-Te(2) = 2.544 (1), Fe(2)-Te(1) = 2.539 (1) and Fe(2)-Te(2) = 2.549 (1) angstrom. Fe(1) and Fe(2) have two terminal carbonyl ligands and one triphenylphosphine ligand; the phosphine ligands are coordinated equatorially to Fe(1) and axially to Fe(2). The apical Fe(3) atom has three terminal carbonyl ligands

SYNTHESIS AND CHARACTERIZATION OF THE NEW CLUSTERS RU4(CO)11(MU-4-TE)2, RU3(CO)6(PPH3)3(MU-3-TE)2, RU4(CO)10(PPH3)(MU-4-TE)2, AND RU4(CO)9(MU-PH2PCH2PPH2)(MU-4-TE)2

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SELENIUM-BRIDGED CLUSTERS - SYNTHESIS AND CHARACTERIZATION OF SELENIUM-BRIDGED FE-MO CLUSTERS CP2MO2FE2SE3(CO)6, CP2MO2FE2SE2(CO)7, AND CP2MO2FESE(CO)7

Reflux of a benzene solution containing Fe3(CO)9Se2 and Cp2Mo2(CO)6 yielded the known cluster Cp2Mo2Fe2Se3(CO)6 (1) and the new clusters Cp2Mo2Fe2Se2(CO)7 (2) and Cp2Mo2-FeSe(CO)7 (3). Compound 2 was also isolated from the room temperature reaction of Fe2(CO)6Se2 with Cp2Mo2(CO)4. In solution, 2 was found to slowly convert to 1; on thermolysis, the conversion occurs rapidly. Both 2 and 3 have been characterized by spectroscopic and crystallographic methods. 2 crystallizes in the orthorhombic space group Pna2(1) with a = 13.289(3) angstrom, b = 12.059(2) angstrom, c = 13.045(3) angstrom, V = 2090.5(7) angstrom 3, and Z = 4. The structure refined to R = 3.56% and R(w) = 3.65% for 2109 unique reflections (F(o) greater-than-or-equal-to 4sigma-(F(o))). The structure of 2 consists of a Mo2Fe2 tetrahedron with the Fe-Fe edge bridged by a CO group. Triply bridging Se atoms cap the two Mo2Fe faces, and there is a semitriply bridging CO group above one of the MoFe2 faces. The remaining CO groups are terminally bonded. 3 crystallizes in the monoclinic space group C2/c with a = 30.756(7) angstrom, b = 8.590-(1) angstrom, c = 15.115(3) angstrom, beta = 102.86(3)-degrees, V = 3893.4(13) angstrom 3, and Z = 8. The structure refined to R = 4.81% and R(w) = 6.00% for 3103 unique reflections (F(o) greater-than-or-equal-to 4sigma(F(o))). The structure of 3 consists of a Mo2FeSe tetrahedron. Each Mo atom has one Cp and two terminally bonded CO groups, while the Fe atom has three CO groups bonded to it

Mixed Fe/Mo mixed-chalcogenide 'hour-glass' clusters, [Fe4Mo(Co)(14)(mu(3)-E)(2)(mu(3)-E')2] and [Fe3Mo(CO)(11)(mu(3)-E)(mu(3)-E')-(mu-E'-E')] (E, E' = S, Se or Te)

The room-temperature reactions of [Fe-2(CO)(6)(mu-EE')] (EE' = SeTe, STe, SSe, S-2 or Se-2) with [Mo(CO)(5)(thf)] (thf = tetrahydrofuran) yielded two types of mixed-metal, mixed-chalcogenide 'hour-glass' clusters: [Fe4Mo(Co)(14)(mu(3)-E)(2)(mu(3)-E')(2)] (E, E' = Se, Te 1; S, Te 2; S, Se 4; S, S 7; Se, Se 9) and [Fe3Mo(CO)(11)(mu(3)-E)(mu(3)-E')(mu-E'-E')] (E, E' = S, Te, E'-E' = Te-Te 3; E, E' = S; Se, E'-E' = Se-Se 5; E, E' = S, S, E'-E' = S-Se 6; E, E' = S, S, E'-E' = S-S 8; E, E' = Se, Se, E'-E' = Se-Se 10). The crystal structures of 2, 5, 6 and 8 were elucidated by X-ray methods. The structure of 2 consists of two distorted square-pyramidal cores in each of which the alternate corners of the base are occupied by Fe and chalcogen atoms and a Mo atom occupies the common apical site. In 5, 6 and 8 a Mo atom occupies the common apical site of a square-pyramidal core and a tetrahedral core. The base of the square-pyramidal unit consists of alternate Fe and chalcogen atoms and the tetrahedral base consists of a Fe atom and two chalcogen atoms