POLYCHAETE ASSEMBLAGE OF AN IMPACTED ESTUARY, GUANABARA BAY, RIO DE JANEIRO, BRAZIL

Thirty-eight stations were sampled in Guanabara Bay, Rio de Janeiro, Brazil, to assess the spatio-temporal diversity and biomass of sublittoral polychaetes. Samples were collected during the dry (September 2000) and rainy season (May 2001) in shallow sublittoral sediments. The polychaete spatial composition showed a heterogeneous distribution throughout the bay. A negative gradient of diversity and biomass was observed towards the inner parts of the bay and sheltered areas. A wide azoic area was found inside the bay. Some high-biomass and low-diversity spots were found near a sewage-discharge point. In these areas, the polychaete biomass increased after the rainy season. A diversified polychaete community was identified around the bay mouth, with no dramatic changes of this pattern between the two sampling periods. Deposit-feeders were dominant in the entire study area. The relative importance of carnivores and omnivores increased towards the outer sector, at stations with coarse sediment fractions. Guanabara Bay can be divided into three main zones with respect to environmental conditions and polychaete diversity and biomass patterns: A) High polychaete diversity, hydrodynamically exposed areas composed of sandy, oxidized or moderately reduced sediments with normoxic conditions in the water column. B) Low diversity and high biomass of deposit and suspension-feeding polychaete species in the middle part of the bay near continental inflows, comprising stations sharing similar proportions of silt, clay and fine sands. C) Azoic area or an impoverished polychaete community in hydrodynamically low-energy areas of silt and clay with extremely reduced sediments, high total organic matter content and hypoxic conditions in the water column, located essentially from the mid-bay towards the north sector. High total organic matter content and hypoxic conditions combined with slow water renewal in the inner bay seemed to play a key role in the polychaete diversity and biomass. Sedimentation processes and organic load coming from untreated sewage into the bay may have negatively affected the survivorship of the fauna.

Effect of Feed Strategy on Methane Production and Performance of an AnSBBR Treating Effluent from Biodiesel Production

The aim of this work was to investigate the effect of different feeding times (2, 4 and 6 h) and applied volumetric organic loads (4.5, 6.0 and 7.5 gCOD L-1 day(-1)) on the performance of an anaerobic sequencing batch biofilm reactor (AnSBBR) treating effluent from biodiesel production. Polyurethane foam cubes were used as inert support in the reactor, and mixing was accomplished by recirculating the liquid phase. The effect of feeding time on reactor performance showed to be more pronounced at higher values of applied volumetric organic loads (AVOLs). Highest organic material removal efficiencies achieved at AVOL of 4.5 gCOD L-1 day(-1) were 87 % at 4-h feeding against 84 % at 2-h and 6-h feeding. At AVOL of 6.0 gCOD L-1 day(-1), highest organic material removal efficiencies achieved with 4-h and 6-h feeding were 84 %, against 71 % at 2-h feeding. At AVOL of 7.5 gCOD L-1 day(-1), organic material removal efficiency achieved with 4-h feeding was 77 %. Hence, longer feeding times favored minimization of total volatile acids concentration during the cycle as well as in the effluent, guaranteeing process stability and safety.

Integration of processes induced air flotation and photo-Fenton for treatment of residual waters contaminated with xylene

Produced water in oil fields is one of the main sources of wastewater generated in the industry. It contains several organic compounds, such as benzene, toluene, ethyl benzene and xylene (BTEX), whose disposal is regulated by law. The aim of this study is to investigate a treatment of produced water integrating two processes, i.e., induced air flotation (IAF) and photo-Fenton. The experiments were conducted in a column flotation and annular lamp reactor for flotation and photodegradation steps, respectively. The first order kinetic constant of IAF for the wastewater studied was determined to be 0.1765 min(-1) for the surfactant EO 7. Degradation efficiencies of organic loading were assessed using factorial planning. Statistical data analysis shows that H2O2 concentration is a determining factor in process efficiency. Degradations above 90% were reached in all cases after 90 min of reaction, attaining 100% mineralization in the optimized concentrations of Fenton reagents. Process integration was adequate with 100% organic load removal in 20 min. The results of the integration of the IAF with the photo-Fenton allowed to meet the effluent limits established by Brazilian legislation for disposal. (C) 2011 Elsevier B.V. All rights reserved.