Influence of organic loading on an anaerobic sequencing biofilm batch reactor (ASBBR) as a function of cycle period and wastewater concentration

The effect of organic loading on the performance of a mechanically stirred anaerobic sequencing biofilm batch reactor (ASBBR) has been investigated, by varying influent concentration and cycle period. For microbial immobilization 1-cm polyurethane foam cubes were used. An agitation rate of 500 rpm and temperature of 30+/-2 degrees C were employed. Organic loading rates (OLR) of 1.5-6.0gCODl(-1)d(-1) were applied to the 6.3-l reactor treating 2.0 l synthetic wastewater in 8 and 12-h batches and at concentrations of 500-2000mgCODl(-1), making it possible to analyze the effect of these two operation variables for the same organic loading range. Microbial immobilization on inert support maintained approximately 60 gTVS in the reactor. Filtered sample organic COD removal efficiencies ranged from 73 to 88% for organic loading up to 5.4gCODl(-1)d(-1). For higher organic loading (influent concentration of 2000mgCODl(-1) and 8-h cycle) the system presented total volatile acids accumulation, which reduced organics removal efficiency down to 55%. In this way, ASBBR with immobilized biomass was shown to be efficient for organic removal at organic loading rates of up to 5.4gCODl(-1)d(-1) and to be more stable to organic loading variations for 12-h cycles. This reactor might be an alternative to intermittent systems as it possesses greater operational flexibility. It might also be an alternative to batch systems suspended with microorganisms since it eliminates both the uncertainties regarding granulation and the time necessary for biomass sedimentation, hence reducing the total cycle period.     

Environmental mutagenicity and toxicity caused by sodium metabisulfite in sea shrimp harvesting in Piauí, Brazil

Sodium metabisulfite is used in marine shrimp harvesting to prevent the occurrence of black spots. Shrimps are soaked in a sodium metabisulfite solution in ice, which is disposed of in sewages that run into marine canals, creating an environmental hazard. This study evaluates the toxicity and mutagenicity caused by sodium metabisulfite in sea waters and sediments collected in a shrimp farm in Cajueiro da Praia (Luis Correia), state of Piauí, Brazil, using the Allium cepa assay. Water and sediment samples were collected in the dry and in the rainy seasons, in three sites: upstream the shrimp farm (Site 1), at the point sodium metabisulfite is discharged (Site 2), and 100 m downstream the farm (Site 3). Three sample dilutions were used (50%, 25% and 10%) for all samples. A negative control (well water) and a positive control (copper sulfate 0.0006 mg mL⁻¹) were used in each experiment. At the end of the 72-h exposure period, onion roots were measured and removed. Mutagenicity analysis included the determination of mitotic index, chromosomal aberrations and the detection of micronuclei; analysis of root size and mitotic index were used as an index of toxicity. The A. cepa assay revealed that the water and sediments samples collected in the Piauí coast contaminated with sodium metabisulfite induce toxicity. The results demonstrate that the assay may be used as a regular tool in the analysis of water parameters in shrimp farms in the coast of Piauí state, and in strategies to preserve the region’s marine ecosystem.     

Adsorption mechanism of chromium(III) using biosorbents of Jatropha curcas L.

Environmental Science and Pollution Research - The removal of Cr3+ from water solutions by biosorbents from the rind, endosperm, and endosperm + episperm of the Jatropha curcas was evaluated....     

Decentralized management of sewage using septic tanks and anaerobic filters and its potential to comply with required standards in a developing country: a case study in Brazil

Environmental Science and Pollution Research - To investigate the feasibility of implementing decentralized sewage treatment systems aiming to meet environmental standards, the performance of three...     

Fast extraction of polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran in sewage sludge and soil samples

The current environmental legislations recommend monitoring chemical contaminants such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans before the use of sewage sludge on the agricultural land. In this study, a solid–liquid extraction with low-temperature purification (SLE-LTP) was optimized and validated to determine 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran in sewage sludge and soil samples. The analyses were performed by gas chromatography-mass spectrometry operating in the selective ion mode (GC-MS-SIM). Acetonitrile:ethyl acetate 6.5:1.5 (v/v) was the best extraction phase, and the recoveries percentages were close to 100%. The linearity was demonstrated in the range of 1.25–25 µg L^?1 of 1.25–20 µg L^?1 for sewage sludge and soil, respectively. Matrix effect was proved for the two compounds and in the two matrices studied. Extraction percentages were between 78 and 109% and relative standard deviations ≤ 19%. The proposed method is faster than methods described in the literature because showed a few steps. The quantification limits (LOQ) in sewage sludge were 6.4 and 32 ng TEQ kg^?1 for 2,3,7,8-TCDF and 2,3,7,8-TCDD, respectively. In soil, LOQs were 0.8 and 8.0 ng TEQ kg^?1 for 2,3,7,8-TCDF and 2,3,7,8-TCDD, respectively. These values are lower than the maximum residue limits established by European Legislation. The method was applied to 22 agricultural soil samples from different Brazilian cities and 2,3,7,8-TCDF was detected in one of these samples.     

Determination of three cresol isomers in sewage sludge by solid-liquid extraction with low temperature purification and gas chromatography-mass spectrometry

Abstract

Cresols are chemical contaminants derivative from phenol which can be found in sewage sludge. However, little attention has been given to monitoring these compounds in environmental matrices in the literature. Thus, the objective of this study was to develop a simple method based on solid-liquid extraction with low temperature purification for determining three cresol isomers in sludge. The quantification of these compounds was performed by gas chromatography coupled to mass spectrometry with a previous derivatization step. After a detailed study, the cresol recovery was higher than 91%, with relative standard deviation lower than 12% and a limit of quantification of 20?μg kg^?1. Linearity was achieved between 10 and 90?μg L^?1 (R² > 0.98) with the standard solutions prepared in matrix extracts due to the trouble caused by the matrix effect. The proposed method was applied with success for monitoring cresols in sewage sludge samples coming from six different wastewater treatment plants. All samples showed contamination by cresols, mainly p-cresol with values between 32.3 and 516.9?μg kg^?1. The majority of the analyzed samples showed a total sum of the isomers higher than the maximum residue limit established by Brazilian legislation (160?μg kg^?1).