Terephthalate (TA) is one of the top 50 chemicals produced worldwide. Its production results in a TA-containing wastewater that is treated by anaerobic processes through a poorly understood methanogenic syntrophy. Using metagenomics, we characterized the methanogenic consortium inside a hyper-mesophilic (that is, between mesophilic and thermophilic), TA-degrading bioreactor. We identified genes belonging to dominant Pelotomaculum species presumably involved in TA degradation through decarboxylation, dearomatization, and modified b-oxidation to H 2 /CO 2 and acetate. These intermediates are converted to CH 4 /CO 2 by three novel hyper-mesophilic methanogens. Additional secondary syntrophic interactions were predicted in Thermotogae, Syntrophus and candidate phyla OP5 and WWE1 populations. The OP5 encodes genes capable of anaerobic autotrophic butyrate production and Thermotogae, Syntrophus and WWE1 have the genetic potential to oxidize butyrate to CO 2 /H 2 and acetate. These observations suggest that the TA-degrading consortium consists of additional syntrophic interactions beyond the standard H 2 -producing syntroph-methanogen partnership that may serve to improve community stability. The ISME Journal (2011) 5, 122-130; doi:10.1038/ismej.2010; published online 5 August 2010Subject Category: integrated genomics and post-genomics approaches in microbial ecology Keywords: metagenomics; methanogenesis; syntroph; microbial diversity; carbon cycling Introduction Terephthalate (TA) is used as the raw material for the manufacture of numerous plastic products (for example, polyethylene TA bottles and textile fibers). During its production, TA-containing wastewater is discharged in large volumes (as high as 300 million m 3 per year) and high concentration (up to 20 kg COD (chemical oxygen demand) m À3 ) (Razo-Flores et al., 2006). This wastewater is generally treated by anaerobic biological processes under mesophilic conditions (B35 1C). However, anaerobic processes operated at hyper-mesophilic (46-50 1C) and thermophilic (B55 1C) temperatures may be preferable because of the ability to achieve higher loading rate (van Lier et al., 1997;Chen et al., 2004), which reduces the reactor volume. Moreover, TA wastewater is usually generated at 54-60 1C, and does not require additional energy input for maintaining reactor temperature (Chen et al., 2004). The microbial biomass usually occurs in the form of granules or biofilms attaching on the surface of porous media. Under such environments, TA degradation has been hypothesized (Kleerebezem et al., 1999) to be based on a syntrophic microbial relationship whereby fermentative H 2 -producing bacteria (syntrophs) convert TA through benzoate to acetate and H 2 /CO 2 , and acetoclastic and hydrogenotrophic methanogens further convert the intermediates to methane by physically positioning themselves close to the syntrophs to overcome the www.nature.com/ismej thermodynamic barrier (Stams, 1994;Conrad, 1999;Dolfing, 2001).In practice, the complexities of TA-degrading communities are not...

Four techniques (microscope sizing, calculation from settling velocities. image and laser analysis) are available nowadays for determining the particle size distribution of upflow anaerobic sludge blanket (UASB) reactor sludge. These techniques present however the disadvantage of being either tedious, imprecise or expensive and hardly applicable in full scale treatment plants. There was then the need for a simple and low cost technique. In this study, a granulometry procedure based on manual humïhsievïng was evaluated. It was shown that no solid loss occured during the screening and that the particle size profiles were reproducible when performed with sludge samples of 5. 10.25 and 150 ml. but not I ml. Only the results between 10 and 25 ml were however fully identical. It was shown also that the sieving could be performed on sludge samples stored for as long as 50 days at refrigerator temperature and that tap water could be use for [he wash' and backwash operations without any impact ori the particle size profile. The granulometry obtained by image analysis was not comparable to that given by sieving. Ne\,ertheless. no evidence of granule erosion could be found. In any case, the technique allowed us to follow [he evolution of sludge granulometry perfectly over lime. As a consequence. the manual humid sieving appears to be an adequate technique for determining the granule size distribution of UASB sludges. Q 1999 Published by Elsevier Science Lid on behalf of the IAWQ. All rights reserved.

Three mesophilic bacteria (strains AMX 26BT , UR374_02 and 12-3 T ) isolated respectively from an anaerobic digester, human urine and urban riverside soil were characterized. Cells were Gram-negative, motile, non-sporulating, straight to curved rods with one polar flagellum and had a strictly respiratory metabolism with O 2 as the preferential terminal electron acceptor. Phylogenetic analysis based on 16S rRNA gene sequences revealed that all strains clustered within the Xanthomonadaceae branch of the Proteobacteria. Isolates AMX 26BT and UR374_02 exhibited 100 % 16S rRNA gene sequence similarity and both were related to strain 12-3 T (99?6 % similarity

Spent caustic is a waste from oil refineries which is difficult to treat and dispose of due to its noxious properties such as high content in paraffins and asphaltenes hydrocarbons which form all sorts of emulsions and solutions, from 5 to 18% of free NaOH, up to 35 g of Cl-/L, phenol compounds, and organic and inorganic sulfur compounds. Its composition depends on the source of the fuel being desulfurated. This mixture is very reactive and therefore its characterization is difficult and dependent on the way the sample is handled. Samples have to be collected cold from the storage container with no more than 6 h of having been rejected from the process. The sampling container must be sealed and pressure-proof. Part of the sample has to be acidified in situ for certain analysis. The spent caustic from Tula refinery in Mexico has 320 g of COD/L from which 114 come from sulfur organic compounds (3.6 g COD/g of S), 153 from phenolic compounds (phenol 78 g of COD/L) and the rest from other petroleum derivatives such as asphaltenes, paraffins, and mercaptans. Present treatment processes involve incineration of spent caustics, and an effort is needed for biological treatment in order to cut maintenance costs.

With 14.4 million tons produced in 1993, purified terephthalic acid (PTA) and dimethylterephthalate (DMT) are the main monomers used in the world polyester production. Even though there are ten industrial digestors treating the effluents of both products, little is known about the influence of their organic components, terephthalic (TA), p-toluic (p-tol), benzoic (BA) and phthalic (PA) acids as well as 4-carboxybenzaldehyde (4-CBA) on methanogenesis. This study shows that the concentrations of 4-CBA, p-tol and TA required to inhibit by 50% the hydrogenotrophic methanogenic activity are respectively 5.4, 34 and more than 100 mM. At the maximum concentration tested (10 mM), the inhibition of the acetoclastic methanogenic activity by the same compounds was less than 12%. The results indicate that at the concentration of TA, p-tol and 4-CBA found in PTA and DMT wastewater, no significant inhibition of the methanogenic activity should be observed for PTA but that the hydrogenotrophic activity could be reduced by as much as 30% in the case of DMT. The degradation of TA was completely inhibited by the presence of BA and glucose while the presence of phthalate had no effect. According to these results, it is concluded that it is at least possible to anaerobically treat the easily biodegradable compounds of these effluents (acetic, benzoic and formic acid) as they would not be significantly inhibited by TA, p-tol or 4-CBA.

The use of a down-flow fluidized bed (DFFB) reactor for the treatment of a sulfate-rich synthetic wastewater was investigated to obtain insight into the outcome of sulfate reduction in a biofilm attached to a plastic support under a down-flow regime. Fine low-density polyethylene particles were used as support for developing a biofilm within the reactor. The reactor treated a volatile fatty acids mixture of acetate or lactate, propionate, and butyrate at different chemical oxygen demand (COD) to sulfate ratios ranging from 1.67 to 0.67 (g/g). Organic loading rate changed from 2.5 to 5 g COD/L x day and sulfate loading rate increased from 1.5 to 7.3 g SO(4) (2-)/L x day. At the beginning of continuous operation, methanogenesis was the predominant process; however, after 187 days, sulfate reduction became the main ongoing biological process. After 369 days, a COD removal of 93% and a sulfate removal of 75% were reached. Total sulfide concentrations in the reactor ranged from 105, when the reactor was mainly methanogenic, to around 1,215 mg/L at the end of the experiment. The high sulfide concentrations did not affect the performance of the reactor. Results demonstrated that the configuration of the DFFB reactor was suitable for the anaerobic treatment of sulfate-rich wastewater.

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Salvinia minima has been reported as a cadmium and lead hyperaccumulator being the adsorption and intracellular accumulation the main uptake mechanisms. However, its physicochemical properties, the effect of metal concentration and the presence of organic and inorganic compounds on its hyperaccumulating capacity are still unknown. Furthermore, the specific adsorption and accumulation mechanisms occurring in the plant are not clear yet. Thus, based on a compartmentalization analysis, a bioadsorption (BAF) and an intracellular accumulation factor (IAF) were calculated in order to differentiate and quantify these two mechanisms. The use of kinetic models allowed predicting the specific type of uptake mechanisms involved. Healthy plants were exposed to five lead concentrations ranging from 0.80± 0.0 to 28.40±0.22 mg Pb 2+ l −1 in batch systems. A synthetic wastewater, amended with propionic acid and magnesium sulfate, and deionized water were used as media. The BAF and IAF contributed to gain an indepth insight into the hyperaccumulating lead capacity of S. minima. It is clear that such capacity is mainly due to adsorption (BAF 780-1980) most likely due to its exceptional physico-chemical characteristics such as a very high surface area (264 m 2 g −1 ) and a high content of carboxylic groups (0.95 mmol H + g −1 dw). Chemisorption was predicted as the responsible mechanism according to the pseudo-second order adsorption model. Surprisingly, the ability of S. minima to accumulate the metal into the cells (IAF 57-1007) was not inhibited at concentrations as high as 28.40±0.22 mg Pb 2+ l −1 .