The biodegradation kinetics of anionic (sodium laureth sulfate - SLES), amphoteric (disodium cocoamphodiacetate - DSCADA), and nonionic surfactants (polyalcohol ethoxylate - PAE) were assessed in this laboratory study. Similar degradation behavior was observed for all surfactants with only a fraction of the parent compound readily biodegradable. Biodegradation, as estimated by COD removal, was initially (i.e., within 24 h) rapid, however only 40-70% of the surfactant molecules were readily biodegradable. Intrinsic kinetic parameters were successfully quantified for the readily biodegradable component of the surfactant. Inhibition was not observed and microbial kinetics of SLES, DSCADA, and PAE degradation fit the Monod model well. Average μ-S curves were generated for each surfactant. Based on these results, complete degradation of the target surfactants using biological waste treatment would be limited.

The prevalence and diversity of antibiotic resistant enterococci populations in samples collected four times from urban sewage treatment plant in Tehran, Iran between June 2005 and July 2006 were studied. Filtered samples were grown on mEnterococci medium containing 4 μg/ml vancomycin after which the enterococci isolates were identified to the species level. All strains were then tested for their resistance against nine antibiotics. Of the 131 isolates, 98 (75%) isolates were identified as Enterococcus gallinarum, followed by 24 (18%) and 9 (7%) for E. faecium and E. casseliflavus, respectively. All E. gallinarum isolates carried vanC1 gene with 64 (65%) and 14 (14%) isolates concomitantly harboured either vanA or vanB gene, respectively. Some E. casseliflavus concomitantly harboured vanA and vanC2 or vanB and vanC2. Typing the total enterococci isolates with a high resolution biochemical fingerprinting method showed a high diversity (D i = 0.91). We have shown by biochemical fingerprinting the presence of highly diverse glycopeptide resistant E. gallinarum and E. casseliflavus that have captured vanA and vanB genetic determinants under natural conditions. To our knowledge this is the first report in this geographical region showing high frequency antibiotic resistant enterococcal populations in particular E. gallinarum carrying assorted vancomycin resistance genes.

Sewage sludge is a cost-effective media for the production of Bacillus thuringiensis (Bt) based biopesticides. To enhance the entomotoxicity of the fermentation broth, pretreatments of sewage sludge by alkali and ultrasonic were applied in this study. Effects of alkaline and ultrasonic pretreatments on the soluble COD (SCOD) and total COD (TCOD) were evaluated by altering the alkali addition dose and the ultrasonic specific energy. Suitable pretreatment conditions were optimized with 5 g l-¹ sodium hydroxide (NaOH) for alkaline treatment and 1.2 x 10⁵ kJ kg-¹ of total solid for ultrasonic treatment. Fermentations of raw and pretreated sludge for biopesticides were carried out in a bench scale fermentor. Results revealed that both pretreatments were effective for Bt growth and metabolism. Higher viable cells (VC) and viable spores (VS) counts, δ-endotoxin yields and entomotoxicity were achieved in the pretreated sludge. The enhancement was attributed to more available nutrients and better oxygen transfer. Moreover, ultrasonic pretreated sludge was superior to alkaline pretreated sludge for δ-endotoxin production and entomotoxicity owing to its higher soluble C/N ratio and finer particles.

In order to gain insight into the community structure and the biodegradative potential of bacteria residing in a BTEX-contaminated field site, with benzene as main pollutant, an investigation strategy with a variety of cultivation-independent and -dependent approaches was undertaken. Based on 16S ribosomal DNA sequence analysis, sampling stations in the center of the pollution plume were found to be dominated by a bacterial consortium affiliated with various members of the class of Proteobacteria and Firmicutes, including different sporulating and non-sporulating sulfate-reducing bacteria and members of the genus Geobacter. Non-polluted samples retrieved from outside the plume revealed several phylotypes which were also observed in the centre of the plume. Bacterial sequences retrieved from the fringe of the plume were dominated by several genera of beta Proteobacteria subclass which were not associated with other phylotypes obtained in this study. All sampling stations were tested positive for catechol 2,3-dioxygenase genes, indicating the presence of microorganisms with the genetic potential degrading aromatic compounds via the meta-cleavage pathway. The groundwater system at the down-gradient edge of the plume was characterized, in contrast to all other sampling stations in the center and outside the plume, by high numbers of cultivable bacteria and cultivable aerobic benzene and toluene degraders. These findings are also in accordance with the investigations based on fluorescent in situ hybridization (FISH) with rRNA-targeted oligonucleotide probes, suggesting the presence of an actively benzene degrading bacterial community of beta Proteobacteria at the fringe of the pollution plume.