Citric acid wastewater as electron donor for biological sulfate reduction

Citrate-containing wastewater is used as electron donor for sulfate reduction in a biological treatment plant for the removal of sulfate. The pathway of citrate conversion coupled to sulfate reduction and the microorganisms involved were investigated. Citrate was not a direct electron donor for the sulfate-reducing bacteria. Instead, citrate was fermented to mainly acetate and formate. These fermentation products served as electron donors for the sulfate-reducing bacteria. Sulfate reduction activities of the reactor biomass with acetate and formate were sufficiently high to explain the sulfate reduction rates that are required for the process. Two citrate-fermenting bacteria were isolated. Strain R210 was closest related to Trichococcus pasteurii (99.5% ribosomal RNA (rRNA) gene sequence similarity). The closest relative of strain S101 was Veillonella montepellierensis with an rRNA gene sequence similarity of 96.7%. Both strains had a complementary substrate range

HOT SUBTERRANEAN BIOSPHERE IN A CONTINENTAL OIL-RESERVOIR

THE presence of high concentrations of hyperthermophilic archaea in Alaskan oil fields has been attributed to viable hyperthermophiles in low concentrations in the injected sea water, but the existence of an indigenous community within the reservoir was ruled out(1). Here we present evidence for the existence of indigenous thermophilic bacteria and hyperthermophilic archaea from a continental petroleum reservoir about 1,670 m below the surface. The thermophilic isolates were repeatedly obtained from different wells and thrived in media similar to conditions in the wells, suggesting that these isolates are members of a deep indigenous thermophilic community. The unexpected presence of marine hyperthermophilic archaea in a deep continental environment extends the known ecological habitat of this group of organisms, and their unusual coexistence with terrestrial bacteria suggests that thermophiles may be widespread deep in the crust of the earth

Effect of Mixed-Species Biofilm on Copper Surfaces in Cooling Water System

This study aimed to investigate the formation and effect of a biofilm on copper heat exchangers in full-scale system conditions. A modified Pedersen device with copper coupons was installed in parallel to a heat exchanger system to investigate several physico-chemical parameters, such as bacterial enumeration, carbohydrate content of exopolymeric substances, weight loss of test/control coupons, Cu concentrations, and corrosion products over ten months. Findings of this study showed that planktonic bacterial cells attach to each other and form a mixed-species biofilm on the copper coupon surface even though copper is toxic to a variety of microorganisms. These results also revealed that the mixed-species biofilm has a corrosive effect on copper surfaces used in cooling water systems despite the presence of biocide and the corrosion inhibitor. Additionally, it was demonstrated that a shock-dosed biocide application increased the corrosion rate on copper surface in a real system. Preventing risk of microbiologically influenced corrosion entails appropriate material selection and proper/regular chemical treatment of cooling systems. The current study provides useful insights through the evaluation of corrosion of materials with microbiological techniques