Anammox bacteria community and nitrogen removal in a strip-like wetland in the riparian zone

Bioaccumulation and degradation of atrazine in several Chinese ryegrass genotypes

Soil pollution with herbicides is a global problem. Before phytoremediation technology is developed for the plant-based clean-up of polluted soils, investigation of potential plants that can be used to accumulate and degrade herbicides is a critical step. In this study, three selected genotypes of ryegrass were comprehensively analyzed with regard to the atrazine accumulation, degradation and toxicological response. Under the conditions of soil with 0.8 mg kg(-1) atrazine, the maximum value for atrazine accumulation was 2.70 mg kg(-1) in shoots and 0.58 mg kg(-1) in roots. The residue of atrazine in soil with ryegrass cultivation was much lower than that in soil without ryegrass cultivation. Also, the content of atrazine residues in the rhizosphere was significantly lower than that in the non-rhizosphere soil. Activities of several enzymes (urease, invertase, polyphenol oxidase, acid phosphatase and alkaline phosphatase) in soil were assayed. These enzymes were depressed by atrazine but activated by ryegrass cultivation, even in the presence of atrazine. Finally, comparative studies have been conducted on the ryegrass genotypes in response to atrazine. They showed different capacities of degradation and bioaccumulation of atrazine. One of the grass cultivars Changjiang II (CJ) had better growth and higher levels of chlorophyll, but displayed less oxidative injury than two others, Abode (AB) and Jiewei (JW), under atrazine exposure.

Influence of the type and source of inoculum on the start-up of anammox sequencing batch reactors (SBRs)

Anammox (anaerobic ammonium oxidation) is an attractive option for the treatment of wastewaters with a low carbon/nitrogen ratio. This is due to its low operating costs when compared to the classical nitrification-denitrification processes. However, one of the main disadvantages of the Anammox process is slow biomass growth, meaning a relatively slow reactor start-up. This becomes even more complicated when Anammox microorganisms are not present in the inoculum. Four inocula were studied for the start-up of Anammox sequencing batch reactors (SBRs) 2 L in volume agitated at 100 rpm, one of them using zeolite as a microbial support. Two inocula were taken from UASB reactors and two from aerobic reactors (activated sludge and SBR). The Anammox SBRs studied were operated at 36 ± 0.5°C. The results showed that the only inoculum that enabled the enrichment of the Anammox biomass came from an activated sludge plant treating wastewaters from a poultry slaughterhouse. This plant was designed for organic matter degradation and nitrogen removal (nitrification). This could explain the presence of Anammox microorganisms. This SBR operated without zeolite and achieved nitrite and ammonium removals of 96.3% and 68.4% respectively, at a nitrogen loading rate (NLR) of 0.1 kg N/m(3)/d in both cases. The lower ammonium removal was due to the fact that a sub-stoichiometric amount of nitrite (1 molar ratio) was fed. The specific Anammox activity (SAA) achieved was 0.18 g N/g VSS/d.