Enhancement of anammox performance by Cu(II), Ni(II) and Fe(III) supplementation.

This study explored the influence of metal ion addition on specific anaerobic ammonium oxidation activity (SAA). Batch assays were used to demonstrate the enhancement of the SAA upon the addition of Cu2+, Ni2+ and Fe3+. The SAA was enhanced by 41.0% when the Cu2+ concentration was below 1 mg L−1, while it was improved by 63.5% at Ni2+ concentrations below 1.74 mg L−1. An enhancement of 533.2% was obtained when 3.68 mg L−1 Fe3+ was supplied. The effects of Fe3+, Cu2+ and Ni2+ on the SAA were analyzed and optimized by a response surface methodology, which demonstrated that the interaction between Fe3+ and Cu2+ was significant and that 6.61 mg Fe3+ L−1, 1.18 mg Cu2+ L−1 and 1.11 mg Ni2+ L−1 were the optimal values for metal dosing. Subsequently, an Fe3+­Cu2+­Ni2+ continuous test was carried out under optimal conditions and revealed that the addition of Fe3+, Cu2+ and Ni2+ could stimulate the reactor potential at ambient temperature. The maximum nitrogen removal rate (NRR) of the test reactor was 52.8% higher than that of the control reactor (8.1 versus 5.3 kg N m−3 d−1). Moreover, a continuous test conducted by adding Fe3+ achieved an average nitrogen removal efficiency and maximum NRR of 67.4% and 4.9 kg N m−3 d−1, respectively, while the corresponding values of the control test were 64.7% and 4.1 kg N m−3 d−1, respectively. Altogether, appropriate dosages of Cu2+, Ni2+ and Fe3+ can significantly enhance the SAA and improve the reactor capacity at ambient temperature.

Low levels of lead exposure induce oxidative damage and DNA damage in the testes of the frog Rana nigromaculata.

We have investigated the chronic effects of low concentrations of lead (Pb) on oxidative damage and DNA damage in testes of the frog Rana nigromaculata. Sixty adult male frogs were randomly divided into six groups of ten. Based on the levels of the Integrated Wastewater Discharge Standard (GB 8978-1996) of China, five groups (II-VI) were treated by epidermal absorption with a PbNO(3) solution at concentrations of 0.1, 0.2, 0.4, 0.8, 1.6 mg/l, respectively. The first group (I), which served as a control, was treated with distilled water only. Thirty days after treatment, all frogs were sacrificed and the testis tissues removed for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels. DNA damage, including indicators of damage rate, DNA tail length (TL), and DNA tail moment (TM), was also analyzed by comet assays. Our data suggest that MDA levels in all treatment groups and GSH levels in the 0.2-1.6 mg/l Pb groups increased significantly relative to the controls (P < 0.01). Treatment with Pb at concentrations >0.4 mg/l also increased DNA damage rate and TM, while TL increased when the Pb level was >0.2 mg/l (P < 0.01 for DNA damage rate and TM, P < 0.05 for TL). Positive correlations were also found between DNA damage levels in the testes and MDA levels (r = 0.796 for DNA damage rate, r = 0.811 for TL, r = 0.796 for TM; P < 0.01 for all) as well between MDA and GSH levels (r = 0.455, P < 0.05) in the testes. Results from MDA measurements indicated that Pb-induced DNA damage in the testes of R. nigromaculata was possibly due to oxidative damage. Taken together, we conclude that Pb can induce male reproductive toxicity in R. nigromaculata.