Improve Niche Colonization and Microbial Interactions for Organohalide-Respiring-Bacteria-Mediated Remediation of Chloroethene-Contaminated Sites.

Organohalide-respiring bacteria (OHRB)-mediated reductive dehalogenation is promising in in situ bioremediation of chloroethene-contaminated sites. The bioremediation efficiency of this approach is largely determined by the successful colonization of fastidious OHRB, which is highly dependent on the presence of proper growth niches and microbial interactions. In this study, based on two ecological principles (i.e., Priority Effects and Coexistence Theory), three strategies were developed to enhance niche colonization of OHRB, which were tested both in laboratory experiments and field applications: (i) preinoculation of a niche-preparing culture (NPC, being mainly constituted of fermenting bacteria and methanogens); (ii) staggered fermentation; and (iii) increased inoculation of CE40 (a Dehalococcoides-containing tetrachloroethene-to-ethene dechlorinating enrichment culture). Batch experimental results show significantly higher dechlorination efficiencies, as well as lower concentrations of volatile fatty acids (VFAs) and methane, in experimental sets with staggered fermentation and niche-preconditioning with NPC for 4 days (CE40_NPC-4) relative to control sets. Accordingly, a comparatively higher abundance of Dehalococcoides as major OHRB, together with a lower abundance of fermenting bacteria and methanogens, was observed in CE40_NPC-4 with staggered fermentation, which indicated the balanced syntrophic and competitive interactions between OHRB and other populations for the efficient dechlorination. Further experiments with microbial source tracking analyses suggested enhanced colonization of OHRB by increasing the inoculation ratio of CE40. The optimized conditions for enhanced colonization of OHRB were successfully employed for field bioremediation of trichloroethene (TCE, 0.3-1.4 mM)- and vinyl chloride (VC, ∼0.04 mM)-contaminated sites, resulting in 96.6% TCE and 99.7% VC dechlorination to ethene within 5 and 3 months, respectively. This study provides ecological principles-guided strategies for efficient bioremediation of chloroethene-contaminated sites, which may be also employed for removal of other emerging organohalide pollutants.

Comparison of the MBBR denitrification carriers for advanced nitrogen removal of wastewater treatment plant effluent.

The moving bed biofilm reactors (MBBRs) were used to remove the residual NO3(-)-N of wastewater treatment plant (WWTP) effluent, and the MBBR carriers for denitrification were compared. The results showed that high denitrification efficiency can be achieved with polyethylene, polypropylene, polyurethane foam, and haydite carriers under following conditions: 7.2 to 8.0 pH, 24 to 26 °C temperature, 12 h hydraulic retention time (HRT), and 25.5 mg L(-1) external methanol dosage, while the WWTP effluent total nitrogen (TN) was between 2.6 and 15.4 mg L(-1) and NO3(-)-N was between 0.2 and 12.6 mg L(-1). The MBBR filled with polyethylene carriers had higher TN and NO3(-)-N removal rate (44.9 ± 19.1 and 83.4 ± 13.0%, respectively) than those with other carriers. The minimum effluent TN and NO3(-)-N of polyethylene MBBR were 1.6 and 0.1 mg L(-1), respectively, and the maximum denitrification rate reached 23.0 g m(-2) day(-1). When chemical oxygen demand (COD)/TN ratio dropped from 6 to 4, the NO3(-)- N and TN removal efficiency decreased significantly in all reactors except for that filled with polyethylene, which indicated that the polyethylene MBBR can resist influent fluctuation much better. The three-dimensional excitation-emission matrix analysis showed that all the influent and effluent of MBBRs contain soluble microbial products (SMPs)-like organics and biochemical oxygen demand (BOD), which can be removed better by MBBRs filled with haydite and polyethylene carriers. The nitrous oxide reductase (nosZ)-based terminal restriction fragment length polymorphism (T-RFLP) analysis suggested that the dominant bacteria in polyethylene MBBR are the key denitrificans.

[Pretreatment of high-concentration acrylic acid wastewater by the multi-stage microaerobic biological fluidized bed reactor].

A multi-stage microaerobic biological fluidized bed reactor was used for the pretreatment of synthetic wastewater containing high concentration of acrylic acid (AA). The effect of influent load was investigated and the intermediate products of acrylic acid degradation were analyzed. It indicated that the removal rate of AA was above 95% with effluent acrylic acid less than 150 mg x L(-1) and COD removal rate of 15%-30%, under the following conditions: hydraulic retention time of 12 h, waste water temperature of 25 degrees C, influent acrylic acid concentration of 3 000-9 000 mg x L(-1), volume load of 6.0-18.0 kg x (m3 x d)(-1). The main intermediate products of acrylic acid degradation were acetic and propionic acids. The multi-stage microaerobic biological fluidized bed reactor can transform each 1.00 mol acrylic acid into 0.22 mol acetic acid and 0.36 mol propionic acid, and achieve the pretreatment of acrylic acid wastewater at high loads.

[Treatment of acrylate wastewater by electrocatalytic reduction process].

High-concentration acrylate wastewater was treated by an electrocatalytic reduction process. The effects of the cation exchange membrane (CEM) and cathode materials on acrylate reduction were investigated. It indicated that the acrylate could be reduced to propionate acid efficiently by the electrocatalytic reduction process. The addition of CEM to separator with the cathode and anode could significantly improve current efficiency. The cathode materials had significant effect on the reduction of acrylate. The current efficiency by Pd/Nickel foam, was greater than 90%, while those by nickel foam, the carbon fibers and the stainless steel decreased successively. Toxicity of the wastewater decreased considerably and methane production rate in the biochemical methane potential (BMP) test increased greatly after the electrocatalytic reduction process.

[Discussion of protective mechanism of Lyceum barbarum polysaccharides on ovarian tissue in female senile rats].

OBJECTIVE: To study the protective mechanism of Lyceum barbarum polysaccharides (LBP) on ovarian tissue in female senile rat. METHODS: Senile rats of 14 months old were divided randomly into model group, positive drug group, LBP low dosage group, LBP medium dosage group and LBP high dosage group. SD female rats of 4 months old formed a youth group. 30 days after administration,rat blood was taken, radioimmunoassay was employed to determine the levels of estrone and progesterone and enzyme immunoassay was used to determine the levels of IGF-I. Then ovarian tissue was taken to determine the levels of IGFBP-1 and IGFR. RESULTS: Daily oral LBP(60,40,20 mg/kg body weight) for 30 days significantly recovered uterine atrophy and restored serum IGF-I level, estrone and progesterone levels that were decreased in elder rats, reduced the expressing of IGFBP-1 in ovarian tissue that were increased in elder rats. CONCLUSION: LBP has a notable protection on rat ovarian system.