[Effects of Biochar on Growth and Pollutant Accumulation of Lettuce in Soil Co-contaminated with Tetracycline and Copper].

Through lettuce potting experiments, the effects of different types of biochar (apple branch, corn straw, and modified sorghum straw biochar with phosphoric acid modification) on lettuce growth under tetracycline (TC) and copper (Cu) co-pollution were investigated. The results showed that compared with those under CK, the addition of biochar treatment significantly increased the plant height, root length, shoot fresh weight, and root fresh weight of lettuce (P < 0.05). The addition of different biochars significantly increased the nitrate nitrogen, chlorophyll, and soluble protein content in lettuce physiological indicators to varying degrees, while also significantly decreasing the levels of malondialdehyde, proline content, and catalase activity. The effects of biochar on lettuce physiological indicators were consistent during both the seedling and mature stages. Compared with those in CK, the addition of biochar resulted in varying degrees of reduction in the TC and Cu contents of both the aboveground and underground parts of lettuce. The aboveground TC and Cu levels decreased by 2.49%-92.32% and 12.79%-36.47%, respectively. The underground TC and Cu levels decreased by 12.53%-55.64% and 22.41%-42.29%, respectively. Correlation analysis showed that nitrate nitrogen, chlorophyll, and soluble protein content of lettuce were negatively correlated with TC content, whereas malondialdehyde, proline content, and catalase activity were positively correlated with TC content. The resistance genes of lettuce were positively correlated with TC content (P < 0.05). In general, modified biochar was found to be more effective in improving lettuce growth quality and reducing pollutant accumulation compared to unmodified biochar, with modified sorghum straw biochar showing the best remediation effect.

Effects of Fe(II) concentration on the biosynthesis of schwertmannite by Acidithiobacillus ferrooxidans and the As(III) removal capacity of schwertmannite.

The effect of Fe(II) concentrations on schwertmannite bio-synthesis and the As(III) removal capacity of schwertmannite were investigated in this study. Acidithiobalillus ferrooxidans (A. ferrooxidans) were inoculated into five FeSO4 systems with initial concentrations of 50, 100, 200, 300, and 400 mmol/L, respectively, to bio-synthesize schwertmannite. The Fe(II) of the systems were almost completely oxidised at 48, 72, 120, 168, and 192 h, respectively, and the bio-schwertmannite yield was 1.99, 3.81, 9.36, 12.42, and 21.60 g/L. The results of this study indicate that all minerals harvested from the different systems are schwertmannite. As the initial Fe(II) concentration increases, the effect of the minerals removing As(III) decreases; moreover, the structure and extracellular polymeric substance (EPS) of schwertmannite may regulate the As(III) removal process. The EPS generated by the A. ferrooxidans can absorb As(III). The outcomes of this study provide fresh insights into the bio-synthetic regulation of schwertmannite and play a significant role in treating As-containing groundwater.

Effect of pH regulation on the formation of biogenic schwertmannite driven by Acidithiobacillus ferrooxidans and its arsenic removal ability.

The effect of pH regulation on schwertmannite bio-synthesis and its As removal ability were investigated in this study. The total Fe precipitation efficiency in a conventional schwertmannite bio-synthesis system (CK) reached 26.5%, with a mineral weight of 5.21 g/L and a mineral specific surface area of 3.18 m2/g. The total Fe precipitation efficiency increased to 88.4-95.8%, the mineral weight increased to 17.10-18.62 g/L, and the specific surface area increased to 3.61-90.67 m2/g of five different treatments in which the system pH was continually adjusted to 2.50, 2.70, 2.90, 3.10, and 3.30 every 3 h, respectively. The very small amounts of schwertmannite were transformed to goethite when the system pH was periodically adjusted to 2.90, 3.10 and 3.30. The increased specific surface area of bio-schwertmannite was due to the contribution of mesopores, with most pores having a diameter of 2-20 nm. For actual As-containing groundwater (27.4 µg/L), the As removal rate was 52.9% for bio-schwertmannite collected from the CK system. However, the removal rate of As increased to 92.7-97.8% for minerals which were collected after five adjusted pH treatments. The outcomes of this study provide a fresh insight into the bio-synthesis regulation of schwertmannite, and have great significance for the treatment of As-containing groundwater.

[Mineralogical characteristics of biogenic schwertmannite amended with different pretreatment methods and the effects on As(III) absorption].

Biogenic schwertmannite has better absorption performance for As(III) than other adsorbents, but there is obvious agglomeration of mineral particles due to the polysaccharides secreted by the bacteria during the synthesis of schwertmannite. The aim of this study was to find out a best pretreatment method to further reduce the agglomeration of mineral particles and enhance the As(III) absorption capacity by comparing the effects of different pretreatment methods on the mineralogical characteristics and adsorption performance of schwertmannite. The pretreatment methods of the biogenic schwertmannite induding the treatments with NaOH, NaCl, thermal activation at 200 degrees C and ethanol-ultrasound. The results showed that the mineral phases were not altered after pretreatment, however, different physical and chemical properties of schwertmannite were found after different pretreatment methods were used. Compared with the original mineral, the mineral surface area, Fe/S molar ratio, SEM image and As(III) adsorption were significantly changed. The highest As(III) sorption capacity was obtained for the pH 12 NaOH treated schwertmannite with the maximum absorbance at room temperature increased from 101.9 mg x g(-1) to 143.3 mg x g(-1), and the surface area enhanced from 45.63 m2 x g(-1) to 325.18 m2 x g(-1). Besides, aggregation of mineral particles was remarkably decreased.

[Effect of microbial nutrient concentration on improvement of municipal sewage sludge dewaterability through bioleaching].

In this study, shaking flask batch experiments and practical engineering application tests were performed to investigate the effect of microbial nutrient concentration on the dewaterability of municipal sewage sludge with 2%, 3%, 4% and 5% solid contents via bioleaching. Meanwhile, the changes of pH value and the utilization efficiency of microbial nutrients during bioleaching were analyzed in this study. The results showed that the pH value decreased gradually at the beginning and then maintained a stable state in the treatments with different solid contents, and the nutrients were completely used up by the microorganisms after 2 days of bioleaching. It was found that the SRF of 2%, 3%, 4%, 5% sludges decreased quickly and then rose gradually with the extension of bioleaching time. In addition, the higher solid content the greater the increase. It was determined that the optimum microbial nutrient dosage for sludge with solid content of 2%, 3%, 4% and 5% were 3.0 g x L(-1), 4.5 g x L(-1), 8.3 g x L(-1) and 12.8 g x L(-1) respectively. At this point, the lowest SRF of sludge with each solid content were 0.61 x 10(12) m x kg(-1), 1.22 x 10(12) m x kg(-1), 3.09 x 10(12) m x kg(-1) and 4.83 x 10(12) m x kg(-1), respectively. Through the engineering application, it was showed that diluting the solid content of sewage sludge from 5% to 3% before bioleaching was feasible. It could not only improve the dewaterability of bioleached sewage sludge (the SRF declined from 3.29 x 10(12) m x kg(-1) to 1.10 x 10(12) m x kg(-1)), but also shorten the sludge nutrient time (shortened from 4 days to 2.35 days) and reduce the operation costs. Therefore, the results of this study have important significance for the engineering application of bioleaching of municipal sewage sludge with high solid content.

[Effect of different sludge retention time (SRT) on municipal sewage sludge bioleaching continuous plug flow reaction system].

A plug-flow bio-reactor of 700 L working volume for sludge bioleaching was used in this study. The reactor was divided into six sections along the direction of the sludge movement. Fourteen days of continuous operation of sludge bioleaching with different sludge retention time (SRT) under the condition of 1.2 m3 x h(-1) aeration amount and 4 g x L(-1) of microbial nutritional substance was conducted. During sludge bioleaching, the dynamic changes of pH, DO, dewaterability (specific resistance to filtration, SRF) of sewage sludge in different sections were investigated in the present study. The results showed that sludge pH were maintained at 5.00, 3.00, 2.90, 2.70, 2.60 and 2.40 from section 1 to section 6 and the SRF of sludge was drastically decreased from initial 0.64 x 10(13) m x kg(-1) to the final 0.33 x 10(13) m x kg(-1) when bioleaching system reached stable at hour 72 with SRT 2.5d. In addition, the sludge pH were maintained at 5.10, 4.10, 3.20, 2.90, 2.70 and 2.60, the DO value were 0.43, 1.47, 3.29, 4.76, 5.75 and 5.88 mg x L(-1) from section 1 to section 6, and the SRF of sludge was drastically decreased from initial 0.56 x 10(13) to the final 0.20 x 10(13) m x kg(-1) when bioleaching system reached stable at hour 120 with SRT 2 d. The pH value was increased to 3.00 at section 6 at hour 48 h with SRT 1.25 d. The bioleaching system imbalanced in this operation conditions because of the utilization efficiency of microbial nutritional substance by Acidibacillus spp. was decreased. The longer sludge retention time, the easier bioleaching system reached stable. 2 d could be used as the optimum sludge retention time in engineering application. The bioleached sludge was collected and dewatered by plate-and-frame filter press to the moisture content of dewatered sludge cake under 60%. This study would provide the necessary data to the engineering application on municipal sewage sludge bioleaching.

[Improvement of municipal sewage sludge dewaterability by bioleaching: a pilot-scale study with sequence batch reaction model].

To observe the bioleaching effect on sewage sludge dewaterability, three consecutive batch bioleaching experiments were conducted through a bioleaching bio-reactor with 700 L of working volume. Subsequently, the bioleached sludge was dewatered by using chamber filter press. The results show that the 1st batch bioleaching process can be finished within 90 hours if the aeration amount was 1.2 m3/h with the 1: 15 mixing ratio of bioleached sludge to raw sludge. The pH of sludge declines from initial 6.11 to 2.33 while ORP increased from initial -134 mV to finial 507 mV. The specific resistance to filtration (SRF) of the tested sludge was decreased from original 1.00 x 10(13) m/kg to final 0.09 x 10(13) m/kg after bioleaching. For the subsequent two batch trials, the bioleaching process can be finished in 40 hours and 46 hours, respectively. Likewise, sludge SRF is also significantly decreased to 0.19 x 10(13) m/kg and 0.36 x 10(13) m/kg if the mixing ratio of bioleached sludge to fresh sludge is 1:1 although the microbial nutrient substance dosage is reduced by 25% and 50% for 2nd, and 3rd batch experiments, respectively. The harvested bioleached sludge from three batch trails is dewatered by chamber filter press with 0.3-0.4 MPa working pressure for 2 hours. It is found that the moisture of dewatered sludge cake can be reduced to 58%, and that the dewatered sludge cake is of khaki appearance and didn't emit any offensive odor. In addition, it is also observes that sludge organic matter only changed a bit from 52.9% to 48.0%, but 58% of sludge-borne Cu and 88% of sludge-borne Zn can be removed from sludge by bioleaching process. Therefore, dual goals for sludge-borne heavy metal removal and sludge dewatering of high efficiency can be achieved simultaneously through the approach mentioned above. Therefore, bioleaching technique is of great engineering application for the treatment of sewage sludge.

[Influence of bioleaching on dewaterability of cattle biogas slurry].

The dewaterability of cattle biogas slurry facilitated by bioleaching was investigated through batch experiments with co-inoculation of different Acidophilic thiobacilli (Acidithiobacillus thiooxidans TS6 or Acidithiobacillus ferrooxidans LX5). The experiment was set the following 5 treatments: (1) original biogas slurry (CK), (2) 4 g x L(-1) Fe(2+) (uninoculation), (3)2 g x L(-1) S(0) + 25 mL A. t, (4) 4 g x L(-1) Fe(2+) + 25 mL A. f and (5) 2 g x L(-1) S(0) + 4 g x L(-1) Fe(2+) + 12.5 mL A. t + 12.5 mL A. f. During bioleaching, dynamic changes of pH, ORP, Fe(2+), F(3+), total Fe, the settleability, the turbidity of the supernatant after settling for 12 h, and the dewaterability (expressed as specific resistance to filtration gamma or capillary suction time, CST) of biogas slurry were monitored. Results show that specific resistance gamma and CST of bioleached biogas slurry are reduced drastically for the treatments of original biogas slurry spiked with only Fe(2+), the treatment of original biogas slurry co-spiked with Fe(2+) and Acidithiobacillus ferrooxidans LX5, and the treatment of original biogas slurry co-spiked with Fe(2+), S(0) and two Acidophilic thiobacilli. Taking the dewaterability, settleability, the turbidity of the supernatant fluid after settle 12 h and economical cost into account, the treatment of original biogas slurry co-spiked with Fe(2+) and Acidithiobacillus ferrooxidans LX5 is the most suitable pattern for cattle biogas slurry bioleaching. After bioleaching, 1.14% of organic matter, 0.09% of N, 0.05% of P, and 0.1% of K are lost in the bioleaching process, but it don't affect its fertilizer efficiency. Meanwhile, the 63.2% of Cu and 91.3% of Zn are removed from the biogas slurry, and elimination efficiencies of total coliforms in bioleached slurry exceed 99%. This study might provide a new approach for treatment and disposal of biogas slurry.

[Improvement of municipal sewage sludge dewaterability by bioleaching: a pilot-scale study with a continuous plug flow reaction model].

A plug-flow bio-reactor of 700 L working volume for sludge bioleaching was used in this study. The reactor was operationally divided into six sections along the direction of the sludge movement. Ten duration of continuous operation of sludge bioleaching with Acidibacillus spp. and 1.2 m3 x h(-1) aeration amount was conducted. In this system, sludge retention time was 2.5 d, and the added amount of microbial nutritional substance was 4 g x L(-1). During sludge bioleaching, the dynamic changes of pH, dewaterability (specific resistance to filtration, SRF) of sewage sludge in different sections, the moisture content and moisture evaporation rate of dewatered bioleached sludge cake obtained by chamber filter press were investigated. The results showed that the SRF of sludge significantly decreased from initial 1.50 x 10(13) m x kg(-1) to the final 0.34 x 10(13) m x kg(-1). The wasted bioleached sludge was collected and dewatered by chamber filter press under the following pressures as 0.3 MPa for 4 h (2 h for feeding sludge, 2 h for holding pressure), 3 h (1.5 h for feeding sludge, 1.5 h for holding pressure), 2 h (1 h for feeding sludge, 1 h for holding pressure), and 1 h (0.5 h for feeding sludge, 0.5 h for holding pressure). Correspondingly, the moisture of dewatered sludge was reduced to 57.9%, 59.2%, 59.6%, and 63.4% of initial moisture, respectively. Moreover, the moisture content of bioleached sludge cake was reduced to about 45% and less than 10% if the cake was placed at 25 degrees C for 15 h and 96 h, respectively. Obviously, sludge bioleaching followed by sludge dewatering using chamber filter press is a promising attractive approach for sludge half-dryness treatment in engineering application.

[Isolation, identification, and degrading effect of a pyrene-degrading strain SE12].

Using pyrene as the sole carbon and energy source, and by the method of plate sublimation, a strain SE12 was isolated from a contaminated soil near Woniushan Coking Plant in Xuzhou, China. According to the morphological, biochemical, and 16S rDNA analyses, this strain was identified as Mycobacterium sp., with 98% of homology to the rapid-growth nonpathogenic strain M. austroafricanum ATCC 33464. The optimum pH and temperature for the degradation of pyrene by SE12 were pH 9 and 30 degrees C. When the soil samples were added with 100 and 200 mg x kg(-1) of pyrene and inoculated with 10(7) CFU x g(-1) of SE12, the degradation rates of pyrene reached to 97% and 99%, respectively after 28 days incubation at 30 degrees C. By using primer-pairs nidAF/nidAR and nidBF/nidBR for amplification of ring-hydroxylating dioxygenase genes, it was shown that SE12 had the fragments of encoded large and small subunits of dioxygenase genes. Sequence analysis showed that these fragments were highly homologous to the known dioxygenase genes from pyrene-degrading Mycobacteria sp.