Applied Mechanics and Materials Vols. 295-298

Abstract: Water-lifting aeration technology is one of the effective in-situ algae control technologies in deep reservoirs. Effects of water-lifting aerator type on the in-situ algae inhibition using water-lifting aeration technology was numerically analyzed with the help of FLUENT software. Under stable state, one large clockwise circulation flow was generated outside non-submerged and submerged water-lifting aerators, but the core algae inhibition zone was farther away from the non-submerged aerator under each water depth. When the water depth was increased from 77.25 m to 97.25 m, the percentage of the core algae inhibition zone to the whole flow domain was decreased from 56.01% to 47.34% for the submerged water-lifting aerator case, while that was decreased from 55.48% to 40.15% for the non-submerged water-lifting aerator case.

Abstract: To solve the problem of short-circuit of individual current constructed wetland, a baffled constructed wetland was designed and applied to treat domestic sewage by our research group. The wetland plants were composed of Eichhormia crassipes, Oenanthe javanica, Cyperusalternifolius, Phragmites communis and Aquatic. The results of 18 month indicated that the optimal hydraulic load of baffled constructed wetland was 2.0~2.2 m3/(m2•d). At the hydraulic load of 2.0m3/(m2•d), the COD, TN and TP removal rates of baffled constructed wetland could be over 76.40%, 76.12%, 65.37%, respectively, at 24°C. When the temperature decreased to 12°C, the COD, TN, TP removal rates of system decreased to 67.56%、62.75% and 61.33%, respectively; The SS removal rate of the first 6 compartments was about 79.5% and that of system could maintain 87.18% during the operation of system. Based on the results of trial, the mechanisms of extending the baffled constructed wetland's operational life was owed to high efficient SS removal rate of the first 6 compartments which was used as constructed wetland and anaerobic baffled reactor (ABR). As a result, the long-term stable operation of system in treatment of domestic sewage was explained with extending about 5 times service life than that of individual current constructed wetland. The mechanisms of higher efficiency of baffled constructed wetland in treatment of domestic sewage were owed to the longer flow line of system and the up-down flow of domestic sewage makes pollutant more intimate contact with roots of wetland plants.

Abstract: Microorganisms can be the important biosorbents for heavy metal remediation of contaminated soils or wastewater. A BJKD1 strain isolated from coal gangue piles was identified as a member of the Paecilomyces sp., which can tolerate to 3200 mg/L Cd2+. Favorable condition for BJKD1 growth was at pH 4.0-9.0. The presence of heavy metals, such as 36 mmol/L Cd2+, 1 mmol/L Cu2+, 80 mmol/L Zn2+, 7 mmol/L Ni2+ and 100 mmol/L Mn2+, retarded the growth of BJKD1, however, BJKD1 showed more tolerance for Mn2+. The activity of superoxide dismutase (SOD ) and Catalase (CAT ) in BJKD1 was increased under high metals concentration, indicated BJKD1 has the potential for biological repair of heavy metal pollution in coal gangue piles.

Abstract: The minimum energy required for destratification of a source water reservoir is important to determine the design capacity of mixing system used to improve the source water quality. Taking Jinpen Reservoir in Xi’an, as a study case, the water volumes under different water levels of the reservoir were numerically calculated using the geometry data obtained with a RTK system. The total potential energy (PE) was determined by integrating the PE in each thin sub-layer over the water depth with density dependent on the water temperature. The average water temperature after complete mixing was calculated based on the heat exchange theory, and was consistent with the numerical result of temperature simulation. The difference of total potential energy before and after mixing was calculated for each month with the data of water temperature, water density and water volume. The minimum energy required for destratification increasing with the temperature gradient, was relatively high during the period from June to October, and reached a peak of 2412.92 kW·h in July.

Abstract: The research introduces a kind of new technology of utilizing sediment from the Yellow River for filling and reclamation of coal mining subsidence area. Through analyzing the water and sediment conditions in downstream of the Yellow River for filling subsidence, detail design on sediment fetching position, scale, method, equipment, pipe and pump station, technical costs assessment and economic benefits analysis are conducted to find a new less cost and big benefit way to comprehensively solve the problems of sediment in the Yellow River and coal mining subsidence land.

Abstract: As the lack of carbon source is a key problem of in-situ denitrification in groundwater, choosing appropriate solid carbon source materials is very important. In this study, wheatstraw and sawdust were selected as potential carbon sources to evaluate the performance for in-situ biological denitrification in groundwater by three laboratory-scale column experiments operated at a flow rate of 2.0 cm³/min for 78 d. The results showed that sawdust was a suitable carbon source with less release of nitrogen compounds and relatively stable release of organic carbon, compared with wheatstraw, and was applicable for further use as a filling material in in-situ groundwater bioremediation.

Abstract: [Objective] The aim is to study the pretreatment effect of herbicides production wastewater by spherical micro-electrolysis media. [Method] Spherical micro-electrolysis media is preferred for the pretreatment of herbicides production wastewater and effects of PH, amount of media and reaction time on the pretreatment was investigated. The change of pre- and post-processing herbicides production wastewater was determined; the operation cost was also analyzed. [Result]The optimum reaction conditions are as follows: the PH was 3; the amount of media was 1.0kg/L wastewater; and the reaction time was 3.0h. Under the optimum reaction conditions, the removal of COD, Chromaticity and TP reached 26.3%, 86.4% and 95.6% respectively; BOD5/COD varied from 0.10 to 0.35, and the biodegradability was improved greatly; the cost of pretreatment was 1.0yuan/t, and it was lower than that of electrolysis. [Conclusion] The pretreatment of herbicides production wastewater by spherical micro-electrolysis media has good effect, low cost and no soiling hardening, so it provides a good foundation for subsequent biological treatment.

Abstract: The remediation effects of a real urban river water body was studied using four floating bed systems, in which Caldesia parnassifolias, Sagittaria sagittifolia, Cyperus alternifolius, Ipomoea aquatica Forsk. were planted. A compared system without plant was also carried out. The results showed that all the 4 planted floating systems had obvious removal rates of TN and TP. After 7 days, both the TN and TP were removed speedily in the C. parnassifolias system and their levels were below “environmental surface water quality standards” class II, for which the concentration of TN and TP were 0.5 mg/L and 0.1 mg/L respectively. However, concentrations of TN and TP changed little in control. Further, TN and TP contents in the plants increase gradually, while TN and TP in the water reducing, because the nitrogen and phosphorus were necessary elements for plant growth. This research showed that building floating bed systems to purify water was effective. Since the effect of C. parnassifolias was significant and C. alternifolius has remarkable low temperature adaptability, they were more fitting for building the floating bed systems for urban river remediation.

Abstract: This paper review the chemical stabilization in arsenic contaminated soil use the in situ chemical stabilization technology. Application of iron oxide, alkaline material and phosphorus are very effective agents to fix the arsenic-contaminated soil. In addition, the future study on remediation technology for arsenic-contaminated soils was prospected.

Abstract: To study and select the proper hyperaccumulator plants and their growing method for rapid and effective heavy metal contamination cleaning is of great significance for heavy metal contamination restoration and treatment. This research takes Phytolacca acinosa Roxb as experimental material with lead chloride (PbCl2) of various concentrations as different treatment factors, uses potting plant sto simulate natural environment polluted by heavy metal, analyzes the accumulation characteristics of Phytolacca acinosa Roxb on Heavy Metal Pb. The results show that as the concentration of PbCl2 increases, the accumulation of Pb in Phytolacca acinosa Roxb also increases; when the concentration of PbCl2 content reaches a maximum level of 200 mg/Kg, the Pb content of overground part shows a highest level of 1.763mg/g DW, while the Pb content of foot end part is 0.402 mg/gDW. The experiment indicates that accumulation amount of the overground part (S) to that of the foot end (R) is S/R >1, which shows the basic characteristics of Pb Hyperaccumulator.