Denitrification capacity of bioreactors filled with refuse at different landfill ages

The denitrification capacity of refuse at different landfill ages in bioreactor landfill system was studied. Three reactors filled with 1-year-old refuse (R1), 6-year-old refuse (R6) and 11-year-old refuse (R11), respectively, were operated in the experiment. Nitrate solution (1000 mg NO₃⁻-N L⁻¹) was added into each reactor. The results showed that the reactors were all able to consume nitrate. However, 1-year-old refuse in R1 had both a higher nitrate reduction rate and concentration of N₂. In addition, vertical differences in nitrate removal along the depth of R1 were observed. The bottom-layer refuse and the middle-layer refuse both showed higher efficiency in nitrate depletion than the top layer. Furthermore, N₂O accumulation was found in R11 with the concentration up to 19.3% of the released gas. These results suggested that 1-year-old refuse, which was partly degraded, was more suitable to use as denitrification medium.     

Numerical model to predict settlements coupled with landfill gas pressure in bioreactor landfills

Landfills settle due to its weight and biodegradation of waste. Biodegradation-induced settlement is a direct result of rearrangement of waste skeleton in response to the conversion of waste mass into landfill gases. Traditionally, the compressibility index based on settlement of clays is used to explain the settlement of waste. Literature review showed that there are limited research attempts of landfill settlement predictions by coupling with landfill gas generation and transport. This research describes a model which couples settlement in a bioreactor landfill with the generation and subsequent upward movement of landfill gases. The mass balance of the landfill gas was used to link settlement and gas pressures. In the absence of a closed-formed analytical solution, a computer program was developed to numerically predict the settlements and gas pressures in a bioreactor landfill using landfill geometry and waste properties. Explicitly computed settlement values were then used to predict the pressure profile implicitly. To test the mathematical formulations, a numerical exercise was performed using a single-cell hypothetical bioreactor landfill. The numerical simulation produced satisfactory trends of the settlement and the landfill gas pressure profiles.     

膜生物反应器脱氮除磷工艺处理城市污水的工程应用

为强化城市污水脱氮除磷,研发了厌氧/缺氧/好氧/缺氧-膜生物反应器(A2/O/A-MBR)新工艺,并建设了设计处理规模为2万m3/d实际工程.对该工程的长期监测表明,出水C()D、TN、NH4+-N和TP的平均浓度分别为20.6、6.67、1.05、0.19 mg/L,优于《城镇污水处理厂污染物排放标准》中的一级A标准...     

Nitrate removal in a closed marine system through the ion exchange membrane bioreactor

The accumulation of nitrate in closed marine systems presents a problem for both the marine life and the environment. The present study, proposes the application of the ion exchange membrane bioreactor (IEMB) concept for removing nitrate from marine systems, such as aquaculture tanks or marine aquariums.     

纳滤膜在北京阿苏卫填埋场渗滤液改扩建工程中的应用

在阿苏卫垃圾卫生填埋场渗滤液改扩建工程中,以膜生物反应器(MBR)的出水为研究对象,考察了在一定的pH、进水流量、操作压力下纳滤膜对CODcr、NH3-N和电导率的去除情况.结果表明:在设备初期运行阶段,在pH为7、操作压力为0.5 MPa时,纳滤膜对CODcr的去除率达75%;对NH3-N的去除率较低,出水的NH3-N值略低于进水;对电导率的平均去除率达55%.此外,还分析了纳滤膜的运行性能以及与原有反渗透处理工艺联合使用等问题.     

Cyanide removal from cassava mill wastewater using Azotobactor vinelandii TISTR 1094 with mixed microorganisms in activated sludge treatment system

Cassava mill wastewater has a high organic and cyanide content and is an important economic product of traditional and rural low technology agro-industry in many parts of the world. However, the wastewater is toxic and can pose serious threat to the environment and aquatic life in the receiving waters. The ability of Azotobactor vinelandii TISTR 1094, a N₂-fixing bacterium, to grow and remove cyanide in cassava wastewater was evaluated. Results revealed that the cells in the exponential phase reduce the level of cyanide more rapidly than when the cells are at their stationary growth phase. The rate of cyanide removal by A. vinelandii depends on the initial cyanide concentration. As the initial cyanide concentration increased, removal rate increased and cyanide removal of up to 65.3% was achieved. In the subsequent pilot scale trial involving an activated sludge system, the introduction of A. vinelandii into the system resulted in cyanide removals of up to 90%. This represented an improvement of 20% when compared to the activated sludge system which did not incorporate the strain.     

Phase formation in the B-BN-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system at high pressures and temperatures: The wettability of the phases with copper-based melts

Multiphase materials, including the B₆N boron subnitride, B₆O boron suboxide, and cBN cubic boron nitride, have been obtained from the initial β-rhombohedral or amorphous boron, hBN hexagonal graphite-like boron nitride and B₂O₃ amorphous boron oxide at a pressure of 8 GPa and temperatures from 2100 to 2900 K in a toroid high-pressure apparatus. The hardness of the resulting materials has been measured. The formation of ternary phases in the B-BN-B₂O₃ system has not been observed. The wettability of the resultant materials with copper-based melts has been studied. An addition of 10 mol % Ti to the copper melt has been found to decrease the contact angle to a value lower than 20 deg.