Study of Coagulation Process with Lime in Treatment of Landfill Leachate from Fkih Ben Salah City (Morocco)

The leachates are the seat of complex processes which give them a heterogeneous character. Their compositions vary according to several factors: nature of the waste, conditions of their deposition, climatic conditions, their durations of stay, etc. They contain important quantities of organic, mineral matters even of bacteria, which require their treatment in order to safeguard the environment. To do this, several methods are used, such as membrane techniques (reverse osmosis, nanofiltration, etc.), biological techniques (activated sludge, SBR, etc.) and physicochemical techniques (Coagulation-flocculation, adsorption on activated carbon, etc.). Among these techniques, the leachate treatment by coagulation process with the lime showed interesting reduction of the various pollutants: 92.95% of turbidity, 88.23% of suspended matter, 89.89% of COD, 90.83% of BOD5, 78.39% of Fe, 77.78% of Mo, 38.29% of Cd, 48.75% of Al, 50.24% of S2-, 20.57% of K+, 27.24% of phosphorus and 19.53% of Cl-. Based on these results, the coagulation with the lime reveals interesting because it allows to reduce at a lesser cost the pollutants present in leachates.

Research on Treatment of Landfill Leachate Polluting Groundwater by Orthogonal Test

Through PRB simulated device and orthogonal test,we discussed the treatment effect of groundwater polluted by landfill leachate with three reaction mediums of zero-valent iron powder,activated carbon and zeolite. We considered four factors of iron powder mass,activated carbon mass,particle size of iron powder and zeolite mass,and designed a two-level orthogonal test. It concluded that effluent pH appeared to fall or rise as the reaction proceeded,which changed during 7- 8. The removal rates of CODCrin eight reactors were during 60. 7%- 78. 3%,and the removal rates of NH3-N were during 34. 0%- 58. 8%. Activated carbon mass and the interaction of iron powder mass and activated carbon mass had significant influences on the removal of CODCr,while iron powder mass,particle size of iron powder and zeolite mass had insignificant influences on the removal of CODCr. Zeolite mass and activated carbon mass had significant influences on the removal of NH3,while iron powder mass,particle size of iron powder and the interaction with activated carbon mass had insignificant influences on the removal of NH3-N.

Removal of Pb^(2+) and Cd^(2+) by adsorption on clay-solidified grouting curtain for waste landfills

Pb2+ and Cd2+ in leachate were adsorbed on clay-solidified grouting curtain for waste landfills with equilibrium experiment. The cation exchange capacity was determined with ammonium acetate. And the concentration of heavy metal cations in leachate was determined with atomic absorption spectrophotometer. Their equilibrium isotherms were measured, and the experimental isotherm data were analyzed by using Freundlich and Langmuir models. The results show that the adsorption capacities of the heavy metal cations are closely related to the compositions of clay-solidified grouting curtain, and the maximum adsorption appears at the ratio of cement to clay of 2∶4 in the experimental conditions. At their maximum adsorption and pH 5.0, the adsorption capacities of Pb 2+ and Cd 2+ are 16.19mg/g and 1.21mg/g. The competitive adsorption coefficients indicate that the adsorption of clay-solidified grouting curtain for Pb2+ is stronger than that for Cd 2+ . The adsorption process conforms to Freundlich’s model with related coefficient higher than 0.996.

Leachate treatment using a demonstration aged refuse biofilter

Approximately 7000 m^3 of aged refuse （AR） with a placement of over eight years was excavated from Shanghai Refuse Landfill, the largest landfill in China, and used for the construction of a two-stage bioreactor （AR biofilter） media for the biological treatment of 100 m3 of refuse landfill leachate. It was found that over 64% of COD, 96.9%-99.8% of NH4^＋-N, and 95.8%-99.8% of BOD5 could be removed by the AR biofilter, when the leachate with initial COD, BOD5, and NH4^＋-N concentrations were 986-4128 mg/L, 264--959 mg/L,m and 538-1583 mg/L, respectively. The corresponding concentrations in the effluent were reduced to below 30（000 mg/L, 2-12 mg/L, and 10-20 mg/L, respectively. The effluent was clear and pale yellow with suspended solid below 150 mg/L and color below 150 Pt/Co degree. Meanwhile, the total nitrogen removal was only 49%-63%, indicating a relative poor denitrification capacity of AR biofilter. The effluent pH was neutral and the population of Escherichia coli was less than 10^-1 CFU/mL. Hence, it was considered that the demonstration project can work well for the effective treatment of leachate.

Chromium phosphide nanoparticles embedded in porous nitrogen-/phosphorus-doped carbon as efficient electrocatalysts for a nitrogen reduction reaction

The resource recovery of heavy metals from effluent has significant environmental implications and potential commercial value.Chromium phosphide nanoparticles embedded in a nitrogen-/phosphorus-doped porous carbon matrix(CrP/NPC)are synthesized via a consecutive Cr^(6+)leachate treatment and resource recovery process.Electrochemical testing shows that CrP/NPC shows excellent nitrogen reduction reaction(NRR)performance,which yields the highest NH_(3) production rate of 22.56μg h^(−1) mg^(−1)_(cat).and Faradaic efficiency(16.37%)at−0.5 V versus the reversible hydrogen electrode in a 0.05M Na_(2)SO_(4) aqueous solution,as well as robust catalytic stability.The isotopic experiments using ^(15)N^(2) as a nitrogen source confirm that the detected NH_(3) is derived from the NRR process.Finally,density functional theory(DFT)calculations show that the electron deficiency environment of the Cr site can significantly reduce the barrier of the NRR process and promote the formation of intermediate species.

Composition and Accumulation of Fouling during Leachate Reverse Osmosis Membrane Treatment in both a Typical Incineration Plant and a Landfill

Reverse osmosis(RO)membrane process has been extensively used for leachate treatment both in incineration plants and landfills.However,operation and maintenance costs caused by membrane pollution limit the wide application of RO membrane.In order to further understand membrane fouling,this study analyzes the influent,effluent,concentrated liquid pollutants and membrane fouling of typical waste incineration plants and landfills in Chongqing,a city in the west of China based on the comparison of three-dimensional excitation and emission matrix fluorescence(3DEEM)and nanometer particle size.In addition,this paper discusses the change law of chemical oxygen demand(COD)and main pollutants in membrane fouling in the disc tube reverse osmosis(DTRO)system in a single operation cycle,analyzes the main components of membrane fouling,and draws the accumulation of RO membrane pollutants,in order to provide a reference for understanding the composition,formation and control of membrane fouling.