Comparison of properties of traditional and accelerated carbonated solidified/stabilized contaminated soils.

The investigation of the long-term performance of solidified/stabilized (S/S) contaminated soils was carried out in a trial site in southeast UK. The soils were exposed to the maximum natural weathering for four years and sampled at various depths in a controlled manner. The chemical properties (e.g., degree of carbonation (DOC), pH, electrical conductivity (EC)) and physical properties (e.g., moisture content (MC), liquid limit (LL), plastic limit (PL), plasticity index (PI)) of the samples untreated and treated with the traditional and accelerated carbonated S/S processes were analyzed. Their variations on the depths of the soils were also studied. The result showed that the broad geotechnical properties of the soils, manifested in their PIs, were related to the concentration of the water soluble ions and in particular the free calcium ions. The samples treated with the accelerated carbonation technology (ACT), and the untreated samples contained limited number of free calcium ions in solutions and consequently interacted with waters in a similar way. Compared with the traditional cement-based S/S technology, e.g., treatment with ordinary portland cement (OPC) or EnvirOceM, ACT caused the increase of the PI of the treated soil and made it more stable during long-term weathering. The PI values for the four soils ascended according to the order: the EnvirOceM soil, the OPC soil, the ACT soil, and the untreated soil while their pH and EC values descended according to the same order.

[Electrolysis of iron promoting for the advanced treatment of landfill leachate].

The advanced treatment of landfill leachate by electrochemical oxidation was carried out in a box-style electrochemical reactor, using oxide-coated titanium anode. The effects of the concentration of FeSO4, reaction time, the initial pH value, and voltage (current) on the removal of contaminants were investigated. The removal efficiency of contaminant was compared when Fe2+ and Fe3+ used. The results show, compared with the traditional oxidation of electrolysis, the electrolysis of iron promoting can enhance the organism removal efficiency prominently. The increase of the concentration of FeSO4 can result in the increasing organism removal, but when it exceeds 1 250 mg x L(-1), the increasing range decreases. The removal progress of contaminants is very fast in the first 30 minutes, and then slows down. The reasonable initial pH value is 3 - 4. To eliminate COD and NH4(+) -N from leachate effectively, voltage and current must be larger than 3.3 V and 4.8 A respectively. Compared with Fe2+, the organism removal efficiency is slightly lower when Fe3+ used. Two tentative ideas, making recycle use of iron and the application of acid waste water in the process, were proposed.

Treatment of sewage using an aged-refuse-based bioreactor.

The refuse in landfills becomes stabilized or aged after years of placement, and the resultant partly or fully stabilized refuse thus obtained is referred to as "aged refuse" in this work. The aged refuse contains a wide spectrum and large quantity of microorganisms, which have been proved to have a strong decomposition capability for both biodegradable and refractory organic matter present in some wastewaters. In this study, the aged refuse excavated from a 10-year old closed landfill compartment at Shanghai Refuse Landfill was used as the substrate in a bioreactor for the biofiltration of sewage taken from the sewage pipeline systems in Shanghai downtown areas. Typically, 120kg of screened aged refuse with a diameter less than 15mm was used as biofiltration material in a round shaped bioreactor with an inner diameter of 80cm and a height of 150cm. Influent sewage with initial COD, BOD, and NH(3)-N concentrations of 400-500, 240-300, and 45-50mg/L, respectively, was introduced into the bioreactor. The corresponding concentrations in the effluent were reduced to below 80-100, 10-20, and 10-15mg/L, respectively, at a hydraulic load of 1000-1200L/m(3) refuse/day, and the treatment efficiencies decreased with increased hydraulic load. The treatment mechanism was also studied. It was found that the pollutant removal efficiencies dramatically decreased when the aged refuse in the bioreactor was preliminarily disinfected using NaClO solutions, indicating that the pollutants in the sewage were biologically removed. The treatment process developed in this work is cost-effective.