Effect of biochar addition on the removal of organic and nitrogen pollutants from leachate treated with a semi-aerobic aged refuse biofilter.

The effect of biochar on the removal of organic and nitrogen contaminants from leachate in a semi-aerobic aged refuse biofilter (SAARB) was investigated. A preset amount of biochar was mixed with the aged refuse to explore the enhancement ability of pollutant removal by characterizing the leachate effluent and gas. The results showed that biochar contributed to the removal of organic and nitrogen pollutants from the leachate and that increasing the amount of biochar added led to higher colour number, chemical oxygen demand, ammonia nitrogen, and total nitrogen removal efficiencies. Furthermore, the addition of biochar significantly increased the removal of large molecule organic pollutants from the leachate. The improved removal of organics was due to the considerable number of surface functional groups and the large surface area of the biochar, which effectively absorbed and removed a significant amount of the organic matter from the leachate. Biochar elevated the dissolved oxygen concentration in the semi-aerobic system, which facilitated the completion of the nitrification reaction. It also promoted denitrification by acting as a supplementary carbon source. The nitrous oxide (N2O) emissions decreased as the amount of biochar added increased. When the biochar proportion reached 3%, the N2O emission was only 1.11% of the original total nitrogen and the di-nitrogen emission was 19.61%. The findings of this study can be used to improve the treatment of leachate using biochar combined with a SAARB.

Controlling waste by waste: a modified landfill leachate coagulation sludge activated peroxymonosulfate process achieves complete BPA degradation.

In this study, a modified coagulation sludge (MCS) from a real landfill leachate coagulation pretreatment was first prepared with polymerized ferric sulfate (PFS) as the activator for PMS to degrade bisphenol A (BPA). The results showed that 43.34% of BPA was adsorbed by MCS when [BPA]0 = 20 mg/L, [MCS]0 = 0.8 g/L, and time = 80 min. Thereafter, by adding 3000 mg/L PMS to initiate the oxidation process, complete BPA removal, i.e. 100%, was achieved in 60 min. In addition, in tap water and municipal wastewater scenarios, 100% and 90.07% removal of BPA were obtained, respectively, and MCS exhibited outstanding performance after repeated use. MCS displayed an excellent adsorption capacity in which chemical adsorption was the main effect, and hydroxyl radicals were the major contributor to BPA degradation. Characterizations of fresh and reacted MCS were conducted, and the results showed that the MCS structure was stable after repeated use, and the surface functional groups, surface defect sites, and iron oxides participated in PMS activation. Overall, this study demonstrated successful recycling of coagulation sludge from landfill leachate pretreatment to activate PMS for environmental pollution control, which is in accordance with the goal of using waste to control waste.

Preparation of biochar and biochar composites and their application in a Fenton-like process for wastewater decontamination: A review.

Biochar is a carbon-rich material that can be obtained from pyrolysis of solid waste (e.g., agricultural solid waste and sludge from wastewater treatment plants). Biochar features low cost, large specific surface area, and strong adsorption capacity. New biochar composites can be produced via modification and loading of nano particles onto biochar. Biochar can contribute to the dispersion and stabilization of nano particles. In addition, nano particles can increase the number of surface-active sites, which improves the physicochemical properties of the material. Biochar and biochar composites have been applied widely in wastewater treatment, and have significantly enhanced the treatment performance of Fenton-like processes (activation of hydrogen peroxide and persulfate) as an advanced oxidation process for organics removal and wastewater decontamination. This paper reviews the preparation methods for biochar and biochar composites to systematically analyze the influential factors on the preparation process. The paper also comprehensively reviews the mechanisms by which biochar removes different organic pollutants. However, due to the vast number of different biochar feedstocks and their preparation methods, it is difficult to compare the properties of one biochar to another. Guidance if provided for the application of biochar and biochar composites for wastewater decontamination.

Dinitrodiazophenol industrial wastewater treatment by a sequential ozone Fenton process.

The ozonation process is efficient in degrading aromatic substances and substances with unsaturated bonds, but cannot effectively destroy small-molecule organic compounds, which accumulate. Likewise, the Fenton process is a classic wastewater treatment method, but requires strict pH control and produces secondary pollution when the concentration of organic substances is high. In this study, we applied a 1stO3-2ndFenton sequential process to treat diazodinitrophenol (DDNP) industrial wastewater and provide suitable reaction conditions for Fenton process. For the 1stOzone process, organics removal increased as O3 dosage increased. At optimized operation, the 1stO3 process provided an acidic effluent (pH = 3) and reduced the organics concentration to a level suitable for the 2ndFenton process. Benzene ring substances as well as nitro group and diazo group compounds were greatly degraded in the 1stO3 process and were further mineralized in the 2ndFenton process. Additionally, the biodegradability of DDNP industrial wastewater was greatly improved. This is the first reported time that ozonation and the Fenton process have been integrated sequentially to treat an explosive production wastewater. The study provides a feasible chemical oxidation method for treating DDNP industrial wastewater by simply combining two classic treatment processes.