Chapter Four - Leachate Pollution Control Technology at Sanitary Landfill

Abstract

Integrated leachate treatment processes are necessary to deal with the variations of pollutants in leachate. Characterization of microalgae–bacteria consortium cultured in landfill leachate for carbon fixation and lipid production was carried out. To save the land and improve the energy efficiency for leachate treatment processes, the leachate recirculation process, deep shaft aeration bioreactor, aged refuse biofilter, and hydration reaction are developed and demonstrated. Deep shaft aeration reactor is efficient for the biodegradable pollutants removal, with a high NH3-N, total nitrogen, chemical oxygen demand (COD), total organic carbon (TOC) removals of 66–94%, 41–64%, 67–87%, 55–92%, at the organic load rate of 1.7–9.4gCOD/Lday and hydraulic retention time of 1–2 day even in the lowest ambient of –3°C, at influent COD of below 7000mg/L. Aged refuse biofilter of three stages are constructed to deal with the leachate, since the aged refuse contains a wide spectrum and large quantity of microorganisms, and have a strong decomposition capability for both biodegradable and refractory organic matter present in wastewaters. The results reveal that over 85% of COD and 96% of ammonia nitrogen can be removed by the three-stage biofilters when the influent leachate COD and ammonia nitrogen concentration are in the range 5478–10,842mg/L and 811–1582mg/L, respectively. Leachate recirculation between alternating aged refuse bioreactors could benefit both for the pollutant removal in leachate and the refuse decomposition. Furthermore, hydration reaction has the potential to combine and solidify some refractory substances in leachate after the biological treatment. It is found that COD and NH3N decreases to 91mg/L and 10mg/L, with the removal rate over 50% and 90% in the first 6days, respectively. The corresponding maximum COD and NH3N removal capacity reached to around 23 and 9mg/g under the test conditions. An internal iron–carbon electrolysis is developed, with the optimum operation condition Fe:C:H2O2=1:1:3, pH=5, the distribution reaction time of FeC:H2O2 1:4, and the dosage of H2O2 8.5gCOD/L or 2.75gTOC/L. Meanwhile, anaerobic and aerobic processes, membrane technologies, etc., are also introduced. Physical, chemical, and biological means should be integrated in order to make the effluent reach the acceptable limits. Adjusting tank with a cover, membrane bioreactor, and reverse osmosis techniques have been applied widely.