A novel technique of semi-aerobic aged refuse biofilter for leachate treatment

We developed a semi-aerobic aged refuse biofilter (SAARB) for leachate treatment and examined its advantages and disadvantages compared to previous aged refuse biofilters (ARBs). To assess its treatment capability, decontamination mechanisms and optimal performance parameters, a single-period experiment and L9(34) orthogonal array design experiments were conducted on artificial leachate. The SAARB markedly enhanced the treatment capability and removal efficiency of organic matter and nitrogen pollutants due to the alternating aerobic–anoxic–anaerobic zones in situ. The reduction in chemical oxygen demand (COD), ammonia nitrogen (NH4+–N) and total nitrogen (TN) exceeded 98%, 94%, and 80%, respectively. After the leachate was distributed onto the SAARB surface, the effluent velocity decreased as a logarithmic function, and there was a concomitant reduction in leachate effluent volume. Based on the capacity for removal of COD, NH4+–N, and TN, the effective height of aged refuse in a SAARB was enough to be 900 mm. An excellent treatment efficiency could be achieved at 20–35 °C, with a leachate distribution time of 1 h once every period of 2–3 days, hydraulic loading of 11–30 L/(m3 day), and COD loading of 550–1200 g/(m3 day). This new SAARB system demonstrates superior efficacy for biofilter compared to other ARB systems, especially for nitrogen removal from leachate.