Effects of Injection Points on the Treatment of Pig Manure Using an Integrated Biofilter System

Organic matter and nutrient in pig manure were treated using an integrated filter system. The influent flowed into an anaerobic filter (AF), and the AF effluent was polished in a biological aerated filter (BAF). The filter system was operated with recirculation ratios of 1–3. The filter system was operated with two recirculation methods. When a filter system was operated under bottom recirculation conditions, the nitrated effluent from the BAF was mingled with the influent in the AF. For upper recirculation conditions, the nitrated effluent from the BAF was injected into a height of 36% from the bottom in the AF. Removal of organic matter and nitrogen under upper recirculation conditions was greater than those under bottom recirculation conditions. The average chemical oxygen demand and solids removals were over 99 and over 97% under upper recirculation conditions. Total nitrogen and total phosphorus removals were over 77 and over 69% at recirculation 3 under upper recirculation conditions.