The treatment of pig slurry by a full-scale Anaerobic-Adding Raw Wastewater-Intermittent Aeration Process

The performance of an Anaerobic-Adding Raw Wastewater-Intermittent Aeration (ANARWIA) process was investigated in a full-scale plant. After 1 year's operation, a successful treatment for swine wastewater had been developed, without adding alkali or external organic matter. The anaerobic unit can maintain chemical oxygen demand (COD) removal efficiencies of approximately 85% during most times of the year, while removing 5% of NH4+-N. The anaerobic unit recovered 5000–7000 m3 d−1 of biogas in summer and 2500–3500 m3 d−1 in winter. In aerobic units, more than 85% of COD could be removed, with a COD concentration of around 300 mg l−1 in the effluent. More than 98% of NH4+-N could be removed with an NH4+-N effluent concentration of about 10 mg l−1. The results confirmed that the addition of raw wastewater to the digested effluent was the key for stable operation of the aerobic unit. It can be concluded that treatment plants using the ANARWIA process can reach similar treatment effects to those plants using the sequence batch reactor (SBR) to directly treat raw wastewater. However, the hydraulic retention time (HRT), the constructing investment for the reactors, the power consumption and the running costs of the ANARWIA process are remarkably lower than those using the direct SBR process.