Integrating an intermittent aerator in a swine wastewater treatment system for land-limited conditions

A full scale swine (300 pigs) waste treatment system, including a solid/liquid separation unit (3 m) with a solids holding tank (1.2 m) and a liquid holding tank (20 m), two anaerobic reactors (10 m each) in series, an intermittent aeration unit (20 m), a sedimentation/polishing unit (20 m) and a sludge dewatering bed (17 m), was used to investigate the impact of integrating an intermittent aeration unit on the overall process performance of the swine waste treatment system. The intermittent aeration unit was used for the treatment of a combination of raw liquid manure and anaerobically treated concentrated manure. Four operational ratios of aeration time to non-aeration time of 60 : 36, 5 : 1, 4 : 2 and 3 : 3 h were investigated. At an HRT of 3.2 days and a ratio of aeration to non-aeration of 3 : 3, the removal eciencies for Biochemical Oxygen Demand (BOD5), Total-N (T-N), TSS and Total-P (T-P) were 98.0%, 92.4%, 95.6% and 59.4%, respectively, for the intermittent aeration unit. E‚uent concentrations of BOD5, NO ÿ 3 ±N, NH ‡ 4 ±N, and TSS were 35 ‹ 12, 2.6 ‹ 0.8, 36 ‹ 28 and 78 ‹ 13 mg/l, respectively. The impact of integrating an intermittent aeration unit in the overall swine waste treatment which included solid/liquid separation, anaerobic treatment and ®nal sedimentation/polishing units is apparent from its high treatment eciency for BOD5 and T-N. Economic evaluation of the swine waste treatment system integrating an intermittent aeration unit was conducted based on 300, 1000, 2000, 3000 and 5000 pigs. It was found that the utilization of biogas and digested sludge is essential for the bene®t or pro®t of operating this treatment system. Integrating the intermittent aeration unit in the swine waste treatment system provides reduction of energy consumption cost and reuse/disposal of treated wastewater without causing deterioration of environmental quality. The integrated system also provides the possibility of developing a fabricated-packaged treatment plant or a central swine waste processing plant for application in landlimited tropical/subtropical areas. Ó 1999 Elsevier Science Ltd. All rights reserved.