A study on nitrogen and phosphorus treatnment process for livestock wastewater to meet nationnal discharge standards

In recent years, pig livestock husbandry sector in Vietnam has grown strongly in which its meat production reached 3160 thousand tons in 2012. Such livestock development has discharged a large amount of wastewater with high organic contamination (e.g. in the ranges of 4480 - 9720 mg/l with COD, 2670 - 5150 mg/l with BOD5, specially, 267- 428mg/l with Total of Nitrogen and 87 - 172mg/l with Total of Phosphorus). Research on separating nitrogen, phosphorus from livestock wastewater applied MAP is a reasonable solution. This method not only contributes to simplify the treatment technology, significantly reduces treatment cost, but also recovers useful by-product which has high nutrition value for crops. The study results indicated that separating nitrogen, phosphorus from livestock wastewater in the form of MAP was highly effective. The Nitrogen and phosphorus recovering efficiency reached at 58.3÷ 63.6% and 92.3÷95.1%, respectively. The gained MAP crystals had dimension in the range of 404.5 ÷547.8µm. The wastewater after separating MAP was sent to UASB equipment for anaerobicaltreatment process and biogas recovery. . With the retention time of 36 hours, the treatment efficiency reached 86.2 ÷ 89.66% COD removal and 90.6 ÷92.3% BOD5 removal. The gasification rateo was found to be highest at 0.46 litter of biogas per 1g of metabolic COD. Finally, wastewater was aerobically treated to meet QCVN24: 2009/BTNMT standard (B level) prior to being discharged into the environment.