ASSESSMENT OF LIVESTOCK WASTEWATER TREATMENT EFFICIENCY WHEN USING AN ANAEROBIC DIGESTER COMBINED WITH A BIOLOGICAL POND IN NAM ANH, NGHE AN, VIETNAM

Aim of the study: This study focuses on assessing the efficiency of the anaerobic digester combined with biological pond to provide overview data and can be used as a reference for similar studies in Nghe An province. Material and methods: Wastewater properties at 3 stages of livestock wastewater treatment process (input, after digester, after biological pond) in Nam Anh were investigated. A total of 81 samples were collected across 9 locations between March and May 2020. Shapiro-Wilk test (α = 0.05), Kruskal-Wallis test and Dunn test (α = 0.05) was preformed to estimate the significance differences. Cluster analysis was utilized to compare the parameters between the sampling locations and to classify the locations. Results and conclusions: The results showed that all parameters exceeded the allowable limit many times specified by QCVN 40:2011/BTNMT and TCN 678 – 2006. The wastewater after being treated by anaerobic digester was significantly reduced. The treatment efficiency for BOD5 was 66-73%, COD was 74-80%, SS reached 78-84%, reaching 10-27% for TN, 7-25% for TP and coliform ranged from 28.2-85.3%. Wastewater after being treated through the digester combined with the biological pond had a very high treatment efficiency: 95 - 97% for BOD5, 96- 97% with COD, SS was up to 96-97%, 45 - 57% with TN, 35 - 70% with TP and coliforms reached 77.4 - 98.4%. The treatment efficiency had a linear correlation between object locations. Applying anaerobic digestion in combination with biological pond has proven to be a highly effective solution, and should be prioritized in the treatment of livestock wastewater.