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 an anaerobic digester combined with a biological pond in order to provide overview data that 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 (at the input, after passing through the digester, after passing through the 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 (alpha = 0.05), Kruskal-Wallis test and Dunn test (alpha = 0.05) were preformed to estimate the significance differences. Cluster analysis was applied with the view to comparing the parameters between the sampling locations, and in order to classify the respective locations. Results and conclusions The results have shown that all parameters by far exceeded the allowable limit specified by the QCVN 40:2011/BTNMT and TCN 678-2006 norms. The wastewater after being treated by anaerobic digester was significantly reduced. The treatment efficiency for BOD5 was 66-73%; for COD, it was 74-80%; 78-84% for SS; 10-27% for TN; 7-25% for TP; and for coliform, it ranged between 28.2-85.3%. Wastewater after being treated through the digester combined with the biological pond displayed a very high treatment efficiency: 95-97% for BOD5; 96-97% for COD; up to 96-97% for SS, 45-57% for TN; 35-70% for TP; between 77.4-98.4% for coliforms. The treatment efficiency demonstrated a linear correlation between object locations. Applying an anaerobic digester in combination with a biological pond has proven to be a highly effective solution, which should be prioritized in the treatment of livestock wastewater.