Analysis and Characterization of the Nutrient Concentration of Thatluang Marsh Attributed to Wastewater Discharges from Vientiane City, Lao PDR

doi: 10.14456/mijet.2015.12

Abstract

The analysis and characterization of the nutrient concentration of Thatluang Marsh is needed in order to evaluate the ability of a natural marsh to assimilate waste as well as to develop management schemes to maintain and enhance the integrity of the marsh. This study is mainly concerned with the analysis and characterization of the temporal and spatial variation of nutrient concentrations in Thatluang marsh (i.e., a natural marsh) as well as its major tributary rivers and canals located in the Makhiao river basin. The marsh area is about 20 km² and mainly occupied by residential areas and some agricultural areas. Monthly nutrient concentration and daily water discharge observed from October 2011 to August 2012 were used in this study. In particular, the nutrient data from the marsh and major tributary rivers and canals were sampled for nitrogen and phosphorus species in the form of ammonium-nitrogen (NH_4-N), nitrite-nitrogen (NO_2-N), nitrate-nitrogen (NO_3-N), total nitrogen (TN), phosphate-phosphorus (PO_4-P) and total phosphorus (TP). The nutrient concentrations at Kae canal were the highest compared to the other stations during the study period with values of 16.04 mg/l for TN and 14.80 mg/l for TP. The NH_4-N concentration at Kae canal and the outlet sometimes exceeded the water quality for irrigation water by FAO standards. The results indicate that relatively high amounts of NH4-N emanate from the municipal area. The NH_4-N, NO_2-N and NO_3-N concentrations were low during the entire observation period at Khae river and Papiao river, compared to Kae canal. The low concentrations might be attributed to the low population density upstream of these sampling points. The TN and TP loads at the outlet of the marsh were higher than the sum of the loads at the other gauging points.