Soutenance de thèse de Huong Thi Mai Nguyen

Title: Faecal indicator bacteria and organic carbon in the Red River (Viet Nam): measurements and modelling

Le jury sera composé de :

Pierre SERVAIS, Professeur, Université libre de Bruxelles, rapporteur
Kim Dinh DANG, Professeur, VAST, rapporteur
Hung Quoc LE, Professeur, VAST, examinateur
Sylvain HUON, Maître de conférences, UPMC, examinateur
Emma ROCHELLE-NEWALL, Directrice de recherche IRD, directrice de thèse
Quynh Thi Phuong LE, Chargée de recherche VAST, co-directrice de thèse
Josette GARNIER, Directrice de recherche CNRS, co-encadrante, invitée
Gilles BILLEN, Directeur de recherche CNRS, co-encadrant, invité

VAST : Vietnam Academy of science and technology à Hanoï

Abstract: In many developing countries, poor water quality poses a major threat to human health and the lack of access to clean drinking water and adequate sanitation is a major brake on development. The Red River is the second largest river in Vietnam and constitutes the main water source for the population of North Vietnam. This thesis presents the results from observations and modeling of both faecal indicator bacteria (FIB) and organic carbon (OC) in the Red River system, North Vietnam. The objective of this work was to measure FIB numbers and OC concentrations in this system and then to model these parameters in order to investigate scenarios for 2050 when population in the area is estimated to have doubled. The dataset was then modeled using the Seneque/Riverstrahler model in order to investigate the dynamics and seasonal distribution of FIB and OC in the Red River and its upstream tributaries. A scenario, based on the predicted changes in future demographics and land use in the Red River system for the 2050 horizon, showed only a limited increase of FIB numbers compared with the present situation. This was particularly the case in Hanoi even though the population is expected to triple by 2050. The OC inputs and the resulting heterotrophic respiration of this OC resulted in a system that was a strong CO2 source. The model results also reflected the importance of land use, discharge and the dominance of non-point sources over point sources for FIB and OC in the Red River. This thesis provides some new information on FIB in the Red River as well as providing a base for discussion with decision makers on the future management of wastewater in the Red River.