| Author | Amena, Zebunnesa |
| Call Number | AIT Thesis no.WM-02-07 |
| Subject(s) | Water quality--Laos--Vientiane
|
| Note | A thesis submitted in partial fulfillment of the requirements
for the degree of Master of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Water quality deterioration of surface water bodies because of the disposal of
wastewater is a very common problem in many of the developing countries. Lack of
proper sewage systems and pre-disposal treatment facilities are mainly responsible for
this. The Nam Pasak II channel in Vientiane, Lao P.D.R is one such example, which
disposes domestic wastewater as well as storm water from a large area of the
Southwest part of the Vientiane city. The blackish- brown water and the high nutrient
contents (Phosphorus and Ammonia) of this channel is the indication of pollution
there.
This study presents detail of the water quality modeling for the Nam Pasak II channel
in Vientiane to evaluate the option recommended by SIDA to improve the water
quality in the channel.
The recommended option of SIDA for nutrient removal is to harvest vegetation in the
channel. In this study, I-dimensional modeling tool MOUSE was used for dry
weather flow simulation, wet weather flow simulation and nutrient uptake modeling.
An alternative approach (Box modeling) was used for the nutrient uptake modeling,
which involves division of the channel into a number of interconnected boxes and the
outflow concentration in each box was computed using 1st order decay equation.
Dry weather flow simulations were carried out to calibrate the model for roughness
coefficient, dispersion coefficient and travel time and also to test the sensitivity of the
model parameters. Salt was used as tracer for calibration. The model was not
sensitive to the volume of water mixed with salt slug and the injection period but the
concentration and location of salt slug and input flow location influence the model result.
Wet weather flow simulations were carried out to visualize the risk of flooding in
design, present and vegetated conditions. In design condition the channel does not
overflow if the rainfall intensity does not exceed 10 year rainfall intensity. In both
present and vegetated conditions the channel exceeds its bankful capacity for 2-year
return period rainfall but for 1-year rainfall there is no overflow.
Water quality modeling was carried out to evaluate the nutrient removal efficiency.
The nitrogen and phosphorus uptake rate of water hyacinth was used to calculate the
decay constant of total phosphorus and ammonia. Harvesting plant in the channel
reduces phosphorus and ammonia content; for MOUSE the percentage reduction was
20% of total phosphorus and 10% of ammonia and for Box modeling it was 14% of
total phosphorus and 7% of ammonia.
Because of the unavailability of sufficient data, some engineering assumptions and
justifications were made in the course of the study to generate the required data. So,
the methodology followed here can be treated as a general modeling approach for
similar cases for other polluted streams in developing countries where limited data is
available. |
| Year | 2003 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Water Engineering and Management (WM) |
| Chairperson(s) | Mark, Ole ;Luketina, David |
| Examination Committee(s) | Sutat Weesakul ;Tawatchai Tingsanchali ;Babel, M. S. ;Vought, Lena |
| Scholarship Donor(s) | DANIDA |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2003 |