| Author | Nguyen, Thi Kim Oanh |
| Call Number | AIT Diss. no. EV-94-2 |
| Subject(s) | Sewage--Purification
|
| Note | A doctoral dissertation submitted in partial fulfillment of the requirements for the degree of
Doctor of Engineering, School of Environment, Resources & Development |
| Publisher | Asian Institute of Technology |
| Abstract | To reduce accidental discharges and spills, hence to benefit both revenue and environment, a
wastewater monitoring program for industrial process control is developed. The program, which
is considered as applicable to a wide range of industrial process, was in the present study mainly
applied on BAPACO, a Vietnamese mill producing bleached kraft pulp and paper. The mill was
found to operate under highly unstable production conditions. Consequently, the accidental
discharges and spills were frequent, which resulted in high specific pollution loads in terms of
BOD and COD. The specific wastewater flow from the pulp and paper manufacturing process
was also high. These specific discharges were approximately 3-6 fold to the untreated discharges
from an average modern Scandinavian kraft mill. The accidental discharges and spills were
estimated to contribute 40 kg/t of CODf in the combined effluent (27 % of the total CODf load)
and 20 kg/t of the cooking chemical loss, expressed as Na2S04 (20% of the chemical make-up).
The fiber loss in the effluents was around 100 kg/tor 10% of the paper production.
Rapidly assessed pollution parameters (RAPP) were used to express material losses, i.e.
settleable solids after 15 minutes of settling (SetS15) and conductivity for the fiber and the
cooking chemical losses, respectively. Averages of these parameters under normal discharge were
used as the targets for loss control. Resulting plots of the principal component analysis for
monitoring data sets were analyzed along with production data to derive the normal discharge
level. Targets were proposed for the effluents with a high potential of material losses. Simple
loss control charts were constructed for the effluent from a paper machine and a spill stream
from a cooking and evaporation plant. The loss in revenue was estimated to demonstrate possible
gains. A general proposal for a monitoring program of the process control was made .
. Environmental impacts of the industry were studied using a combination of biological tests and
chemical analyses. The effluent was found to be only mildly acute toxic. Amongst the three
organisms used to test the toxicity of the BAPACO combined effluent the micro-algae test
(Selenastrum capricornutum) appeared to be the most sensitive (EC50=25%), the Microtox was
second (EC50 =45 % ) and the duckweed test (Lemna aequinoctialis) was not sensitive
(EC50> 100%).
The high chlorine consumption in the bleaching process at BAPACO (70 kg/t) resulted in a high
specific discharge of adsorbable organic halogens (4.7 kg/t) and polychlorinated phenolics (32
g/t) which eventually end up in the environment. Only low levels of dioxins (0.03 ng/kg dw NTEQ) and EOCl (0.4-0.8 mg/kg dw) were, however, found in Red River sediment.
The small overflow of the BAPACO combined effluent (0.1-0.2 % ) to the rice field and the fish
pond resulted in low levels of dioxins and PCBs in fish, crab and mollusc samples. The highest
levels were found in the soft tissue and hepatopancreas of the crab sample. No bound
chlorophenolics were identified in rice from the rice field but the concentration of chlorophenolic
compounds in a sediment was notable.
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Analysis of heavy metals did not indicate any significant increase in rice, but a mollusc sample
was found to contain high levels of heavy metals. Adverse effects of wastewater on the receiving
soil were found.
A model was formulated to provide a quantitative approach to the optimal choice of sampling
methods, flow-proportional composite, time-proportional composite or grab sampling. Another
model was developed to estimate the optimum sampling frequency. The obtained diagrams were
checked against actual monitoring data and the agreement was 80 % for the first model and 75 %
for the second. The optimal set of monitoring parameters was determined through various
correlations and ratios between pollution parameters. A monitoring program for the
environmental audit of the industry was constructed.
A limited environmental audit was also done for COGIDO, a Vietnamese small scale kraft pulp
and paper mill, and some Microtox toxicity tests were conducted for a Thai mill. The discharge
from COGIDO was incomparably high since the mill did not have a chemical recovery system
(CODf load was 800 kg/t). The toxicity in term of the toxicity emission factor from the bleaching
plant was found to be the highest for a Thai mill (15,000), followed by COGIDO (1,200) and
the least at BAPACO (800). |
| Year | 1994 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Reutergardh, Lars Bertil ;Bengtsson, Bengt-Erik
|
| Examination Committee(s) | Nagarur, Nagendra N. ;Stoll, -Ing. Uwe ;Brannland, Rolf
|
| Scholarship Donor(s) | Australian Government |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1994 |