In Thailand, most of the natural waterways serve as
sewerage for domestic and industrial waste water. A
study in Bangkok Metropolitan Area estimated that 60–
70% of domestic waste was discharged to the Chao
Phraya River and eventually to the Gulf of Thailand
without prior treatment. Table 1 and Fig. 1 show the
BOD load from the major coastal zones of Thailand
namely: central basin, eastern seaboard, eastern south
and western south. The central basin contributes the
highest BOD load with 34 376 t/year, of which 29 033 t/
year are from domestic sources and 5343 t/year are industrial.
These untreated wastes are discharged directly
or indirectly to canals, rivers and sea, causing high BOD
values and bacterial contamination close to populated
and industrialized areas. This is because there are not
* enough waste water treatment facilities in the area.