ydrilla unit was under suspicion. The data of SS
removal in this experiment are shown in Figure 3.
c) 5-day Biochemical Oxygen Demand
The requirement of the Hat Yai Municipality Central Wastewater Treatment Plant
specified BOD5 in effluent at 10 mg/l to be compatible with a nearby canal (Klong Kud) that is
less than the Thailand Effluent Standards (20 mg/
l). As shown in Table 2 and Figure 4, both lotus
and hydrilla units could meet this regulation. The
stems and leaves of aquatic plants provide a good