Organic Waste Recycling

278 Organic waste recycling: technology and management

Sharma et al. (1987) investigated the variation with time of DO levels at
dawn and COD concentrations in the pond water fed with septage at various
organic loadings. Their experiments were conducted at AIT campus, Bangkok,
under ambient, tropical conditions. Because the pond system used was static and
non-flow-through, and septage loading was undertaken once a day, the total and
filtered COD concentrations of the pond water increased gradually with respect
to time (Figure 6.8 a and b). The increase in COD consequently resulted in a
decrease of DO at dawn as observed in Figure 6.8 c.

Figure 6.8 Variations of COD and DO in septage-fed ponds at various COD loadings
(Sharmaet al. 1987; reproduced by permission of Elsevier Science Publishers, B.V)

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(a) Variation of total COD

(b) Variation of filtered COD

(c) Fluctuation of dissolved oxygen (DO) at dawn

Total COD, mg/L Filtered COD, mg/L

Dissolved oxygen, mg/L

Time, days Time, days

Time, days

(a) (b)

(c)