and 121 mg/l, respectively. It shows that the BOD5
and COD values met National Environmental Quality
Standards (NEQS) limits of Pakistan, which is 80 mg/l
for BOD and 150 mg/l for COD. The values of effluent
SS were also within the limits of NEQS. So the
activated sludge process operated at 5 days detention
time shows good results for dairy wastewater as shown
in Fig. 3, Fig. 4, and Fig. 5.
Fig. 6 reveals that a maximum removal efficiency
of 96% was achieved at a detention time of 5 days
for both BOD5 and COD. The major change in
percentage removal of SS is noted between a detention
time of 5 and 7 days when it increased from 84% to
97%.
The data indicates that food to mass ratio (F=M)
and removal efficiency were inversely proportional
to each other and hence an increase in F=M ratio
resulted in a decrease in efficiency. F=M ratio for
the BOD in kg BOD (kg MLVSS)