Therefore,the sludge generated from flotation can be recycled as a fertilizer.Furthermore,no
malodour had evolved from this waste and did not generate an environmental nuisance to the public.
Sludge as a biodiesel. Table2 reveals that the mean heating value (6690 cal / g )of the sludge
from flotation was near the same as that of coal in the high range [34 : 5815 – 6643 cal / g ]while it was
higher than that of wood [34:4707–5067cal/g].Therefore, the sludge generated from flotation can be
recycled as a biodiesel.
Kurian et al. [31] and Viitasaari et al. [19] showed that the wastewater of a typical foodstuff
industry was rich in oils and fats,proteins and carbohydrates, therefore ,the sludge maycontainthese
organic matters . The United States Department of Agriculture (USDA) [28] claimed that the energy
values are 4.0 kca l / g for protein , 9.0 kcal/ g for fat and 4.0 kca l / g for carbohydrates . In other words,the
calorific value of proteins and carbohydrates is only about
half that of oils and fats,respectively.In fact,
the sludgefrom flotation may include proteins and carbohydrate other than oils and fats alone [19,31]
so that the mean heating value of the sludge from flotationwaslowerthanthatofthefreeoilsamples
( i . e. 8550762 cal /g)collected from the ST and used cooking oil [38:8891–9058 cal/g].However,the
sludge from flotation should be driedto lower water content before it can be utilizedas a biofuel.