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Combined methods for the treatment of a typical hardwood soaking basin wastewater from plywood industry
Klauson, D.; Klein, K.; Kivi, A.; Kattel, E.; Viisimaa, M.; Dulova, N.; Velling, S.; Trapido, M. & Tenno, T.
Abstract
In this research, various combinations of physicochemical
(coagulation, Fenton process and ozonation)
and biological (aerobic oxidation) treatment methods were
used to purify wastewater originating from wood soaking
basins in plywood production industry. Although the
wastewater has good biodegradability (92 %), there is a
high fraction of organic material expressed as recalcitrant
chemical oxygen demand (COD) of approximately
360 mg L-1. High fraction of organics is caused by woodoriginating
water-soluble material, i.e. extractives, including
lignin and tannins. It was found that optimal treatment
method for hardwood soaking basin wastewater is the
combination of biological pre-treatment, chemical treatment
with Fenton reagent and biological post-treatment.
Under optimal conditions of combined process performance,
up to 99 % removal of the organic loads, nitrogen
and phenols was achieved. Besides achieving target discharge
limits stated for industrial wastewater, the effluent
met the requirements set for municipal wastewater treatment
plants, making the treated water acceptable for subsequent
discharge into natural water bodies: treated water
COD = 90 ± 3 mg L-1; BOD7 = 10 ± 1 mg L-1. The
main result of the present work was the establishment of
sustainable, efficient and economically feasible process to
treat the wastewater with minimised chemicals consumption.
This differs considerably from approaches such as
coagulation or wet oxidation, used to treat similar water
types according to the literature, and is readily applicable
for the production facilities of various scales, including
small and medium enterprises, without the need to make
changes in existing technological schemes.
Keywords
Wood processing wastewater; Physicochemical treatment; Biological oxidation; Multistage wastewater treatment
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