TITLE:
Unsaturated Flow Drying Bed (UFDB): An Alternative for Treatment of Septic Tanks Sludge
AUTHORS:
Gnagne Théophile, Yéo Ténénan Martial, Kouamé Yao Francis, Konan Koffi Félix
KEYWORDS:
Sludge, Clogging, Drying Bed, Unsaturated Zone, Aeration Pores
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.6 No.5,
April
25,
2014
ABSTRACT: Unsaturated
Flow Drying Bed (UFDB) principles are based on the ones of wastewater treatment
by infiltration-percolation on the one hand and septic tanks sludge
solar-drying beds on the other hand. With UFDB, sludge charges are split with
low heights, leading to the drying of suspended solids in 2 days, and the
infiltration of the flow of liquid in unsaturated middle. For average charges
reaching 12.5 cm/d, the treatment efficiency of total oxygen demand and Total
Kjeldahl Nitrogen, respectively 95 and 96%, correspond to a treatment capacity
of 0.5 kg of O2/d/m2 of drying area. Bacteria reductions
of 4 Ulog are obtained from filtrates outlet, with average fecal coliforms
charges less than 103 CFU/100 ml. Monitoring the hydrodynamic behavior through
rates, moisture, organic matter and respiratory activity demonstrates that the
clogging of the massifs is linked to a biofilm growth within them. A four week
resting period allows biofilm resorption. Thus, the drying of the infiltration
surface in two days, the elimination of carbon, nitrogen and bacterial
pollutions, as well as the reversibility of clogging show that UFDB is a
credible alternative for the treatment of septic tank sludge in the
socio-economic context and climate of tropical Africa.