Abstract

GIL-VILLANUEVA, Alfonso  and  NATIVIDAD-MARIN, Leynard. Pilot-scale residual sludge dehydration in a convective rotary dryer, Case: Santa Clara wastewater treatment plant Lima, Peru. Tecnia [online]. 2023, vol.33, n.1, pp.21-33. ISSN 0375-7765.  http://dx.doi.org/10.21754/tecnia.v33i1.1550.

ABSTRACT This research aims to improve sludge management at Santa Clara wastewater treatment plant (Lima, Peru) by decreasing the sludge volume using a heating dryer. Sludge volume decrease could reduce transport cost to sanitary landfill, and its reuse as fertilizer. This study was developed in laboratory and in a pilot scale heating dyer setup within the wastewater treatment plant. Preliminary tests measured the approximate sludge composition: water (85.90%), non-volatised solids (4.93%), and volatised solids (9.17%). Moreover, the Ca (OH)2 optimum quantity to be added to the sludge was determined as 9.09% to stabilise the sample at 12pH. The pilot scale sludge dehydration was accomplished by a continuous rotational convective dryer, a mixing tank, a screw feeder, an air heating system, a cyclone collector, and a gas scrubber. The assessed process variables were the drying temperature (120°C, 150°C and 200°C) and the sludge retaining time within the dryer drum (20, 40, and 60 minutes). The drying tests were performed by feeding the sludge to the mixing tank, using 20Kg, 40 kg and 200 kg of wet sludge. The drying at 200°C and 60 minutes of sludge retaining time achieved 17.74% average sludge moisture. In each experiment, Escherichia Coli and Helminth eggs were measured before and after drying. No Helminths Eggs in sludge samples before and after drying were detected. Sludge samples containing Ca (OH)2 showed a reduction in Escherichia Coli concentration from 2.4×103 NMP /1 g ST - 1.6×105 NMP/1 g ST range to values lower than 18 NMP /100 g ST. Additionally, chemical analysis in the dehydrated sludge showed presence of nutrients (N, P, C, etc.), suggesting its possible use as a fertilizer, however, it is recommended further research due to metal presence in the sample.

Keywords : Residual sludge; convective dehydration; fertilizer; Escherichia Coli; sludge hygienization.

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