Stabilization pond systems: Cost estimation for the treatment of piggery waste

This work presents the results from monitoring the three pond systems for the treatment of piggery waste, carried out over 12 months, with the objective of determining operational design parameters to minimize the treatment system costs. The first system consisted of two anaerobic and one facultative pond, the second and third systems were constituted by two anaerobic, two facultative, and one maturation pond, on a pilot scale, arranged in series. The three-pond systems achieved an efficiency of 91 % for the removal of total chemical oxygen demand (TCOD) and 87% for total Kjeldahl nitrogen (TKN). A mathematical model to minimize treatment costs for these wastes was developed, within economic concepts. A simulation of costs was made for a treatment system with a flow rate of 20 m(3)/day and an efficiency level of about 90% for TCOD and TKN removal. The costs were US$812.40 for earth, US$6,360.60 for construction, US$4,530.90 for lining, and US$6,760.70 for pond maintenance, resulting in a total cost of US$18,464.60 for this flow rate and a unitary cost of the order of US$1.30 per swine/year.