Stabilization ponds have been used to treat piggery waste. In order to better understand the interactions among
the variables and the factors governing the process of degradation in the ponds and to identify the predominant factors in every stage (pond) of the treatment system, the principal components analysis (PCA) was employed in this study. The work was performed in an experimental treatment system comprising a primary (an equalizer, a settling tank, and two anaerobic ponds), a secondary (a high rate algal pond), and a tertiary treatment step (two maturation ponds and one water hyacinth pond), in series. The PCA was applied for the secondary and the tertiary steps of the treatment. It was evident that in the high rate algal pond (HRAP), the main artificial factors were: nutrient removal, algae growth and stabilization process; in the first maturation pond (MP1), nutrient removal, aerobic conditions and organic matter concentration; in the second maturation pond (MP2), nutrient removal and algae growth; and in the water hyacinth pond (WHP), nutrient removal, temperature, and algae growth. The PCA showed the importance of the aerobic conditions associated with the efficient performance of the treatment system.

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