Tertiary treatment of piggery wastes in water hyacinth ponds

This work was developed in two stages: initially in water hyacinth ponds un der batch conditions (pilot-scale) and later in full-scale ponds under a co ntinuous slate, so as to determine local parameters for the operation of th is kind of pond for piggery wastes treatment. Seasonal variations are impor tant features influencing plant productivity and performance. The water hya cinth ponds were able to remove around 50% of the applied organic loads (CO D, BOD, TN, TP), even in case of elevated values (110 kg/ha/day) applied fo r total nitrogen surface loads. An hydraulic retention time of 20 days was shown to be ideal for the treatment. The utilization of water hyacinths as a complement for the animal diet closes the productive cycle in a sustainab le way. The results have demonstrated the feasibility of the proposed treat ment system.