ABSTRACT
Stabilization ponds used for the treatment of piggery wastes accumulate sludge over time, which is commonly used in agriculture. The objective of this study was to evaluate the agronomic potential of this kind of sludge. The samplings were collected in two different phases. The first in two anaerobic ponds (AP1 and AP2) and in one facultative pond with 5 transverse baffles and, the second in the same facultative pond with aeration. The removed sludge of AP1 and AP2 was characterized as rich sludge in volatile solids and with low stabilization, there was a great accumulation of the total phosphorus in the sludge of AP2. The facultative pond presented greater retention of nutrients in the sludge in relation to the anaerobic ponds. The annual accumulation of sludge was 13.3 cm/year in the AP1 and 6.70 cm/year in the AP2, while in the pond with aeration this was on the average of 0.5 cm/year, due to the aeration regime. The sludge can be used as a fertilizer in agriculture, if the chemical characteristics of the soil are taken into account so as to avoid the accumulation of nutrients and damage to plants.
Subject(s)
Manure , Nitrogen/metabolism , Phosphorus/metabolism , Sewage/microbiology , Waste Disposal, Fluid/methods , Agriculture , Animals , Bacteria, Anaerobic/physiology , Biodegradation, Environmental , Conservation of Natural Resources , Facility Design and Construction , Fertilizers , Sewage/chemistry , SwineABSTRACT
This work investigates the optimal management of water hyacinth ponds for the improvement of piggery waste treatment. The optimal harvesting strategy for the water hyacinth was studied using a single mathematical model. The water hyacinth optimal harvesting problem was formulated as an optimal control problem that was solved by application of Pontryagin's Maximum Principle. The optimization of the water hyacinth control in the pond indicates that the plant density should be reduced whenever it reaches half of the maximum capacity for growth. Two experimental systems were used to validate the mathematical model, one in real scale and the other in pilot scale. The results demonstrated the feasibility of the proposed harvesting strategy. For example, a comparison of the total nitrogen removal in the different pilot ponds confirmed the modeling results, in that the performance of the pond maintained with 50% water hyacinth cover was better than the others.
Subject(s)
Eichhornia/physiology , Models, Theoretical , Waste Disposal, Fluid/methods , Animals , Biodegradation, Environmental , Nitrogen/isolation & purification , Nitrogen/metabolism , SwineABSTRACT
This paper shows the performance of a baffled facultative pond for the treatment of piggery wastes. The full-scale system is composed of an equalizer, one decanter (DP), two anaerobic ponds (LA1 and LA2), one facultative pond (LF), with five baffles, and one maturation pond with water hyacinths (LAG). The studies were conducted over a 12 month period in the west region of Santa Catarina, Brazil. The system was supplied daily with a volume of 3 m3/day of farm wastes. A good performance of the treatment system was obtained with average removal efficiencies of 98% for chemical oxygen demand, 93% for total solids, 98% for total phosphorus, 92% for total nitrogen, 7 log units of faecal coliforms and 5 log units of total coliforms. The facultative pond performed well, removing 43% of the chemical oxygen demand, 47% of total nitrogen and 54% of total phosphorus. It was found that the first baffle in the facultative pond was mainly responsible for the efficiency of this pond, and compared with another study the introduction of the baffles improved the removal efficiency by 20% for total phosphorus.
