Abstract
The objective of this study was to evaluate the efficiency of anaerobic digestion on the treatment of effluent from poultry slaughterhouse. The experiment was conducted at the Laboratory of Waste Recycling from Animal Production/FCA/UFGD. During four weeks, eight experimental digesters, semi-continuous models, were loaded and set according to the hydraulic retention time (HRT) of 7, 14, 21 and 28 days, and according to the solid fraction treatment, separated with 1 mm sieve or without separation. The average weekly production of biogas and methane as well as the methane concentrations, the potential production per amount of chemical oxygen demand (COD) added and reduced, the concentrations of N, P and K at the beginning and end of process, and the most likely numbers of total and thermotolerant coliforms were evaluated. For data analysis, a completely randomized design was performed in a 4 × 2 factorial arrangement (4 HRT: 7, 14, 21 and 28 days and separation with 1 mm sieve or without separation), with repetition over time. The highest production of biogas and methane was statistically significant for the HRT of 7 and 14 days (5.29 and 2.38 L of biogas and 4.28 and 1.73 L of methane, respectively). There was an interaction between HRT and the separation of the solid with sieve and the highest production was obtained in the treatment without separation. Similar behavior was observed for the potential production with a maximum of 0.41 m³ methane.kg-1 COD added with an HRT of 7 days without separation of the solid fraction. The separation of the solid fraction is not recommended in the pretreatment of liquid effluent from poultry slaughterhouse, once the potential for production and production of methane and biogas were reduced with this treatment.
Highlights
The poultry industry has increased its production due to the high commercial demand that has stimulated this sector which turned Brazil into the third largest broiler producer, with 10.9 million tons produced in late 2009 (UBA, 2009).The generation of waste from the slaughtering of broilers has increased proportionally to the growth of production
The liquid effluent without the solid fraction was less efficient at the production of biogas and methane, which resulted in lower values, representing only half of the values that were obtained in the treatment without separation of the solid fraction
When comparing the production parameters by manual separation of solid fraction, it was found that the highest yield was achieved by the treatment without separation of the solid fraction with a hydraulic retention time (HRT) of 7 days for chemical oxygen demand (COD) added and in the period of 7 and 14 days taking into account the amount of COD reduced
Summary
The poultry industry has increased its production due to the high commercial demand that has stimulated this sector which turned Brazil into the third largest broiler producer, with 10.9 million tons produced in late 2009 (UBA, 2009). The generation of waste from the slaughtering of broilers has increased proportionally to the growth of production. According to Silva (2005), the amount of effluent generated is of about 15 liters for each slaughtered bird, which is characterized by containing a large amount of organic matter that is biodegradable, suspended and colloidal (Kobya et al, 2006), as well as microorganisms. The use of anaerobic processes is widely practiced in the treatment of waste, since anaerobic microorganisms degrade the organic matter, which generates biogas and biofertilizer as final products (Lianhua et al, 2010; Nges, 2010). The burning of biogas is beneficial for reducing the global warming potential, which was reported by data of UNFCCC (2006) as 21 for methane and 310 for nitrous oxide in regards to the pattern 1 that is referred as the carbon dioxide
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