Anaerobic Technology Influence on Pig Slurry Biofertirrigation: Evaluation of Enteric Bacteria

Abstract

Pig slurry is characterized by showing high concentration of total nitrogen (0.5–4.0 g l−1), organic matter (20–110 g l−1 CODT), fecal coliforms (103–108 CFU ml−1), and liquid phase content (around 90 %). The high total nitrogen and liquid phase content, makes its use as biofertilizer very interesting. However, in order to avoid greenhouse gas emissions, transformation of organic matter into methane by anaerobic technology comes to be essential. On the other hand, groundwater microbiological contamination by soil transport of pathogens from excreta makes slurry treatment very important. The aim of this study was to evaluate anaerobic technology influence on biofertirrigation onto silty soil using raw and anaerobically treated pig slurry, considering lactose (+) enteric bacteria as main indicators of fecal contamination. Total nitrogen load rates of 350 and 700 kg N ha−1 year−1 were used. The experimental design consisted in soil immobilized in columns. The system fed with raw pig slurry of 700 kg N ha−1 year−1 showed 99 % of bacterial retention, while the system fed with anaerobic effluent of 350 kg N ha−1 year−1 presented a retention of 86.2 %. A positive relation between bacterial retention and organic matter content in slurry was observed. On the other hand, almost the whole amount of the total nitrogen from the leachates corresponded to soil nitrates, and 99.46 %, 99.51 %, 99.35 %, and 99.29 % of ammonium fed was retained in the systems of raw pig slurry of 700 kg N ha−1 year−1, anaerobic effluent of 700 kg N ha−1 year−1, raw pig slurry of 350 kg N ha−1 year−1, and anaerobic effluent of 350 kg N ha−1 year−1, respectively.