[Continuous dry fermentation of pig manure using up plug-flow type anaerobic reactor]

To solve the problems of ammonia inhibition and discharging difficulty in continuous dry fermentation of pig manure, under the experimental conditions of temperature of (25 +/- 2) degrees C and organic loading rate (TS) of 4.44 g x (L x d) (-1), a lab-scale up plug-flow type anaerobic reactor (UPAR) was setup to investigate biogas production, ammonia inhibition, effluent liquidity, and the feasibility of continuous dry fermentation of pig manure using up plug-flow type anaerobic reactor. The experiment was operated for 160 days using the pig manure with four different TS mass fractions (20%, 25%, 30%, 35%) as feeding. Results showed that the feeding TS mass fraction exerted a significant influence on the dry fermentation of pig manure; the stable volumetric biogas production rates of four different feeding TS mass fractions were 2.40, 1.73, 0.89, and 0.62 L x (L x d)(-1), respectively; the biogas producing efficiencies of the reactors with feeding TS mass fractions of 20%, 25% and 30% were obviously superior to that with feeding TS of 35%. With feeding TS mass fraction increased from 20% to 35%, obvious inhibition to biogas producing occurred when concentration of ammonia nitrogen reached more than 2 300 mg x L(-1). When the feeding TS mass fraction was 35%, the concentration of ammonia nitrogen could accumulate to 3 800 mg x L(-1) but biogas production rate decreased 74.1% of that with feeding TS of 20%. Additionally, while the feeding TS mass fraction was 35%, the effluent TS mass fraction achieved 17.1%, and the velocity of effluent was less than 0.002 m x s(-1) the effluent of UPAR could not be smoothly discharged.