Kinetic evaluation on the degradation process of anaerobic digestion fed with piggery wastewater at different OLRs

• A kinetic model considerring the factor of pH, H2 and H2S was developed.
• With the increase of OLR, H2 and H2S inhibited the degradation of organic matters.
• Initial concentration of COD was the most sensitive parameter.

A kinetic model was developed to predict the degradation of organic matters,biogas production and the intermediate products considering the inhibition of pH, H2 and H2S. The sensitivity of COD, acetate, butyrate and propionate to the kinetic parameters and the influence of pH, H2 and H2S were also analysed. The results showed that the model could be well used to predict the anaerobic process. The maximum kinetic constants corresponding to the degradation of organic matters appeared at 5.3 kg COD/m3. From the degradation kinetic values of acetate, butyrate and propionate, it could be seen that the order of VFAs converted into methane was propionate > butyrate > acetate; From the degradation kinetic value of COD, it could be seen that the order of COD converted into VFAs was acetate > butyrate > propionate. With the increase of OLR, there were inhibitions existing in the anaerobic digester which showed up in the increase of concentration of H2 and H2S. Through the sensitivity analysis, the initial concentration of COD was the most sensitive parameter which made great influence on the anaerobic digestion process.