Kinetic Model of Biogas Production from Co-digestion of Thai Rice Noodle Wastewater (Khanomjeen) with Chicken Manure

This study aimed to evaluate the bio-methane potential (BMP) of Thai rice noodle wastewater co-digested with chicken manure. Batch anaerobic digestion systems were operated at room temperature (28-30 ºC) for 45 days. Five different amounts of chicken manure were added to Thai rice noodle wastewater operating in 5 digesters (10g, 20g, 30g, 40g and 50g of chicken manure added respectively). Time-rate derivative models including Gompertz model and its related extensions were used to represent the experimental data. In the biogas production, the Gompertz model becomes popular to describe growth and product formation data because it is simplicity and well-fitting to batch data. Chemical analysis showed that all digesters had the higher nitrogen content (or low COD: N ratio) which was in the range of 16.15-17.62. It was also found that, the digester supplemented with 30g of chicken manure gave highest BMP. This was due to more suitable pH and the ratio of volatile fatty acid to alkalinity (VFA/ALK). The initial pH and alkalinity had a strong effect on the BMP. In general, well nutrient balance, suitable initial pH, and VFA-to-ALK ratio promoted the growth of microorganisms and hence increased the biogas production rate. These were indicated by the kinetic parameters such as the maximum methane production rate (Rm, ml/d) and the methane production potential (P, ml) but not for the shorter lag-phase period (λ, day).