Abstract

The normal practice in Thailand is that the wastes from pig-farms and households are treated separately. Nutrient imbalance as well as other physico-chemical characteristics of each waste cause the anaerobic digestion process to work at suboptimal rates. This work is an attempt to describe the kinetics of anaerobic co-digestion of wastewater mixture from a pig-farm and domestic organic waste to understand the effect of their ratio on the biogas production efficiency in batch digesters which mimic a similar industrial practice. The batch experiments were carried out at three different temperatures (28 oC, 32oC and 35oC), with and without initial pH adjustment (pH 7), and four levels of total solid (8%,12%,16% and 20% TS). It was found that the best operating condition was 35 oC, 16% TS and the pig-manure-to-domestic-waste ratio of 75:25. The modified Gompertz equation was used to estimate some Monod parameters and biomethane potential. Then modified two-substrate Monod equation was used to estimate the maximum specific biogas production rate (MBPR). It was also used to describe the microbial growth, substrate consumption and biogas production satisfactorily.