Comprehensive monitoring of a fluidised bed reactor for anaerobic treatment of high strength wastewater

Abstract

Attempts at validation of models of the anaerobic degradation process in high-rate reactors have generally been inconclusive as a result of the lack of sufficiently comprehensive sets of reported experimental data. In most cases, the data have not been self-verifying, as a result of insufficient analysis of all the components in the biogas, no comparison of the total carbon in the volatile fatty acids with measured total organic carbon, or failure to measure all the components in the carbon and nitrogen balances. This paper reports a study of a pilot-scale reactor treating a glucose substrate, in which these shortcomings were largely overcome. Daily samples of biogas were taken for immediate determination of hydrogen, methane, carbon dioxide and nitrogen. Approximately daily samples of the effluent were analysed for nine volatile fatty acids, total organic carbon, biochemical oxygen demand, suspended solids, sugars and protein content, in addition to the physical variables of temperature, pH and redox potential. The height of the fluidised bed and the head loss through it were also measured daily, as were the effluent flow, the recycle flow and the flow rate of the biogas. The duration of the run was 41 days. The paper reports on the relative consistency of these measurements and their use in calculating the carbon and nitrogen balances on a daily basis. These balances lead to estimates of the rate of increase of biomass within the fluidised bed, which can then be used to estimate mean bioparticle diameter and variations in pore space.