Cost optimal operation of an industrial two-stage high-rate anaerobic treatment plant

An economic model which incorporates the major costs associated with the operation of an industrial anaerobic reactor was developed. This model was then used to optimise the operation of a two-stage anaerobic treatment plant through manipulation of the acidification tank pH and recycle flowrate. The most effective operating strategy was to maximise the recycle flowrate and to then optimise the acidification tank pH. For this particular case study it was found that by reducing the acidification tank pH from 6.0 to 5.9 the consumption of caustic was reduced by 10 percent. Furthermore, by increasing the recycle flowrate from 72.7 to 100 m3/h the total cost of operation was reduced by 62 percent. This investigation highlights the need to develop more effective control strategies for the two-stage process and to consider the operational optimisation of the process at the design stage so as to maximise the possible savings that can be made when treating organic wastes.