AN IN-HOUSE COMPUTER-BASED DATA ACQUISITION AND CONTROL SYSTEM FOR ANAEROBIC FERMENTATION PROCESSES

A computer-based Data Acquisition and Control System (DACS) capable of monitoring the temperature, pH and gas production as well as maintaining a pre-determined temperature profile and feeding regime in anaerobic reactors was developed and tested. The hardware for the DACS was a series-based system consisting of a host processor which drives three modules-a digital input mode (MODULE 255), an analog input node (MODULE 254) and a digital output node (MODULE 253)-through a Serial Communication Adaptor connected to the serial asynchronous communication port of the host processor. The system was tested using two sets of laboratory model reactors maintained under two diurnally cyclic temperature ranges of 20-40°C and 15-25°C. Hydraulic retention time was varied from 10 to 25 days using the control system. The temperature and pH of the reactors were monitored at 30 sec interval. Results showed that the system was able to maintain the desired temperature to within ±2.5°C for the 20-40°C and ±1.0°C for the 15-25°C cycle. It was also able to maintain the desired feeding regime and to monitor and record the temperature, pH and gas production at the desired interval of time.