Abstract
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.
Highlights
Despite the advantages of anaerobic digestion, the process in which organic materials are decomposed in the absence of free oxygen to yield methane (CH4), Carbon Dioxide (CO2) and small quantities of other gases
The hardware for the Data Acquisition and Control System (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
Compared to other biological treatment processes, anaerobic digestion has several advantages including: (a) A useable biogas that is about 60-80% methane with a fuel value of 22.4 MJ/m3 is produced in the process (Ghaly and Echiegu, 1993), (b) the digested residue is almost odourless with reduced solids content, enhanced fertilizer value, lower pathogenic bacteria content and loss of
Summary
Viability of contained weed seeds (Engeli et al, 1993; Allan et al, 2003; Eckford et al, 2012). Compared to other biological treatment processes, anaerobic digestion has several advantages including: (a) A useable biogas that is about 60-80% methane with a fuel value of 22.4 MJ/m3 is produced in the process (Ghaly and Echiegu, 1993), (b) the digested residue is almost odourless with reduced solids content, enhanced fertilizer value, lower pathogenic bacteria content and loss of. 1991b; Ghaly and Ramkumar, 1999; Ghaly et al, 2000) It is, important that these parameters be monitored and controlled continuously for successful operation of anaerobic digesters. Presented in this study is a computer based data acquisition and control system developed for the continuous monitoring of the temperature, pH and gas production of a pilot scale anaerobic digestion system. The system is designed to control the temperature and feeding rate of the digesters
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