Development of the manometric principle based device for wastewater characterisation through continuous monitoring of BOD in a long term

Abstract

Biochemical Oxygen Demand (BOD) is one of the important parameters in environmental analysis allowing to estimate the organic pollution level which is biodegradable in the aerobic condition. Although the determination of BOD for long-term (about 20 days) at a high frequency (up to 5 mins/1 sampling time) can provide more useful information about wastewater characteristics, the available commercial BOD devices have not yet met the above target. Through this research, a novel BOD device based on the manometric principle has been successfully developed, and it can help to continuously monitor the BOD of wastewaters in more than 20 days. This device can be operated using a relative piezoresistive pressure sensor with the range of 0 to 138 mbar, the accuracy of 0.05%, and the linearity R² >0.997. The output parameters are thermally compensated by a temperature sensor installed inside the device and then displayed on LCD, stored in ROM and transferred to the hyphenated computer over a serial communication interface RS232. The performance of the device is evaluated through the comparison with that of a commercial device of HACH company. This solution not only allows to follow the fluctuation of BOD in a long time but also has a low cost and exhibits high potentials for wide application in Vietnam.