SHORT RESEARCH AND DISCUSSION ARTICLE Simple approach for the rapid estimation of BOD 5 in food processing wastewater Le Thi Bao Ngoc 1,2,3 & Tran Anh Tu 2 & Luu Thi Thanh Hien 2 & Duong Nhat Linh 4 & Nguyen Tri 3,4 & Nguyen Phuc Hoang Duy 3 & Hoang Tien Cuong 3 & Pham Thi Thuy Phuong 3 Received: 3 February 2020 /Accepted: 31 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract A simple approach was developed for the rapid and accurate estimation of 5-day biochemical oxygen demand (BOD 5 ) in food processing wastewater. Immobilization of the natural microbial consortium that was collected from an aerobic compartment of a food processing wastewater treatment plant was simply performed by adhesion using a low-cost porous carrier. Pseudomonas aeruginosa, Bacillus cereus, and Streptomyces, whose salt-tolerance and ability to break down organic compounds have been widely reported, were found to be predominant. These microorganisms may cause an enhancement of the bioreactor response in the presence of sodium chloride. Consequently, a modified glucose-glutamic acid (GGA) calibration standard was proposed in which an appropriate amount of NaCl was added; this solution was found to be more effective in terms of accuracy and practicality than both conventional GGA and the synthetic wastewater recipe from the Organisation for Economic Cooperation and Development (OECD). The calibrated self-built packed-bed bioreactor exhibited good precision of 3% or less in predicting BOD 5 in influent, which is similar to the performance of the most common commercial biochemical oxygen demand (BOD) bioreactors. There was a statistical agreement between the results obtained from this rapid BOD biosensor and the conventional methods, even when testing treated wastewater samples. Keywords Bioreactor . BOD biosensor . GGA . Calibration standard . Dilution factor . Salt-tolerant bacteria Introduction In Vietnam, the food processing industry is a key part of the national development strategy for the period to 2025. This sector has been expanding rapidly, with an annual growth rate of 9%, and it has significantly contributed to Vietnam’ s gross domestic product over the past 5 years (Huong et al. 2017). However, it is apparent that the rapid growth in the food pro- cessing industry is a leading cause of environmental deterio- ration. Wastewater from seafood processing and canned food factories poses pollution problems due to its high chemical oxygen demand (COD) and biochemical oxygen demand (BOD), which are 500 – 8000 mg O 2 /L and 400 – 6500 mg O 2 /L, respectively (Dieu 2003; Hoa et al. 2017); thus, the timely measurement of COD and BOD plays a cru- cial role in the prevention of environmental pollution. However, while COD can be measured immediately, the stan- dard technique for determining BOD is problematic, in that it requires 5 days and involves complex procedures, as well as measurement devices (Jouanneau et al. 2014). Although BOD biosensors have recently been shown to have potential as ef- fective devices for fast determination and online monitoring of pollution levels in wastewater, they cannot produce real BOD 5 values (Ejeian et al. 2018); only predicted BOD 5 values are obtained, and their accuracy depends on calibration and using the correct standard solution. Many kinds of BOD biosensor have been studied and have shown high correlation with the standard method when using Responsible editor: Ta Yeong Wu * Pham Thi Thuy Phuong pttphuong@ict.vast.vn 1 Ho Chi Minh City University of Science, 227 Nguyen Van Cu Street, District 5, Ho Chi Minh City, Vietnam 2 Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam 3 Vietnam Academy of Science and Technology-Institute of Chemical Technology, 1 Mac Dinh Chi Street, District 1, Ho Chi Minh City, Vietnam 4 Ho Chi Minh City Open University, 97 Vo Van Tan Street, District 3, Ho Chi Minh City, Vietnam Environmental Science and Pollution Research https://doi.org/10.1007/s11356-020-08703-6