2.3. Standard solutions of AWW and GGA
In this study,AWW and GGA were used as the two standard solutions. The BOD5 test method [1] and most BOD biosensors have used GGA as the standard solution for calibration. GGA solution was prepared according to the Japanese Industrial Standard,in which a mixture of 150 mg/L glucose and 150 mg/L glutamic acid is equivalent to a BOD value of 220 mg/L with a standard deviation of 10 mg/L [34]. AWW was employed as a standard solution for the biosensor to evaluate BOD in rivers, especially for low BOD sources such as drinking water.The constituents of AWW solution per liter are as follows: nitrohumic acid,4.246 mg;gumar abic,4.696 mg;NaLS,2.427 mg;tannic acid,4.175 mg;LAS,0.942 mg.The AWW solution
is equivalenttoaBOD5 andCODMN valueof3.7mg/Land5.89mg/L,
respectively [32].