Ammonium ion concentration measurements were carried outusing a Thermo Scientific Orion ISE meter 4-Star along with a Thermo Scientific Orion ammonium ion selective electrode (No.9512BNWP). Prior to measurement, pH buffer (ISA Orion 951211)was added to the sample in a ratio 50:1. To prevent any contamination,the electrode was washed before and after measuring the sample with DI water and dried with a lint-free tissue. All ammonium
ion solutions, including calibration solutions, were made up from ammonium chloride (NH4Cl).