Ammonium was analyzed using an ammonium electrode
(5002A-10C; Horiba, Kyoto). Nitrate ion was measured
spectrophotometrically using the methods of the
Japanese industrial standard for industrial wastewater
(Japanese Industrial Standard, 1998). Nitrate was determined
at 410 nm with 4-aminobenzenesulfonamide (Wako)
and brucine (Tokyo Kasei Kogyo, Tokyo).